Functional Polymeric Plastic for Bakery Products
Subjects: Polymer Science
Contributor: , , , , , , , , , ,

Polymeric materials including plastic and paper are commonly used as packaging for bakery products. The incorporation of active substances produces functional polymers that can effectively retain the quality and safety of packaged products. Polymeric materials can be used to produce a variety of package forms such as film, tray, pouch, rigid container and multilayer film. 

  • functional polymer
  • bakery products
  • antimicrobial
  • bakery packaging
  • active packaging system

1. Introduction

Polymer materials are a vital part of bakery packaging, as seen in Table 1 and Table 2. They play an important role in protecting food, ensuring freshness and modifying barrier properties such as water vapor and oxygen permeability. Polymer materials also influence mechanical properties of tensile strength and elongation at break, while releasing active compounds which inhibit microorganism growth and extend bakery product shelf life. These polymeric materials can be used to make many product forms including film, tray, rigid container, multilayer film and pouch. The active packaging system can involve non-volatile compounds, volatile compounds, edible mixed polymers, coated polymers, active paper and paperboard, oxygen scavenging, and ethanol emitters (Table 1).
Table 1. Functional polymers and packaging technology for bakery products.
Functional Packaging Active Agents Packaging Form Type of Bakery Remarkable Results References
Non-volatile active compounds Zinc oxide nanoparticles Chitosan-carboxymethyl cellulose film Preservative-free soft sliced wheat bread
Coated films had decreased water vapor permeability, maintained higher moisture content, and increased water activity than the control
ZnO 1% and 2% inhibited Aspergillus niger and no mold growth on the bread for 15 days
[36]
Natamycin Chitosan-natamycin vacuum packaged and spraying Phyllo pastry
Chitosan and natamycin preserved sensory attributes for 17 days at 4 °C storage and inhibited Enterococci and Clostridium spp. up to 18 days
[37]
Sodium propionate Polypropylene-sodium propionate film Bread
Enhanced mechanical and thermal stability, increased hydrophilicity
Films showed antimicrobial activity against both Gram-negative and Gram-positive microbials, and bread showed less spoilage by mold on day 7 during storage
[38]
Silver nanoparticles Polyvinyl chloride film Sliced Bread
Ag-nanoparticles 1% inhibited microorganisms in bread for 15 days of storage at 26 °C
Improved the properties of PVC material
[39]
ε-poly-L-lysine (ε-PL) Starch film Bread
Inhibition against A. parasiticus and P. expansum and diminished aflatoxin by more than 93.90% after 7 days of testing
[40]
ZnO nanoparticles Gelatin- polyethylene film Sponge cake
Prevented fungal growth for 28 days and maintained cake chemical and organoleptic quality
[41]
TiO2 Potato starch film Sliced bread
1% TiO2 coating increased water vapor barrier properties and inhibited the growth of Bacillus subtilis and Escherichia coli
[42]
Chitosan Chitosan-PLA film Sliced bread
All modified chitosan nanoparticles (CSNPs) showed capacity to inhibit S. aureus as high as > 98%, improved elongation at break and maintained oxygen permeation ability in a standard range for food packaging
[43]
Sulfur quantum dot Alginate film Bread
Integrated film improved tensile strength by 18%, UV barrier by 82% and antioxidant activity, while maintaining stiffness and WVP; sulfur-based compounds had antibacterial action against L. monocytogenes and E. coli, as well as against fungi such A. niger and P. chrysogenum and delayed the appearance of mold on bread for 14 days
[44]
Sorbate anion Polypropylene bag White bread
The coated film retained organoleptic characteristics, moisture analysis, peroxide evolution and mold count on bread for up to 12 days at ambient temperature and inhibited growth of Escherichia coliPseudomonas aeruginosaSalmonella enterica subsp. Arizona, Staphylococcus aureus and Campylobacter jejuni
[45]
Volatile active compounds Cinnamaldehyde Gliadin films Sliced bread
Highly effective against fungal growth for both in vitro and food packing systems; cinnamaldehyde volatility from the solution forming film inhibited activity of P. expansum and A. niger over 10 days
[25]
Oregano essential oil Nonwoven tissue/polypropylene-based sachet Preservative-free sliced bread
Inhibited the growth of E. coliSalmonella Enteritidis and Penicillium sp., bread texture increased with storage time, but sachets had no effect; higher OEO concentration imparted unpleasant sensory effects (bitter taste and strong odor)
