Effect of Different Preservatives on Microbial Load of Zobo Drink and Molecular Characterization of its Bacterial Flora

Abstract

The potentials of various combinations of three preservation techniques: the use of chemical preservative (sodium benzoate), pasteurization and lime to preserve zobo drink at room temperature (28±2 ºC) were evaluated over six days. The samples were treated and stored for six days during which the proximate composition, physiochemical and microbiological properties of the zobo drink were determined daily. Isolates obtained were subjected to molecular characterization and identification. The proximate composition of zobo drink before treatment showed that it contains 92.52% moisture content, 0.56% ash content, 1.05% fat and oil, 2.16% protein, 0.17% fibre and 3.54% carbohydrate. The pH values ranged from 2.8 to 3.4, while the titratable acidity ranged from 0.2586 to 0.2816 %. There was increasing acidity of the zobo samples with storage (reduction in pH and increase in the titratable acidity). Bacterial counts ranged from 3.0 x 102 to 3.15 x 103 cfuml-1 while fungal count ranged from 3.5 x 102 to 2.35 x 103 cfuml-1. Six organisms comprising of four bacteria: Bacillus cereus ZB1 (MH566234), Lactobacillus brevis ZB2 (MH566235), Staphylococcus aureus ZB3 (MH559826), Micrococcus luteus and two fungi: Aspergillus niger and Penicillium citrinum were found in the zobo drink samples. Combining pasteurized with addition of preservatives was the most effective in reducing bacterial load followed by lime and sodium benzoate. This study revealed that the synergistic effect of pasteurization and lime, pasteurization and sodium benzoate introduction into zobo sample can be used to minimize bacterial load to acceptable limit for at least six days after production.