Food Applications of W1/O/W2 and O1/W/O2 DEs

Food Applications of W₁/O/W₂ and O₁/W/O₂ DEs: Comparison

Please note this is a comparison between Version 2 by Catherine Yang and Version 1 by Fatemeh Ghiasi.

Double emulsions (DEs) present promising applications as alternatives to conventional emulsions in the pharmaceutical, cosmetic, and food industries. Generally, double emulsions are classified into two main categories, water-in-oil-in-water emulsions denoted by W₁/O/W₂ and oil-in-water-in-oil emulsions denoted by O₁/W/O₂, to distinguish between two aqueous and oil phases with different compositions

double emulsion
food application
encapsulation
fat reduction

1. Fortification Purposes

The formulation of nutritionally fortified foods has gained considerable importance due to the increasing demand for health beneficial foods. However, some food ingredients and micronutrients with health promoting properties, such as vitamins, minerals, and polyphenols, are sensitive to environmental conditions (e.g., pH, light, oxygen, heat, etc.) and, hence, cannot be added directly to foods. DE is an appropriate carrier for micronutrients that, in addition to protecting them against degradation, provides the possibility of co-encapsulation of both hydrophilic and hydrophobic compounds to produce enhanced health benefits [13]^[1]. In this context, Dai et al. [14]^[2] co-encapsulated vitamin C and β-carotene within the W₁ and oil phase of a DE, respectively; stabilized by different concentrations of Sipunculus nudus salt-soluble proteins. The values of encapsulation efficiency (EE) for vitamin C at 1% and 2% of protein concentrations were 87.3% and 91.2%, respectively. While β-carotene showed more EE (99.7% and 99.8%), which was not affected by protein concentration. Measuring the antioxidant ability of the samples after 28 days of storage at 4, 37, and 55 °C showed a decrease in the antioxidant ability of vitamin C and β-carotene during this time, especially at higher temperatures. However, comparing the encapsulated and free vitamin C and β-carotene indicated the excellent ability of the DE to protect them against degradation, resulting in higher antioxidant ability.

Co-encapsulation of hydrophobic astaxanthin and hydrophilic phycocyanin in a pH-responsive DE-filled gellan was carried out by Yu, et al. [13]^[1]. The highest EEs of astaxanthin (90.82%) and phycocyanin (94.1%) were achieved at 0.5% and 0.7% gellan concentrations, respectively. Examining the storage stability of the free and encapsulated active compounds showed attenuation rates of 79.9% and 48.1% for solutions of astaxanthin and phycocyanin, respectively, after 10 days of storage; while 25.6% and 16.8% degradation was reported in the encapsulated forms after the same time. In vitro release digestion showed that the DE structure remained intact in acidic conditions with a maximum 25% release of the total encapsulated astaxanthin and phycocyanin. In simulated intestinal fluid (SIF), due to the pH-responsive activity of gellan, the DE structure was destroyed under the effect of an alkaline pH, resulting in higher releases of astaxanthin and phycocyanin (>60%). In another work, Barbosa and Garcia-Rojas [15]^[3] encapsulated iron in the inner phase of a DE and investigated its release and bioaccessibility in adults and infants. The DE samples were prepared using different concentrations of whey protein isolate (WPI), polyglycerol polyricinoleate (PGPR), tara gum, and sucrose. Increasing WPI led to a higher EE of iron. The addition of sucrose caused a higher EE and, therefore, the highest EE (96.9%) was exhibited by the sample with 12% WPI and 2% sucrose after preparation. The EE decreased for all samples after 7 days of storage; however, the lowest reduction was obtained at 2% sucrose. In vitro digestion in adults occurred in the oral (8.36% release), gastric (38.56% release), and intestinal (51.47% release) stages, while in infants, in vitro digestion and release of iron occurred under gastric (27.22%) and intestinal (41.45%) conditions. In addition, the bioaccessibility of iron after digestion was 49.54% for adults and 39.71% for infants. Encapsulation of Magnesium (Mg) in the inner phase of the DE was also performed to make a fortified Mg cake by Kabakci et al. [16]^[4]. Lentil flour was used as a stabilizing agent in the DE. It was observed that increasing the lentil flour decreased EE, so that at 15% and 30% lentil flour, the EE was 97.54% and 92.42%, respectively. Using a high-shear homogenizing method of emulsification resulted in higher EE than ultrasonic homogenization. The addition of Mg to the DE and single emulsion (SE) led to lower hardness than free Mg. The volume of the cake was not affected by the DE and the weight losses of the cakes with DE and SE were higher than of that containing free Mg. The crust color of the three cakes was similar. Sensory analysis showed the lowest score for the cake with free Mg and the taste of the cakes with DE was similar to those without Mg, indicating the ability of DE to mask the unpleasant taste of Mg. The heat protection of the DE was 12.5% higher than the SE during the baking process and 79–83% of the Mg was preserved by the DE at different lentil flour concentrations during baking. In vitro digestion of the Mg in the DE and free Mg samples was similar and both the encapsulated and free Mg were digested under gastric and intestinal conditions. Su et al. [17]^[5] encapsulated different amino acids in a DE stabilized by gum Arabic (GA) and xanthan. It was observed that EE was affected by xanthan content and, at concentrations higher than 0.3%, the EE decreased. Therefore, a DE with 50% W₁/O, 2% gum Arabic, and 0.3% xanthan was prepared. The EE values of aspartic acid, glycine, and lysine as acidic, neutral, and basic amino acids were 82%, 92%, and 83%, respectively. The highest release rate was reported for glycine at 25 °C after 28 days of storage. After 14 days, more than 50% of the glycine was released. The lowest content release rate was reported for lysine (<20% after 28 days). Amino acid leakage was lower at 4 °C compared to 25 °C, resulting in the release of only 40% of glycine with more hydrophobicity after 28 days. Li et al. [18]^[6] used a W₁/O/W₁ DE for vitamin B₁₂ encapsulation in the W₁. The EE and in vitro digestion were assessed under the effects of the W₁/O-to-W₂ ratio and stabilizers of the outer emulsions (Tween 20, soy lipophilic protein (LP), and a LP-methyl cellulose (MC) complex). Using LP and LP-MC resulted in higher vitamin B₁₂ EE than Tween 20. The reduction in EE after 14 days of storage was higher in samples containing Tween 20. An LP: MC ratio of 3:1 favored EE and resulted in a higher value. During in vitro digestion, continuous release of vitamin B₁₂ occurred. At an LP: MC ratio of 1:3, 60% of the vitamin B₁₂ leaked (oral stage) and the highest release was recorded for the Tween 20-stabilized DE in this stage. Meanwhile, the sample with a W₁/O-to-W₂ ratio of 4:6 and an LP: MC ratio of 3:1 showed sustained release during digestion.

In conclusion, the high sensitivity of bioactive compounds such as vitamins, minerals, amino acids, etc., as well as their possible adverse interactions with other food ingredients, are considered to be one of the main concerns in the food industry. The above publications confirmed that DEs can be used for efficient (co-)encapsulation of different sensitive compounds to protect them against degradation and increase their bioavailability in fortified food products without significant effects on the food’s sensory properties. The release of these bioactives can be modulated by using appropriate biopolymers in DE formulation to design target release systems. Therefore, fortification purposes have been the most common applications of DEs in recent decades.

2. Preservation Purposes

2.1. Improved Antimicrobial Properties

Natural food compounds with antimicrobial characteristics hold significant importance for the future of the food industry and customer health. The encapsulation of these antimicrobial compounds, such as essential oils, natural extracts, and peptides, is considered an interesting approach to enhancing their physicochemical and microbiological stability as well as providing for their controlled release in the food matrix. In addition, the challenges related to the limitation of their consumption due to their possible interactions with other food ingredients, as well as their organoleptic taste, can be overcome by encapsulation in emulsion droplets [33,34]^[7][8]. Previous works have reported that the increased specific surface area of the emulsion-dispersed droplets can also improve the biological activities of essential oils and natural extracts; hence, lowering their required concentrations [35]^[9]. Therefore, several researchers have investigated the effect of DEs on the preservation effects of encapsulated antimicrobial agents, as evidenced in Table 21. Tessaro et al. [36]^[10] investigated the preparation of a “Pitanga” leaf hydroethanolic extract (PLHE)-loaded DE under the effects of tween 80 concentration (3–5%, and 8%) and the ratios of emulsion phases (30:70 and 40:60) [37,38]^[11][12]. According to antimicrobial activity measurements on PLHE, the PLHE diluted in the same concentration in the DE (PHLEd), and the most stable DE with a 40:60 W₁/O/W₂ ratio and 3% Tween 80, all samples showed an inhibition zone against P. aeruginosa, Salmonella, and S. aureus bacteria, but did not against E. coli. However, the antibacterial activity of PLHE (1.8–2.2 cm) was greater than that of the PLHE-loaded DE (0.6–0.7 cm). This fact could be related to the lower diffusion rate of encapsulated PLHE from W₁ into the agar in disk diffusion tests as well as the possible reduction of extract during the emulsification process. In another study, the antibacterial properties of a honeybee pollen (HBP)-loaded DE against Streptococcus pyogenes were investigated using agar diffusion methods and serial dilutions [39]^[13]. The control HBP extract presented a lower inhibition zone (12 cm) compared to the encapsulated formulation (23 cm), suggesting its improved antibacterial activity. Interestingly, those DEs without HBP (only ethanol as the internal aqueous phase) also inhibited bacterial growth (22 cm), which might be due to the antimicrobial activity of chitosan hydrochloride in the formulation. The minimum inhibitory concentration MIC of the HBP-loaded DE was also significantly lower than its free form. In addition, the destruction of DEs using ethanol increased their antibacterial activity due to the higher release of HBP from internal layers of DE. Ji et al. [40]^[14] also developed DE-like intermediates through a dynamic encapsulation process by controlling the turbulent fluid flow at high temperatures to encapsulate hydrophilic nisin. The low inhibition-growth activity effect of nisin against L. monocytogenes under the effect of different shear stresses (12,500, 18,750 and 25,000 s⁻¹) and temperatures (25–60 °C) confirmed the successful encapsulation approach to protect its antimicrobial activity as well as its sustained release in food systems. Moreover, microscopic images and surface observation recommended an even distribution of nisin within the polymer matrix and on the particle surface to enhance its activity. In addition, the microbiological aspect of gelled DEs incorporating perilla oil, a rich source of n-3 fatty acids, was studied in the presence or absence of hydroxytyrosol (Hyt) in W₁ after 1 month of storage at 4 °C [41]^[15]. Microbial counts were relatively low at the initial time and the addition of Hyt resulted in the reduction in total viable counts by nearly 1 log. Bacterial growth increased significantly during storage in all formulations; however, it was delayed and lowered after the addition of Hyt during the first two weeks. The Hyt did not show positive inhibition activity on the growth of yeast and molds.

To conclude, encapsulation of antimicrobial agents in DE systems can enhance their microbial growth inhibition effect, increase the food’s shelf-life, and decrease microbial growth through the extended release of antimicrobial compounds without any interaction with the food matrix. Moreover, by changing the droplet size of the emulsion to smaller sizes, the larger ratio of surface area to mass can result in a unique interaction with microorganisms and host cells.

Table 21.

Overview of the past decade’s publications on enhanced antimicrobial properties of natural compounds encapsulated by W

₁

/O/W

₂

double emulsions (DEs).

