Eureka! Institutional Repository

The increased interest in edible coatings has been motivated by the consumer demand for safe, stable and high-quality foods with extended shelf life. Edible coatings and films are widely used in food, as an alternative to synthetic packaging. Their application mainly achieves the reduction of the oxidative process and the inhibition of the growth of microorganisms, while the most important advantage is the no negative environmental effects of their use. Oxygen is responsible for the degradation process in foods, such as lipid oxidation, micro-organism growth, enzymatic browning and vitamin loss. The oxidation of the fat results in off-flavour, off-color and nutrient loss. Edible coatings made from proteins or carbohydrates are excellent barriers to oxygen, due to their tightly packed, ordered hydrogen-bonded network structure. Also, edible coatings can improve the quality of the fresh and frozen products by retarding the microbial activity, reducing lipid oxidation and moisture loss, and functioning as a carrier of food additive such as antimicrobial and antioxidant agents. Fishes and seafood are highly perishable and have a short shelf-life. Sardines are very popular fish products in Greece and have high content of vitamins, minerals and polysaturated fatty acids. The microorganism growth and the oxidation process lead to the organoleptic degradation and the reduction of fish shelf life. Most of the researches include the application of carbohyrate films and coatings in fishes, with any commercial interest for our country contrary to sardines. Also, few studies examined the application of the incorporation of herbal extract in gelatin coatings into sardines’ fillets and the effect on the microbiological and oxidative stability of fillets. The objective of this study was to evaluate the effect of gelatin edible coatings with or without the addition of herbal extract on the microbiological and oxidative stability of sardine’s fillets in order to prolongate the shelf life under refrigerator storage. In the first experimental part of the study, the microbial stability of the sardines was evaluated. According to the results, the application of gelatin 8% and gelatin 8% with herbal extract 2% edible coatings did not significantly decrease the growth of total mesophilic bacteria. Although, treatments with coating showed the lowest values but no significantly different compared to the fillets without coating. While, according to the results of enterobacteriacea counts, the samples with 8% gelatin coating and 2% herbal extract showed the lowest average (P<0.05). The second part of the study was about the evaluation of oxidative stability as examined factor of qualitative degradation and products shelf life. The lipid oxidation values showed that the gelatin 8% coating had no positive contribution to the oxidative stability of the fillets, with lower TBARs values than the fillets without coating but no statistically significantly different. On the contrary, according to the findings of the study, the 2% addition of antioxidant herbal extract (rosemary, thyme, lemon balm, salvia) in gelatin 8% coating provided significant antioxidant effects (P<0.05). Remarkable is the difference between fillets without and with gelatin-herbal coating on day 4, the oxidation index was reduced by 50%. In conclusion, according to the present study, gelatin edible coating did not provide any significant antimicrobial protection to the sardine’s fillets, but the incorporation of herbal extract into gelatin coating delayed the lipid oxidation of sardine’s fillets measured using TBARs. Further studies should be carried out to optimize the percentage of addition of gelatin and herbal extract into edible coatings in order to improve the microbial and oxidative stability of fish products