The Synergistic Effects of Thymus daenensis and Camellia sinensis Hydroalcoholic Extracts on Chemical and Microbial Properties of Frozen Rainbow Trout

Fish meat is as one the most important source of protein and high spoilage feature. Therefore, the aim of this study was to evaluate the synergistic effects of Thymus daenensis (TD) and Camellia sinensis (CS) hydro-alcoholic extracts on chemical and microbial properties of rainbow trout during frozen storage. In this experimental study, hydro-alcoholic extracts of TD and CS were extracted using maceration method and determined their compounds by HPLC. Extracts in 0.5% concentrations were studied separately and in combination for coating rainbow trout meat. The coated fish fillet was kept at -18 °C for 60 days and subjected to pH-testing, total volatile nitrogen (TVN), thiobarbituric acid (TBA), count of Listeria monocytogenes and sensory evaluation every 10 days. Major compounds in Thymus daenensis and Camellia sinensis extracts were thymol (39.4 mg/g), carvacrol (36.27 mg/g) and epigallocatechin gallate (105.88 mg/g), epicatechin gallate (41.2 mg/g), epigallocatechin (29.55 mg/g) and caffeine (29.45 mg/g), respectively. The results showed that during the storage period, all treatments reduced TVN, pH, TBA, count of L. monocytogenes compared to the control sample. Also, combination treatment (0.5% thyme and 0.5% green tea) significantly improved the chemical, microbial and sensory properties of fish fillet during storage.Therefore, green tea and thyme can be used as antimicrobial and antioxidant compounds in meat industry.