W₁	O	W₂	Phase Ratio		Remarkable Results	Reference
W₁	O	W₂	Remarkable Results	Reference	Remarkable Results	Reference	W₁:O
W₁:O	W₁/O:W₂		Remarkable Results	Reference
W	₁/O:W₂
W₁:O	W₁/O:W₂
- Honeybee pollen (0.7–1.5 mL)
- Monascus pigment	- Lauroglycol 90^® (900–1200 mg), span 80 (360 mg), and Lipoid P75^® (60 mg)	- Flaxseed gum (0.75%)- Chitosan (6–24 mg in 3.5 mL) - Pluronic F68 (230–700 mg	- Soybean oil in 3.5 mL)	-	- PGPR (6%)	-	- Droplet size: 90 nm - Zeta potential: +33 - EE ˃ 78%	- Pea protein isolate (5%)	20:80
- NaCl (5.84 mg/mL) - Crocin (65 mg/mL)	- Cinnamaldehyde (33%)	40:60	- ↑ Stability under SIF and storage		- ↑ ORAC and antibacterial activity (inhibition zone) against Streptococcus pyogenes = 23 mm than free extract	- ↑ Flaxseed gum led to ↑ size, ↓ instability index and ↓ mean square displacement - Results of sausage properties incorporating 0–30% DEs: Texture: ↓ hardness and ↑ cohesiveness by fat replacing with DE, the highest chewiness and gumminess at a 30% DE level - ↓ Lipid from 11.22% to 5.09%, ↑ protein from 15.77% to 17.02%, ↑ PUFA from 23.36% to 59.63%, ↑ WHC and oxidative stabilitycompared control - ↑ Lightness by fat replacing with DE	-PGPR (8%)	[[80]^[55]
-WPI (8.5%)	50:50	30:70	- Persian gum-based film:		- ↓ Opacity by incorporating DE than free bioactive - ↓ Moisture content, water solubility, WVP, and swelling compared to the free and single-emulsion addition strategy - ↑ Contact angle more than control but less than the free and single-emulsion addition - ↑ Tensile strength and elongation at break as compared to control film and free and single emulsion addition - ↑ UV and visible barrier properties, ↑ photostability of crocin against fluorescent and UV lights, ↑ thermal and pH stability of crocin and cinnamaldehyde, ↑ antioxidant activity after 14 days compared to free bioactives	39]^[13]
[	84	]	^[	⁵⁹	^]	- Pitanga leaf hydroethanolic extract	- Soybean oil - PGPR (3%)	- Tween 80 (3–8%) - SC (0.5%)	20:80	- Full-fat almond emulsion containing almond protein isolate (3.5%), almond oil (4%), and sugar (4.5%)	- Almond oil - PGPR (2%)	- Full-fat almond emulsion containing almond protein isolate (3.5%), almond oil (4%), and sugar (4.5%)^• scavenging at higher concentrations of BCEP - ↑ PV six to ten times lower (4.86–7.47) than control DE (47 meq O₂ kg⁻¹) during storage at 37 °C for 60 days - ↑ Conjugated dienes and trienes during storage at 37 °C for 60 days less than control DE	[46]^[21]
- Brassinolide (0.008%) - Gelatin (1%) - NaCl (0.1%)	- Olive oil - Cinnamon essential oil (2.66%) - PGPR (1.66%)	- Different emulsifiers including whey protein concentrate (WPC)-gum arabic and WPC - high methoxyl pectin (HMP) at 1:3; 1:1; 3:1 ratio	10:30	10:30	- Optimized formulation: DE stabilized by WPC-HMP (1:3) with largest particle size (581.30 nm), lowest PDI (0.23) and zeta potential (−40.31 mV), and highest EE of brassinolide (92%) and cinnamon essential oil (88%). - Results of broccoli coating: ↑ Chlorophyll content and ↓ activities of chlorophyllase (9%) and magnesium-dechelatase (24%), and a lower rate of respiration after storage than control broccoli - Activated energy metabolic enzymes (SDH, CCO, H+-ATPase, Ca2+-ATPase), ↑ ATP, and energy charge.	[49]^[24]
- Murraya koenigii berries extract (MKB) - NaCl (0.6%)	- Soybean oil - PRPG (6%)	- WPC (6%) - NaCl (0.6%)	50:50	70:30	- ↑ Emulsion stability, cooking yield, hardness and lightness of meat batter - ↓ Shrinkage and redness values of meat batter - ↑ G′, G″, and η* of meat batter - The order of TBARS during storage at 4 °C for 9 days: meat batter with vegetable oil > animal fat > control DE > DE and free MKB > MKB-loaded DE - ↑ Oxidation stability of lipid phase and meat batter	[47]^[22]
- Emblica officinalis (EEO) extract (15–50%) - NaCl (1–2%)	- Rice bran oil - PGPR (2–4%).	- Different emulsifiers (0–4%) including low methoxy pectin (LMP), gum Arabic, WPC, SC	30:70	30:70	- Optimized DE: 2% NaCl, 50% EEO, 4% PGPR, 2% LMP - D_4,3: 72.95 µm, high EE (>90%), ↓ during storage - Viscosity: 0.715 Pa.s, ↓ during storage - Zeta potential: −32.17 mV, ↓ during storage - ↑ Encapsulation efficiency at higher EEO concentration - ↑ Antioxidant stability than free extract - ↓ Antioxidant stability after 3 months at cold storage less than free extract (↓ ABTS of control and DE from 7872 and 7473 to 753 and 2969 mM TE g⁻¹, respectively)	[45]^[20]
- Catechin (750 µg/mL) - Gelatin (3%)-NaCl (2%) - Ascorbic acid (0.2%)	- Olive oil - PGPR (6%) - Curcumin (0.1%)	- Tween 80 (1%) - Ascorbic acid (0.2%) - NaCl (2%)	25:75	25:75	- D_4,3: ↓ from ≈3.88 for the blank to ≈2.8–3.0 µm for curcumin and/or catechin-loaded as well as co-delivery DE - Zeta potential ≈ −20 mV - EE: 88% for curcumin, 97% for catechin, >80% for co-delivery DE. - Loading efficiency: 0.1% for curcumin, 0.075% for catechin, 0.175% for co-delivery DE - In vitro release: controlled release of curcumin from curcumin- and co-loaded DE, burst release of catechin from catechin- and co-loaded DE (≈30% within 30 min and >45% within 1 h) - In vitro bioaccessibility: ≈72% for curcumin-loaded, 68% for curcumin in co-delivery DE, ≈16% for free curcumin, ≈60% for catechin-loaded, ≈54% co-delivery DE, and ≈10% for free catechin	[50]^[25]

The * in η* is a symbol of complex viscosity.

3. Protection of Enzyme Activity

Enzymes are multipurpose biological molecules with extensive applications in food, pharmaceutics, and medicine. To date, different approaches have been investigated to enhance their environmental sensitivity and low bioavailability during processing, storage, and oral administration including genetic engineering approaches, immobilization, and encapsulation [51,52]^[26][27]. In this regard, DEs can be considered an efficient tool for the protection of enzymes and hence improve their stability and activity (Table 43). For instance, Li, et al. [51]^[26] designed a DE delivery system stabilized by complexes of soybean protein isolate (SPI) and polyglutamic acid (PGA) at different volume ratios of 5:1, 3:1, 1:1, 1:3, and 1:5 for encapsulation of nattokinase (NK). The highest value of EE (97.19%) for hydrophilic NK was found for DE coated with a 1:3 ratio complex compared to individual SPI and PGA coatings. The fact was related to the increased exposure of lipophilic amino acids and hydrophobic interactions, resulting in the superior stability of the colloidal network in DE. Similarly, the highest NK bioavailability (80.69%) was observed for DE coated with a 1:3 ratio complex, while PGA-stabilized DEs, with their loose emulsified structures, had the lowest bioavailability. Indeed, SPI-PGA complexes presented a controlled release profile due to the PGA gelation, obtaining a delayed oil phase release. However, a higher PGA ratio affected the hydrolysis of the interfacial layer and reduced the release of NK from the W₁ phase. Similarly, Wang, et al. [53]^[28] developed nattokinase-loaded DE systems under the effects of different concentrations and compositions of W₁: a lipid phase type and emulsifier type. Sustained release behaviors of the nattokinase-loaded DE at optimized emulsification conditions in four media, including water, phosphate buffer solution, HCl solution, and acetic acid-sodium acetate buffer, were confirmed, with the highest and lowest values obtained at pH 1.21 and 6.8, respectively. The high encapsulation efficiency (86.8%) showed a good protection effect of optimized DE formulation. In addition, pharmacodynamics evaluation revealed the effective prolog effect of the encapsulation of nattokinase in the DE on the whole blood clotting time in mice as well as enhancing mouse tail thrombosis in comparison with normal saline and nattokinase solution, suggesting the potential application of DEs for nattokinase protection against a gastric acid environment and hence provide an enhanced efficiency during oral administration. In another study, Souza, et al. [54]^[29] microencapsulated microbial lactase (originated from Aspergillus oryzae and Kluyveromyces lactis) in DEs followed by complex coacervation. The best microcapsules at the optimum concentration ratio of core solution-to-total polymer (1%) presented low a_w (≤0.4) and particle size (≤93.52 μm), and high EE (≥98.67%). Significant enhancements of pH stability, storage stability, and temperature stability for the encapsulated lactase were reported as compared to the free form. Moreover, the encapsulation of lactase in a DE presented a low release rate (10–20%) in simulated gastric fluid (SGF) and a high release rate (>80–95%) in SIF, mainly due to the effects of pH, pancreatic activity, and bile salt, to improve the demulsification of the microcapsules.

Table 43.

Overview of the past decade’s publications on enzyme encapsulation by W

₁

/O/W

₂

double emulsions (DEs).

W₁	O	W₂	Phase Ratio		Remarkable Results	Reference
W₁	O	W₂	W₁:O	W₁/O:W₂	Remarkable Results	Reference
- Nattokinase (20%)	- Soybean oil - PGPR (6%)	- SPI (1%) - Polyglutamic acid (PGA) (1%) - Complex SPI:PGA (1%) at different ratios (5:1, 3:1, 1:1, 1:3, 1:5)	30:70	30:70	- Smaller droplet size of complexes than individual SPI and PGA - Higher zeta potential of complexes than individual SPI and PGA by stronger repulsive force - Highest apparent viscosity for the 1:5 ratio complex - Highest EE (97.19) for the 1:3 ratio complex - ↓ Release rate of FFA for in vitro simulated digestion for complex-stabilized DEs - Highest bioavailability (80.69%) for the 1:3 ratio complex	[51]^[26]
- Lactase (100 U) - Potassium phosphate buffer (0.02 M)	- Corn oil - PGPR 90 (0.5%)	- Gelatin (5%) - Gum Arabic (5%)	30:70	40:60	- Droplet size: 4.71–5.28 µm - Zeta: −30–−37.4 mV	40:60	- Optimized formulation: 40/60 ratio and 3% Tween 80 - ABTS: 482 TE mg/g - FRAP: 2176 µmol TE/g - Inhibition zone against E. coli, P. aeruginosa,	20:80	Salmonella ssp., S. aureus, were 0, 11, 8, and 13 mm, respectively	[36]^[10]
- Results of set-type yoghurt-like		- Tween 80	- Corn oil - Span 20 - Oregano essential oil (170–680 ppm)	- Mixture of Tween 80 and Span 20 (13:87; 9.75%) - Inulin (3%)	40:60	20:80 30:70	- ↑ Antifungal activity against A. niger - Dose-dependent antifungal activity - The smallest droplet size during 20 days (2.68 and 3.05 μm) prepared at 20:80 ratio and 5800 rpm - The highest particle size and creaming at a 30:70 ratio at 2900	[42]^[16]
- NaCl (0.584%) - Hydroxytyrosol (Hyt; 0.125%)	- Perilla oil - PGPR (6%)	- SC (0.5) - NaCl (0.584%)	20:80	40:60	- Gelation with 4% bovine gelatine and 2% microbial transglutaminase—higher droplet size (3.72 μm) after Hyt addition than the control (2.55 μm) - Gel-like behavior, no frequency dependent properties, formation of weaker gels after Hyt addition - ↓ Hardness and chewiness and ↑ antioxidant activity after Hyt addition - ↓ Total viable count after 30 d at 2 °C	[41]^[15]

