Impact of gelatin nanogel coating containing thymol and nisin on the microbial quality of rainbow trout fillets and the inoculated Listeria monocytogenes

This study aimed to assess the effects of edible gelatin nanogel coating containing thymol and nisin on the inhibition of microbial flora and inoculated Listeria monocytogenes in fish fillets during a 12-day storage period at the temperature of 4 degrees C. Data were collected and analysed on several factors of microbiological change, including total viable count, total psychrophilic count, lactic acid bacteria and hydrogen sulphide-producing bacteria count, and the inhibitory effects of the coating on inoculated Listeria monocytogenes were determined during 3-day intervals. The highest reduction rate of total viable bacteria (0.95 log CFU/g), total psychrophilic (0.92 log CFU/g), Hydrogen sulfide producing bacteria (0.66 log CFU/g), lactic acid bacteria (0.95 log CFU/g) and L. monocytogenes count (0.65 log CFU/g) were observed in gelatin nanogel containing thymol and nisin in comparison with control samples. Furthermore, the separate use of these compounds led to the significant growth inhibition of the bacteria compared with the control. Therefore, it was concluded that the gelatin nanogel coating without an antimicrobial agent could not be effective in bacterial growth control, and the added thymol and nisin would be beneficial in the preservation of foods such as fish and its products.