[46]
Apricot kernel essential oil Chitosan film Sliced bread
The blended film decreased WVP, lower solubility and moisture content enhanced tensile strength and scavenging activity for both H2O2 and DPPH
Delayed bacterial growth as Bacillus subtilis and Escherichia coli protected against fungal growth of sliced bread within the packaging on day 10
[47]
Grapefruit seed extract/Chitosan Poly(ε-caprolactone)/chitosan film Preservative-free bread
Grapefruit seed extract incorporation led to increased pits on the film surface but there was no mold growth on packaged bread with film containing ≥ 1.0 mL/g grapefruit seed extract after 7 days
[48]
trans-cinnamaldehyde PLA/PBAT film Bread
Increased trans-cinnamaldehyde contributed to reduced barrier properties and decreased mechanical properties due to plasticization and pores embedded in films
Films with trans-cinnamaldehyde from 2% and above effectively inhibited the microbial growth of bacteria and fungi for more than 21 days at 30 °C
[24]
Eugenol and citral Corn starch microcapsule sachet Sliced bread
The EOs-containing sachets were effective in inhibiting the growth of molds and yeasts in media and sliced bread without affecting the sensory properties of bread
[49]
Thymol PLA/PBSA film Preservative-free bread
Effective against fungal growth up to 9 days and improved thermal and barrier properties as well as decreased glass transition temperature, melting temperature and crystallinity
Thymol decreased the permeability of water vapor, oxygen and carbon dioxide, tensile strength and Young’s modulus but increased elongation at break
[50]
Sorbitol/Grapefruit seed extract Corn starch-chitosan film Bread
Inhibition against A. niger and extended bread shelf life up to 20 days at 25 °C and 59% RH
Had low moisture content, water vapor permeability, solubility, high tensile strength and high antifungal activity
[51]
Cymbopogon citratus essential oil Cashew gum-gelatin film Bread
The incorporated film extended shelf life to 6 days compared with the control at only 3 days
[52]
Carvacrol PLA/PBAT film Preservative-free bread
PLA/PBAT blend ratio controlled the strength, permeability and release behavior of carvacrol
Film showed delayed fungal growth and sporulation of Penicillium sp. and Rhizopus sp. with 2.0–2.3 times increased shelf life
[53]
Cinnamon oil Natural rubber pressure-sensitive adhesive patch Banana cake
NR-PSA/CO patch delayed the growth of bacterial and fungal strains as Escherichia coliStaphylococcus aureusAspergillus niger with extension of the 4-day shelf life
[54]
Piper betel Linn extract Poly (vinyl alcohol) film Sliced bread
Films had high UV blocking and antimicrobial efficiency
Inhibition against bacteria such as E. coliS. typhimuriumS. aureus and P. aeruginosa with 3% of extract concentration and preserved bread quality for 45 days at room temperature
[55]
Cinnamaldehyde
Limonene
Eugenol
Fish gelatin-based nanofiber mat Bread
The incorporated mat had radical scavenging activity, ferric reducing antioxidant power and better encapsulation with the electrospinning method
Inhibited the growth of E. coliS. aureus and A. niger
There was no fungal spot on bread antimicrobial packing
[56]
Thyme essential oil Poly (3-hydroxybutyrate-co-4-hydroxybutyrate) film White bread
Films containing 30% v/w of thyme essential oils extended the shelf life of bread up to 5 days depending on visible mold growth observation
Films enhanced both water vapor permeability and elongation at break
[57]
Schiff base PLA film Bread
Delayed growth of fungi on bread slices to day 5 compared with the control at day 3
Films also killed the bacteria plasma membrane as an inhibition zone
[58]
Functional paper and paperboard PLA Coated paperboard -
PLA-coated paperboards improved water barrier properties through decreasing water vapor permeability and increase in water contact angle
[59]
Vanillin with dimethyl sulfoxide, ethyl alcohol, and chitosan Coated paper -
Each coating successfully inhibited growth of bacteria; however, efficiency varied depending on mixture concentration
[60]
Wax Coated paper Milk cake
Maintained sensory acceptability up to 21 days because the coated paper minimized moisture loss from milk cake
[61]
Cinnamon essential oil Coated paper -
Significantly reduced mold growth by direct migration in packaging and demonstrated resistance to Rhizopusstolonifer growth at 4% concentration
[62]
Ag/TiO2-SiO2, Ag/N-TiO2, or Au/TiO2 Paper modification “Pave” bread
Characteristics of the paper including busting, tensile, tearing and breaking resistance decreased as the composite content increased.
