## 3 Edible Coatings
### Materials  
Edible coatings and films can be made of polysaccharides, proteins, lipids, and their combinations to obtain composite materials with better physicochemical properties compared to packaging materials obtained based on a single material (Figure 1). Due to their biodegradable and non-toxic properties, they are intended to replace the existing synthetic polymers [77; 78; 79]. In general, polysaccharide edible coatings are characterised by their hydrophilic properties as a poor barrier to moisture, and some of them are also less permeable to oxygen. Coatings made from cellulose, amylose, or chitosan are resistant to fats and oils, with considerable strength, flexibility, and transparency [80]. Disadvantages of polysaccharide coatings include difficulties in processing and performance, especially when coating moist products. Edible coatings made from protein sources, on the other hand, are hydrophilic. Usually, the proteins must be denatured by heat, acid, alkali, and/or solvent. The aim is to create a more elaborate structure, which is required for coating formation. The most commonly used plant proteins for coating production are, e.g., corn zein, soy protein, and wheat gluten, while animal proteins include gelatin, casein, and keratin. Lipid coatings are used mainly for their hydrophobic properties, which help create a good barrier against moisture loss. Additionally, coatings made from them are thicker and more brittle [81]. Figure 1: Division of coating materials. Edible coatings can act as a barrier against various atmospheric gases, moisture, water vapour, carbon dioxide, and microbes and also slow down respiration and the rate of oxidation reactions in food. However, to ensure adequate protection, they are used in combinations of more than one material, with the addition of low-molecular compounds, showing active and plasticising properties, providing additional properties. Plasticisers are usually polyols such as glycerol, honey, mannitol, propylene glycol, sucrose, or fatty acid esters, which impart strength and flexibility to the coatings, as well as improve the water vapour and gas permeability of the coatings. Active substances added to edible coatings include antimicrobial, antioxidant, taste, colour, or nutritional enhancers, as well as essential oils, dyes, flavours, or nanoparticles [82]. All biopolymers used for edible coatings and films must be recognised as safe by the U.S. Food and Drug Administration (FDA). It is expected that the creation of biodegradable films and edible coatings cannot completely replace artificial packaging materials, but they can be a substitute for basic, conventional packaging [83]. Coatings applied to fruit can be produced from different materials, also obtained from agricultural by-products [84], and they should be characterised by low water vapour permeability, preventing drying, as well as low oxygen and carbon dioxide permeability to slow down respiration and metabolic activity, affecting the ripening process [85]. Pectins (e.g., apple pectin, citrus pectin), a non-starch polysaccharide, are by-products of agricultural processing and are often used to create edible coatings. Pectin is obtained from the cell walls of almost all types of fruit and vegetables, and due to its diverse structure, it has a wide range of applications [86]. Currently, pectin-based edible coatings are commonly used to coat low-moisture fruits due to their hydrophilic nature and in food production as stabilisers, thickeners, and gelling agents, as well as encapsulation agents [87]. Pectin gelation and film formation largely depend on the degree of esterification, which is why modifications are introduced consisting of combining the hydrophilic structure with a hydrophobic lipid compound [3]. Pectins are generally classified as high and low methoxy, having a degree of esterification above and below 50%, respectively, making pectin one of nature's most complex macromolecules.