2.2. Improved Antioxidant Activities

BHA, BHT, and TBHQ, as powerful synthetic antioxidants, are extensively utilized in fat-rich foods and emulsion-based formulations to inhibit or delay lipid oxidation. However, their safety is always a concern, resulting in a growing interest in natural antioxidant compounds to provide healthy diets [43]^[17]. Unfortunately, low water solubility, instability during processing and storage, and undesirable organoleptic characteristics, and poor availability, absorption, and permeability profiles make it challenging to formulate food products rich in these natural antioxidants [39]^[13]. As can be seen in Table 32, DEs offer the opportunity to deliver and protect various hydrophilic and hydrophobic antioxidants via different antioxidant mechanisms within different emulsion phases, potentially obtaining a synergic effect in food formulations. For instance, Silva, et al. [44]^[18] studied the lipid oxidation of DEs formulated with a blend of olive, linseed, and fish oils in the presence of gallic acid and quercetin in the internal and external aqueous phases under an accelerated condition at 60 °C for 1 month. The synergistic effect of both antioxidants resulted in lower hydroperoxide levels compared to control DEs, which was more noticeable after 12 days. Moreover, gallic acid and quercetin limited the possible formation of secondary oxidation products during mechanical stress and heating, as evidenced by a gradual increase up to nearly 21 days followed by a significant increase up to the end of the storage period. However, this process was much slower than the control sample. In another study, Ghiasi, Golmakani, Eskandari, and Hosseini [2]^[19] developed a structured PUFA-rich W₁/O/W₂ DE stabilized by gelation of the W₁ and O phases and investigated its oxidation kinetics in the presence of gallic acid encapsulated in W₁ and α-tocopherol in the O phase. They reported an extended induction period after the individual addition of both antioxidants (9–12 days), while the oxidation rate showed a significant reduction, confirming higher oxidative stability compared to the control DEs. However, α-Tocopherol offered a superior antioxidant effect, as evidenced by it producing higher values of antioxidant activity and stabilization parameters than gallic acid, due to its hydrophobic nature, resulting in its better location at the O/W₁ interface as well as its strong placement at the gel state of the interface. Chaudhary, et al. [45]^[20] also investigated the chemical stability of different concentrations of a water-soluble extract of Emblica officinalis (EEO) encapsulated in the internal aqueous phase of a DE during storage at 4 °C for 63 days. The encapsulation efficiency exhibited a significant increase from 56.93% to 95–74% with increasing EEO concentrations from 15% to 50%; potentially due to the high binding capacity and hydrophilic character of the extract which resulted in a limited diffusion through the oil phase. According to the results of the DPPH, ABTS, and FRAP assays, the longer the storage time, the lower the antioxidant stability of DE. However, this reduction trend was significantly lower than the free EEO extract, suggesting a relatively strong protective effect of the DE structure. Eisinaitė, et al. [46]^[21] found the positive effect of black chokeberry pomace extract on the oxidative stability of the DE by increasing peroxide values and conjugating dienes less than the control DE without extract during convenient storage for 60 days. According to the results of DPPH^• scavenging, higher concentrations of BCPE exhibited powerful antioxidant activity after 21 days of storage due to the significant amounts of polyphenolics. Moreover, the control DE presented a higher rate of PV than pure oil due to the larger interfacial area of the emulsion droplets, resulting in more contact with the oxidants. However, the presence of encapsulated BCPE enhanced oxidation resistance, particularly at higher concentrations which could be related to the higher viscosity of W₂ and hence decreases in the diffusion of prooxidants. Oxipres and Rancimat analysis in accelerated storage also confirmed that the BCPE in W₁ can prolong the oxidation induction period remarkably and in a dose-dependent manner. In another study, Kumar and Kumar [47]^[22] reported lower TBARS values in reduced-fat meat batter formulated with a Murraya koenigii berry (MKB)-extract-loaded DE, as compared to DEs formulated with vegetable oil and animal fat. Interestingly, the MKB-loaded DE samples presented more oxidation stability in meat batter in comparison with a non-encapsulated extract, thus confirming the positive effect of DE structure on the prolonged antioxidative activity of bioactive compounds.

Therefore, the adverse effects of lipid oxidation in terms of developing off-flavors and loss of nutritional quality are always challenging, particularly in lipid-rich foods. Due to increasing customer demand for a healthy diet, the application of natural antioxidants is needed. In this regard, DEs can remove the limitations of using natural antioxidants, such as those with a high degradation rate during processing and storage, to provide higher oxidation stability. Moreover, DEs offer a chance to use the synergistic antioxidant effect of both polar and non-polar natural antioxidants by co-encapsulation. Additionally, by modulating the droplet size (interface area) and location of the added antioxidant agent in DE systems, the oxidation rate of foods can be decreased considerably.

Table 32.

Overview of the past decade’s publications on enhanced antioxidant properties of natural compounds encapsulated by W

₁

/O/W

₂

double emulsions (DEs).

W₁	O	W₂	Phase Ratio		Remarkable Results	Reference
W₁	O	W₂	W₁:O	W₁/O:W₂	Remarkable Results	Reference
- Hyssop extract	- Soybean oil - Span 80 (25%)	- Different emulsifiers including soy protein isolate (SPI; 3%)/chia seed gum (0.1%) - SPI (6%)	7:93	30:70	- ↑ EE with SPI/chia seed gum (87.69%) than SPI (80.71%) - Shear-thinning behavior - Oxidative stability: ↑ PV and p-Anisidine time-dependently; lower PV and p-Anisidine with SPI/chia seed gum than SPI and free extract - Higher zeta potential SPI/chia seed gum (31.533 mV) and smaller droplets (190.833 nm) than SPI	[48]^[23]
- Gallic acid (200 ppm) -NaCl (100 mM) - Fe₂(SO₄)₃ (5mM) - In gelled emulsion:κ-carrageenan (1%), KCl (100 mM)	- Linseed oil - PGPR (7.5%) - Monoglyceride (7.5%) - α-tocopherol (1045 ppm)	- Tween 80 (4%)	20:80	33:6640:60	- ↓ D4,3 and ↑ stability after O phase gelation - ↑ Negative values of zeta potential for all formulations - Rheology: weak frequency-dependent and higher viscoelastic behaviors after O phase gelation	- Not mentioned	- Higher values of PV, TBAR, p-Anisidine, and conjugated diene during storage, especially after O gelation - ↑ Induction period after antioxidant addition, higher effectiveness of α-tocopherol than gallic acid based on polar paradox	- Optimum core solution concentration: 1% - ↑ Storage stability due to the low water activity (≤0.4) and particle size (≤93.52 μm) - ↑ EE (≥98.67%) - ↑ Significant pH stability, temperature stability, and storage stability of enzymes compared to the free-form	[2]^[19]
	- ↓ and ↑ of both release rate and lactase activity in SGF and SIF, respectively, after encapsulation	[	54	]	^[	^29]	- Black chokeberry pomace extract (BCEP) (15–35%) - NaCl (0.5%)	- Rapeseed oil - PGPR (3%)	- Milk protein solution (14%)	20:80	30:70	- High thermal stability (100–91.2%) at 4 °C for 60 days - D
Nattokinase (20 mg/mL)	_4,3	- Different oils (MCT, liquid paraffin) and emulsifiers (10–25%) including Abil EM90, Arlacel P135, andSpan 80	: ranged from 61.66 μm to 37.65 μm, ↓ D	Labrasol (10–20%)	30:70 40:60 70:30	_4,3 at higher concentration of BCEP and during storage	10:90 20:80 30:70 40:60 50:50 60:40 70:30 80:20 90:10	- ↑ Viscosity at higher concentrations of BCEP - High EE (>95%) during storage - ↓ DPPH^• scavenging after 21 days of storage at 4 °C from 36.32–44.50% to 12.12–15.40% - ↑ DPPH	- ↑ Emulsifying capacity of MCT as oil phase and EM90 as emulsifier - Optimized condition: 20% Abil EM90, 15% Labrasol, and 40% W₁ - ↓ D_4,3: 5.3 to 4.7 μm after 30 days - Initial EE: 86.8% - ↓ EE to 82.6% after 30 days at 25 °C - Improved sustained in vitro release (30% after 8 h) - The release rate in vitro under pH values: 1.21 > H₂O > 4.50 > 6.80 - ↑ Blood clotting time in mice at all doses (111.3–194.1 s) as compared with free forms - Enhanced carrageenan-induced tail thrombosis outcome	[53]^[28]

In summary, DEs can be introduced as successful carriers to increase enzyme stability against different environmental conditions, resulting in higher bioavailability, prolonged activity, and controlled target release as well as providing their recycling capacity.

4. Improved Viability of Probiotics

Probiotics are a group of live bacteria that confer health beneficial effects on their host. To exert their effects on the human body, certain concentrations (more than 10⁶–10⁷ CFU/g or CFU/mL) of the probiotics should reach the colon; however, the susceptibility of the microorganisms during processing and storage, as well to the acidic nature of some foods and gastrointestinal (GI) conditions, makes it challenging to prepare probiotic-loaded food products. To sustain the viability of probiotics, encapsulation in W₁/O/W₂ DEs has been suggested to protect the cells against environmental conditions [55,56]^[30][31]. Table 54 presents recent successful applications of DEs for probiotic encapsulation. In this regard, Frakolaki, et al. [56]^[31] successfully encapsulated Bifidobacterium animalis subsp. Lactis BB-12 within a W₁/O/W₂ DE using the extrusion technique. The probiotics were added to the W₁ and then extruded using encapsulating materials. The cell viability was examined during storage and through passing SGF. They reported the highest viability of BB-12 cells encapsulated within DE at 4 °C after 1 month of storage (>10⁶ CFU/g) compared to those encapsulated through conventional extrusion and those within the W₁ of DE before extrusion. The survival rate of the cells within the DE was also higher (68.6–86.1%) than the cells encapsulated through a conventional extrusion (48%) during passing SGI. Exposure to different pH values in the range of 4–8 showed higher viability at pH 7–8. However, BB-12 cells encapsulated in the DE had more than 80% viability even at low pH values (compared to the 67.32% cell viability in the conventional extrusion), indicating its high efficiency in protecting the probiotic cells. Marefati, et al. [55]^[30] used a DE to encapsulate Lactobacillus reuteri within the internal aqueous phase. They reported that storage of the DE samples at 6 °C did not affect the cell viability after 3 days, and then the cell count decreased by 5.2 and 2.82 log CFU/mL on the 15th and 30th days of storage, respectively. However, the control sample (the probiotics encapsulated within the outer phase (W₂) of the DE), showed a decreasing trend in the cell count from the 1st day and reached 0 after 30 days. Investigation of the cell viability in simulated GI condition showed a survival rate of 70% for encapsulated L. reuteri and 2.8% for the free cells (control sample) under gastric conditions. Under intestinal conditions, the encapsulated cells showed a gradual reduction and reached 4.46 log CFU/mL from 6.53 CFU/mL after 180 min; however, the free cells count had a sharp reduction under intestinal conditions and decreased from 4.7 to 2.69 log CFU/mL in 180 min. This study indicated the role of W₁/O/W₂ DE in protecting probiotics in GI until reaching the colon. In another study, by Qin, et al. [57]^[32], a pH-sensitive DE was designed to encapsulate and colon release Lactobacillus plantarum. In this study, the DE was stabilized by WPI-epigallocatechin gallate (EGCG) conjugate particles and pH-sensitive alginate-Ca-EDTA was added to the W₁. It was observed that the free probiotics count experienced a steep decrease under the simulated GI conditions, especially under the gastric conditions (from 7.81 × 10⁷ to 0.14 × 10⁷ CFU/mL); however, the encapsulated probiotics (in W₁) experienced a small count reduction under the gastric conditions due to the resistance of the Ca-alginate hydrogel to the acidic conditions and pepsin. In the SIF, the middle oil phase (medium-chain triglycerides (MCTs)) protected the cells against bile salts and digestive enzymes and, hence, a small loss occurred (from 7.79 × 10⁷ to 7.39 × 10⁷ CFU/mL). It was shown that the DE at a 3% WPI-EGCG particle concentration, 0.6% MCT oil concentration, and 3% PGPR resulted in the highest protective effect against GI conditions and can be used as a colon-targeted release vehicle for probiotics. In a study by Jiang, et al. [58]^[33], Lactobacillus acidophilus was encapsulated in a W₁/O/W₂ DE. It was observed that the cell viability of the encapsulated and free probiotics in SGF was 85.1% and 9.8%, respectively, and, in SIF, the encapsulated cells had a 70.8% viability (4.95 × 10⁶ CFU/mL), while the free ones showed 7.8% (3.86 × 10⁵ CFU/mL). The effect, on the viability of the probiotic cells, of adding fish oil and SA to the oil phase and the outer aqueous phase, respectively, was assessed. It was concluded that fish oil can promote cell growth and enhance the DE’s protective effect against GI, and SA could reduce the cell release in simulated GI conditions by creating a layer around W₁/O. In another study, the viability of Lactobacillus plantarum in W₁/O/W₂ DE-loaded alginate capsules under simulated GI conditions was examined and compared with the viability of free cells and cells loaded in the DE without alginate capsules. The free cells underwent a 3.9 log cycle reduction under the gastric conditions (120 min) and then further reduction occurred after incubation under intestinal conditions (a 5.79 log cycle reduction). Remaining under the intestinal conditions for 2 more hours did not change the cell count. The reduction of encapsulated L. plantarum in the DE under gastric conditions was only 1.02 log cycle and the DE structure remained intact; however, it was destroyed under the in vitro intestinal conditions and caused a considerable decrease in the cell count. The DE-loaded alginate capsule provided the highest protection against GI conditions (a 0.81–1.19 log cycle reduction in the gastric and a 3.04–3.22 log cycle reduction in the intestinal conditions, depending on the time needed for Ca gelation). The best result for this sample appeared after 20 min of gelation with Ca. The storage stability of the encapsulated cells in DE after 42 days of storage at 37 °C indicated a gradual decrease in the cells until the 21st day and then a sharp decrease until the end of storage (survival rates of about 95% and 62% in the 7th and 42nd days of storage were reported, respectively) [59]^[34]. Abbasi, et al. [60]^[35] investigated the viability of L. plantarum encapsulated in the inner phase of a W₁/O/W₂ DE under the effects of heating and pH in the presence of various gelling agents (gelatin, alginate, tragacanth gum, and carrageenan) in W₂. They reported that the initial count of free cells (9.95 log CFU/mL) reached 9.97, 8.10, 6.37, and 0 log CFU/mL after 2 min of heating at 30, 50, 63, and 72 °C, respectively. The control sample (encapsulated cells in a DE without any gelling agent) also showed a significant decrease from 9.95 log CFU/mL to 5.47 log CFU/mL after heating at 72 °C. However, in the presence of the gelling agents, the probiotics were better protected against heat and their count remained constant (in the range of 6.69–7.33 log CFU/mL after heating at 72 °C). The cell viability at different pH values (2, 3, 6.5, and 7) showed the highest cell reduction at a pH of 2 for all samples with the lowest viability seen in the free cells and the highest in those encapsulated in DE in the presence of carrageenan. It was concluded that gelation of the outer phase could increase the viability of the cells and carrageenan was introduced as the most efficient gelling agent to enhance viability. The authors declared that, in addition to creating a physical barrier, the positive role of carrageenan was related to its prebiotic activity. Silva, et al. [61]^[36] prepared a sweet mango dessert containing L. plantarum encapsulated in the W₁ of a DE and then studied the cell viability of the probiotics under in vitro digestion. The measured numbers of probiotics encapsulated in the DE and those dispersed directly in the formulation of mango candy were 7.92 and 7.61 log CFU/mL at time 0, respectively, and did not decrease during the emulsification process. The presence of glucose and lactose in the formulation promoted the growth and viability of the cells. Exposing to GI condition showed that DE could provide good protection to the cells against SGF; however, the protection was not enough against the intestinal conditions and the cell count decreased. The free cells survived in the gastric condition and their count was close to that of the encapsulated ones in the SIF.

