Comparison of antimicrobial activities of brine salting, Chlorinated solution and <i>Moringa oleifera</i> plant extracts in fish from Lake Victoria basin of Kenya

Abstract

Chemical preservatives can be used to reduce the overall microbial populations in fish and fish products. This study was set to determine the antimicrobial activities of brine salting, chlorinated solution, and Moringa oleifera plant extracts treatments on enteric bacteria in Rastrineobola argentea and Oreochromis niloticus fish collected from beaches and markets in Lake Victoria basin of western Kenya. Using a cross-sectional samples collection design, fresh fish (Rastrineobola argentea and Oreochromis niloticus) samples were randomly collected from three fish landing beaches (Dunga, Luanda Rombo and Sirongo) and from three markets (Kisumu, Luanda and Bondo), in the Lake Victoria Basin of western Kenya and taken to the laboratory within 4 hours for processing and treatments with preservatives. The preservatives were sodium chloride solutions (3%, 6%, 9% and 12%), sodium hypochlorite (50ppm, 100ppm, 150ppm and 200ppm), and Moringa oleifera n-hexane and ethanol extract solutions (20ìg/ml, 40ìg/ml, 60ìg/ml, and 80ìg/ml), respectively. The treatments were done for 0hrs, 2hrs, 4hrs, 6hrs and 8hrs, before bacteria growth analysis using most probable number and aerobic plate count methods. Statistical differences in effectiveness of the preservatives was determined by one factor ANOVA with P<0.05 value considered statistically significant. The results showed that with increase in salt concentration and after 8 hours treatment duration, there was a significant reduction of microbial load in R. argentae and O. niloticus fish samples, P<0.05, one factor  ANOVA. The effectiveness of chlorinated solution (sodium hypochlorite) against the bacteria decreased with time but increased with increase in concentration. As M. oleifera n-hexane and ethanol extracts concentrations increased and after 8 hours treatment duration, there was significant decrease in microbial loads, P<0.001 by one factor ANOVA. Overall, sodium chloride at 12% concentration was the most effective and chlorine solution even at 200ppm was the least effective while the M. oleifera plant extracts solutions were moderately effective against bacteria in fish. These results show that other than the traditional sodium chloride, M. oleifera plant extracts can also be used as antimicrobial agent for processing and preservation of fish.

Key words: enteric, preservatives, extracts, antimicrobial, effectiveness