Joint effect of heat, pH and grape extract on spores survival in a rice solution.

Rice due to its high carbohydrate content, is an ideal medium for growth, a spore-producing microorganism. The objective of this study was to determine the antimicrobial activity of a grape extract in combination with heat treatments and different pH against spores in a rice solution. The survivor data obtained were fitted to the Weibull survival function, and the values of parameters and (scale and shape indexes, respectively) were determined. Results showed that the grape extract affected the survival of spores at 90 °C and 95 °C, reaching greater logarithmic reductions in acidic pH values. This behaviour was reflected in parameter of the Weibull survival function which decreased as the temperature increased and at acidic pH values. In addition, a secondary model was developed by relating the logarithm of to the independent variables (temperature and pH). A global model relating inactivation with temperature and pH was developed, and validated by calculating the accuracy factor. The results demonstrate the usefulness of grape extract as a by-product, which can be used as an additional control measure for rice, especially when combined with mild heat treatments and acidic pH values.