The Effects of Liposomal Encapsulated Thyme Extract on the Quality of Fish Mince and Escherichia coli O157:H7 Inhibition During Refrigerated Storage

ABSTRACT

The effects of liposomal encapsulated and unencapsulated (0.3 and 0.5% w/w) thyme extract (TE) on the quality of silver carp (Hypophthalmichthys moltrix) mince during chilled storage (4 ± 1°C) were examined over a period of 15 days. The samples were analyzed by microbiological (total viable count, psychrotrophic count) and chemical (peroxide value and total volatile nitrogen) experiments. Also, the efficacy of the encapsulated extract in control in the population of Eschershia coli O157:H7 inoculated in silver carp mince was investigated. Results showed that the samples containing 0.5% of encapsulated thyme had fewer changes in peroxide value and total volatile nitrogen in comparison to other treatments (p < 0.05). Encapsulated thyme also could inhibit the growth of mesophilic and psychrotrophic bacteria in the samples compared to the control and the samples containing unencapsulated extract during the storage period. Moreover, 0.5% encapsulated TE reduced the population of E. coli O157:H7 below the acceptable level (< 2) from Day 9 until the end of the storage period. In conclusion, the results obtained from this study suggest that liposomal encapsulation may help to obtain higher antimicrobial activity in lower TE concentrations in minced fish.

KEYWORDS:

• Silver carp
• thyme extract
• encapsulation
• liposome
• fish mince