Table 54.

Overview of the past decade’s publications on probiotics encapsulation by W

₁

/O/W

₂

double emulsions (DEs).

W₁	O	W₂	Phase Ratio		Remarkable Results	Reference
W₁	O	W₂	W₁:O	W₁/O:W₂	Remarkable Results	Reference
- L. acidophilus (5.1 × 10⁷ CFU/g) - NaCl (0.15 M)	NaCl (0.25–1%)- MCT oil - Fish oil (0–10%) - PGPR (1–5%)	- Different emulsifiers including SPI, (0.5–2%) and SA (0.25–1%)	- Sunflower oil - PGPR (6%) - Monoglyceride (8%)	10:90 20:80 30:70 40:60	30:70 40:60 50:50 60:40	- ↑ W₁ from 10% to 30% led to ↑ stability—the only stable DE in 7 days at 4 °C: at 10% W₁ - ↑ Fish oil and SA led to ↑ viability in SGF and SIF - ↓ GI release by SA and fish oil - ↑ Cell count and ability to adhere to the intestinal mucosa by the addition of fish oil - ↑ Viscosity, stability, and probiotic EE in the presence of SA - The highest EE 0–7.5% fish oil, 1.5% SPI, 0.27–0.75% SA	- Modified starch (4%)- ↑ SPI and ↑ SA led to ↑ viscosity	20:80		40:60	- ↑ SA led to ↓ size	- ↑ EE by oil gelation - The results of preparation of a low-salt burger: - ↓ 25% salt by replacing DE in the burger with desirable saltiness ↑ Antioxidant stability and ↓ color changes during storage in the presence of cinnamaldehyde in the oil phase - ↓ Cooking loss by adding DE	[58]^[33]
	- Undesirable changes in textural properties by adding DE	[	72	]	^[	^47]	- L. plantarum (11 log CFU/g) - Different emulsifiers including gelatin (2%), - Alginate (2%)/CaCl₂ (100 mM), tragacanth gum (2%), carrageenan (2%)/KCl (100 mM)
- Bitter peptide (50%) - Tartrazine (2%) - Gelatin (0–2%)	- Olive oil - PGPR (6%)	- Palm oil - Camellia oil - PGPR (4%)- Tween 80 (4%)	20:80	40:60	- Gelatin (0–2%) - SC (2.5%)- Size range: from 6.4 (tragacanth) to 14.7 µm (alginate) - Zeta range: −21.1 to −46.2 mV - The least stability was for carrageenan (>80%) - The highest EE (97.4%) by carrageenan - ↑ Heat protection by gelling agents - Best gelling agent: tragacanth due to increased viability at low pH and heating to 28.05% and 16.74%, respectively - The highest viscosity by alginate	40:60	40:60	- Size range: 9.38–52.3 µm - ↑ Gelatin led to ↓ size - ↑ Viscosity and ↑ physical stability by gelatin - EE > 80% by gelation - ↑ EE and ↓ release by W₁ gelation - ↑ Bitter taste masking by W₂ gelation - ↓ Peptide release ↑ gelatin	[60]^[35]
[	65	]	^[	⁴⁰	^]	- L. plantarum F1 - Different prebiotics including mannitol (2%) and trehalose (2%) - Guar gum (0.5%) - Tween 80 (5%)
- 2,3-diacetyl - Citric acid - Sodium sulphate buffer - SA(0.5%)	- Sunflower oil
- “Pitanga” leaf hydroethanolic extract (10%)	- Soybean oil - PGPR (3%)	almond-based gels incorporating 0–30% DE:	- Tween 80 (3%) - SC (0.5%)		No differences in size and cohesiveness at different DE contents	20:80	- ↓ Water holding capacity, ↓ hardness, and ↑ syneresis by ↑ DE content - The highest viscosity at 30% DE - No difference in sensory properties of low-fat (containing DE) and full-fat yoghurt	40:60	- Lecithin (5%) - Lipophilic sea buckthorn pomace extract (LSBPE, 5%)	- Alginate (2%) - Tween 80 (5%)	- Soybean oil	40:60		40:60	- Beeswax (BW, 0–8%) - PGPR (2%)- Best condition: Mannitol as prebiotic due to high encapsulation yield (82.19%), good cell survival rate (76.99%), and low chemical degradation of the oil (PV: 3.8 meq O₂/kg fat) after 42 days Size: 2.2–2.3 µm - ↑ Oxidative stability by LSBPE - ↓ 1.02 and 5.79 log encapsulated and free cells in SGF, respectively	- Bacterial cellulose (1%) - ↑ Gelation time led to ↑ cell count and gel hardness	30:70[	50:50	- ↑ Size by ↑ BW up to 4% - G′ < G″ at BW 2–4% - ↑ BW led to ↑ stress at the crossover point and shear thinning behavior - ↑ BW led to ↑ viscosity and ↑ friction coefficient - ↑ BW led to ↓ ∆BS and ↓ thickness, ↓ osmotic pressure and ↑ stability at 6–8% - BW 6–8% led to ↓ aroma release with no difference at 25 and 37 °C, extended aroma release by BW (smallest decreasing amplitude for 8%)	59]^[34]
[	68	]	^[	⁴³	^]	- L. plantarum (10.4 log CFU/g) - Sucrose (10 g/L) - Glucose (4.6 g/L)	- Corn oil - PGPR (1.5%)
- MgCl₂ (5%)	- Tween 80 (0.75%)	- Tara gum (1.5%)	30:70		30:70	- Na-caseinate (0.5%)- Size: 12 µm - Pseudoplastic behavior (index 0.63) - EE: 86% (7.92 log CFU/mL) - Results of mango dessert incorporating 25% DE: - ↑ Cell by glucose and lactose - ↑ Viability in DE - Low protection in the small intestine - 3.85 log CFU/mL count in large intestinal	[61]	- Olive oil - PGPR (1–6%)	- Saccharose (≤15% of total DE) - Na-caseinate (12.5%)	40:60	40:60 35:65 30:70^[36]
- Smaller droplets at 40:60 (8.58 µm)		- Shear thinning and pseudoplastic behavior (n < 1)		- The lowest viscosity at 40:60	- The lowest hydrolysis degree (of oil) in GI at 35:65 - ↑ Sweetness of DE (40:60) compared to O/W by closely 75%	[64]^[39]	- L. reuteri (10.69 log CFU/mL)
- Mg₃(C₆H₅O₇)₂ (0.025 M) - MgSO₄ (0.075 M) - MgCl₂ (0.075 M) - Mg(C₃H₅O₃)₂ (0.075 M) - Mg(C₃H₅O₃)₂ (0.075 M) + Lactose (0.225 M) - CaCl₂ (0.075 M) - NaCl (0.075 M) - CsCl (0.075 M) - CsCl	- MCT - PGPR (5%)	- Poloxamer 407 (2.5%)	(0.15 M)	20:80	20:80	- Miglyol oil - PGPR (5%)- Size: 13.4 µm, no changes in size in 30 days - EE: 7.23 Log CFU/mL during cold storage - ↓ Stability lower than control (from 6.18 to <1 Log CFU/mL) compared to encapsulated bacteria (from 7.23 to 2.82 Log CFU/mL). - 70% survival in GI for encapsulated bacteria - No changes in cell count after 3 days at 6 °C - 5.2 and 2.82 log CFU/mL on the 15th and 30th days	SC (3.1%) Lactose (0.125 to 3 M)	40:60	10:90	- Anion and cation affect the release rate of salts - ↑ Release of each encapsulated salt from W₁ to W₂ during storage - ↑ Complexation constant of Mg²⁺ with its counterion led to ↓ the release - ↓ Hydration enthalpy of Mg²⁺ counter ion led to ↓ the release - ↑ Release rate for chloride ions in case of monovalent ions (Cs⁺ and Na⁺) than divalent ions	[55]^[30]
[	73	]	^[	⁴⁸	^]	- L. Plantarum - Fructooligosaccharides (2%)
- Fish protein hydrolysate (12%) - NaCl (4%) - Vitamin B12 (4%)	- MCT - PGPR (0.5–5%)	- Na₂EDTA - CaCl₂ - Alginate (2%) - WPI - EGCG conjugates (0.5 to 5%)	20:80 40:60 60:40 80:20	50:50	- ↓ Size with ↑ PGPR, ↓ oil phase, and ↑particle conjugate - ↓ pH led to ↑ G′ - Hydrogel state at pH ≤ 4 - Low loss in GI (from 7.79 × 10⁷ to 7.39 × 10⁷ CFU/mL) at PGPR content of 5%	[	- Fish oil - PGPR (6–10%)	- WPC - Inulin - WP/inulin ratios: 1/1, 1.608/1, 2.5/1, 3.39/1, 4/1	30:70	50:50 61.65:38.34 71.47:28.57 77.22:22.78 80:20	- The optimum parameters: 2:1 ratio of wall/core, 2.12:1 ratio of WPC/Inulin, and 6.28% PGPR ↓ WPC/inulin and ↑ PGPR led to ↓ release of the vitamin - ↓ WPC/inulin, ↓ W1O/W2, and ↑ PGPR led to ↓ creaming - ↓ WPC/inulin and ↑ PGPR led to ↑ EE - Interaction between W1/O/W2 and WPC/inulin led to ↓ encapsulation stability of the vitamin - WPC/inulin and W1O/W2 led to positive and negative effects on the encapsulation stability of the vitamin - Results of fortified yogurt with DE - Optimized DE condition for sensory analysis led 2:1 mass ratio of W1/O to W2, 2.12:1 ratio of WPC to inulin, and 6.28% PGPR The addition of a flavoring agent was recommended	57]^[32]
[	67	]	^[	⁴²	^]	Bifidobacterium lactis subsp. lactis BB-12 (11.35 log CFU/g) - Glycose (5%) - Inulin (2%)	- Olive pomace oil - Span 20 (2.5%) - Tween 40 (2.5%)	- Different encapsulating agents including SA (2%), pectin (1%), gelatin (1%), casein (1%), and gum Arabic (1%)	20:80	15:85	- Zeta: (−0.14)–(−3.36) mV - SA as the best encapsulating agent - Results of coating of beads with chitosan with two methods: EE: 72.48–81.68%, 68.6–86.1% survival rate in GI- >10⁶ CFU/g count after 1 month, combining the extrusion/DE emulsification as compared to cells encapsulated through conventional extrusion (survival rate 46.8%) after 15 days - 80% viability at acidic pHs - Higher viscosity (283.4 cP) for alginate-pectin DE	[56]^[31]
- L. plantarum - Aguamiel or sweet whey - Panodan SKD (1.6%)	- Canola oil - PGPR 90 (6.4%)	- Mesquite gum (13.2%) - Maltodextrin DE10 (3.4%) - Gum Arabic (3.4%)	30:70	30:70	- Larger size with aguamiel (than sweet whey) - Small size increment after 14 days - Results of cheese preparation incorporating DE: ↑ Cell viability with DE (compared to free cells in cheese), ↑ heat protection by aguamiel DE (than sweet whey DE) - After melting, ↓ Log CFU/g by 2.18, 1.42, and 1.94 for control cheese, cheese formulated with DE/sweet whey and cheese formulated with DE/aguamiel, respectively, - ↑ Viability at low and high pH values in DE (especially aguamiel DE)	[62]^[37]

It is concluded that the encapsulation of probiotic bacteria in a W₁/O/W₂ emulsion can be considered a novel encapsulation approach that can enhance their viability during storage and retard their release under GI conditions without requiring sophisticated equipment. However, to achieve higher cell availability and provide higher levels of protection, additional treatments such as gelation of the aqueous phase/phases and adding prebiotics to W_1, are recommended.

