Microencapsulation of Essential Oils by Coacervation: Comparison
Please note this is a comparison between Version 2 by Jessie Wu and Version 3 by Jessie Wu.

Essential oils (EO) are called essential in the sense that it contains the essence of the aroma of the plant it is derived from, whereas the term “oil” is used because it contains the oil-soluble chemicals in the plant, not only because it feels oily. EOs are also known as volatile oils, ethereal oils, or aetheroleum. The wider use of essential oils in the food industry is severely limited. This is because these substances are highly sensitive to light, oxygen, and temperature. This creates problems with their processing and storage. In addition, they have a strong smell and taste, which makes them unacceptable when added to the product. The solution to this situation seems to be microencapsulation through complex coacervation.  To reduce the loss of essential oils and the undesirable chemical changes that may occur during their spray drying—the most commonly used method—complex coacervation seems to be an interesting alternative. 

  • essential oils
  • proteins
  • microencapsulation

1. Essential Oils

Essential oils (EO) are multi-component, hydrophobic mixtures containing up to several hundred volatile compounds (usually 100 to 200 chemicals per essential oil) in different concentrations. Essential oils can be characterized by two or three major components at relatively high concentrations (20–70%), which determines the biological properties of EOs. The main ingredients chemically are terpenes, aldehydes, ketones, phenols, alcohols, and others [1][2][3]. This complex chemistry gives them their therapeutic properties and explains why different essential oils may have overlapping effects [4][5][6][7]. Some examples of major components can be cited—carvacrol and thymol represent, respectively, 30% and 27% of the composition of EO from oregano (Origanum compactum). EOs from coriander (Coriandrum sativum) have in their constitution 65% linalool. Menthol (59%) and menthone (19%) are found in EOs from peppermint (Mentha piperita) [8][9].
Essential oils are characterized by having many pharmacological properties, including anti-inflammatory, antispasmodic, sedative, analgesic, and digestive-supporting properties. Due to their very rich and diverse chemical composition, one essential oil can have several positive effects. For example, rosemary essential oil has the effect of improving digestion, enhancing appetite, and being anti-flatulence. In addition, they have well-documented antimicrobial activity against bacteria, yeasts, and molds [4][5][10]. Again, thanks to its complex composition, one essential oil can effectively inhibit the growth of both bacteria and fungi. The same rosemary EO inhibits the growth of Gram-positive (Enterococcus spp.) and Gram-negative (Salmonella spp.) bacteria, yeasts (Candida spp.), and molds (Penicillium spp.) [11][12][13]. For this reason, EOs can be an alternative to the commonly used food-preservation agents.
This is indicated by studies conducted, inter alia, by Coimbra et al. [14]. The team tested the applicability of thyme essential oil (Thymus zygis) to Listeria monocytogenes in four food matrices (chicken juice, lettuce leaf model, ultra-high-temperature (UHT)-treated skim, and whole milk). EO inhibited the growth of L. monocytogenes 13305 in a model medium with chicken juice and lettuce. A significant reduction in the number was observed for the two highest concentrations of EO tested from 4 to 14 days for chicken juice and from 2 to 14 days for the model medium with lettuce. Research on the possibility of using essential oils for preserving food products was also conducted by Shah et al. [15]. Thymol concentrations used in apple cider resulted in complete bacterial inhibition or were bacteriostatic at 35 °C for E. coli and 32 °C for L. monocytogenes. Attempts have been made to use essential oils also for preserving such products as romaine lettuce, iceberg lettuce, mature bunched spinach, and baby spinach [16], snacks based on meat and seafood [17][18][19], juices [20], milk, yogurts, and other milk products [21][22][23] or chocolates [24], but also fruits or vegetables coated with edible coatings with the addition of EO [25][26].
Nanodispersion of eugenol (the basic ingredient of clove oil) in whey protein isolate and maltodextrin did not change its antimicrobial properties against E. coli O157: H7 and Listeria monocytogenes. However, nanodispersion allowed eugenol to be evenly distributed in the milk at concentrations above the solubility limit of the antimicrobial agent, which improved the antimicrobial efficacy in milk. Thus, nano-delivery systems hope to reduce the amount of antimicrobials without altering the turbidity of food products [21].
The stability of meat products during storage is a primary factor that is compromised by lipid oxidation and microbial growth. Hemmatkhak et al. [27] researched the use of active papers soaked in a nanoemulsion or Pickering emulsion containing cumin seed essential oil (CSEO). The effect of active papers on the quality and shelf-life of beef hamburgers stored at 4 °C for 7 days and at −18 °C for 60 days was investigated. Research results indicate good antioxidant and antimicrobial activity of cellulose papers impregnated in CSEO capsules. Packing beef burgers in contact with the produced active papers had a significant effect on extending the shelf life of hamburger samples by significantly reducing TBARS, the total number of mesophilic bacteria and psychrophilic. Furthermore, the sensory characteristics of the hamburgers did not changed.
It also seems important that many essential oils are on the Generally Recognized As Safe (GRAS) list published by the US Food and Drug Agency (FDA). Among the EOs that are approved for use in food are clove, rosemary, oregano, basil, mint, lavender, sage, cinnamon, and laurel [28][29][30]. Considering the above, essential oils can be not only a natural replacement for artificial preservatives but also a functional additive.

