Effect of Chilling on Microbiological, Biochemical and Sensory Attributes of Whole Aquacultured Rainbow Trout (Oncorhynchus mykiss Walbaum, 1792)

Abstract

The effect of chilling (0-2ºC) on the quality deterioration of whole ungutted aquacultured rainbow trout ( Oncorhynchus mykiss , Walbaum,1792) was studied by integrated evaluations of microbiological, biochemical, and sensory attributes. The counts of aerobic mesophilic, psychrotrophic bacteria and Pseudomonas increased exponentially. An initial lag phase was noticed for H2S producing bacteria, Aeromonas and Enterobacteriaceae. Presence of pathogens such as Aeromonas hydrophila and A. sobria are of concern in the case of delay in icing or temperature abuse during storage. The pH values increased from an initial value of 6.74 to 7.13. PV showed fluctuations. Of the chemical indicators of spoilage, Thiobarbituric acid (TBA) values increased very slowly reaching final value of 16.56 μg MA g -1 . Total Volatile Base Nitrogen (TVB-N) values exceeded 27. 87 mg N 100 g -1 on day 14 when the psychrotrophic counts exceeded 10 7 cfu g -1 indicating that this value may be useful as a measure of degree of freshness for whole ungutted rainbow trout. Based on the TVB-N and microbiological limits, the shelf life of trout at 0-2º C was 9-12 days.