5. Improved Sensory and Color Attributes

The sensory properties (e.g., texture, appearance, and flavor) of a food emulsion are influenced by the initial emulsion characteristics (i.e., the properties of the continuous phase, dispersed phase, and interfacial region). The behavior of the food emulsion during mastication also plays an important role in its sensory properties as a result of the changes in its structure and composition brought about by saliva dilution, chewing, and surface coating. The term ‘flavor’ is an integrated response of taste, aroma, texture, and mouthfeel. Therefore, in addition to the aroma and taste, mouthfeel and texture play key roles in the perceived flavor. The optical properties of (multiple) emulsions, including color and opacity, are affected by the microstructure and composition (i.e., particle size, particle concentration, and refractive index contrast) [63]^[38]. The overall flavor properties of emulsion systems are influenced by the distribution of the flavor molecules within different phases (e.g., water, oil, interface, headspace), and their release behavior during consumption. The release of the flavor molecules from food emulsions is evaluated by their mass transport kinetics and their equilibrium partition coefficients. In W₁/O/W₂ DE systems, the middle oil phase is a filler that does not contribute to taste but affects it in two different ways: (1) Oil droplets increase the concentration of taste components in W₂. At a constant concentration of a taste compound, increasing the oil fraction in the DE leads to increasing the taste compound concentration and consequently more intense precipitation. And (2) the oil, as a barrier in the middle phase between the two aqueous phases, can prevent the migration of a taste compound in W₁ from reaching W₂. As in intact DE systems, only W₂ touches the taste buds on the tongue surface, the W₁ in the DE can be used to encapsulate unpleasant taste compounds to mask them during oral consumption [64]^[39]. Table 65 shows the potential applications of DEs in improving sensory characteristics. Polypeptides derived from the enzymatic hydrolysis of proteins have positive physiological and health beneficial effects. However, their bitter taste is the main limiting parameter for their consumption. Among different encapsulation methods suggested for bitter polypeptides (PBs), using a W₁/O/W₂ DE seems to be one of the most appropriate ones. Gao, et al. [65]^[40] encapsulated PBs in the W₁ of DE and then examined the effect of adding gelatin (as a gelling agent) at 1% and 2% concentrations to W₁, W_2, or both aqueous phases of the DE, on the DE’s properties and BP release (DE-1: DE without gelatin, DE-2: 2% gelatin in W₁, DE-3: 2% gelatin in W₂, DE-4: 2% gelatin in both W₁ and W₂, and DE-5: 1% gelatin in both W₁ and W₂). It was observed that the presence of gelatin could decrease the size of the DE droplets, especially when it was added to both W₁ and W₂ (D_3,4: DE-1 178.3 µm, DE-4 9.38 µm). In addition, 2% gelatin was more efficient in terms of size reduction than 1%. Gelatin addition also increased the viscosity and physical stability of the DE samples (DE-1 < DE-2 < DE-3 < DE-5 ≤ DE-4). The encapsulation efficiency (EE) of BPs was significantly increased after gelatin addition. Gelation in W₁ had a more predominant effect in this regard and, hence, the EE of DE-3 was lower than the other gelled samples. Assessing masking the bitter taste by DE showed the ability of DE to mask bitterness in the presence of gelatin and the higher importance of the gelation of W₂ than W_1, with no significant differences between the 1% and 2% gelatin concentrations. In vitro release of BPs in a dialysis bag proved that the gelation of W₁ or W₂ could retard BP release (DE-1 < DE-3 < DE-2 < DE-5 < DE-4). In vitro digestion of DE-4, as the best sample, was performed under simulated GI conditions and indicated that the DE sample remained intact in the oral stage and resulted in a very low bitterness in terms of sensory evaluation. Under the gastric conditions, the DE protected the BPs from the acidic conditions and enzymes and, finally, released them under the small-intestinal condition (as the desired site of release). The simultaneous inoculation of Zygosaccharomyces rouxii and Tetragenococcus halophilus in the internal W₁ and external W₂ phases of W₁/O/W₂ DEs with reduced NaCl and/or substitution with KCl in the moromi stage of soy sauce fermentation was carried out by Devanthi, et al. [66]^[41]. In the presence of the 18% NaCl, the growth of T. halophilus was stopped during the first two weeks, while partial substitution of NaCl (6% NaCl and 12% KCl) promoted its growth and enhanced lactic acid production. However, the final aroma was different from that obtained in the presence of 15% NaCl (original method), and lower amounts of alcohols, acids, esters, furan, and phenol were detected. At a reduced salt concentration, T. halophilus grew faster when it was simultaneously incubated with Z. rouxii compared to sequential incubation and, by producing volatile components such as some alcohol and ester types under simultaneous incubation, could compensate for the low-salt conditions, making it possible to produce soy sauce at low-salt concentrations with an aroma profile close to that achieved using the original method. This study demonstrated the effective application of DEs for delivering the mixed cultures in low-salt soy sauce without compromising its quality. Jamshidi, et al. [67]^[42] used a DE to encapsulate fish protein hydrolysate and fish oil within the W₁ and the middle oil phase, respectively, to mask the unpleasant flavor and taste. After optimizing the DE formulation, it was freeze dried and added to yogurt for fortification. Sensory analysis of the fortified and control yogurts showed no differences between the homogeneity before consumption (appearance) and in the month, and samples did not have any rancid or bitter taste after fortification. However, the high concentration of fish oil caused a fishy taste that can be masked more efficiently by using flavoring agents. Buyukkestelli and El [64]^[39] used a DE to enhance the sweetness of saccharose and formulate reduced-sugar foods. They designed a DE at a 16:24:60 (W₁:O:W₂) ratio and a single emulsion (control) at a 40:60 (O:W) ratio. Saccharose at a 15 g/100 g concentration was added to the outer phase of each emulsion. The results of the sensory evaluation to assess and compare the sweetness of the two samples revealed more intense sweetness for the DE despite the same saccharose concentration being present in both samples. In fact, the saccharose concentration that contributed to perceptions of the flavor and interacted with the taste buds was 25 g/100 g for the DE and 19.74g/ 100 g for the control. In a study by Chen, et al. [68]^[43], the gelling of the middle oil phase of a Pickering W₁/O/W₂ DE by beeswax (BW) was used to control the release of aroma (2,3-diacetyl) from W₁. In this study, the effects of different BW concentrations (0–8%), temperature (25 and 37 °C), and time (7 days) on aroma release were examined. It was shown that by increasing the BW content the flavor release considerably reduced. At a BW concentration of 0%, there was no difference between flavor release at 25 °C and 37 °C. At 2% and 4% BW, a greater extent of flavor release occurred at 37 °C due to the partial melting of fat crystals that facilitate the aroma release. At 6% and 8%, aroma release was not significantly different at the two temperatures due to the high compactness of the fat crystals. Investigation of aroma release during the initial storage period showed a burst release in the absence of BW (51.04% aroma decrease). Gelation of the oil phase caused an extended aroma release and the smallest decreasing amplitude (28.21%) was recorded for 8% BW, showing the slowest release due to the steric barrier of the fat crystals and the higher strength of the gelled oil phase at this concentration.

On the other hand, the color of foods is also considered an important parameter in achieving visual attraction to improve consumer appetite and overall acceptance. Encapsulation by DEs is an interesting method to improve the physicochemical stability, bioaccessibility, and controlled release of food colorings. Table 65 lists potential applications of W₁/O/W₂ emulsions in improving color stability and hence the biological properties of natural pigments. To this end, Nunes, et al. [69]^[44] compared the potential of applications of DEs to enhance the stability and bioaccessibility of lutein with a single O/W emulsion. They designed three different DEs, W₁/O/W₂ without lutein, W₁/O-L/W₂ containing lutein in the oil phase, and W₁-L/O/W₂ containing lutein in the WPI nanoparticles in W₁ during the desolvation process. Lutein content in all fresh samples was in the range of 18.3–19.9 µg.g⁻¹ which decreased to 11.3–12.4% after 14 days of storage. The DEs showed higher EE (>99%) than the O/W emulsion (94%). The highest (43.1%) and the lowest (31.8%–34.3%) lutein losses under LED sunlight lamps were reported for W₁-L/O/W₂ and both W₁/O_L/W₂ and O/W, respectively. This was related to the protective effect of oil and/or PGPR in terms of the chemical stability of lutein. Color stability during storage confirmed the better potential of DEs than SEs, as evidenced by more yellow color. According to an in vitro digestion study, lutein recovery (98.7–99.9%) and bioaccessibility (20.8–28.2%) for DEs were significantly higher than the W/O emulsion (90.3% and <10%), suggesting that it is less prone to degradation during digestion after being incorporated into DE structures. In another study, Li, et al. [70]^[45] investigated the color changes of anthocyanin-loaded DEs as affected by temperature storage. Their results represented increases in lightness, yellowness, and ΔE values, and a decrease in redness in all anthocyanin after storage at 4 °C and 25°C for 28 days in a dark place. However, changes in the color parameters at 25 °C were significantly higher than 4 °C due to the higher sensitivity of both emulsions and anthocyanin under higher temperatures. The greater yellowness and less reddishness were attributed to the reduction in flavylium cation and the hydrolysis of a double bond in the anthocyanin molecule. Moreover, the EE of anthocyanin decreased from 95.3% in the fresh samples to 93.2% and 88.9% at the end of storage at 4 °C and 25 °C, respectively. This was mainly due to the anthocyanin leakage from W₁ to W₂ by osmotic pressure, and the higher temperature could accelerate this driving force. Tang, et al. [71]^[46] also introduced Pickering DEs stabilized by sugar beet and pectin-bovine serum albumin nanoparticles as a reliable delivery system for improving the stability and bioaccessibility of betanin and curcumin. The blue appearance of control DE changed to purplish-blue in betanin-loaded DE and green in curcumin-loaded DE. No color change was observed for all DE samples during storage at 25 °C for 3 and 7 days. In contrast, the color of free betanin progressively faded and degraded to brownish as a result of light excitation and nucleophilic attack. Similarly, free curcumin changed gradually from brilliant yellow to greenis-yellow. After 7 days of storage, the content losses of free betanin and curcumin were 56.5% and 42.1%, respectively; while incorporating DEs increased the retention of betanin and curcumin to 76.6% and 81.5%, respectively. Moreover, the EE values of curcumin and betanin were 84.1% and 65.3%, respectively. Meanwhile, the loading efficiency (LE) of betanin was more than that of curcumin. The DEs strategy also remarkably increased the bioaccessibility of free betanin and curcumin after digestion from 15.6% and 23.1% to 42.7% and 53.5%, respectively. Therefore, the susceptibility of the encapsulated colorants to acidic pH was decreased by incorporation into DEs. Co-delivery of betanin and curcumin by DEs also synergistically limited the growth of cytotoxic A549 cells. In addition, Yu, et al. [13]^[1] successfully developed a novel design of pH-sensitive DE-filled hydrogel containing hydrophobic astaxanthin and hydrophilic phycocyanin by adding gellan gum. The visual appearance of the DEs was yellow due to the brown color of the astaxanthin. Indeed, the blue color of phycocyanin was shielded due to its encapsulation in W₁. The EE was increased by increasing gellan gum concentrations and the maximum values for astaxanthin (90.82%) and phycocyanin (94.1%) were achieved at gellan gum concentrations of 0.5% and 0.7%, respectively. The DE network also enhanced the storage stability of astaxanthin and phycocyanin as evidenced by there being no color changes after 10 days of storage, while the apparent yellow color of the astaxanthin solution and blue color of the phycocyanin solution faded, indicating their rapid breakdown. The degradation rates of the free form of astaxanthin and phycocyanin were 33.2% and 23.4% after 3 days, which increased to 79.9% and 48.1% after 10 days. After encapsulation in DEs, the degradation rates of astaxanthin and phycocyanin decreased to 25.6% and 16.8% after 10 days, respectively. According to in vitro study, the DEs efficiently protected the phycocyanin and astaxanthin during gastric digestion by decreasing their release rates (<25%), which reached more than 60% after digestion in the small intestine. Moreover, the low values of bioaccessibility for the free phycocyanin (12.54%) or astaxanthin (14.27%) in water increased significantly after encapsulation in DE and DE emulsion gels due to the formation of mixed micelles.