2. Microencapsulation as a Solution for Essential Oils Application Limitations

There are limitations to the use of pure essential oils in food products. First of all, their characteristic strong aroma and taste can cause undesirable organoleptic changes. In addition, EOs are very sensitive to the influence of the external environment —light, oxygen, and temperature. Other limitations are their lipophilic nature and hence low water solubility, low bio-accessibility, and bio-availability [3][31]. These problems can be solved by microencapsulation—an effective method of preserving the quality of sensitive substances. Microencapsulation is defined as a method of coating or encapsulating a given material or mixture of materials within the shell of a specific material or system. The substance that is encapsulated is called “active”, “encapsulate”, “payload”, or “core” and constitutes 30–99% of the total weight of the capsule. The core material can be a single substance or a mixture of solid, liquid, and gaseous forms. The enclosing polymer is called “shell”, “wall”, “matrix”, or “coating” [31][32][33]. The wall material is usually insoluble and non-reactive with the core material. The wall can be made of gums, proteins, lipids, and synthetic polymers. The wall material is generally applied as a liquid (solution, suspension, or molten material) to permit enrobing of the core material. Because the task of the shell is to protect the encapsulated substance, it should have excellent film-forming and barrier properties against oxygen, water, pressure, heat, and/or light [33][34]. A single microcapsule may have a round or irregular shape, depending on the method of producing the microcapsule, the type of active, and wall materials (Figure 1). The average size of the microcapsules is 100–500 µm [35]. Therefore, this process can provide many benefits to the use of EOs in food recipes, including protecting them from harsh conditions (light, shear, oxygen, moisture, heat, and others), improving their solubility and bioavailability, increasing their controlled release, and preventing their interaction with other food ingredients. This also allows for the reduction of volatilization of volatile substances, slowing mass transfer or modifying the physical properties of the core material. It reduces the evaporative loss of liquids and the reactivity of the core material, and extends the duration of its activity [32]. Encapsulation facilitates application by transforming the liquid into a solid phase, ensuring precise dosing, improving stability, and masking the encapsulated substance’s taste and/or smell. In addition, microencapsulation of essential oils can be a viable and effective approach to liquid food matrices with high water content by increasing their dispersibility. Facilitating the distribution of EOs in food areas where microorganisms thrive (water phase) and minimizing their particle diameter may also contribute to improving their antimicrobial properties. The smaller size of the molecules favors the migration and attachment to the bacterial cell walls [3][36]. Commonly used microencapsulation techniques are emulsification, spray-drying, coaxial electro-spray system, freeze-drying, coacervation, in situ polymerization, extrusion, fluidized-bed-coating, and supercritical fluid technology [31][33].
Figure 1. Schematic illustration of various morphologies formed by microencapsulation: monolayer and mononuclear microcapsule (A), multilayer and mononuclear microcapsule (B), multilayer and multinuclear microcapsule (C), and microparticle (D), own elaboration [35].

