PRODUCTION AND EVALUATION OF MICROBIAL QUALITY AND STORAGE STABILITY OF TIGERNUT (Cyperus esculentus) MILK USING LIME (Citrus aurantiifolia) JUICE AS NATURAL PRESERVATIVE

Abstract

Lime (Citrus aurantiifolia) juice preservative potentials were evaluated for the microbiological quality and storage stability of tigernut milk. The aqueous extract of tigernut milk (Cyperus esculetus) was preserved with lime juice. Pasteurized at 75⁰C for 20 minutes and stored at ambient temperature (28⁰C) for 14 days followed which was investigated by determining pH, total microbial counts and determination of percentage occurrences of microorganisms. Bacterial counts ranged of 1.53±0.02^b to 1.73±0.01^alog10cfu/ml of the samples preserved using lime juice; the fungal counts recorded range from 1.70±0.07^a to 1.93±0.03^alog10cfu/ml while the control tiger nut milk ranges from 2.32±0.05^a to 2.55±0.03^alog10cfu/ml respectively. The tiger nut milk was acidic with a range of 4.50±0.1^a to 4.60±0.5^a pH value. At Week 0 the samples containing preservative recorded a low microbial count. There was significant reduction in microbial load as the effects of the preservative became evident at Week 1 and Week 2. Moreover, the antimicrobial activities of the preservative revealed that samples at concentrations 300mg/ml were most effective against microbes than the 200mg/ml and 100mg/ml. This shows that the active ingredients in the preservative exhibited more potential at higher concentration than at lower concentration. Samples without preservatives recorded high microbial counts throughout the storage period. Staphylococcus aureus, Streptococcus spp, Bacillus spp, and Pseudomonas spp were isolated. While Saccharomyces cerevisiae, Aspergillus niger, Aspergillus flavus and Penicillium spp were fungi isolated. Staphylococcus aureus and Saccharomyces spp remained the predominant organisms throughout the storage period.