Determination of Survival Rates of Bacteria in Contaminated Fresh Fruit Juice Samples

Aims: To determine the survival rates of bacteria in contaminated fresh fruit juice samples
Place and Duration of Study: Biosciences and Biotechnology Department, Babcock University, Ilisan Remo, Ogun State, Nigeria, between November, 2012 and May, 2013.
Methodology: Freshly extracted juice samples were obtained from intact pineapple (Ananas comosus Merr.) and watermelon (Citrillus lanatus Thunb.) were pasteurized before being contaminated with Escherichia coli ATCC 25922 and Lactobacillus acidophilus. While the pH and the sugar contents were determined at interval after being contaminated with the bacterial strains, the contaminated juice samples were sampled for 150 min to determine colony forming unit per milliliter (cfu/ml) at different sampling time.
Results: In pineapple juice, the log of concentration of E. coli was reduced from 6.452 at 0 min to 5.079 at 150min. In watermelon, the log of concentration of E. coli was reduced from 6.301 at 0min to 5.954 at 150min. While the log of concentration of L. acidophilus in pineapple juice was between 6.204 at 0 min and 6.262 at 150min, its log of concentration in watermelon juice ranged between 6.228 at 0 min and 6.291 at 150min. The pH was reduced to 2.9 and 3.7 by E. coli while L. acidophilus reduced the pH to 2.5 and 3.0 for pineapple and watermelon juices respectively. After 150min, the sugar contents of pineapple and watermelon juices decreased from 1.181 and 1.060mg/ml to 0.011 and 0.004mg/ml by the E. coli while L. acidophilus reduced the sugar contents to 0.003mg/ml for pineapple juice and 0.018mg/ml for watermelon juice. The reduction in the pH values of each of the fruit juices showed that the activities of each bacterial strain resulted in increase in the production of acid in the growth medium.
Conclusion: The inability of coli form (E. coli) to survive in the fruit juices suggested that the fruit juices may not harbor and/or disseminate enteric pathogens if allowed to stay for a while before packaging.