The increasing popularity of traditional milk-based foods has placed emphasis on the need for microbial safety in food-chain establishments, as there are ample possibilities for foodborne pathogens to occur as postprocessing contaminants. The behavioral pattern of an enterotoxigenic strain of Escherichia coli D 21 introduced as a postprocessing contaminant in shrikhand, a traditional sweetened lactic fermented milk product, was studied with variables of initial inoculum (4.3, 5.3, and 6.3 log10 CFU/g), storage temperature (4, 10, and 16°C), and storage period (4, 9, and 14 days). During storage of shrikhand prepared individually with Lactobacillus delbruecki ssp. bulgaricus CFR 2028 and Lactococcus lactis ssp. cremoris B-634, there was a steady decrease in the viable count of E. coli that was proportional to the initial inoculum of E. coli introduced into shrikhand. The data were subjected to multivariate analysis, and equations were derived to predict the behavior of E. coli in shrikhand. The predicted values for the probable survival of E. coli showed good agreement with the experimental values with a majority of these predictions being fail-safe. The values of statistical indices showed that the model fits ranged between extremely good and satisfactory. Response surface plots were generated to describe the behavioral pattern of E. coli. The derived models and response surface plots enabled prediction of the survival of E. coli in shrikhand as a function of initial inoculum levels, storage temperatures, and storage periods of shrikhand. These predictions were valid within the limits of the experimental variables used to develop the model.
A response surface methodology study on the effects of some phenolics and storage period length on vegetable oil quality: change in oxidation stability parameters
