STUDY ON THE EFFECTIVENESS OF PRESERVATIVES AT DIFFERENT CONCENTRATIONS IN CONTROLLING MICROBIAL GROWTH IN SOFT DRINKS

Abstract

Soft drinks are the carbonated non-alcoholic beverages, which contain water and carbon dioxide as major ingredients. Sugar, colors, flavors, acids, liquid heading, essence and preservatives are also used as ingredients. Soft drinks do not normally susceptible for the microbial spoilage because of their acidity and carbonation. However during processing and storing soft drinks can be contaminated by bacteria, yeast and moulds and it will be spoiled. So it can impact taste and flavor. For this reason a small amount of preservatives are added. There are two permitted preservatives mainly used in soft drinks, benzoic acid and SO2 in different concentrations. The present study was carried out to determine the best concentrations of preservative to incorporate in carbonated soft drinks. When studying on the effectiveness of preservatives of different concentration, in soft drinks,microorganisms were enumerated aseptically using sterilized equipments and media.Nutrient media was used to enumerate total colony counts and yeast extraction agar media was used to enumerate yeast and moulds counts. Benzoic acid and SO2 were added as sodium benzoate and potassium metabisulphaite (KMS) respectively in order to get preservative action. The effect of benzoic acid and S 0 2 individually and as a mixture were studied.Total colonies w€re incubated at 30-35 °C for 48 hours and yeast and moulds were incubated at room temperature for 72 hours. For the preservation of soft drinks the suitable optimum concentration of benzoic acid was 45 ppm and it was 49 ppm for S02 . The best combination of concentrations were 39/95 ppm of benzoic acid and S 0 2 respectively when they were used as a mixture