Increased whiteness of the paper
Ag/TiO2-SiO2-paper and Ag/N-TiO2-paper extended bread shelf life by more than 2 days compared to unmodified paper in both ambient and refrigeration conditions by offering an efficient control on acidity and yeast and mold growth; Au/TiO2 had no influence on shelf-life extension indicating that nano-Ag had preservation activity and photoactivity
[63]
Chitosan Coating paper -
Coating increased the glossiness of paper as the chitosan filled surface porosity and improved moisture resistance, mechanical characteristics and flexibility
[64]
TiO2
Ag-TiO2
Ag-TiO2-zeolite
Bleached paper Bread
Improved barrier properties such as air permeability, water vapor permeability and reduced grease permeation
Bread packed in Ag-TiO2 paper had an extended shelf life for 2 more days than the control package based on yeast and mold growth
[65]
Nano-carbon Wrapping paper Brownie cake
Activated carbon-modified bamboo wrapping paper preserved nutrients in food and specifically reduced the level of microbial contamination on brownie cake
[66]
Blending of alginate, carboxymethyl cellulose, carrageenan, and grapefruit seed extract Coated paper Mined fish cake
The biopolymer coating improved water and grease resistance, surface hydrophobicity and tensile properties of paper
Coated paper showed strong antimicrobial activity against L. monocytogenes and E. coli
[67]
Chitosan/Ag/TiO2 Coated paper Clarified butter
Coated paper had better opacity values, reduced water vapor and oxygen permeabilities and decreased oil permeability
Inhibition against E. coli at 70.36% on an agar plate and 73.28% in butter samples, as well as against yeasts and molds at 77.02% on an agar plate and 79.28% in butter samples
After six months, the peroxide value increased 6.47-fold with P-CH-Ag/TiO2 compared to uncoated at 36.71-fold
[68]
Starch, NaCl, Aquaseal Paper bag Bread
Relative humidity (RH) of sandwich paper rose to 72% and enhanced bread sensory quality and freshness up to 72 h of storage, extending the shelf life
[69]
Geraniol Paper sachet Sliced bread
PBS/geraniol-10% exhibited inhibition against Escherichia coli and Bacillus cereus with degradation of white bread with total plate count, yeasts, and mold count on day 42 with an antimicrobial sachet, whereas no fungus was spotted on white bread surface preserved with an antimicrobial sachet for the entire 63-day test period
[70]
Schiff base
PLA
Kraft paper coating Bread
Paper properties showed increased smoothness, maintained heat-sealing strength, decreased air porosity value and higher oil-grease resistance
[58]
Edible and non-edible coating Lactobacillus acidophilus Edible starch/probiotic coating Bread
Probiotic coating technique obtained microencapsulation of Lactobacillus acidophilus and starch-based material coated onto surface of baked breads resulting in better protection on bread crust and sensory acceptability
[71]
Ag/TiO2 nanocomposite HDPE film White bread
Bread stored in Ag/TiO2-based packaging inhibited proliferation of yeast/molds, Bacillus cereus and Bacillus subtilis due to scavenging more water and oxygen molecules in the packaging headspace
[72]
Potassium sorbate and citric acid Potato starch, inverted sugar, sucrose coating solution Mini panettones
Panettones with an edible coating containing both additives showed fungal growth from 40 days, and with 1 g/kg potassium sorbate only, yeast and mold growth were not detected until 48 days
During storage, there was reduced water activity, moisture, elasticity and cohesiveness of panettones with additives, whereas the reverse occurred in the controls
[73]
Triticale flour Edible coating and spraying Muffin
Triticale film coating worked well to prolong the staling process, keeping the fresh muffins softer during 10 days of storage because of delaying crumb-firming kinetics
[74]
Star anise essential oil and thymol PP/SAEO/PET/TH/LDPE film Preservative-free sliced wheat bread
Insect repellent activity sustained the bread for up to 23 days and prevented antimicrobial growth for 14 days; the developed film had low tensile strength and elastic modulus
[75]
Garlic extract and Bread aroma Coating on PE film Preservative-free sliced pan loaf
PE film coated with zein containing 0.5% garlic extract and bread aroma maintained bread free of mold growth for 30 days
[76]
Lactic acid bacteria Edible lactic acid bacteria coating Wheat bread