Consequently, DE offers a simple and easy-to-handle approach to both masking and enhancing flavors. The encapsulation of a compound in W₁ can mask its aroma. Moreover, the gelation of each of the three phases of a DE can retard releasing the compound. Generally, the addition of a compound to W₂ of a DE can enhance its flavor compared to the same concentration of it in the aqueous system. In addition, a W₁/O/W₂ DE offers an efficient carrier system to encapsulate and protect natural colorant agents in food systems with increased stability against environmental conditions and harsh processing and to improve their bioaccessibility, as well as offering the possibility of controlled release.

Table 65.

Overview of the last decade’s publications on enhanced antimicrobial properties of natural compounds by W

₁

/O/W

₂

double emulsions (DEs).

W₁	O	W₂	Phase Ratio		Remarkable Results	Reference
W₁	O	W₂	W₁:O	W₁/O:W₂	Remarkable Results	Reference
-
- Gelatin, chitosan, and gelatin–chitosan composite films:		- ↑ Opacity		- ↓ Roughness, contact angle, solubility, and WVP	- ↑ Tensile strength and elastic modulus for gelatin and chitosan-based films but ↓ for gelatin–chitosan film, ↑ elongation at break for both gelatin and gelatin–chitosan films - Inhibition of bacterial growth just below the disks - ↑ Folin–Ciocalteu reducing capacity and antioxidant activity	[79]^[54]
[	86	]	^[	⁶¹	^]	- Gellan gum (0.4%) - CaCl₂ (0.5%)	- Refined pork oil - PGPR (3%)	- SC (0.1%)	40:60	80:20	- Size: 5.38 µm - Results of sausage properties incorporating 0 and 20% DE - ↓ Fat and energy values and ↑ water compared to high- and low-animal fat sausages - Cooking loss (9.63%) less than high-fat sausages - Texture: equal adhesiveness and springiness in all sausages, ↓ hardness than high-fat sausages
- Pitanga leaf hydroethanolic (10%)	- Soybean oil - PGPR (3%)	- Tween 80 (3%) - SC (0.5%)	[	77	20:80	]	40:60	- Gelatin, chitosan, and gelatin–chitosan composite films with nanocellulose (NC): ↓ Moisture content, solubility, WVP and ↑ opacity, tensile strength, and elongation at break after DE addition - ↑ FCRC, ABTS•+, FRAP after DE addition - Antimicrobial activity only in G-based film incorporating DE against S. aureus in the region of contact of the film	^[52]
	- Light barrier order: gelatin-NC/DE > gelatin–chitosan-NC/DE > C-NC/DE > gelatin-NC > chitosan-NC > gelatin–chitosan-NC	[	87	]	^[	^62]	- Hydrolysable tannin (10%) - Phosphate buffer	- Sunflower oil (4%) - Lecithin (2%) - span 80 (2%)	- Gum Arabic (3%)	20:80	40:60
-	- Sunflower oil - Lecithin (0.7%)	- Results of fat-reduced short-dough biscuits incorporating 0–60% DE:		- ↑ hardness, ↓ biscuit height, ↑ spread ratio, ↑ antioxidant capacity, and ↓ loss of hydrolysable tannin with ↑ DE	- The highest astringent flavor masking and highest acceptability by replacing 40% fat with DE	- Coffee Byproducts (pectin and cellulose (3:7); 0.8–2.4%) - SC (0.5)	[78]^[53]
15:85	5:95	- Coffee byproduct-based film: Droplet size: 0.38–1.23 μm under the different times of homogenization		- ↑ Thickness (0.15 to 0.25 mm), transparency (3.10–5.28%), WVP (3.76–15.96 g mm/m	²hKpa), tensile strength (1.26–1.79 MPa), and elongation (3.40–5.20%) with ↑ polymer concentration - Antioxidant activity: (EC50; kg film/mol DPPH): ↑ from 2.47 to 4.35 with ↑ polymer concentration	[88]^[63] (2023)	- WPI(10–25%) - Rice protein (RP, 10–25%) - Pumpkin seed protein (PSP, 10–25%)	- PGPR (1%) - Span 80 (1%)	- Milk	40:60	5:95	- Higher viscosity (1.8 Pas) and serum index (5.2%) for RP-stabilized DE - The largest and the smallest size related to RP and WPI-stabilized DE - Results of fat-reduced cheese incorporating 5% DE: ↑ Hardness, ↑ cheese diameter, ↑ oil loss (except in WPI cheese) than full-fat cheese	[81]^[56]
- NaCl (0.6%)	- Olive oil - PGPR (6.4%)	- SC (10%) - NaCl (0.6%)	50:50	70:30	- Results of model meet emulsion incorporating 0–30% DE: ↑ Fat replacing by DE led to ↓ jelly and fat separation, ↑ WHC, ↓ total expressible fat - ↑ TBAR after 60 days of storage, the lowest TBAR at 10% fat replacement by DE - ↑ DE led to ↓ hardness, ↑ cohesiveness, and ↓ gumminess and chewiness than full-fat control	[82]^[57]	- NaCl (6%) - Z. rouxii (10⁵ CFU/mL)	- Soybean oil - PGPR (2%)
- NaCl (0.6%)	- Olive oil - PGPR (6%)	- NaCl (6%) Tween 80 (1%) - T. halophilus (10⁶ CFU/mL)	- SC (0.5%)/	20:80		20:80	- NaCl (0.6%) - WPC (6%)- The results of reduced NaCl and/or substitution with KCl in soy sauce fermentation: - Non-newtonian behavior	20:80	- ↑ Brine to koji led to ↓ viscosity - ↓ Size during fermentation (27.88 to 11.40)	40:60	- ↓ Size by adding DE to moromi - Partial NaCl substitution led to ↑ T. halophilus growth and ↑ lactic acid - ↓ NaCl led to ↑ T. halophilus growth to 8.88 log CFU/mL, faster sugar depletion, and ↑ lactic acid production. - Simultaneous incubation led to ↑ T.halophilus growth and production of volatile compounds	- ↑ Size by WPC (compared to SC), wider size distribution during storage for SC DE - ↑ Thermal stability and ↑ creaming index at 0 °C compared to 7 °C - Results of meat system incorporating 0–34% DE: ↓ Total fluid released by adding DE - Similar hardness, cohesiveness, and springiness for meat systems with/without DE - ↑ Chewiness in fat reduced WPI DE - ↑ Lightness by adding DE	[66]^[41]
[	83	]	^[	⁵⁸	^]	- Gelatin (10%) - NaCl (0.4%)	- Sunflower Oil - PGPR (4–9%)	- WPI (1%) - NaCl (0.2%)	30:70 40:60 50:50	30:70 50:50	- 70% W₂ and ↓ oil content (↑ % fat replacing) led to ↓ droplet size, ↓ viscosity, and ↑ expelled gelatin in W₂ - 50% W₂ and ↓ oil led to ↑ expelled gelatin in W₂, ↑ viscosity and ↑ yield - Improvement or no change in sensory properties up to 40% fat replaced by DE (with gelled W₁)	[74]^[49]
- Mulberry anthocyanins (0.5%)	- Walnut oil - PGPR (6%)	- Pectin (1%) - Proclin 300 (0.05%) - GDL (0–2%)	40:60	40:60	- No delamination of DEs after 28 d of storage at 4 °C as compared to 25 °C - Particle size: ↑ from 625 to 1781 and 2316 nm after storage at 4 °C and 25 °C, respectively; - Zeta potential: ↑ from −48 to −40 and −25 mV after storage at 4 °C and 25 °C, respectively; - ↑ Yellowness and ↓ reddishne ssafter storage at 4 °C and 25 °C, respectively; - EE: ↓ from 95.3% to 93.2% and 88.9% after storage at 4 °C and 25 °C, respectively - Rheology: ↑ G′ and G″ after the addition of GDL during the frequency sweep test, suggesting gel-like behavior - ↑ 3D printing ability by GDL, particularly at 1.6%	[70]^[45]
- WPI (2%) - Lutein (0.002%)	- Sunflower oil - PGPR (4%) - Lutein (0.002%)	- WPI (2%) - Xanthan gum (0.5%)	10:90	20:80	- Droplet size of DEs: 40–49 µm - ↑ Lutein stability against light - ↑ Lutein bioaccessibility after in vitro digestion in DEs rather than W/O - ↓ Lutein content from 18.8 to 12.3 µg/g and 19.9 to 11.3 µg/g after 14 days for W/O-L/W and W-L/O/W, respectively. - ↑ Lutein recovery (99%) after digestion for W/O-L/W and W-L/O/W - The highest color stability in W-L/O/W	[69]^[44]
- Sample A: NaCl (0.1 M), glycerol (3%), Opuntia stricta var. dillenii (OPD extract; 750 mg) - Sample B: OPD extract (750 mg), gelatin (6%)	- Sample A: MCT, PGPR (5%) - Sample B: MCT, PGPR (14%), phosphatidylcholine (4%)	- Sample A: NaCl (0.1 M), Tween 20 (2%), - Sample B: NaCl (1.3%), glycerol (13%), and a mixture of caseinate (3%), guar gum (0.175%), and gum Arabic (0.265%)	- Sample A: 25:75 - Sample B 30:70	Sample A: 25:75 - Sample B 30:70	- Higher a* (red to green) value of sample B than sample A Zeta = −32.7 (sample A) and −49.2 (sample B) - The lowest size (1.75 µm) and stability for sample A - EE: 68.2–98%, sample B was more efficient - In vitro gastro-intestinal digestion: ↑ and ↓particle size for sample A and B, respectively. - ↑ Bioaccessibility of the individual betanins and phenolic compounds after encapsulation (67.1 to 253.1%) in comparison with the non-encapsulated ones (30.1 to 64.3%), except for neobetanin	[75]^[50]
- Gelatin (10%) - Phycocyanin (0.2%)	- Soybean oil - PGPR (4%) - Astaxanthin (2%)	- SC (3%) - Gellan gum (0.1%, 0.2%, 0.3%, 0.4%, 0.5%, and 0.7%)	20:80	60:40	- Droplet size: ↓ from 14.98 μm for DE without gellan gum to 7.11 μm at a concentration of 0.7% due to the ↑ viscosity of W₂ -Rheology: ↑ G′ and ↑ G″ after gellan gum addition - ↑ Water holding capacity at higher gellan gum concentrations - ↓ serum separation, ↑ ionic and heat stability at gellan > 0.3% - ↑ EE with ↑ the concentration of gellan gum (90.82% for astaxanthin at 0.5% and 94.1% for phycocyanin at 0.7%) - ↑ Color stability as evidenced by no color change after 10 days In vitro release: <25% for phycocyanin and astaxanthin in SGF and >60% in SIF - Successful pH-controlled release - Significant ↑ bioaccessibility of phycocyanin (12.54%) and astaxanthin (14.27%) in DE and DE gels	[13]^[1]
- Gelatin (5%) - Betanin	- MCT - PGPR (5%) - Curcumin (0.75 mg/mL)	- Sugar beet pectin-bovine serum albumin Pickering nanoparticles (0.5−2%)	20:80	10:90 to 90:10	- D_4,3: ↓ from 95.7 to 34.8 μm by ↑ Pickering nanoparticles from 0.5% to 2%, respectively. ↑ by increasing volume fraction of primary emulsion; - Rheology: change from liquid-like behavior at 0.5% and 1.0% Pickering nanoparticles to gel-like behavior - EE: 84.1% and 65.3% for curcumin and betanin, respectively; - LE: <20% and >20% for curcumin and betanin, respectively; - ↑ Color stability in DEs as compared to free forms of colorants - ↑ Storage stability in DEs (57.9% to 81.5% (curcumin) and 43.5% to 76.6% (betanin)) as compared to free forms - ↑ Extent and rate of FFA released after encapsulation as compared to free MCT - ↑ Bioaccessibility of betanin (42.7%) and curcumin (53.5%) as compared to free forms	[71]^[46]
- Grape seed proanthocyanidin (GSP; 2 mg/mL) - Sucrose (3%)	- Olive oil - PGPR (5%)	- WPI (3%) - Konjac glucomannan (KGM) (0–1.75%)	30:70	30:70	- ↑ WHC, rheological and texture properties after KGM addition - ↑ Heat stability of GSP with ↑ KGM concentrations - Freeze–thaw stability: ↓ syneresis and GSP retention with up to 1.5% KGM - The highest UV stability 1.5% KGM - In vitro digestion: ↓ hydrolysis of protein and oil droplets and ↑ bioavailability of GSP after KGM addition - ↑ EE and encapsulation stability and ↓ LE, of GSP after 14 days with ↑ KGM - Color: ↑ L* and b* values and ↓ a* values with ↑ KGM	[76]^[51]

The * in L*, a*, and b* is a symbol of color parameters.

