W. Braide., S. Oranusi and A.I. Peter-Ikechukwu
The effect of some commonly used chemical preservatives (acetic acid and sodium benzoate), natural plant extracts (clove, garlic, ginger and lime) and pasteurization on the elongation of shelf-life of zobo beverage were investigated by determining total counts and characterization of microorganisms before and during storage at ambient temperature for 14 days. Five bacterial species, namely Staphylococcus aureus, Micrococcus leteus, Micrococcus rosues, Bacillus subtilis and Enterococcus faecalis were predominant isolates. Two fungal species, namely, Saccharomyces cerevisiae and Rhizopus stolonifer were also isolated. Bacillus subtilis and Saccharomyces cerevisiae remained the predominant organisms throughout the storage. The role played by some of the isolates in food spoilage, deterioration and intoxication had been discussed. The microbial population increased for two days as the organisms utilize the nutrients present in the sample. There was a drastic reduction in microbial load as the effects of the preservative became evident, except for the control sample. Antimicrobial activities of the preservatives revealed that samples with chemical preservatives were most effective against bacteria and fungi species, followed by the natural plant extracts samples. Pasteurization confers temporary preservation as its effect was short lived. The phytochemical and antimicrobial activities of the plants used had been reported. Of all the samples, only those treated with chemical preservatives remained organoleptically attractive after preservation for 14 days. The overall reduction in the microbial population could be a concerted effort of the preservatives and exhaustion of nutrients in the zobo drink. The study recommends the use of chemical and natural preservatives to enhance the keeping quality of zobo beverage which conforms to good manufacturing practices globally.
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