Coating with Streptococcus salivarius subsp. thermophilus, Lactobacillus delbrueckii subsp. Bulgaricus, Lactobacillus acidophilus, sodium alginate, whey and glycerol had the best protective properties against microbial spoilage
Incorporation of lactic acid bacteria in a coating containing alginate ensured good viability for 120 h
Coating diminished A. niger and P. chrysogenum in wheat bread
[77]
Okra mucilage Edible okra mucilage gum surface coating Biscuit
Coated biscuits were preserved from deterioration and microbial spoilage with improved moisture barrier quality
[78]
Absorber/
Emitter
Iron-based oxygen absorber Sachet (FreshPax®) Cracker
Prevented oxidation and extended the shelf life of military ration crackers packaged in hermetically sealed tin cans for 44 weeks
[79]
Oxygen absorber and ethanol emitter Sachet Wheat bread
Ethanol emitter increased the shelf life of bread by up to 24 days based on sensory and microbiological formation, and by up to 30 days when both ethanol emitters and oxygen absorbers were used
[80]
Iron-based oxygen scavenger sachets Sachet Sliced wheat bread
Maintained wheat bread quality for up to 7 days of storage
[81]
Ethanol emitter Sachet Ciabatta bread
Ethanol emitter extended shelf life to 16 days while maintaining acceptable microbiological quality, whereas the usage of ethanol spray revealed no effect on product sensorial properties
[82]
Oxygen absorber and ethanol emitter Sachet Chinese steamed bread
The shelf life of Chinese steamed bread with an oxygen absorber and 1 v% ethanol emitter was extended by up to 11 days
[83]
Oxygen scavenger and ethanol emitter Pouch Sponge cake
The oxygen scavenger and ethanol emitter have high barrier packaging and extended shelf life of sponge cake to at least 42 days by delaying lipid oxidation, color change, cake hardening, and microbial growth
[84]
Oxygen absorber Nylon/LLDPE/cast polypropylene film Preservative-free Chinese pastry (kha-nom pia)
Nylon/CPP film retarded microbial growth better than Nylon/LLDPE and extended shelf life up to 25 days
Hardness of crust and firmness of filling decreased during storage
Oxygen absorber effectively inhibited the growth of total microbial count and yeasts and molds, with no visible mold appearing on the pastries
[85]
Iron-based oxygen scavenger Sachet Preservative-free white bread
The oxygen scavenging sachet’s shelf life lasted for only 4 days
Bread shelf life was prolonged up to 5–7 days with a low initial oxygen level of 5% by volume
When packaging film possesses a high oxygen barrier, an oxygen scavenger is unnecessary
[86]
Vacuum conditioning Bag Chinese steamed bread
Thermal–vacuum packaging kept a higher water content and a longer shelf life, and maintained good taste with lower retrogradation rate of the bread
[87]
Iron based oxygen absorbers Bag Sourdough sliced bread
The most effective application was the high-capacity oxygen absorber combined with 100% N2, giving 12 days of a shelf life
With 50% CO2 + 50% N2, oxygen conc. increased above 2% due to the trapped O2 in the pores of bread and had a shelf life of only 3 days
Atmospheric conditions prolonged the shelf life for 6 days
[88]
Oxygen scavenging compound—pyrogallol Film -
Adding the films to the package contributed to lowering oxygen levels in the package headspace for storage at 4, 25, and 50 °C
The maximum oxygen absorption capacity of pyrogallol-incorporated films was 23.0 mL O2/g films
[22]
Ethanol emitter, Oxygen absorber
Moisture absorber
Sachet Refined wheat bread (RWF) and Whole wheat bread (WWF)
Bread packed in a combination of ethanol emitter, oxygen absorber and moisture absorber inhibited growth of microbes effectively. Maximum shelf lives of RWF and WWF were 16 and 8 days, respectively
[89]
Palladium-based oxygen scavenger Film Par-baked bun and toast bread
Scavenger reduced initial oxygen concentration in the headspace from 21% to 2% but was still insufficient to extend the mold-free shelf life
CO2 modification in the packaging system extended shelf life to 10–12 days
[90]
Pyrogallic acid LDPE/sodium carbonate film Fish cake
Pyrogallic acid as oxygen scavenging coated on LDPE-based film showed stabilized fish cake quality by improving oxidation properties and inhibiting microbial growth during storage period of 30 days
[91]
Table 2. Previous recent patents related to packaging technology for bakery products.
