Effect of Zataria multiflora Boiss irradiated with moderate dose of gamma rays on the shelf life of rainbow trout fillet (Oncorhynchus mykiss) containing active coating based on sodium caseinate

In order to evaluate the effect of moderate dose gamma irradiation (10 KGr) on ​​antioxidant and antibacterial properties of Zataria multiflora Boiss, edible active coating containing normal and irradiated extract (1.5%) on base of Na-caseinate solution (8%) was prepared and shelf life of coated rainbow trout fillet was evaluted. An experiment was carry out with 4 treatments without coating (control), fillets coated with Na-caseinate (T1), and fillets coated with Na-caseinate enriched with  normal (T2) or irradiated (T3) Zataria multiflora Boiss extract and 4 replicates during 10 days at refrigerated (4±1oC) storage. Chemical (TVN, TBA, PV) and microbial (TVC and PTC) tests were measured on days 0, 3, 6 and 10. The results showed irradiation of Zataria multiflora Boiss with a moderate dose of gamma rays, despite the possitive effects, did not cause significant changes in its antioxidant and antibacterial properties. But at the end of the storage period, the lowest levels of TBA (3.23±0.23 mg MDA/Kg), TVN (25.23±1.12 mg/100g) and psychrophilic bacteria counts (5.00±0.13 log cfu/g) was found in fillets containing active coating of Na-caseinate and irradiated Zataria multiflora Boiss extract (p <0.05). Therefore, Zataria multiflora Boiss extract can be used as normal or irradiated in the active coating of Na-caseinate, to increase the shelf life and quality of rainbow trout fillets at refrigerator temperature for at least 10 days.