# Sustainability in Bio-Based Edible Films, Coatings, and Packaging for Small Fruits
## 5 Edible Film and Coating Functionalities Important for the Small Fruit Industry
### Bioactivity of the Edible Films and Coatings
#### 5.1.1 Antimicrobial Properties
Antimicrobial activity was also confirmed for films made from some proteins, such as casein or hydrolysates of milk proteins [158], and lipids, e.g., candellilla wax [159]. Very often, edible coatings are a composition of two or more polymers mixed in various proportions. Such a solution not only modifies the physicochemical properties of the obtained coatings but, at the same time, can enhance biological properties, including antimicrobial ones [160]. [PERSON] et al. [161] demonstrated that blends of triazole betaine chitosan (TBC) with succinyl chitosan sodium salt (SC-Na) significantly increased antibacterial properties compared to SC-Na alone. A better effect for _E.coli_ (Gram-) than _S. aureus_ (Gram+) was observed. Gram-positive bacteria are more susceptible to antibacterial compounds than Gram-negative, which have a less permeable, lipid-based outer membrane [162]. Biologically active compounds are added to the film-forming solutions to enhance the antimicrobial properties of edible films and coatings. These can be typical preservatives, such as potassium sorbate or benzoic acid. They can be bacteriocins but are often very effective; they are essential oils with well-documented antimicrobial activity. Natural and safe antimicrobial agents from the crucial oil group include thymol, carvacrol, eugenol, cinnamaldehyde, rosmears, and citral. Strong antimicrobial properties were demonstrated by the essential oil of carvacrol and cinnamic aldehyde added to the edible film. Similarly, adding lemon and bergamot essential oil as an antimicrobial agent to the coating based on whey protein isolate with glycerol as a plasticizer effectively combats Escherichia coli and Staphylococcus aureus [162]. A film-forming mixture of chitosan and quinoa proteins  
Figure 5: Schematic representation of antimicrobial agents used in the production of edible coatings. enriched with thymol oil used as a coating on blueberries showed strong antimicrobial properties against _Salmonella_ Typhimuriumurium, _Staphylococcus aureus_, and _Listeria innocua_[129]. The level of antimicrobial activity was increased by adding essential oils from lemongrass, mint [163], or Chinese orange [164] to the films. Antifungal activity was effectively increased by incorporating edible coatings based on pectin with lemon oil [158] or whey protein-based film with cinnamon essential oil addition [141]. Coatings based on gum Arabic, carrageenan, and xanthan with lemongrass essential oil significantly reduced yeast and mold count compared to uncoated strawberries during storage [165]. Coatings containing Argentine propolis extract applied to raspberry fruits showed strong antifungal properties [135]. More and more often, metabolites of lactic acid bacteria are used as antimicrobial agents added to film-forming solutions. They are natural probiotics and antagonists of pathogenic microflora. These metabolites include, among others, bacteriocins or bacteriocin-like inhibitory substances, i.e., proteins or peptides with documented antibacterial properties, such as nisin, pediocin, lacticin, and entercin. They can also be antifungal compounds, e.g., propionate, phenyl acetate, or cyclic dipeptides. Similarly, organic acids (benzoic, sorbic), some fatty acids, hydrogen peroxide, or diacetyl, formed in lactic fermentation, can effectively inhibit the development of harmful microorganisms [125]. A promising addition to edible coatings used to protect berries against microorganisms are various plant extracts containing biologically active compounds with a diverse chemical structure. [PERSON] et al. [130] showed that blueberry leaf extract (BLE) showed a significant effectivity against _E. coli_ and _S. aureus_ with an inhibition zone \(>\)7.5 mm. Blueberries coated with chitosan enriched with 8-12% BLE lower the decay rate of fruit during extended storage compared to uncoated control [130].