Effects of fasting period on post-harvest flesh quality of Clarias gariepinus

Abstract

Post-harvest fasting period in aquaculture is carried out to empty the gut of fish, thereby reducing intestinal bacterial load, spread of gut enzymes and potential pathogens, thus preserving flesh quality. Time required for fasting is however unclear, as weight reduction is associated with food deprivation. This present study investigates the effect of fasting period on post-harvest flesh quality of Clarias gariepinus. Fifty C. gariepinus (Mean weight 2.98±0.12kg) were randomly distributed into five plastic tanks (0H, 24H, 48H, 72H and 84H) at 10fish/500L. 0H, 24H, 48H, and 72H were slaughtered at 0, 24, 48, and 72 hours of fasting respectively. However, 84H was not starved but slaughtered at 84 hours. Immediately after slaughtering, 3 fish per treatment were filleted for proximate composition and digestive enzyme activity analysis, while the remaining fish per treatment were processed for organoleptic assessment using five-man trained assessors. Data were subjected to ANOVA at α0.05. Fish biomass decreased with increase in fasting period with 72H recording the highest weight loss (190g). Crude protein, ash and lipids content were significantly higher (P<0.05) in dry samples of 0H and 84H, but were higher in 24H, 48H and 72H for wet samples. Protease and lipase activities decreased significantly (P<0.05) with increasing starvation periods while increase in amylase was observed. Protease activity ranged from 15.2U/mg protein (0H), through 12.1U/mg protein (84H) to 7.5 U/mg protein (72H), while Lipase activity ranged from 11.4 U/mg protein (0H) through 9.7 U/mg protein (84H) to 6.8 U/mg protein (72H). Sensory scores revealed that 0H had the best scores for colour, taste, smell, texture and flavor (≥ 8), followed by 84 h. This study revealed a loss in body weight after a fasting period of 48 hours. Also flesh quality was negatively affected with increased periods of fasting. Therefore, for premium quality of flesh, prolonged starvation of C. gariepinus beyond 48h prior slaughter should be avoided.