ABSTRACT

Tomato is one of the most popular consumed vegetable crops worldwide mainly as fresh or processed products. The antimicrobial potentials of lactic acid bacteria metabolites against tomato paste spoilage microorganisms were evaluated.  Cow milk and Tomato samples were purchased. The tomato samples were processed into tomato paste. Standard microbiological methods were used in isolation, microbial count and identification of organisms. Cow milk samples were used for the isolation of lactic acid bacteria. Antimicrobial effects of the isolated lactic acid bacteria metabolites were carried out on the spoilage isolates from tomato paste samples using the agar well diffusion method, while shelf-life study was done on the tomato paste samples using the lactic acid bacteria metabolites as biopreservative agents for a period of 14 days. The results showed that total viable count ranged from 2.81 x 10⁷Cfu/ml - 1.3 x 10⁶Cfu/ml, the coliform count from 6.5 x 10⁴Cfu/ml – 1.1 x 10⁴Cfu/ml, while the fungal count was from 3.0 x 10⁴Cfu/ml – 1.5 x 10⁴Cfu/ml. The bacterial isolates from the tomato samples were Bacillus sp and Pseudomonas sp, while the fungal isolates were Rhizopus sp, Saccharomyces sp, Fusarium sp, Apergillus sp and Mucor sp. Lactic acid bacteria isolates from the cow milk samples were Lactobacillus fermentum M6, Lactobacillus fermentum LF-12 and Lactobacillus fermentum M8.The strains of Lactobacillus fermentum were able to grow at different temperature, pH and NaCl concentration and also produced antimicrobial compounds with Lactobacillus fermentum LF-12 recording the highest lactic acid (0.98 g/l), diacetyl (1.77 g/l) and hydrogen perioxide (1.60 g/l). The metabolites from strains of Lactobacillus fermentum were all potent against the spoilage microorganisms with zones of inhibition ranging from 2 mm to 12 mm. There were significant differences (p<0.005) in the activities of the metabolites of the strains of Lactobacillus fermentum. The result of the shelf-life study revealed a great reduction in bacterial load and growth over a period of 14 days of storage. This shows that strains of Lactobacillus fermentum can be used as bioperservative agents in preserving tomato paste as an alternative to chemical preservatives.