Development of a Quality Index Method (QIM) Scheme to Evaluate Freshness of Ice Stored Lake Victoria Nile Perch (Lates niloticus).

Abstract

Despite the Nile perch contributing about 67% of Kenya’s total annual fish export earnings, no specific method exists for evaluating the freshness of the fish when landed and its shelf life when kept in ice. Currently the European Union (EU) sensory scheme is used in sensory evaluation of all commercial fish species available in the Kenyan fishery. This study was conducted to develop a suitable Quality Index Method scheme, that is specific for the Nile perch, using a set of selected sensory parameters to help follow its deterioration profile in order to estimate changes in its freshness in the course of storage in ice. Fish samples for the study were obtained from the beaches. The fish samples from each location were divided into two groups; ungutted and gutted. The selected sensory parameters were correlated with selected biochemical and microbiological parameters. Significant increase (p ≤ 0.05) in the levels of sensory, microbiological and chemical parameters was observed on the 10th and 14th day onwards for the ungutted experimental and control samples, respectively and on the 14th and 18th day for the gutted experimental and control fish samples, respectively. The Quality index scores had a correlation of 0.98 with H 2 S producing bacteria, 0.93 with total viable counts (TVC), 0.97 with total volatile basic nitrogen (TVBN), 0.96 with free fatty acids (FFA) and 0.97 with pH. The ungutted fish from the beaches and fishing ground had a shelf life of 22 and 28 days, respectively. The gutted fish samples from the beaches and fishing grounds had a shelf life of 26 and more than 28 days in ice, respectively. Gutting extended the shelf life of the Nile perch by about 4 days for both the beach - purchased and controls. The microbial, sensory and chemical parameters levels increased with increase in storage days both for ungutted and gutted fish samples from the beaches and fishing ground. The protein content decreased with increasing storage time in the ungutted experimental and control samples than in the gutted fish samples. There was no significant variation (p ≥ 0.05) in the moisture, lipid and ash content for both ungutted and gutted fish samples. The study is useful setting standards and guidelines which will be used by the Fish Inspectors in the enforcement of sensory quality of fish destined for the domestic and export markets. This will prevent occasional interruptions of exports to the European Union markets thereby minimizing the resultant huge financial losses to the industry hence creating steady employment to the locals.