3. Complex Coacervation of Essential Oils

The process of microencapsulating essential oils by complex coacervation occurs in stages. The first one is hydration and preparation of wall materials solution. The essential oils and an emulsifier (e.g., Tween 20, 60, 80) are then added to these solutions, and the emulsification process is carried out. This step is essential because the quality of the emulsion and the interaction between its droplets directly affect the stability of the microcapsules produced later. The final step is curing by spray drying or freeze-drying [37][38].
Microencapsulation of essential oils using complex coacervation allows for their controlled release. It is the process of delivering EO delayed after administration or incorporation into the food matrix for an extended period [37][39]. This process is influenced by environmental conditions (type of food matrix), type of EO, the composition of microcapsules (proteins, polysaccharides), and microcapsule architecture. Essential oils can be released from their microcapsules through a variety of mechanisms. The swelling mechanism involves increasing the pore size as the matrix swells, which promotes the release of the encapsulated Eos. The mechanism of erosion is the dissolution of the outer part of the support (surface erosion) or all of the support (bulk erosion), often due to enzymatic or chemical hydrolysis. The mechanism of fragmentation is the rupture or breakage of the support matrix, which often occurs due to mechanical forces. The resulting increase in surface area and shorter diffusion paths mean that the bioactive agents are released from the fragments faster than the original carrier. The diffusion mechanism involves the diffusion of the bioactive component through the carrier matrix into the surrounding environment. EO microcapsules should be designed to be used in a specific product because food is exposed to a variable temperature, ionic strength, pH and mechanical conditions and stress during processing and storage [40][41][42][43]. The preparation of microcapsules of essential oils produced by complex coacervation can be an effective method to preserve their physicochemical properties. At the same time, it can contribute to increasing the applicability of essential oils in food as natural additives with a preservative effect and increasing the nutritional value of the final product. EO microcapsules can be an effective way to reduce the use of synthetic food additives while enabling the creation of interesting products placed in the functional food segment.

