M.A. Thesis:

Investigating the effect of edible coating based on fish gelatin containing Nepeta binaludensis extract on shelf life of cleaned shrimp at refrigerator

Abstract Fishery products are prone to both microbial and oxidative spoilage. Therefore, it is desirable to use a preservative with both antioxidant and antimicrobial properties. In this study, the effect of edible coating based on fish gelatin containing Nepeta binaludensis alcohol extract (NE) on fresh shrimp characteristics during storage for a period of 18 days at 4°C was investigated. For this purpose, six treatments were prepared including: C: control (without coating), T1: sample coated with gelatin coating without extract; T2: sample coated with gelatin solution containing 0.5% NE, T3: sample coated with gelatin solution containing 1.0% NE, T4: sample coated with gelatin solution containing 1.5% NE and T5: sample coated with gelatin solution containing 2.0% NE and the amounts of pH, total volatile base nitrogen (TVB-N), free fatty acid (FFA), thiobarbituric acid index (TBA), bacteria total count (PCA), psychrophilic bacteria and sensory characteristic of shrimp treatments (including: texture, color, odor and overall acceptability) were examined during refrigerated storage. Experiments were performed in a factorial form in a completely randomized design with the software of SPSS 22.0. The obtained results demonstrated that pH, FFA, TVB-N, TBA values and bacterial load of all shrimp treatments significantly were increased in the duration of storage (p<0.05). The usage of gelatin edible coating containing different levels of NE lead to minimize the chemical and microbial changes during storage than control. By increasing the NE concentration in coating solution, the shrimp properties and its shelf life were improved significantly (p<0.05), so that, the sample coated with gelatin solution containing 2.0% NE had the highest microbial shelf life with at least a 12-day extension of shelf life and the sensory characteristics of this treatment were acceptable until the last days of refrigerated storage. Overall, this study clearly stated that the effect of gelatin edible coating containing Nepeta binaludensis alcohol extract on shrimps was to retain their good quality characteristics and extend the shelf life during refrigerated storage, which was supported by the results of chemical, microbiological and sensorial properties. Finally, the shrimp coated with gelatin solution containing 2.0% NE can be introduced as the best treatment.

Keywords: Keywords: Shrimp, Edible coating, Gelatin, Nepeta binaludensis, Shelf life