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 0-2˚C was 9-12 days.

Biochemical, textural, microbiological and sensory attributes of gutted and ungutted sutchi catfish (Pangasianodon hypophthalmus) stored in ice

“…The initial count of Enterobacteriaceae was 2.3 log 10 cfu g −1 which increased to a final levels of 5.4 and 5.6 log 10 cfu g −1 in whole ungutted and gutted catfish respectively while stored in ice. However, the initial level of Enterobacteriaceae noticed in the present study is lower than the earlier observations made on farmed freshwater trout (Ninan et al 2011) and farmed brackish water fish such as pearl spot (Ravishankar et al 2008) and milkfish (Sneha 2011). Assessments of the levels of Enterobacteriaceae in foods allow an estimation of their general bacteriological condition ('indicator' function) and to a certain extent the risk of presence of pathogenic enteric organisms ('index' function) (Mossel 1982).…”

“…Ninan et al (2011) reported that spoilage of fresh trout stored aerobically in ice was due to the activity of more than one specific spoilage organism and genera Moraxella, Acinetobacter, Pseudomonas, Shewanella, Aeromonas and Flavobacterium dominated in the microflora. In contrary, in the present study, towards the end of storage, the specific spoilage organisms were limited to Pseudomonas and Aeromonas alone, whereas significant number of members of Stenotrophomonas and Burkholderia was observed among the microflora.…”