6. Fat Reduction Purposes

Since a fraction of the oil phase is replaced by the dispersed water droplets (W₁), DEs can be utilized to decrease the fat content of food products. The dispersed phase volume fraction and the particle size distribution of DEs can be modulated in such a way that low-fat DEs exhibit sensory and physicochemical properties similar to full-fat simple emulsions. However, the utilization of DEs for fat replacement and the development of low-calorie products has not been extensively studied. Details of studies regarding the fabrication of low-fat foods using the DE system are presented in Table 76. Zhang, et al. [77]^[52] used a gel/oil/water (G/O/W) DE as a fat replacer of pork oil in the formulation of emulsified sausages. Gellan gum was used as the gelling agent of the inner phase. The droplet size of the G/O/W was 5.38 µm, close to that of the fat particles in common sausage (5.5 µm). Comparing sausage samples prepared either from pork oil (20% fat, 20F) or G/O/W DE (12% fat and 20% DE, 20DE), and with excess water (8%, 8W) as fat replacers, the 20DE sample had the lowest fat content and highest water content. The energy values for 20F, 8W, and 20DE were 13.55, 9.48, and 7.91 Kj/g, respectively. While the cooking loss of 20DE was higher than the two other samples, their compression loss was not significantly different. Texture analysis of the samples showed that the springiness and cohesiveness of 8W and 20DE were not significantly different from 20F. Adhesiveness and chewiness in the presence of 8W were equal to those of 20F and lower than 20DE and the hardness of this sample of 8W was lower than 20F and higher than 20DE, concluding that partial fat replacement by G/O/W would not affect the textural properties significantly. In a study by Rakshit and Srivastav [78]^[53], DE containing hydrolysable tannin (HT) was used as a fat replacer in short-dough biscuits. Different samples, including short-dough without HT and DE (control), short-dough containing unencapsulated HT, and short-dough samples containing HT-loaded DE replacing 20%, 40%, and 60% of the fat, were formulated and assessed in terms of sensory properties and storage stability using fuzzy logic and quantitative analysis. Adding free HT caused a reduction in the diameter and width of the biscuits after baking due to the interaction between HT and proteins. More than a 24% cooking loss of encapsulated HT was observed in the samples. Based on the results of sensory evaluation, the obtained score of the sample with 40% of fat replaced was higher than the other samples and the lowest score was related to the sample containing free HT due to the astringent flavor of tannin, indicating the ability to use DE as an efficient carrier in masking astringent flavors. The shelf life of the sample containing the 40% fat replacer, as the sample with the highest acceptance, based on measuring moisture absorbance, was 98 days. No changes in color occurred during the storage time; however, hardness and HT decreased. This study indicated the ability of DE to formulate low-fat and fortified biscuits. Zhao, et al. [79]^[54] used different concentrations of DE (5%, 10%, 20%, and 30%, termed D5, D10, D20, and D30, respectively) as fat replacers in almond-based yoghurt and compared their effect with their counterpart control samples (without DE, termed C5, C10, C20, and C30) on different properties of the product. The results revealed that by increasing DE from 5% to 30%, the water holding capacity (WHC) increased and D20 and D30 had significantly higher WHC than their control counterparts. A positive correlation was also observed between WHC and gel strength. The addition of a DE (at 20% and 30%) reduced syneresis of the yoghurt samples compared to the controls and increasing DE content resulted in a significant decrease in syneresis from 9.77% for D5 to 2.58% for D30. Higher DE content also led to higher hardness value of the gel. Therefore, the D30 sample showed a significantly harder gel and higher viscosity than C30. Sensory analysis of D30 (as the sample with the most appropriate physical properties) and C30 showed equal overall acceptance for both samples, indicating that despite a considerable decrease in the fat content, the consumers could not distinguish differences between the almond-based yoghurt samples with and without DE.

Table 76.

Overview of the past decade’s publications on fat reduction purposes by encapsulation in W

₁

/O/W

₂

double emulsions (DEs).

W₁	O	W₂	Phase ratio

According to these results, using DE in a variety of food formulations as a fat replacer can decrease calories without changing or even improving (at an appropriate replacement percentage) the sensory properties of the final products, and can also offer opportunities for food fortification by providing blends of unsaturated fatty acids in agreement with dietary recommendations.

7. Improved Edible Packaging Quality

Today, edible coatings or films are considered ideal alternative eco-friendly primary packaging materials for the replacement of synthetic plastics. The potential applications of edible coatings or films as efficient barriers to gas, microbial and chemical contamination, as well as to improve sensory perception and extended shelf life, have been well documented. Due to the highly hydrophilic nature of biopolymer-based edible films, emulsion-based edible films have gained more attention for their better functionality, particularly in terms of mechanical and moisture barrier properties as well as their capacity to deliver and protect sensitive bioactive material in the film matrix [84,85]^[59][60]. At present, there is a limited number of publications on the preparation of edible films based on DE strategies as compared to SE approaches (Table 87). In this connection, Ghiasi and Golmakani [84]^[59] investigated the preparation of a novel design of Persian gum-based films functionalized by crocin and cinnamaldehyde using SE and DE methods. In terms of the visual aspects, the addition of DE droplets had higher effects on opacity than SE, due to the larger droplet size. The effects of DE addition in terms of reducing the moisture content, solubility, swelling, and water vapor permeability of edible films were more pronounced in comparison with SE, which was mainly attributed to the more homogenous distribution of emulsion droplets. This result was in good agreement with the higher enhanced mechanical properties and smoother surface after the addition of DE droplets. In contrast, the addition of bioactives to both the free and SE forms led to a weaker texture and rougher microstructure. Moreover, higher protection effects of DE droplets on the storage stability of encapsulated crocin in the W₁ as compared to SE confirmed its higher antioxidant activity after 14 days. In addition, DE was a more effective strategy to improve the pH and thermal stability of crocin and cinnamaldehyde as well as to inhibit the light degradation of crocin in the film matrix due to the secondary encapsulation and presence of a thicker interfacial layer. In another study, Tessaro, et al. [86]^[61] investigated the effect of the addition of “pitanga” leaf extract-loaded DE on the different properties of films based on gelatin, chitosan, and a gelatin–chitosan composite. Visually, the addition of the DE increased ΔE and opacity for all films, indicating that these films were more intense in color. SEM micrographs revealed some migration of the oil droplets to the surface during drying resulting in more heterogeneous structures. All films showed high UV/Vis light barrier properties, especially for those incorporating DE due to the light dispersion effect of the oil droplets. Incorporating a DE resulted in a high Folin–Ciocalteu reducing capacity and antioxidant activity (based on ABTS^•+ and FRAP) of the films, suggesting the effective encapsulation and protection of extracts by the DE. However, the low concentration of the encapsulated extract, as well as the limitation of its diffusion from the film matrix into agar, contributed to the non-formation of an inhibition zone during the antimicrobial activity study.

Table 87.

Overview of the past decade’s publications on improved edible film properties by incorporating W

₁

/O/W

₂

double emulsions (DEs).

W₁	O	W₂	Phase Ratio		Remarkable Results	Reference

In conclusion, incorporating a DE into edible films and coatings can reinforce their mechanical and barrier properties (against water vapor, light, pH, etc.) and make it possible to fabricate active packaging incorporating sensitive colorants and bioactive components, maintaining their properties for a longer time. However, further studies are required on the application of these new generations of edible films on real food products to investigate their efficacy in terms of extending the foods’ shelf life.

