Chemical and antimicrobial properties of silver carp surimi enriched by Thyme leaves extract

In this study, effect of Thyme (Thymus vulgaris) ultrasonic extract on the quality of Hypophthalmichthys molitrix surimi was evaluated. For this purpose, the leaves of Thymus vulgaris were dried, grinded and soaked in methanol (1:10 w/v) for 30 min at 45˚C and sonicated at 30 kHz for 15 min at 40˚C. The extract was suspended by Dimethyl sulphoxide and mixed with surimi (0.4 and 0.8% w/w). Then, the analysis of chemical (free fatty acid, peroxide value, Thiobarbituric acid and total volatile base nitrogen) and microbial (mesophilic and psychrotrophic viable count) properties of the samples were done at specific intervals after zero, 4, 8, 12 and 16 days of storage at 2 ºC. Results of chemical and microbial analysis showed that 0.8% concentration of T. vulgaris could increase the shelf life of Hypophthalmichthys molitrix surimi and there is significant difference between control and treated samples. Moreover, the results could be claimed that the T. vulgaris due to marvelous antioxidant and antimicrobial component such as thymol (52.17%), ρ-cymene (14.42%), carvacrol (9.11%) and γ- terpinene (4.45%) has significant effect on preventing the Hypophthalmichthys molitrix surimi oxidation and microbial growth. The results also showed ultrasound was the effective way to extract the Thymus vulgaris beneficial compounds.