*3.3. Other Food Products*

Aside from meat and fishery products, other food products are also susceptible to be coated or packaged into gelatin-based solutions or films. Potential applications of gelatin edible films in the food industry may include the transport of gases (O2 and CO2), water vapour, and flavours for fruits and vegetables [112]. As an example, refrigerated Red Crimson grapes were coated with gelatin type A, starch and glicerol films obtained by the casting technique [2]. As a result, an increase in gelatin concentration in the mixture provided an increase in thickness, WVP and mechanical resistance reducing the total weight loss without influencing consumers acceptance. Also, the incorporation of red bean powder as colorant and flavouring agent into gelatin films was studied for use in candies and brewing food as it was reported in CN 103589173A patent [113]. In another patent, gelatin and glucomannan films with garlic juice were described as antimicrobial and favouring agents (CN 103589168A patent) [114]. Other vegetables and fruits recently reported to be coated or wrapped with gelatin-based films and coatings are carrots [115], cherry tomatoes [116], calyx from physalis [117], oranges [118], banana and eggplant epicarps [119], fresh-cut melons [120], peppers [121], strawberries [122], blueberry fruit [123], pineapple fruit [124] and minimally processed persimmon [125].

Gelatin films prepared from cold-water fish show significantly lower WVP values than those from warm-water fish, due to their higher hydrophobicity directly related to lower amounts of two aminoacids, proline and hydroxyproline. As a consequence, cold-water fish gelatin films are particularly useful for applications related to reducing water loss from refrigerated or frozen food systems [126].

Residues generated by fruit and vegetable processing are well-studied sources of antioxidants, bio-polymers and dietary fibres [127]. Indeed, large amounts of oil nutraceutical capsule waste from coconut, chia, safflower and linseed, composed mainly of gelatin, are being generated with high waste

treatment costs for industry. A reduction in the oxidative rancidity of sunflower oil exposed to films developed from chia oil nutraceutical capsule wastes by the casting technique after storage at 40 ◦C in the presence of light for 13 days was obtained [128]. Gelatin was extracted from capsule wastes composed of gelatin (48%), water (30%) and glycerol (22%). Blueberry pomace fibre and extract wastes were used as active additives. All gelatin films retarded oil lipid oxidation during the studied period. However, gelatin films added with fibre and extract significantly reduced lipid oxidation compared to the control film without antioxidants addition after 8 days of the oxidative treatment. Similarly, the effect of films based on beet root residue powder, obtained from peels, stalks, and shavings wastes derived from the production of linseed oil nutraceutical capsules, on the retardation of sunflower oil oxidation was recently reported [47]. Sunflower oil containing no artificial antioxidants was stored for 35 days at 35 ◦C and 54% RH and exposed to fluorescent light with an intensity of 900–1000 lux. Peroxide values were determined at different times. Films with antioxidants had a positive effect on the stability of sunflower oil during the entire storage period and, also, at the end of the experiment, presenting the packed oil peroxide values under the recommended limit of Codex Alimentarius (10 milliequivalent per oil kilogram). As a result, biodegradable films based on residues of beet root and gelatin capsules could be a potential tool to control and retard rancidity of different oils.

#### **4. Conclusions**

The use of gelatin-based edible films and coatings represents a stimulating route for creating new food packaging materials. Due to the hygroscopic properties of gelatin, some research studies have been conducted to evaluate the overall effect of the addition of different substances such as crosslinkers, strengthening agents, plasticizers or additives with antimicrobial or antioxidant properties to gelatin-based products to improve the functional properties of gelatin-based edible films and the shelf-life of food products. An increasing number of publications have reported the development of gelatin-based films for meat applications as coatings to reduce the colour deterioration from red to brown as a consequence of lipid oxidation. Regarding fish products, different studies have been focused on the application of gelatin in combination with other biopolymers or active additives to protect fresh fish against cooking processes and microbial/oxidation deterioration. In addition to fish and meat, some other food products such as fruits and vegetables can be coated with gelatin-based films in order to retard degradation processes due to the transport of gases (O2 and CO2) and water vapour. Extensive research is still needed on new methods for gelatin-based film formation to improve the final properties and potential applications.

**Acknowledgments:** Authors would like to thank Spanish Ministry of Economy and Competitiveness for financial support (MAT-2015-59242-C2-2-R).

**Author Contributions:** Marina Ramos and Ana Beltrán contributed to the definition of the review structure based on available literature survey, to writing, to integration of the different parts and to conclusions. Marina Ramos was also the editor of the manuscript. Arantzazu Valdés and María Carmen Garrigós contributed to writing and formatting. María Carmen Garrigós was also the main reviewer of content.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**


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