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Nutritional composition and shelflife of the lake victoria nile perch (Lates niloticus) stored in ice.
Abstract
Nile perch, the most important commercial fish species from the Lake Victoria fishery, contributes about 67% of Kenya’s total annual fish export earnings. Despite the Nile perch being an important foreign exchange earner, little information is available on its nutritional composition and shelf life on ice, information that is necessary for the development of methods to maintain its freshness, especially in view of the occasional rejection of exports of Nile perch products by the European Union.
This study was, therefore, conducted using a set of physicochemical parameters to follow its deterioration profile in order to estimate its shelf life and freshness in the course of storage. These sensory parameters were correlated with selected biochemical and microbiological parameters to assess the suitability of the quality index scheme developed to determine the quality and shelf life of the iced Nile perch in the course of storage. The protein, lipid, moisture and ash contents were determined. The pH, total volatile basic nitrogen (TVBN), TMAO and free fatty acids
(FFA) contents were the biochemical parameters studied, while total viable counts (TVC) and hydrogen sulphide producing bacterial counts were the microbiological parameters studied at the various stages of storage. The results showed that protein in the edible tissue of the Nile perch varied significantly (p<0.05) between 19.8 and 17.7%; the lipid, ash and moisture contents which varied between 0.59 and 0.63%, 0.55 and 0.63%, and 78.5 and 79.5%, respectively, were not significantly related to
storage time (p>0.05). The sensory characteristics selected for the quality index scheme increased from 3.3 demerit points to 18.1 points (out of 20) at the point of rejection by a sensory panel. The TVBN increased from 8.4±0.7 mgN/100g to 26.0±0.9 mgN/ 100g at the point of rejection. No TMAO was detected. The %FFA increased from 1.9 to 2.7% at the point of rejection, while the TVC and hydrogen sulphide producing bacterial counts increased from 6.6 log cfu/g to 8.0 log cfu/g and 4.3 log cfu/g to 7.3 log cfu/g, respectively. The study established that the ungutted iced Nile perch handled under normal conditions in this fishery with a delay of 3-4
hours before icing, had shelf life of 22 days, while the control which was iced on board had a shelf life of 28 days. The study is significant in designing programmes for reducing post harvest losses of this fish in the Lake Victoria fishery.
This study was, therefore, conducted using a set of physicochemical parameters to follow its deterioration profile in order to estimate its shelf life and freshness in the course of storage. These sensory parameters were correlated with selected biochemical and microbiological parameters to assess the suitability of the quality index scheme developed to determine the quality and shelf life of the iced Nile perch in the course of storage. The protein, lipid, moisture and ash contents were determined. The pH, total volatile basic nitrogen (TVBN), TMAO and free fatty acids
(FFA) contents were the biochemical parameters studied, while total viable counts (TVC) and hydrogen sulphide producing bacterial counts were the microbiological parameters studied at the various stages of storage. The results showed that protein in the edible tissue of the Nile perch varied significantly (p<0.05) between 19.8 and 17.7%; the lipid, ash and moisture contents which varied between 0.59 and 0.63%, 0.55 and 0.63%, and 78.5 and 79.5%, respectively, were not significantly related to
storage time (p>0.05). The sensory characteristics selected for the quality index scheme increased from 3.3 demerit points to 18.1 points (out of 20) at the point of rejection by a sensory panel. The TVBN increased from 8.4±0.7 mgN/100g to 26.0±0.9 mgN/ 100g at the point of rejection. No TMAO was detected. The %FFA increased from 1.9 to 2.7% at the point of rejection, while the TVC and hydrogen sulphide producing bacterial counts increased from 6.6 log cfu/g to 8.0 log cfu/g and 4.3 log cfu/g to 7.3 log cfu/g, respectively. The study established that the ungutted iced Nile perch handled under normal conditions in this fishery with a delay of 3-4
hours before icing, had shelf life of 22 days, while the control which was iced on board had a shelf life of 28 days. The study is significant in designing programmes for reducing post harvest losses of this fish in the Lake Victoria fishery.
