Authors Ncama, K.; Magwaza, L.S.; Mditshwa, A.; Tesfay, S.Z
Fresh produce is recognized as highly beneficial for human health. The substantial changes in the lifestyle of populations and upturn awareness about nutritional aspects of dietary patterns, fresh produce has high demand, In developing countries, postharvest losses can reach up to 50%, and improper storage can cause serious food safety and quality-related issues. To fulfill the ever increasing demand of fresh produce, more attention should be given to reduce postharvest losses in addition to increase the production, Postharvest operations are one of the promising approaches for regulating food safety and security, fresh produce; postharvest, losses; food safety and quality; Nutrition properties; Bio-edible coating, consumers demand chemical free fresh product with excellent quality and nutritional profile, edible coating of fresh produce seems to be an effective approach to mitigate produce safety and quality issues, Fresh produce is highly perishable by nature, that is why it is more susceptible to biotic (diseases, insects, parasites) and abiotic (temperature, humidity, rain, floods) challenges that cause postharvest losses. Microorganisms are a major source of postharvest losses in fresh vegetables. Skin damage, spots, and fractures occur because of improper handling of fresh vegetables provide optimum conditions for microbial growth. Many microorganisms enter the food and cause serious health issues, especially pathogenic organisms which can cause food-borne diseases.[5] To enhance quality and safety, fresh produce must need protection from deterioration during processing, storage, and transportation. Numerous techniques are utilized for extending the nutritional attributes and storage life of fresh produce include modified atmospheric packaging (MAP), high temperature storage, low temperature, irradiation, and chemical treatment but these techniques require proper care and sometimes lead to an unacceptable loss in nutritional value of produce, edible coatings and films have piqued the attention of scholars and the food industry to use them as preservative techniques because of their biodegradability, biocompatibility, antibacterial, and antifungal activity and it shown to be very successful in retaining food without compromising its nutritional or organoleptic aspects, Edible coatings would be a good substitute for the commercial synthetic waxes that are now utilized, which are mostly made of oxidized polyethylene, moreover, certain edible coatings may contain useful additives like antioxidants and phytonutrients that help to improve food safety and stability. Sensory properties, water solubility, and other variables all play a role in the selection of coating materials, when purchasing fresh produce, consumers evaluate the quality and wholesomeness of the produce based on its presentation. The most prevalent and challenging problem for fruit industry is to maintain and control fresh quality, avoid spoilage, and retard growth of pathogenic microorganisms, this issue can be solved by using an edible coating. Edible coating adds another layer of protection to fresh fruits and vegetables and may have a similar effect to modify storage atmosphere and controlling inner gas composition, edible coatings with the inclusion of different edible herbs and antimicrobial agents have been created and applied to fresh produce, edible coating is a thin layer that acts as semipermeable membrane and operates as barrier against gases, water leakage, hence, decreases the rate of respiration, enzymatic browning, and release of volatile compounds into the ambient environment, they are employed directly on the produce surface by spraying, brushing, or dipping to create a modified atmosphere. Under conditions of high humidity, edible coatings should be durable and commonly regarded as safe. Edible coatings must be colorless, odorless, tasteless and have strong mechanical characteristics that can be utilized as nutraceutical, as well as act carriers of texture enhancers, to enhance the storage life of fresh produce, various materials were used to cover and wrap them and this material is consumed with foods, both with and without removal, and is known as an edible wrapping, fresh produce with edible coatings has a gleaming appearance. The key benefit of edible coating is that it improves the storage time of fresh or refined food products while also protecting them from postharvest losses and environmental damages, edible coating is added to the outer surface of fruits and vegetables to increase shelf life and shine appearance in order to meet market demand for environment friendly and nutritious foods by improving the nutritional composition of fruits and vegetables without compromising their consistency, Among the major obstacles confronting the global preservation industry is the limited advancement of unique coatings with increased consistency and functionality for both fresh and minimally processed food. It has been documented that development activities have largely turned toward the creation of environmentally sustainable coatings/packaging derived from biodegradable polymers, which may not only minimize packaging needs but also contribute to the transfer of value-added by-products, Multiple methods are employed for coating formation depending upon which coating material is used, for the formation of edible coatings, some methods like solidification of melt, solvent extraction and thermal gelation have been developed, hydrocolloid films contain water soluble polymers derived from animals, plants, or microbial/biological sources. Solvent extraction produces hydrocolloid edible films with a continuous structure. The chemical and physical interactions between molecules enhance the products stability. Water, acetic acid and ethanol are mostly used as solvents with the addition of plasticizers, antimicrobial, and cross-linking agents. Protein films produced by heating the solution result in denaturation, precipitation, or gelation and cooled immediately to produce coagulation and further gelation. Lipid films are solidified and melted, Additives in coatings Additives like antimicrobials, plasticizers, texture enhancers, flavor, probiotics, and anti-browning compounds have been mostly utilized in edible coatings. Incorporation of antimicrobial agent into coatings give an innovative approach to extend the storage life and enhance microbial safety, the generally utilized antibacterial agents in edible coatings are potassium-sorbate, lauric acid, green tea powder, sodium benzoate, trisodium phosphate, pediocin, lactic acid, conalbumin, chitosan, lecithin, nisin, lauric acid, ethylene diamine tetra acetic acid (EDTA), thiosulfonates, imazali, sorbic acid, grape seed extract, essential oils/spices, or their ingredients, benomyl, silver, isothiocyanates, and enzymes. The enzymes glucose oxidase, lactoperoxidases, and lysozyme are utilized as antibacterial agents in coating solutions, however, their applicability is limited due to poor stability (at varying pH and temperature), Antimicrobial compounds derived from plants are encouraged to promote customer acceptance used natural antimicrobials curcumin and limonene and coatings were made from their liposomes and then over-coated with methyl cellulose. One set of each coating type was exposed to simulated local transportation vibration. Vibrated samples had a shorter shelf life than non-vibrated samples, indicating the need for a tough coating that can withstand road vibrations. On the 14th day of storage, limonene liposomes showed substantially lower fungal growth than the control by judging number of strawberries with visible Mold, the impact of four distinct plasticizers (glycerol, polyethylene glycol, sorbitol, and glycerol) on water vapor permeability, and mechanical characteristics of alginate coating. Inclusion of plasticizers changed the mechanical characteristics of alginate coverings, lowering tensile strength (TS), with the impact becoming more evident as the relative humidity (RH) increased, Types of edible coating, edible coatings are chiefly classified into three main groups. Polysaccharides based coatings (starch, chitosan, cellulose, alginate, pectin, gums etc.), protein-based coatings (zein, whey protein, wheat gluten, casein, soy protein, egg albumin, gelatin, etc.), lipid-based coatings (waxes, fatty acids etc.) and composite coatings are formed by combining more than one material or substance depicted the types and subtypes of edible coatings.
