# Sustainability in Bio-Based Edible Films, Coatings, and Packaging for Small Fruits
## 5 Edible Film and Coating Functionalities Important for the Small Fruit Industry  
Eating fresh fruit and vegetables is one of the recommendations for a healthy lifestyle. However, they are only available seasonally in some parts of the world. An equally important issue is post-harvest durability. This applies especially to small berries with high water content. The shelf life of such unprocessed fruits is a maximum of several days. They belong to the group of non-climacteric fruits, which means they do not ripen after being picked. Thus, they must be harvested when fully ripe, making them even more susceptible to rapid spoilage. High water and straightforward sugar content in ripe berries are the main factors contributing to their susceptibility to the development of microorganisms. Generally, fruit losses are estimated at 25-50% of total production. Berries are susceptible to mechanical damage, water loss, and contamination during harvesting, packaging, and storage. Hence, the shelf life of fresh berries such as raspberries, blackberries, boysenberries, and logamberries, even if stored at a temperature around 0 \({}^{\circ}\)C and relative humidity around 90%, is usually between 2 and 5 days [108]. Strawberries are suitable for fresh consumption for 5-7 days [109]. Sweet cherries (2-3 weeks) and grapes (up to 24 weeks) are slightly more durable [110]. In the old days, fresh fruit was consumed only immediately after harvest, often still in the field. With the development of transport and distribution of fruit over long distances, the time from harvest to consumption has been significantly extended. This places significant demands on harvesting, handling, storage, and transport techniques. If appropriate protection systems are not provided, delicate berries spoil, losing their attractive appearance, taste, and nutritional value, and, what is more, they become contaminated with bacteria and molds, which poses a real threat to consumers' health [111]. Edible coatings, i.e., those suitable for consumption, are made from food-grade biopolymers derived from plants, animals, or marine organisms, as well as food processing by-products. These packaging materials can also be used as carriers for various active ingredients that can extend shelf life, improve the nutritional value and organoleptic properties, and even enhance the health-promoting potential of the final product. The efficiency of using edible coatings to extend the shelf life of fresh berries depends on the properties of the polymer itself, which is the basis for producing the film, but also on functional additives such as plasticizers or various biologically active substances [119]. The plasticizer is a necessary additive ensuring the integrity of the coating without pores and cracks. Some of the most commonly used plasticizers are sorbitol, glycerol, or polyethylene glycol. Surfactants such as Tween 20, Tween 80, or oleic acid can improve the wettability and homogeneity of coatings [120]. There are many challenges and expectations regarding post-harvest edible coatings for low-durability fruits. First, these coatings should not contain toxic, allergenic, or indigestible ingredients, ensuring consumer safety. It is also vital to protect these soft and delicate fruits from damage during transport; therefore, these coatings must adhere well and evenly to the surface and be structurally stable. The appropriately selected composition aims to ensure the semi-permeability of the coating to gases and water vapor. None of the coating components should adversely affect the product's nutritional, organoleptic, and aesthetic properties. Biochemical and microbiological stability, i.e., protection against contamination and spoilage, is one of the most critical challenges in the functionality of edible coatings [16]. Additionally, edible films and coatings can be carriers of desired flavor additives, fragrances, colorants, nutrients, or vitamins.