Materials and Components Packaging Form Package Conversion Technology Bakery Key Technology Results References
  • Rigid container
  • Oxygen scavenger and indicator
Oxygen detection system Rigid container with an oxygen detection system Bakery products
  • A rigid container comprising:
    (a)
    An oxygen barrier having an oxygen transmission rate of no more than 100 cc/m2/24 h at 25 °C, 0% RH, 1 atm;
    (b)
    An oxygen scavenger;
    (c)
    An oxygen indicator comprising a luminescent compound wherein the oxygen indicator and oxygen scavenger are substantially shielded by oxygen barriers from environmental air.
  • A rigid container with oxygen barrier properties
  • Can measure oxygen concentration within the headspace of an assembled package
  • Indicates oxygen level with luminescent compound
[92]
  • PET
  • Indium tin oxide
  • Aluminum
  • Silicone-based
  • Chrome complex
  • Wax
Absorbent sheet Absorbent structure compression Bakery products
  • A structure having absorbent and microwave interactive properties containing:
    (a)
    A polymer film: PET, indium tin oxide and aluminum;
    (b)
    A layer of microwave energy interactive material: indium tin oxide and aluminum;
    (c)
    A liquid-absorbing layer;
    (d)
    A liquid-impervious material;
    (e)
    A release coating overlying silicone-based material, chrome complex, wax, or any combination thereof
  • The absorbent sheet had a non-stick food-contacting surface
  • The absorbent sheet can be incorporated into or used with a tray and formed into a roll of absorbent material comprising at least two overlapping absorbent sheets
[93]
  • Paper or paperboard
  • Polymer emulsion
  • Pigment
Coated paper or paperboard Paper or paperboard is coated with a polymer emulsion in one or more coating Bakery products
  • A method of producing a coated recyclable paper or paperboard comprising:
    (a)
    Polymer emulsion (acrylic emulsion, or styrenebutadiene emulsion) 70–90% dry weight, pigment (grade clays, titanium dioxide, calcium carbonate, barium sulfate, talc, zinc sulfate, aluminum sulfate, calcium oxide, lithopone, zinc sulfide, and mixture thereof) 10–30% dry weight;
    (b)
    Applying an aqueous coating layer;
    (c)
    Drying the coating;
    (d)
    Cooling the coated paper or paperboard
  • Coated paper or paperboard had improved barrier properties including water resistance of less than 10 g/m2, moisture vapor transfer rate of less than 120 g/m2 and was heat sealable.
