Combined Effect of Vacuum Packaging and Sodium Acet ate Dip Treatment on Shelf Life Extension of Rainbow Tr out ( Oncorhynchus mykiss ) during Refrigerated Storage

Abstract

The present study evaluated the effect of packagin g (air, vacuum) with or without addition of sodium acetate (2% W /V) on shelf-life extension of rainbow trout ( Oncorhynchus mykiss ) under refrigeration, for a period of 18 days. Fou r different treatments were tested: CAP: control air pack; SAAP : sodium acetate treated aerobic packaging; VP: vacuum packaging in the absence of s odium acetate; and SAVP, sodium acetate under VP. Trimethylamine nitrogen (TMA-N), free fatty acids (FFA) and peroxide values (PV) of SAVP samples were lower com pared to the other treatments during the entire refrigerated storage period. In t he present study, the thiobarbituric acid (TBA) level showed fluctuations during storage indi cating that TBA values may not reveal the actual rate of lipid oxidation. Total vi able counts for fresh rainbow trout stored aerobically exceeded 7 log CFU g -1 after 10-11 days, while treatments SAAP and VP reached the same value on days 12 and 16, respectiv ely. In contrast, SAVP samples did not reach this value throughout the 18-day. Psychro trophic counts of SAVP samples were significantly (P < 0.05) lower compared to the control samples during storage period. As regards sensory evaluation, shelf-life of trout was longest for SAVP (15-16 days), followed by VP (12-13 days), SAAP (9-10 days), and CAP sampl es (6-7 days). The results indicated that the combined effect of vacuum packaging and so dium acetate on fish samples preserved their good quality characteristics and ex tended the shelf-life of the treated samples during refrigerated storage, as supported b y the results of microbiological, chemical, and sensory evaluation analyses. Keywords: Packaging, Quality characteristics, Rainbow trout, Sodium acetate.