Chemoprotective Studies of Some Preservatives against Spoilage Microorganisms Associated with Stored Roselle Juice and Their Resultant Effects on the Juice’s pH and Ascorbic Acid

Abstract

Four different prepared extracts from roselle (Hibiscus sabdariffa Linn.) calyxes were stored differently with chemical preservatives (sodium benzoate, sodium metabisulphite, boric acid, and citric acid) for eight weeks. A control, sample without preservative was also stored for the same period. They were understudied weekly for changes in the pH, ascorbic acid content, and microbial population. The research was carried out to studying the influence of the chemical preservatives on the pH, vitamin C, and microbial population of the extract during storage. Up to the first three weeks of storage, the vitamin C contents of the entire juices were not statistically different (p = 0.05) except, sample preserved with sodium benzoate. In the same manner, with exception of samples stored without preservative and with sodium metabisulphite, other samples were not significantly different (p = 0.05) with respect to pH. With exception of the control, spoilage started between third and sixth week of storage while sodium metabisulphite inhibited the growth of microbes till the end of the studied week. Generally, the results from this study revealed a decrease in pH (increase in acidity), a reduction in ascorbic acid content and an increase in microbial population as the storage time was extended in the entire samples but more explicit in the sample stored without preservative. The rate of change of pH and percentage reduction in ascorbic acid with respect to storage time in the sample without preservative increased tremendously compared to other juices stored with preservatives. This study showed that the chemical preservatives prohibited rapid loss of vitamin C and inhibited the growth of microorganisms that might have caused spoilage of this juice during storage. The use of chemical preservatives to prolong the shelf-life of this juice is therefore advocated so as to make it more available round the year.