[94]
  • Bimodal ethylene
  • 1-butylene
  • C6–C12-alpha-olefin terpolymer
  • LDPE
  • Metallocene-produced
Multilayer film
  • Polymerization
  • Coextruded multilayer film
Frozen food packaging
Bakery product
  • The multilayer film comprised a core layer and two outer layers (O-1, O-2)
    (a)
    Core layer: bimodal ethylene/1-butylene/C6-C12-alpha-olefin terpolymer
    (b)
    Outer layer (O-1): bimodal terpolymer, LDPE, or LLDPE, metallocene-produced
    (c)
    Outer layer (O-2): LDPE, or LLDPE, metallocene-produced
  • The Material had excellent mechanical properties, such as stiffness, toughness, and processability and was suitable for co-extrusion processes
[95]
  • LDPE
  • EVOH
  • Acrylic coating
  • Mustard oil
Coated film Multilayers include coating Gluten-free bread
  • Antifungal active container comprising a high-barrier co-extruded three-layer film with an outer polymeric layer of LDPE, an intermediate polymeric layer of EVOH and an inner polymeric layer of LDPE which carried or incorporated mustard oil
  • Bread samples lasted for 30 days without any fungal growth visible on the surface, whereas the control samples developed a bad taste due to retrogradation of starch
[96]
  • Polyolefin
  • LDPE
  • PVOH
  • Carvacrol
  • Allyl-isothiocyanate (AITC)
Film Coating film Sliced bread
  • Antifungal packaging comprising a polyolefin with a water-soluble polymer coating as a synergistic mixture of volatile natural compounds selected from carvacrol and allyl-isothiocyanate for extending the shelf life of bakery products
  • PVOH had sufficient coating functional properties, showing high uniformity and adhesion to PE, whereas the combination of carvacrol and AITC showed enhanced antifungal activity against the main fungi responsible for damage and spoilage of sliced bread: Aspergillus niger and Penicillium
[97]

2. Non-Volatile Active Ingredients

Numerous natural and synthetic ingredients have been incorporated into conventional and biodegradable plastic polymers to produce functional polymers for active packaging. The antimicrobial and antioxidant capacities of these functional polymers depend on several factors, e.g., release behavior, interaction between polymers and ingredients, and morphology of the matrices. Recent applications of these functional polymers are shown in Table 1. To increase the safety and quality of mini panettones, Ferreira et al. (2016) [73] modified citric acid and sorbate potassium by incorporating with edible coating solution, either separately or in combination, to increase shelf life of mini panettone by three times compared to the control. Thanakkasaranee et al. (2018) [38] found that a film made of polypropylene and sodium propionate with a concentration range of 0.5 to 5% enhanced mechanical properties and thermal stability, while increasing hydrophilicity, and demonstrated antimicrobial activity against both Gram-negative and Gram-positive microbes. Packed bread also showed less mold spoilage on day 7 of storage. Tsiraki et al. (2018) [37] investigated a combination of chitosan and natamycin as an effective antifungal agent that delayed the deterioration of phyllo pastry while preserving the basic freshness, look and acceptable sensory properties of the product. Vacuum packing with chitosan and natamycin prolonged the sensory shelf life by 11 days, and microbiological data showed that mesophilic total viable counts, yeasts and molds, psychotropic bacteria, lactic acid bacteria, Enterobacteriaceae and enterococci of 1 to 3 log CFU/g on the last day were the most prevalent microorganisms (day 18). Kongkaoroptham et al. (2021) [43] determined that PLA packaging films containing chitosan nanoparticles with polyethylene glycol methyl ether methacrylate (PEGMA) inhibited the growth of natural microorganisms on bread slices. All modified chitosan nanoparticles (CSNPs) showed capacity to inhibit S. aureus as high as > 98%, improved elongation at break and oxygen permeation ability in a standard range for food packaging. Sulfur quantum dots (5.3 nm, aqueous suspension) were used by Riahi et al. (2022) [44] in alginate-based multifunctional films for bread packaging. The integrated film revealed tensile strength improvement of 18%, UV barrier property at 82% and antioxidant activity. Film stiffness and water vapor permeability were unaffected. Sulfur-based compounds had antibacterial action against L. monocytogenes and E. coli, as well as against fungi such as A. niger and P. chrysogenum. These delayed the appearance of mold on bread for 14 days. The nanosulfur mechanism disrupted metabolic activities by interacting with the target molecules in the microbial cell wall and altering cellular signals. Furthermore, the reactive oxygen species produced by nanosulfur interacted with and weakened the cell walls of microorganisms, causing cell lysis and death. Another mechanism involved the reaction of sulfur nanoparticles inside bacterial cells under acidic conditions, which interfered with cellular component breakdown or prevented DNA replication. Nanosulfur disrupts enzyme SH capabilities that are required for the metabolism of proteins, lipids, and carbohydrates. This results in the breakdown of cellular machinery and cell death [44].