References

  1. Hyldgaard, M.; Mygind, T.; Meyer, R.L. Essential oils in food preservation: Mode of action, synergies, and interactions with food matrix components. Front. Microbiol. 2012, 3, 12.
  2. Giacometti, J.; Kovačević, D.B.; Putnik, P.; Gabrić, D.; Bilušić, T.; Krešić, G.; Stulić, V.; Barba, F.J.; Chemat, F.; Barbosa-Cánovas, G.; et al. Extraction of bioactive compounds and essential oils from Mediterranean herbs by conventional and green innovative techniques: A review. Int. Food Res. J. 2018, 113, 245–262.
  3. Delshadi, R.; Bahrami, A.; Tafti, A.G.; Barba, F.J.; Williams, L.L. Micro and nano-encapsulation of vegetable and essential oils to develop functional food products with improved nutritional profiles. Trends Food Sci. Technol. 2020, 104, 72–83.
  4. Kunicka-Styczyńska, A. Olejki eteryczne jako alternatywa dla syntetycznych konserwantów żywności—Praca przeglądowa. In Innowacyjne Rozwiązania w Technologii Żywności i Żywieniu Człowieka; Tarko, T., Drożdż, I., Najgebauer-Lejko, D., Duda-Chodak, A., Eds.; Oddział Małopolski Polskiego Towarzystwa Technologów Żywności: Kraków, Poland, 2016; Volume 122, pp. 175–184.
  5. Falleh, H.; Benjemaa, M.; Djeblai, K.; Abid, S.; Saada, M.; Ksouri, R. Application of the mixture design for optimum antimicrobial activity: Combined treatment of Syzygium aromaticum, Cinnamomum zeylanicum, Myrtus communis, and Lavandula stoechas essential oils against Escherichia coli. J. Food Process. Preserv. 2019, 43, 1–11.
  6. Valderrama, F.; Ruiz, F. An optimal control approach to steam distillation of 936 essential oils from aromatic plants. Comput. Chem. Eng. 2018, 117, 25–31.
  7. Falleh, H.; Benjemaa, M.B.; Saada, M.; Ksouri, R. Essential oils: A promising eco-friendly food preservative. Food Chem. 2020, 330, 127268.
  8. Turek, C.; Stintzing, F.C. Stability of Essential Oils: A Review. Compr. Rev. Food Sci. 2013, 12, 40–53.
  9. Veiga, R.D.S.D.; Aparecida Da Silva-Buzanello, R.; Corso, M.P.; Canan, C. Essential oils microencapsulated obtained by spray drying: A review. J. Essent. Oil Res. 2019, 31, 457–473.
  10. Patrignani, F.; Siroli, L.; Braschi, G.; Lanciotti, R. Combined use of natural antimicrobial based nanoemulsions and ultra-high pressure homogenization to increase safety and shelflife of apple juice. Food Control 2020, 111, 107051.
  11. Singletary, K. Rosemary, An Overview of Potential Health Benefits. Nutr. Today 2016, 51, 102–112.
  12. Valková, V.; Ďúranová, H.; Galovičová, L.; Vukovic, N.L.; Vukic, M.; Kačániová, M. In Vitro Antimicrobial Activity of Lavender, Mint, and Rosemary Essential Oils and the Effect of Their Vapours on Growth of Penicillium spp. in a Bread Model System. Molecules 2021, 26, 3859.
  13. Stojanović-Radić, Z.; Pejčić, M.; Joković, N.; Jokanović, M.; Ivić, M.; Šojić, B.; Škaljac, S.; Stojanović, P.; Mihajilov-Krstev, T. Inhibition of Salmonella Enteritidis growth and storage stability in chicken meat treated with basil and rosemary essential oils alone or in combination. Food Control 2022, 90, 332–343.
  14. Coimbra, A.; Carvalho, F.; Duarte, A.P.; Ferreira, S. Antimicrobial activity of Thymus zygis essential oil against Listeria monocytogenes and its application as food preservative. Innov. Food Sci. Emerg. Technol. 2022, 80, 103077.
  15. Shah, B.; Davidson, P.M.; Zhong, Q. Nanocapsular Dispersion of Thymol for Enhanced Dispersibility and Increased Antimicrobial Effectiveness against Escherichia coli O157:H7 and Listeria monocytogenes in Model Food Systems. Appl. Environ. Microbiol. 2012, 78, 8448–8453.
  16. Moore-Neibel, K.; Gerber, C.; Patel, J.; Friedman, M.; Jaroni, D.; Ravishankar, S. Antimicrobial activity of oregano oil against antibiotic-resistant Salmonella enterica on organic leafy greens at varying exposure times and storage temperatures. Food Microbiol. 2013, 34, 123–129.
  17. Kocatepe, D.; Turan, H.; Altan, C.O.; Keskin, I.; Ceylan, A.; Köstekli, B.; Candan, C. Influence of different essential oils on marinated anchovy (Engraulis encrasicolus L.) during refrigerated storage. Food Sci. Technol. 2019, 39, 255–260.
  18. Lages, L.Z.; Radünz, M.; Timm Gonçalves, B.; Silva da Rosa, R.; Fouchy, M.V.; de Cássia dos Santos da Conceição, R.; Gularte, M.A.; Barboza Mendonça, C.R.; Gandra, E.A. Microbiological and sensory evaluation of meat sausage using thyme (Thymus vulgaris, L.) essential oil and powdered beet juice (Beta vulgaris L., Early Wonder cultivar). LWT 2021, 148, 111794.
  19. Snoussi, A.; Chouaibi, M.; Ben Haj Koubaier, H.; Bouzouita, N. Encapsulation of Tunisian thyme essential oil in O/W nanoemulsions: Application for meat preservation. Meat Sci. 2022, 188, 108785.
  20. Bento, R.; Pagán, E.; Berdejo, D.; de Carvalho, R.J.; García-Embid, S.; Maggi, F.; Magnani, M.; Evandro de Souza, L.; García-Gonzalo, D.; Pagán, R. Chitosan nanoemulsions of cold-pressed orange essential oil to preserve fruit juices. Int. J. Food Microbiol. 2020, 331, 108786.
