Controlling Clostridium sporogenes spoilage of “requeijão cremoso” processed cheese: Modeling the growth/no-growth probability as a function of pH, sodium chloride and nisin

Predictive models were developed to assess the growth response of Clostridium sporogenes in "requeijão cremoso" processed cheese, as affected by pH and sodium chloride and nisin concentrations. A complete factorial design was performed using different formulations: pH (5.2, 5.6, and 6.0), sodium chloride (0.5, 0.75, 1.0, 1.25, and 1.5%), and nisin (0.0, 5.0, 7.5, 10.0 and 12.5 mg/kg), totalizing 75 conditions. Packs with 150g of "requeijão cremoso" were inoculated with 103 spores/g following storage at 10 °C for up to 60 days. The counts of C. sporogenes were performed on day zero and at the end of storage after a heat shock (80 °C for 12 min). The formulations that allowed an increase in the population >1 log CFU/g were assigned the value of 1 (growth), and the formulations in which the increase was