Bio-based polymers, including starch, PBAT, and PLA, showed a high potential to produce biodegradable sustainable packaging [98,99,100]. Likewise, Huntrakul et al. (2020) [101] successfully combined edible heat-sealed acetylated cassava starch with pea protein isolated sachets, demonstrating effective protection for soybean and olive oil stored for up to three months. Pea protein improves interaction between the polymer and glycerol and effectively prevents humidity-induced film shrinkage. To extend the shelf life of bread, Luz et al. (2018) [40] investigated the effects of ε-poly-L-lysine (ε-PL) integrated with a starch-based biofilm as an antifungal agent. They found that ε-PL inhibited growth and showed antifungal efficacy against A. parasiticus and P. expansumA. parasiticus, the developer of aflatoxin, was also controlled by ε-PL incorporation and diminished aflatoxin by more than 93.90% after 7 days of testing. Sliced bread was packaged in film-forming packaging that contained nanodispersed titanium dioxide (TiO2) by Shulga et al. (2021) [42]. Results revealed that 1% TiO2 coating increased water vapor barrier properties and inhibited the growth of Bacillus subtilis and Escherichia coli. Viscusi et al. (2021) [45] studied polypropylene film coated with dispersed anionic clay to host sorbate for white bread packaging. The coated film retained organoleptic characteristics, moisture analysis, peroxide evolution and mold count on the bread for up to 12 days at ambient temperature. Moreover, this active packaging inhibited the growth of Escherichia coliPseudomonas aeruginosaSalmonella enterica subsp. ArizonaStaphylococcus aureus, and Campylobacter jejuni. Braga et al. (2018) [39] combined polyvinyl chloride (PVC) and silver nanoparticles as an active film for bread packaging. The PVC characteristics of the film were enhanced, and 1% Ag-nanoparticles suppressed the growth of microbes in bread stored at 26 °C for 15 days. Diffusion inhibited against B. subtilisA. niger, and F. solani growth. However, the utilization of nanoparticles for packaging in the food industry requires safety assessments to ensure compliance with regional and global regulations [102].

3. Volatile Active Ingredients

Volatiles and essential oils are compounds that contribute to characteristic flavors and aromas of food products such as fruits, vegetables, herbs, and spices. These compounds mainly comprise terpenes, alcohols, aldehydes, ketones, terpenoids and apocarotenoids [103]. Natural and synthetic volatile compounds have been incorporated into plastic polymers and used for bakery packaging, as shown in Table 1. Likewise, for white pan bread and butter cake, Klinmalai et al. (2021) [53] noted how this food, when packed in blown-film extrusion of PLA/PBAT integrated with carvacrol essential oils (0, 2 and 5%), showed delayed Penicillium sp. and Rhizopus sp. growth and sporulation by film containing 2 and 5% carvacrol, with the shelf life extended by up to 4 days. PLA/PBAT blend films with plasticized carvacrol functionalization prevented growth of mold in baked products. Sharma et al. (2022) [57] studied the bacterial-based biopolymer, poly (3-hydroxybutyrate-co-4-hydroxybutyrate) or P(3HB-co-4HB) incorporating thyme essential oil as active packaging for white bread shelf life extension. Shelf life was extended up to 5 days compared with 1–4 days for the neat film, with improved film elongation at break and water vapor permeability. Passarinho et al. (2014) [46] developed an antimicrobial sachet containing oregano essential oil that acted against yeasts, mold, and Escherichia coli, Salmonella Enteritidis and Penicillium sp. on sliced bread. During storage, γ-terpenes and φ-cymene inhibited yeast and mold growth on bread slices. Ju et al. (2020) [49] discovered that a mixture of essential oils eugenol and citral (1:1) in corn starch microcapsule sachets decreased molds and yeasts from 100% to 56% at 25 °C and from 90% to 26% at 35 °C of storage conditions. Furthermore, the use of essential oils in sachets had minimal effect on the smell or taste of the bread. Sliced bread packed in LDPE, PP and HDPE bags containing the same essential oil sachets did not develop mold until day 16, 14, and 14, respectively. Mahmood et al. (2022) [56] used electrospinning techniques to produce fish-gelatin-based nanofiber mats embedded with cinnamaldehyde (CEO), limonene (LEO), and eugenol (EEO) at 1, 3, and 5% for bread packaging improvement. Results showed that all essential oils had radical scavenging activity such as CEO = 73.50%, LEO = 51.20%, and EEO = 89.37%, which was the highest at 5% concentration, whereas they also showed ferric-reducing antioxidant power and improved encapsulation with the electrospinning method. They also inhibited the growth of E. coliS. aureus and A. niger because the