Effect of Natural Preservatives (Lemon Grass and Bay Leaf Marinade) on the Microbial Load and Shelf Life of Smoke-dried Clarias gariepinus

Abstract

This study was carried out to determine the effect of lemon grass marinade (sample A), bay leaf marinade (sample B) and a combination of both spices (sample C) on the microbial load of stored smoked-dried Clarias gariepinus. Comparative analysis of the microbial load of each treated fish samples during ambient storage was done biweekly for six (6) weeks and then samples of each treatment were taken to the laboratory periodically. The fish samples were analysed using Potato Dextrose Agar and Nutrient Agar for fungi and bacteria respectively. The initial microbial load before storage showed that the highest number of bacteria counts occurred in smoke-dried Clarias gariepinus treated with bay leaf marinade (4.7´103) while the lowest was in smoke-dried C. gariepinus treated with lemon grass marinade (1.3´103). The highest fungi count was observed in smoke-dried C. gariepinus treated with the combination of both spices (9.5´102) while the least fungi count was in fresh fish sample (1.4´103), although the fresh fish sample had the highest bacteria mean count (5.1´103) when compared with the treated samples. After 6 weeks of ambient storage, the result of smoke-dried C. gariepinus treated with bay leaf marinade was also significantly different from the mean population of smoke-dried C. gariepinus treated with lemon grass marinade and smoke-dried C. gariepinus treated with the combination of both spices. Smoke-dried C. gariepinus treated with bay leaf marinade again had the highest bacteria and fungi mean count of 1.7´105 and 2.3´104 respectively. Smoke-dried C. gariepinus treated with lemon grass marinade and smoke-dried C. gariepinus treated with the combination of both spices had similar bacteria mean count of 1.5´105 while smoke-dried C. gariepinus treated with lemon grass marinade had the lowest fungi mean count of 1.6´104. The study revealed that all three smoked-dried fish sample treatment had a relatively low bacterial and fungal count below the 5 x 105cfu/g recommended by the International Commission of Microbial Specification for Food and Food Products (ICMS, 2002).