The Effect of Thyme and Garlic Oil on the Preservation of Vacuum-Packaged Hot Smoked Rainbow Trout (Oncorhynchus mykiss)

Abstract

Quality and shelf life of filleted hot smoked rainbow trout packaged in vacuum packaging (untreated) and with thyme oil (TO), and garlic oil (GO)-treated, after vacuum-packaged (VP) conditions stored at 2 °C, were investigated by measurement of microbiological, sensory and physicochemical analyses. Acceptability scores for appearance, odour, taste and texture of untreated and treated smoked trout decreased with storage time. The limit of sensory acceptance was reached after 5 weeks for the untreated samples, after 7 weeks for with thyme oil-treated samples (TO + VP) and after 6 weeks for with garlic oil-treated (GO + VP) samples. Total viable count evaluated that thyme oil- and garlic oil-treated vacuum-packaged samples had good results up to 7 weeks compared with 5 weeks in control vacuum packs. Psychrotrophic counts for untreated and treated samples exceeded 6 log cfu/g after 5 and 6 weeks of cold storage, respectively. Treated samples presented the lowest lactic acid bacteria counts. Total volatile basic nitrogen and trimethylamine nitrogen values gave acceptable results for up to 5 weeks for the untreated samples, 7 weeks for thyme- and garlic oil-treated samples. Treated with thyme oil samples presented the lowest thiobarbituric acid index values. The results obtained from this study showed that the shelf life of hot smoked rainbow trout stored in cold storage (2 °C), as determined by overall acceptability of all data, is 5 weeks for vacuum-packaged samples and 7 weeks for thyme- and garlic oil-treated vacuum-packaged smoked fish.