Evaluation of antioxidant and antimicrobial effects of shallot (Allium ascalonicum L.) fruit and ajwain (Trachyspermum ammi (L.) Sprague) seed extracts in semi-fried coated rainbow trout (Oncorhynchus mykiss) fillets for shelf-life extension

This work studied the effects of shallot (Allium ascalonicum L.) fruit and ajwain (Trachyspermum ammi (L.) Sprague) seed extracts on the quality of semi-fried coated rainbow trout (Oncorhynchus mykiss) fillets at refrigerated storage. Chemical analyses (peroxide value, thiobarbituric acid value, total volatile basic nitrogen, trimethylamine nitrogen, acid value), microbiological assays (total viable count, psychrophilic bacterial counts, Pseudomonas spp. bacteria counts) and sensory properties of the samples were evaluated. Comparing to controls, lipid oxidation and microbiological spoilage were significantly delayed in samples treated with the plant extracts (P < 0.05). These extracts also contributed to significantly higher sensory quality and overall acceptability (P < 0.05). The application of 3% ajwain seed extract gave the best antioxidative and antimicrobial activities, as well as sensory scores, up to 15 days of storage, followed by 3% shallot fruit extract. This research demonstrated that the above extracts could be applied as natural preservatives for extending shelf-life of fish products.