# Sustainability in Bio-Based Edible Films, Coatings, and Packaging for Small Fruits
## 3 Biological Sources of the Compounds Used in Films, Coatings, and Packaging
### Animal Processing Byproducts
#### 3.3.1 Materials from the Meat Industry  
Films based on natural components (such as gelatin) are innovative solutions due to their abundance, excellent film-forming properties, low cost, biodegradability, and compostability [66]. Gelatin's use has become famous due to its application in the most varied fields of industry [67]. Gelatin is a natural biopolymer derived from the partial hydrolysis of collagen [68], mainly from untanned skin and animal bones (cattle and pigs, for example), chicken feet [69], and fish by-products [32; 70]. Gelatin consists of a set of protein segments carrying different molecular weights (100 to 300 kDa), together with high molecular weight aggregates and peptide fractions (<100 kDa). The origin and the extraction process influence the average molecular weight of gelatin, hence its ability to form films [71]. According to [PERSON] et al. [72], a Bloom value in the range of 125-250 g is most commonly used in gelatins used in foods. Applying gelatin as an edible coating usually involves dipping the fruit in a gelatin solution and then drying it, forming a thin, colorless, flexible layer. This gelatin-based edible film is safe, cheap, biodegradable, and can absorb ultraviolet light due to the aromatic amino acids present in its structure [73]. Moreover, it has been proven to have antimicrobial and antioxidant properties, extending packaged products' shelf-life [74]. Therefore, gelatin is considered a natural and sustainable alternative, widely used to replace synthetic coatings, especially in products that require good visual presentation and preservation for more extended periods. [PERSON] and his collaborators [74] report that a significant advantage of this product is when combined with other biopolymers as it increases the thermal stability and mechanical and barrier properties of the coating. The non-toxicity of gelatin and chitosan is an essential attribute that expands their possibilities for use in food products. Furthermore, these substances have antimicrobial and antifungal properties, which give them great potential in applications related to food preservation, particularly with their coating. The films obtained by mixing gelatin and chitosan present antioxidant characteristics and exhibit a high suppression of the growth of _Staphylococcus aureus_ and _Escherichia coli_[75; 76]. These multifunctional characteristics make gelatin associated with chitosan versatile and promising options for advancing innovative technologies, especially in areas where sustainability and functional efficiency are essential. Several studies have been carried out to prove this potential. Some examples are the studies by [PERSON] et al. [77], in which fresh grapes were preserved in packaging made of gelatin extracted from chicken feet mixed with zinc oxide and chitosan nanoparticles. This edible coating revealed a decrease in microbial growth and a reduction in browning, remaining attractive after 14 days. Greater firmness, less weight loss, and a total bacterial count were also observed in studies by [PERSON] et al. [78] when they tested a gelatin-based coating with chitosan, nisin, and cornstarch on cherry tomatoes. On the other hand, [PERSON] et al. [79] observed good antioxidant capacity and better stability at higher temperatures using gelatin films with bergamot and lemongrass essential oils as active packaging materials. In recent years, innovative packaging composed of these two components has become a creative solution to improve food conservation [80]. Indeed, among the mechanisms most used in these innovative packaging are active eliminators, which include specific technologies for removing oxygen, moisture, and ethylene [81]. Oxygen scavengers, for example, help prevent food oxidation, slowing down processesthat lead to fat rancidity and the growth of aerobic micro-organisms. Moisture eliminators are essential to avoid mold formation and degradation of water-sensitive foods, while ethylene eliminators effectively preserve fruits and vegetables, delaying ripening and degradation [82].