Quality and Shelf – Life Assessment of Variously Processed Catfish and Tilapia Stored at Ambient Temperature

Aims: The effects of oven – drying (OVD), brining and oven – drying (BOVD) and smoking (SMK) on quality and shelf – life of Catfish (Chrysichthys nigrodigitatus) and Tilapia (T. zillii) were evaluated.
Study Design: Completely randomised block design.
Place and Duration of Study: Department of Environmental Management & Toxicology, Federal University of Agriculture Abeokuta, Nigeria, between February 2011 and August 2012.
Methodology: Life fish were collected and processed using three local preservation methods. Processed fish samples were stored in perforated plastic containers for 11 successive weeks at ambient temperature (25-32ºC) and assessed weekly for weekly for levels of trace metals (Fe, Zn, Cd, Pb) and physical attributes of odour, flavour and texture. Microbial load was assessed by total viable count (TVC) and biochemical activity by total volatile nitrogen (TVN).
Results: This study showed that brined/ oven-dried fish was the most accepted followed by smoked fish. The quality of processed fish under ambient conditions decreased with increasing storage time in the order OVD>SMKD<BOVD. Statistical analysis showed that no significant (P=.05) differences existed between the trace metal contents of the samples from the three processing methods. Also, samples processed using the three processing methods contained levels of trace metals below the recommended limits for trace metals in fish and are therefore safe for human consumption. However, method of processing had significant effects (P=.05) on the TVC and TVN content of fish.
Conclusion: Brined/oven dried samples were most organoleptically accepted and deteriorated the least. Chrysichthys nigrodigitatus deteriorated faster in odour and flavour than Tilapia zilli. Caution should be exercised in the consumption of processed fish stored on open shelf for very long weeks (above 5 weeks) as they could contain higher amounts of microbial cells.