  21. Shah, B.; Davidson, P.M.; Zhong, Q. Nanodispersed eugenol has improved antimicrobial activity against Escherichia coli O157: H7 and Listeria monocytogenes in bovine milk. Int. J. Food Microbiol. 2013, 161, 53–59.
  22. Bedoya-Serna, C.M.; Dacanal, G.C.; Fernandes, A.M.; Pinho, S.C. Antifungal activity of nanoemulsions encapsulating oregano (Origanum vulgare) essential oil: In vitro study and application in minas padrão cheese Braz. J. Microbiol. 2018, 49, 929–935.
  23. Zedan, H.; Hosseini, S.M.; Mohammadi, A. The effect of tarragon (Artemisia dracunculus) essential oil and high molecular weight Chitosan on sensory properties and shelf life of yogurt. LWT 2021, 147, 111613.
  24. Muhammad, D.R.A.; Saputro, A.D.; Rottiers, H.; Van de Walle, D.; Dewettinck, K. Physicochemical properties and antioxidant activities of chocolates enriched with engineered cinnamon nanoparticles. Eur. Food Res. Technol. 2018, 244, 1185–1202.
  25. Wang, H.; Guo, L.; Liu, L.; Han, B.; Niu, X. Composite chitosan films prepared using nisin and Perilla frutescense essential oil and their use to extend strawberry shelf life. Food Biosci. 2021, 41, 101037.
  26. Reis, D.R.; Ambrosi, A.; Di Luccio, M. Encapsulated essential oils: A perspective in food preservation. Future Foods 2022, 5, 100126.
  27. Hemmatkhah, F.; Zeynali, F.; Almasi, H. Encapsulated Cumin Seed Essential Oil-Loaded Active Papers: Characterization and Evaluation of the Effect on Quality Attributes of Beef Hamburger. Food Bioproc. Tech. 2020, 13, 533–547.
  28. Pateiro, M.; Barba, F.J.; Domínguez, R.; Sant’Ana, A.S.; Khaneghah, A.M.; Gavahian, M.; Gómez, B.; Lorenzo, J.M. Essential oils as natural additives to prevent oxidation reactions in meat and meat products: A review. Int. Food Res. J. 2018, 113, 156–166.
  29. Tajkarimi, M.M.; Ibrahim, S.A.; Cliver, D.O. Antimicrobial herb and spice compounds in food. Food Control 2010, 21, 1199–1218.
  30. Generally Recognized as Safe, §182.20 Essential Oils, Oleoresins (Solvent-Free), and Natural Extractives (Including Distillates). Available online: https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/cfrsearch.cfm?fr=182.20 (accessed on 10 June 2022).
  31. Bakry, A.M.; Abbas, S.; Ali, B.; Majeed, H.; Abouelwafa, M.Y.; Mousa, A.H.; Liang, L. Microencapsulation of Oils: A Comprehensive Review of Benefits, Techniques, and Applications. Compr. Rev. Food Sci. 2016, 15, 143–182.
  32. Devi, N.; Sarmah, M.; Khatun, B.; Maji, T. Encapsulation of active ingredients in polysaccharide-protein complex coacervates. Adv. Colloid Interface Sci. 2017, 239, 136–145.
  33. Arenas-Jal, M.; Suñé-Negre, J.M.; García-Montoya, E. An overview of microencapsulation in the food industry: Opportunities, challenges, and innovations. Eur. Food Res. Technol. 2020, 246, 1371–1382.
  34. Shishir, M.R.I.; Xie, L.; Sun, C.; Zheng, X.; Chen, W. Advances in micro and nano-encapsulation of bioactive compounds using biopolymer and lipid-based transporters. Trends Food Sci. Technol. 2018, 78, 34–60.
  35. Mohammadalinejhad, S.; Kurek, M. Microencapsulation of Anthocyanins—Critical Review of Techniques and Wall Materials. Appl. Sci. 2021, 11, 3936.
  36. Almas, I.; Innocent, E.; Machumi, F.; Kisinza, W. Chemical composition of essential oils from Eucalyptus globulus and Eucalyptus maculata grown in Tanzania. Sci. Afr. 2021, 12, e00758.
  37. Muhoza, B.; Xia, S.; Wang, X.; Zhang, X.; Li, Y.; Zhang, S. Microencapsulation of essential oils by complex coacervation method: Preparation, thermal stability, release properties and applications. Crit. Rev. Food Sci. Nutr. 2022, 62, 1363–1382.
  38. Hernández-Nava, R.; López-Malo, A.; Palou, E.; Ramírez-Corona, N.; Jiménez-Munguía, M.T. Encapsulation of oregano essential oil (Origanum vulgare) by complex coacervation between gelatin and chia mucilage and its properties after spray drying. Food Hydrocoll. 2020, 109, 106077.
  39. Basu, S.; Banerjee, D.; Chowdhury, R.; Bhattacharya, P. Controlled release of microencapsulated probiotics in food matrix. J. Food Eng. 2018, 238, 61–69.
  40. Tavares, L.; Noreña, Z.; Pelayo, C. Encapsulation of garlic extract using complex coacervation with whey protein isolate and chitosan as wall materials followed by spray drying. Food Hydrocoll. 2018, 89, 360–369.
  41. Tavares, L.; Noreña, C.P.Z. Encapsulation of Ginger Essential Oil Using Complex Coacervation Method: Coacervate Formation, Rheological Property, and Physicochemical Characterization. Food Bioprocess Technol. 2020, 13, 1405–1420.
  42. Weisany, W.; Yousefi, S.; Tahir, N.A.R.; Golestanehzadeh, N.; McClements, D.J.; Adhikari, B.; Ghasemlou, M. Targeted delivery and controlled released of essential oils using nanoencapsulation: A review. Adv. Colloid Interface Sci. 2022, 303, 102655.
  43. Matalanis, A.; Jones, O.G.; McClements, D.J. Structured biopolymer-based delivery systems for encapsulation, protection, and release of lipophilic compounds. Food Hydrocoll. 2011, 25, 1865–1880.
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