Authors Sahar Seyedzade Hashemi1, Nasim Khorshidian* and Mehrdad Mohammadi*
addition of probiotics to edible films and coatings is an alternative approach for direct application in food matrices that enhances their stability and functional properties. Also, it has been noted that the influence of probiotics on the film properties was dependent on the composition, biopolymer structure, and intermolecular interactions. Recently, the incorporation of probiotics along with prebiotic compounds such as inulin, starch, fructooligosaccharide, polydextrose and wheat dextrin has emerged as new bioactive packaging. The simultaneous application of probiotics and prebiotics improved the viability of probiotic strains and elevated their colonization in the intestinal tract and provided health benefits to humans. Moreover, prebiotics created a uniform and compact structure by filling the spaces within the polymer matrix and increased opacity of edible films. The effects of prebiotics on mechanical and barrier properties of edible films were dependent on the nature of prebiotic compounds, Probiotics are extensively incorporated into functional food products such as dairy, cereal, meat, fruits and vegetable-based products, which exhibit health benefits and techno-functional properties. It has been revealed that the presence of non-digestible carbohydrates or prebiotics can improve the stability and viability of probiotics in food products and the gastrointestinal tract in addition to their beneficial effects on human health. The combination of probiotics and prebiotics is known as synbiotic, in which the prebiotic component enhances the probiotics’ growth and survival, A unique approach can be inserting probiotics in a plasticized thin layer of a natural polymer called edible film, Biopolymer packaging is an eco-friendly system that prevents food deterioration and enhances its quality by protecting against gases and moisture, Also, due to the antimicrobial capacity of probiotic bacteria, they may be employed as an alternative strategy to control pathogenic microorganisms . To enhance probiotics viability, prebiotic compounds have been incorporated into film-forming solutions. It has been declared that prebiotics remarkably boosted the probiotic viability during storage and in simulated gastrointestinal conditions. It has also been reported that symbiotic edible films and coatings positively influenced the microbial and physicochemical quality of the food product, Probiotics are live microorganisms which exhibit health advantages to the host at a specific concentration. Most of the microorganisms currently used as probiotics belong to species of the genera Lactobacillus and Bifidobacterium, but several other genera such as Enterococcus, Pediococcus, Bacillus, Streptococcus, Lactococcus, Bacteroides, Akkermansia, Propionibacterium and Saccharomyces are also considered probiotics. The microorganisms must meet some criteria to be categorized as probiotic such as antimicrobial activity against pathogenic bacteria, resistance to gastric and bile acid, adherence to mucus or human epithelial cells, and ability to alleviate pathogen adhesion to surfaces and bile salt hydrolase activity. Probiotics are generally recognized as safe (GRAS) and provide diverse health benefits, including modulation of the immune system, balancing the intestinal microflora, reduction of cholesterol level and lactose intolerance, production of bioactive compounds (bacteriocins, short-chain fatty acids, B-vitamins, vitamin K2 and enzymes), increasing the bioavailability of nutrients, protection against pathogenic bacteria and different diseases. The main mechanisms involved in beneficial health effects of probiotics include antagonistic effects via generation of antimicrobial substances, competition with pathogens for nutrients and binding sites, immunomodulatory effects and prevention of toxin production by bacteria, Prebiotics are non-digestible carbohydrates that promote the growth of some special microorganisms in the gut. Some sources of prebiotics include fruits and vegetables, soybean, grains, artichoke, chicory and yacon roots. The most common prebiotics are fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS), and trans-galacto-oligosaccharides. Nowadays, polyunsaturated fatty acids and polyphenols are also considered prebiotics because they are selectively used by the host microbiome and have presented potential health benefits (41). Prebiotics help the absorption of minerals, preserve the integrity of the intestinal epithelial layer, increase resistance against pathogenic colonization and decrease the risk of large intestine cancer). The design of prebiotic food not only improves the probiotic viability, but also targets the production of value-added foods. The word symbiotic describes a product consisting of probiotics and prebiotics and implies synergism. This term should be applied to products in which the prebiotic compounds selectively enhance the viability of probiotics. The synergistic combination of prebiotics with probiotics beneficially influences the host by improving the survival and administration of live microbial dietary supplements in the GI tract. It is pointed out that symbiotic has greater health-promoting properties than probiotics and prebiotics individually, Food packaging provides a hindrance against deterioration, dehydration, loss of flavor, appearance and nutritional value during handling, storage, and transportation of foods, applying edible and biodegradable packaging systems (film/coating) as sustainable food packaging is a topic of considerable attraction (48). The materials used in preparation of edible packaging are renewable, recyclable, easily degradable and require minimal or no need of disposal, Edible packaging is described as a film or coating made of food-grade materials and is applied for enrobing different food products to improve their quality and prolong the shelf life, although the terms film and coating are used interchangeably, they indicate different concepts. Films are usually used as a thin layer of cover or wrap, whereas coatings are directly formed on the product’s surface. Edible films and coatings should provide enough mechanical strength to keep the integrity of the products and reduce moisture loss while selectively permitting for controlled exchange of essential gases, such as carbon dioxide, oxygen, and ethylene, which are involved in respiration processes to keep the quality of products. Edible packaging has received several applications since it has the benefits of being consumed together with the food and do not require to be removed. Edible films and coatings can delay the deterioration of highly perishable foods and elevate their quality. The application of edible coatings in fruits can reduce postharvest loss, thus keeping humidity, providing brightness, controlling postharvest pathogens and decreasing respiration and transpiration rates, It has been reported that edible coating restricted lipid oxidation and microbial spoilage of meat, poultry, and seafood. In the case of dairy products, edible packaging control the ripening process, prevent mass transfer and improve the product’s shelf life . Two methods are used to prepare edible films, including wet and dry processes known as solvent casting and extrusion process, respectively. In the casting method, the solubility of biopolymers and additives is an essential factor, while in the extrusion technique, thermoplastic properties, phase transition, glass transition, and gelatinization should be considered. Production of edible films through the casting method involves three steps: dissolving polymers in a proper solvent (ethanol or water), spreading the solution on the mold, and drying the casted solution with an oven, microwave, or vacuum drier. This method is inexpensive without specific equipment requirements and produces more homogenous films due to the better interaction of molecules. Also, it uses low temperature that decreases the possibility of detrimental structural changes. However, long drying time, denaturation of proteins because of using solvents, limited forms of prepared films, production of films with different characteristics and commercialization challenges are the main disadvantages of casting method. In the extrusion method used at the commercial scale, a mixture of biopolymer and additive is fed to the extruder in which mixing, and heating occur and an extruded film is formed. Edible coatings are prepared through dipping, spraying, fluidized-bed processing and panning method. The dipping method mainly used for fruits and vegetables comprises immersion of food product into polymer solution followed by evaporation of solvent and formation of a thin layer on the product’s surface. In the spraying method, which is the most common method, the coating solution in the form of small droplets is sprayed on the surface of the food product. The main disadvantage of this method is the impossibility of spraying polymer solutions with high viscosity. The panning method is putting the food product in a rotating pan and the coating solution is sprayed on the surface. The solvent is evaporated by circulated air and the dried coating is formed on the product’s surface. The fluidized-bed method is used to form thin layers of coatings on small dry food particles and the coating solution is sprayed on the surface of products through nozzles that help to flow the smaller size food with the sprayed solution. The recent studies focusing on the extension of probiotic viability have proved that using symbiotic edible packaging is a promising way to provide enough viable organisms during storage of the foods and through digestion conditions.
