Effect of Chilled-frozen Storage on the Physico-chemical and Microbiological Quality of Silver Catfish (Chrysichthys Nigrodigitatus) from Asejire Lake, Ibadan, Nigeria

Abstract

Fishes are highly perishable and are often discarded or sold at low prices over time due to deterioration. Freezing is a widely accepted preservation technique but fishers often lack freezing equipment on board and at the landing sites. Chilling or icing of fish immediately after the catch has been reported to reduce microbial and enzymatic spoilage before freezing or processing. This study, therefore, investigated microbial and physicochemical changes of frozen and prior chilled Chrysichthys nigrodigitatus obtained from Asejire reservoir, Nigeria. A total of 60 freshly caught samples of Chrysichthys nigrodigitatus (75-230g) were collected from Asejire dam. The fish were gutted and divided into two equal numbers. The first 30 pieces were frozen immediately after gutting (FRZ) while the remaining were chilled in ice for 24 hours before freezing (CBF). Samples of FRZ and CBF were subjected to sensory, proximate and microbial analysis following standard procedures. Crude protein reduced from 15.43±0.35 in FRZ while it increased from 17.13±0.31 to 17.70±0.25 after 24hrs and 12 weeks, respectively. This could be attributed to the higher moisture content in CBF. The initial and final microbial count increased in both FRZ and CBF 3.777x105±0.35 - 7.5x106±0.30 CFU/g and 17.13±0.31% - 17.70±0.25% respectively. FRZ is fit for consumption and had longer shelf life however CBF had higher protein and fat content at the end of the experiment.