The Effect of Natural Edible Coatings on Chemical, Microbial, and Sensory Quality of Tilapia during Frozen Storage

Preserving the quality and safety of fish and its products is a critical concern for food industry. In the present study, the effect of green tea extract and olive leaves extract-based preservative coatings on chemical, microbial, and sensory quality of wild type Nile tilapia (Oreochromis niloticus) was determined during pre-freezing ice and subsequent frozen storage.

Forty-eight ponds raised tilapia, freshly caught in April, 2021, which were divided into three groups: group CT with no coating, group GTE with green tea extract-based coating, and group OLE with olive leaves extract-based coating. Fish samples in all groups were kept in ice for five days (1±2 °C) and then subjected to freezing (-18±2 °C) for 105 days. Chemical (moisture, ash, protein, fat, Total Volatile Basic-Nitrogen (TVB-N), pH) and microbial (Aerobic Plate Count (APC), Total Coliform (TC), Faecal Coliform (FC), Escherichia coli) parameters as well as sensory attributes (appearance, odour, acceptability, flesh color, Total Quality Index (TQI)) of tilapia in all groups were analysed after five days of ice storage and 15, 45, 75, and 105 days of frozen storage.

APC of tilapia treated with preservative coatings remained below the permissible limit (<5×105 Colony Forming Unit (CFU)/g) throughout the storage period. After five days, content of TVB-N in untreated samples of tilapia was 32.94±2.30 mg/100 g compared to 5.05±2.19 and 7.24±2.89 mg/100 g in tilapia treated with green tea and olive leaves extract-based coating, respectively. Fat content of untreated tilapia was significantly (p<0.05) reduced to 0.05±0.01% at the end of the study period from the the initial content of 0.24±0.04%. However, the tilapia treated with preservative coatings achieved significantly (p<0.05) lower scores of TQI compared with the untreated one owing to the coloration of fish with extract solution.

Green tea extract and olive leaves extract-based coatings can, therefore, be used to improve fish quality and safety during storage. However, there is a need to change consumer’s perception about the sensory attributes of fish.