Modelling bacterial spoilage in cold-filled ready to drink beverages by Acinetobacter calcoaceticus and Gluconobacter oxydans

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Abstract
Aims: Mathematical models were created which predict the growth of spoilage bacteria in response to various preservation systems. Methods and Results: A Box‐Behnken design included five variables: pH (2·8, 3·3, 3·8), titratable acidity (0·20%, 0·40%, 0·60%), sugar (8·0, 12·0, 16·0 °Brix), sodium benzoate concentration (100, 225, 350 ppm), and potassium sorbate concentration (100, 225, 350 ppm). Duplicate samples were inoculated with a bacterial cocktail (100 μl 50 ml–1) consisting of equal proportions of Acinetobacter calcoaceticus and Gluconobacter oxydans (5 × 105 cfu ml–1 each). Bacteria from the inoculated samples were enumerated on malt extract agar at zero, one, two, four, six, and eight weeks. Conclusions: The pH, titratable acidity, sugar content, sodium benzoate, and potassium sorbate levels were all significant factors in predicting the growth of spoilage bacteria. Significance and Impact of the Study: This beverage spoilage model can be used to predict microbial stability in new beverage product development and potentially reduce the cost and time involved in microbial challenge testing.