References

Yu, H.; Wang, H.; Su, W.; Song, Y.; Zaky, A.A.; Abd El-Aty, A.; Tan, M. Co-delivery of hydrophobic astaxanthin and hydrophilic phycocyanin by a pH-sensitive water-in-oil-in-water double emulsion-filled gellan gum hydrogel. Food Hydrocoll. 2022, 131, 107810.
Dai, Y.; Lu, X.; Li, R.; Cao, Y.; Zhou, W.; Li, J.; Zheng, B. Fabrication and Characterization of W/O/W Emulgels by Sipunculus nudus Salt-Soluble Proteins: Co-Encapsulation of Vitamin C and β-Carotene. Foods 2022, 11, 2720.
Barbosa, B.S.T.; Garcia-Rojas, E.E. Double emulsions as delivery systems for iron: Stability kinetics and improved bioaccessibility in infants and adults. Curr. Res. Food Sci. 2022, 5, 718–725.
Kabakci, C.; Sumnu, G.; Sahin, S.; Oztop, M.H. Encapsulation of magnesium with lentil flour by using double emulsion to produce magnesium enriched cakes. Food Bioprocess Technol. 2021, 14, 1773–1790.
Su, Y.; Sun, Y.; McClements, D.J.; Chang, C.; Li, J.; Xiong, W.; Sun, Y.; Cai, Y.; Gu, L.; Yang, Y. Encapsulation of amino acids in water-in-oil-in-water emulsions stabilized by gum arabic and xanthan gum. Int. J. Biol. Macromol. 2022, 220, 1493–1500.
Li, L.; He, M.; Yang, H.; Wang, N.; Kong, Y.; Li, Y.; Teng, F. Effect of soybean lipophilic protein–methyl cellulose complex on the stability and digestive properties of water–in–oil–in–water emulsion containing vitamin B12. Colloids Surf. A Physicochem. Eng. Asp. 2021, 629, 127364.
Zanetti, M.; Carniel, T.K.; Dalcanton, F.; dos Anjos, R.S.; Riella, H.G.; de Araújo, P.H.; de Oliveira, D.; Fiori, M.A. Use of encapsulated natural compounds as antimicrobial additives in food packaging: A brief review. Trends Food Sci. Technol. 2018, 81, 51–60.
Aasen, I.M.; Markussen, S.; Møretrø, T.; Katla, T.; Axelsson, L.; Naterstad, K. Interactions of the bacteriocins sakacin P and nisin with food constituents. Int. J. Food Microbiol. 2003, 87, 35–43.
Gahruie, H.H.; Ziaee, E.; Eskandari, M.H.; Hosseini, S.M.H. Characterization of basil seed gum-based edible films incorporated with Zataria multiflora essential oil nanoemulsion. Carbohydr. Polym. 2017, 166, 93–103.
Tessaro, L.; Luciano, C.G.; Martins, M.F.L.; Ramos, A.P.; Martelli-Tosi, M.; do Amaral Sobral, P.J. Stable and bioactive W/O/W emulsion loaded with “Pitanga” (Eugenia uniflora L.) leaf hydroethanolic extract. J. Dispers. Sci. Technol. 2022, 43, 1890–1900.
Garmus, T.T.; Paviani, L.C.; Queiroga, C.L.; Magalhães, P.M.; Cabral, F.A. Extraction of phenolic compounds from pitanga (Eugenia uniflora L.) leaves by sequential extraction in fixed bed extractor using supercritical CO2, ethanol and water as solvents. J. Supercrit. Fluids 2014, 86, 4–14.
Bezerra, I.C.; Ramos, R.T.d.M.; Ferreira, M.R.; Soares, L.A. Chromatographic profiles of extractives from leaves of Eugenia uniflora. Rev. Bras. Farmacogn. 2018, 28, 92–101.
Valdivia-Olivares, R.; Martinez-González, E.; Montenegro, G.; Bridi, R.; Alvarez-Figueroa, M.; González-Aramundiz, J. Innovative multiple nanoemulsion (W/O/W) based on Chilean honeybee pollen improves their permeability, antioxidant and antibacterial activity. Food Res. Int. 2023, 168, 112767.
Ji, S.; Lu, J.; Liu, Z.; Srivastava, D.; Song, A.; Liu, Y.; Lee, I. Dynamic encapsulation of hydrophilic nisin in hydrophobic poly (lactic acid) particles with controlled morphology by a single emulsion process. J. Colloid Interface Sci. 2014, 423, 85–93.
Freire, M.; Bou, R.; Cofrades, S.; Jiménez-Colmenero, F. Technological characteristics of cold-set gelled double emulsion enriched with n-3 fatty acids: Effect of hydroxytyrosol addition and chilling storage. Food Res. Int. 2017, 100, 298–305.
Cardoso-Ugarte, G.A.; López-Malo, A.; Palou, E.; Ramírez-Corona, N.; Jiménez-Fernández, M.; Jiménez-Munguía, M.T. Stability of oregano essential oil encapsulated in double (W/O/W) emulsions prepared with mechanical or high-pressure homogenization and its effect in Aspergillus niger inhibition. J. Food Process. Preserv. 2021, 45, e15104.
Ghiasi, F.; Hashemi, S.M.B.; Abedi, E. Effective enhancement of food oxidative stability induced by Lactobacillus strains: In vitro activity. Food Control 2023, 153, 109912.
Silva, W.; Torres-Gatica, M.F.; Oyarzun-Ampuero, F.; Silva-Weiss, A.; Robert, P.; Cofrades, S.; Giménez, B. Double emulsions as potential fat replacers with gallic acid and quercetin nanoemulsions in the aqueous phases. Food Chem. 2018, 253, 71–78.
Ghiasi, F.; Golmakani, M.-T.; Eskandari, M.H.; Hosseini, S.M.H. Effect of sol-gel transition of oil phase (O) and inner aqueous phase (W1) on the physical and chemical stability of a model PUFA rich-W1/O/W2 double emulsion. Food Chem. 2022, 376, 131929.
Chaudhary, N.; Sabikhi, L.; Hussain, S.A.; Kumar, R.; Choudhary, U. Emblicanin rich Emblica officinalis encapsulated double emulsion and its antioxidant stability during storage. Eur. J. Lipid Sci. Technol. 2020, 122, 1900316.
Eisinaitė, V.; Kazernavičiūtė, R.; Kaniauskienė, I.; Venskutonis, P.R.; Leskauskaitė, D. Effect of black chokeberry pomace extract incorporation on the physical and oxidative stability of water-in-oil-in-water emulsion. J. Sci. Food Agric. 2021, 101, 4570–4577.
Kumar, Y.; Kumar, V. Effects of double emulsion (W1/O/W2) containing encapsulated Murraya koenigii berries extract on quality characteristics of reduced-fat meat batter with high oxidative stability. LWT 2020, 127, 109365.
Ahmadian, S.; Kenari, R.E.; Amiri, Z.R.; Sohbatzadeh, F.; Khodaparast, M.H.H. Fabrication of double nano-emulsions loaded with hyssop (Hyssopus officinalis L.) extract stabilized with soy protein isolate alone and combined with chia seed gum in controlling the oxidative stability of canola oil. Food Chem. 2024, 430, 137093.
Huang, H.; Wang, D.; Belwal, T.; Dong, L.; Lu, L.; Zou, Y.; Li, L.; Xu, Y.; Luo, Z. A novel W/O/W double emulsion co-delivering brassinolide and cinnamon essential oil delayed the senescence of broccoli via regulating chlorophyll degradation and energy metabolism. Food Chem. 2021, 356, 129704.
Aditya, N.; Aditya, S.; Yang, H.; Kim, H.W.; Park, S.O.; Ko, S. Co-delivery of hydrophobic curcumin and hydrophilic catechin by a water-in-oil-in-water double emulsion. Food Chem. 2015, 173, 7–13.
Li, D.; Hu, M.; Hou, L.; Gao, Y.; Tian, Z.; Wen, W.; Fan, B.; Li, S.; Wang, F. The structural and functional properties of soybean protein-polyglutamic acid complex effected the stability of W/O/W emulsion encapsulated Nattokinase. Food Chem. 2023, 414, 135724.
Yun, Y.; Cho, Y.W.; Park, K. Nanoparticles for oral delivery: Targeted nanoparticles with peptidic ligands for oral protein delivery. Adv. Drug Deliv. Rev. 2013, 65, 822–832.
Wang, X.; Jiang, S.; Wang, X.; Liao, J.; Yin, Z. Preparation and evaluation of nattokinase-loaded self-double-emulsifying drug delivery system. Asian J. Pharm. Sci. 2015, 10, 386–395.
Souza, C.J.; Comunian, T.A.; Kasemodel, M.G.; Favaro-Trindade, C.S. Microencapsulation of lactase by W/O/W emulsion followed by complex coacervation: Effects of enzyme source, addition of potassium and core to shell ratio on encapsulation efficiency, stability and kinetics of release. Food Res. Int. 2019, 121, 754–764.
Marefati, A.; Pitsiladis, A.; Oscarsson, E.; Ilestam, N.; Bergenståhl, B. Encapsulation of Lactobacillus reuteri in W1/O/W2 double emulsions: Formulation, storage and in vitro gastro-intestinal digestion stability. LWT 2021, 146, 111423.
Frakolaki, G.; Katsouli, M.; Giannou, V.; Tzia, C. Novel encapsulation approach for Bifidobacterium subsp. lactis (BB-12) viability enhancement through its incorporation into a double emulsion prior to the extrusion process. LWT 2020, 130, 109671.
Qin, X.-S.; Luo, Z.-G.; Li, X.-L. An enhanced pH-sensitive carrier based on alginate-Ca-EDTA in a set-type W1/O/W2 double emulsion model stabilized with WPI-EGCG covalent conjugates for probiotics colon-targeted release. Food Hydrocoll. 2021, 113, 106460.
Jiang, Z.; Tian, J.; Bai, X.; McClements, D.J.; Ma, C.; Liu, X.; Liu, F. Improving probiotic survival using water-in-oil-in-water (W1/O/W2) emulsions: Role of fish oil in inner phase and sodium alginate in outer phase. Food Chem. 2023, 417, 135889.
Šipailienė, A.; Šlimaitė, G.; Jeznienė, S.; Venskutonis, P.R.; Leskauskaitė, D. W/O/W double emulsion-loaded alginate capsules containing Lactobacillus plantarum and lipophilic sea buckthorn (Hippophae rhamnoides L.) pomace extract in different phases. Food Sci. Technol. Int. 2022, 28, 397–407.
Abbasi, S.; Rafati, A.; Hosseini, S.M.H.; Roohinejad, S.; Hashemi, S.S.; Hashemi Gahruie, H.; Rashidinejad, A. The internal aqueous phase gelation improves the viability of probiotic cells in a double water/oil/water emulsion system. Food Sci. Nutr. 2023, 11, 5978–5988.
Silva, J.L.; de Almeida Paula, D.; Lelis, C.A.; Vieira, É.N.R.; Ramos, A.M. Double emulsions containing probiotic cells (Lactiplantibacillus plantarum) added in a mango dessert. J. Food Process. Preserv. 2022, 46, e16783.
Rodríguez-Huezo, M.; Estrada-Fernández, A.; García-Almendárez, B.; Ludeña-Urquizo, F.; Campos-Montiel, R.; Pimentel-González, D. Viability of Lactobacillus plantarum entrapped in double emulsion during Oaxaca cheese manufacture, melting and simulated intestinal conditions. LWT-Food Sci. Technol. 2014, 59, 768–773.
Chung, C.; Olson, K.; Degner, B.; McClements, D.J. Textural properties of model food sauces: Correlation between simulated mastication and sensory evaluation methods. Food Res. Int. 2013, 51, 310–320.
Buyukkestelli, H.I.; El, S.N. Enhancing sweetness using double emulsion technology to reduce sugar content in food formulations. Innov. Food Sci. Emerg. Technol. 2021, 74, 102809.
Gao, Y.; Li, X.; Xie, Y.; Huang, X.; Cheng, C.; McClements, D.J.; Zhang, L.; Chen, X.; Zou, L.; Wei, L. Encapsulation of bitter peptides in diphasic gel double emulsions: Bitterness masking, sustained release and digestion stability. Food Res. Int. 2022, 162, 112205.
Devanthi, P.V.P.; Linforth, R.; El Kadri, H.; Gkatzionis, K. Water-in-oil-in-water double emulsion for the delivery of starter cultures in reduced-salt moromi fermentation of soy sauce. Food Chem. 2018, 257, 243–251.
Jamshidi, A.; Shabanpour, B.; Pourashouri, P.; Raeisi, M. Optimization of encapsulation of fish protein hydrolysate and fish oil in W1/O/W2 double emulsion: Evaluation of sensory quality of fortified yogurt. J. Food Process. Preserv. 2019, 43, e14063.
Chen, M.; Abdullah; Wang, W.; Xiao, J. Regulation effects of beeswax in the intermediate oil phase on the stability, oral sensation and flavor release properties of pickering double emulsions. Foods 2022, 11, 1039.
Nunes, L.; Hashemi, N.; Gregersen, S.B.; Tavares, G.M.; Corredig, M. Compartmentalization of lutein in simple and double emulsions containing protein nanoparticles: Effects on stability and bioaccessibility. Food Res. Int. 2023, 173, 113404.
Li, J.; Guo, C.; Cai, S.; Yi, J.; Zhou, L. Fabrication of anthocyanin–rich W1/O/W2 emulsion gels based on pectin–GDL complexes: 3D printing performance. Food Res. Int. 2023, 168, 112782.
Tang, X.-Y.; Wang, Z.-M.; Meng, H.-C.; Lin, J.-W.; Guo, X.-M.; Zhang, T.; Chen, H.-L.; Lei, C.-Y.; Yu, S.-J. Robust W/O/W emulsion stabilized by genipin-cross-linked sugar beet pectin-bovine serum albumin nanoparticles: Co-encapsulation of betanin and curcumin. J. Agric. Food Chem. 2021, 69, 1318–1328.
Hashemi, H.; Eskandari, M.H.; Hosseini, S.M.H. A novel strategy for simultaneous reduction of salt and animal fat in burger using a taste contrast system based on double emulsion. Curr. Res. Food Sci. 2023, 7, 100644.
Herzi, S.; Essafi, W. Impact of the encapsulated salt characteristics on its release from multiple W/O/W emulsions. J. Food Process Eng. 2021, 44, e13762.
Oppermann, A.; Piqueras-Fiszman, B.; De Graaf, C.; Scholten, E.; Stieger, M. Descriptive sensory profiling of double emulsions with gelled and non-gelled inner water phase. Food Res. Int. 2016, 85, 215–223.
Parralejo-Sanz, S.; Gómez-López, I.; González-Álvarez, E.; Montiel-Sánchez, M.; Cano, M.P. Oil-Based Double Emulsion Microcarriers for Enhanced Stability and Bioaccessibility of Betalains and Phenolic Compounds from Opuntia stricta var. dillenii Green Extracts. Foods 2023, 12, 2243.
Zhuang, H.; Li, X.; Wu, S.; Wang, B.; Yan, H. Fabrication of grape seed proanthocyanidin-loaded W/O/W emulsion gels stabilized by polyglycerol polyricinoleate and whey protein isolate with konjac glucomannan: Structure, stability, and in vitro digestion. Food Chem. 2023, 418, 135975.
Zhang, Y.; Wang, X.; Chen, H.; Ren, F.; Liu, Z.; Wang, P.; Liu, X. Application of gel-in-oil-in-water double emulsions as a pork oil replacer in emulsified sausage. J. Food Process. Preserv. 2022, 46, e16333.
Rakshit, M.; Srivastav, P.P. Sensory evaluation and storage stability of fat reduced shortdough biscuit using hydrolysable tannin encapsulated double emulsion as fat replacer. LWT 2022, 154, 112816.
Zhao, J.; Bhandari, B.; Gaiani, C.; Prakash, S. Fermentation of almond-based gel incorporated with double emulsion (W1/O/W2): A study on gel properties and effectiveness of double emulsion as a fat replacer. Food Struct. 2023, 36, 100322.
Zheng, B.; Li, X.; Hao, J.; Xu, D. Meat systems produced with Monascus pigment water-in-oil-in-water multiple emulsion as pork fat replacers. Food Chem. 2023, 402, 134080.
Paximada, P.; Howarth, M.; Dubey, B.N. Double emulsions fortified with plant and milk proteins as fat replacers in cheese. J. Food Eng. 2021, 288, 110229.
Serdaroğlu, M.; Öztürk, B.; Urgu, M. Emulsion characteristics, chemical and textural properties of meat systems produced with double emulsions as beef fat replacers. Meat Sci. 2016, 117, 187–195.
Cofrades, S.; Antoniou, I.; Solas, M.T.; Herrero, A.M.; Jiménez-Colmenero, F. Preparation and impact of multiple (water-in-oil-in-water) emulsions in meat systems. Food Chem. 2013, 141, 338–346.
Ghiasi, F.; Golmakani, M.-T. Innovative design of bio-functional persian gum-based edible films by incorporating crocin and cinnamaldehyde: Free versus single and double emulsion fabrication techniques. Food Hydrocoll. 2023, 135, 108164.
Galus, S.; Kadzińska, J. Food applications of emulsion-based edible films and coatings. Trends Food Sci. Technol. 2015, 45, 273–283.
Tessaro, L.; Luciano, C.G.; Bittante, A.M.Q.B.; Lourenço, R.V.; Martelli-Tosi, M.; do Amaral Sobral, P.J. Gelatin and/or chitosan-based films activated with “Pitanga” (Eugenia uniflora L.) leaf hydroethanolic extract encapsulated in double emulsion. Food Hydrocoll. 2021, 113, 106523.
Tessaro, L.; Lourenço, R.V.; Martelli-Tosi, M.; do Amaral Sobral, P.J. Gelatin/chitosan based films loaded with nanocellulose from soybean straw and activated with “Pitanga” (Eugenia uniflora L.) leaf hydroethanolic extract in W/O/W emulsion. Int. J. Biol. Macromol. 2021, 186, 328–340.
Le, P.H.; Dao, D.N.; Huynh, H.T.T.; Nguyen, P.T.; Nguyen, V. Formulation of Edible Films Based on W/O/W Emulsions Stabilized by Coffee Byproducts. Food Bioprocess Technol. 2023, 6, 2531–2540.