Effect of Spices, pH and Temperature on the Survival and Multiplication of Staphylococcus aureus in Locally Made Soya Milk Drink

Abstract

This study was carried out to investigate the effects of spices, pH and temperature on the survival and growth of Staphylococcus aureus isolated from stream water samples in Soya milk drink. A total of 12 water samples were drawn from 3 different streams used in Ihiala Local Government Area, Anambra State, and screened for the presence of Staphylococcus aureus using pour plate method. The isolate obtained was characterized and identified using their morphological and biochemical characteristics. The effect of spices, pH and temperature on the isolate was determined by subjecting the isolate to 0.25%, 1.25% and 2.5% of spices (Zigiber officinale and Myristica fragrans), different pH ranges (3-10) and different temperatures (4⁰C, 25⁰C and 37⁰C). Eleven water samples out of twelve samples drawn from the streams showed the presence of Staphylococcus aureus. The spices showed pronounced activity against the organism in both sterilized and non sterilized samples of which the activity increased significantly (P<0.05) as the concentration increased. The activity of Zigiber officinale was significantly (P<0.05) higher than that of Myristica fragrans. The maximum growth of the isolate was significantly (P<0.05) observed at pH 6 and 37⁰C. Little or no growth was observed at 4⁰C. This study has shown that the growth of Staphylococcus aureus in Soya milk drink could be controlled using Zigiber officinale and Myristica fragrans extracts at pH values other than 6, and should best be sold and consumed at refrigeration temperature (4⁰C).