gelatin-based mats had good release of essential oils, with no fungal spots on bread antimicrobial packing. Balaguer et al. (2013) [25] developed gliadin films incorporating cinnamaldehyde that were highly effective against fungal growth both in vitro and in food packing systems. Cinnamaldehyde volatility from the solution forming film inhibited the activity of P. expansum and A. niger over 10 days. Similarly, Fasihi et al. (2019) [104] used the Pickering stabilization method to enrich cinnamon essential oil (CEO) and carboxymethyl cellulose (CMC)–polyvinyl alcohol (PVA) in the solution-forming film and bread coating to increase the anti-UV properties and antifungal properties to prolong bread shelf life. Pickering stabilization impacted CEO by several mechanisms including (i) the generation of a uniform and regular structure of dispersed phase throughout the film matrix leading to increased contact between CEO and fungi, (ii) controlled and regular release of CEO from the film to the outside, which maintained sufficient antimicrobial and antioxidant agents in the headspace, and (iii) protection of CEO from oxidation against undesirable external effects that increased its efficiency as an active compound. PLA and PBAT blend films containing trans-cinnamaldehyde were studied by Srisa and Harnkarnsujarit (2020) [24]. Results showed increased water vapor and oxygen permeability because blending of PBAT/PLA reduced the orientation and non-homogeneity of the network formation. Volatility was higher at increased cinnamaldehyde concentration, and different blending ratios of the film released compounds and inhibited the growth of Aspergillus niger and Penicillium sp., effectively inhibiting microorganism growth for up to 21 days at 30 °C with slightly affected organoleptic properties of cinnamaldehyde taint at 5% concentration. Songtipya et al. (2021) [54] designed a patch that combined natural rubber pressure-sensitive adhesive and cinnamon oil for banana cake packaging. The NR-PSA/CO patch delayed the growth of bacterial and fungal strains of Escherichia coliStaphylococcus aureus and Aspergillus niger with further extension of the 4-day shelf life. Cashew gum and gelatin were combined with ferulic acid and lemon grass essential oil by Oliveira et al. (2020) [52] to develop a casting film that showed increased water vapor permeability, decreased solubility and enhanced mechanical characteristics. The incorporated film also prevented the formation of mold for up to 7 days of storage, but the barrier properties of the film were limited, and bread was harder than commercial packaging (PE). Priyadarshi et al. (2018) [47] produced chitosan (CA) film integrated with apricot kernel essential oil (AKEO) for sliced bread packaging. The blended film increased water vapor barrier performance by up to 41%, with a solubility of only 4.76% and a moisture content of 8.33% compared to the control film of 18.42%, and 16.21%, respectively. This film had enhanced tensile strength and scavenging activity with both H2O2 and DPPH tests. Moreover, it delayed the bacterial development of Bacillus subtilis and Escherichia coli and protected sliced bread against fungal growth within the packaging on day 10 with a low concentration ratio of essential oil of 1:0.125 (CA:AKEO) film. Bui et al. (2021) [55] produced a blended film of poly (vinyl alcohol) and Piper betel Linn. leaf extract to extend bread shelf life. The film showed high UV blocking and antimicrobial efficiency, with inhibitory efficacy against E. coliS. typhimuriumS. aureus and P. aeruginosa at 3% of extract concentration. Moreover, bread quality was preserved for 45 days at room temperature. Jha (2020) [51] produced bio-nanocomposite films based on corn starch chitosan with plasticizer sorbitol and grapefruit seed extract. The film showed maximum inhibition zone against A. niger and extended bread shelf life up to 20 days at 25 ℃ and 59% RH because it had low moisture content, water vapor permeability, solubility, high tensile strength, and high antifungal activity.
Furthermore, based on patents in Table 2, Carolina et al. (2022) [97] found that antifungal packaging comprising a polyolefin with a water-soluble polymer coating such as PVOH with a synergistic mixture of volatile natural compounds selected from carvacrol and allyl-isothiocyanate showed enhanced antifungal activity against the main fungi responsible for damage and spoilage of sliced bread such as A. niger and Penicillium. Bread samples packed in multilayers and coated with a film of LDPE, EVOH, acrylic coating, and mustard oil as an active essential oil showed improved storage for 30 days without any visible fungal growth on the surface of gluten-free bread [96].

This entry is adapted from 10.3390/polym14183793

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