Modelling growth of Bacillus cereus in paneer by one-step parameter estimation

Abstract

Bacillus cereus phylogenetic group III and IV strains are commonly associated with food products and cause toxin mediated foodborne diseases. These pathogenic strains have been identified from milk and dairy products, such as reconstituted infant formula and several cheeses. Paneer is a fresh, soft cheese originating from India that is prone to foodborne pathogen contamination, such as by Bacillus cereus. However, there are no reported studies of B. cereus toxin formation in paneer or predictive models quantifying growth of the pathogen in paneer under different environmental conditions. This study assessed enterotoxin-producing potential of B. cereus group III and IV strains, isolated from dairy farm environments, in fresh paneer. Growth of a four-strain cocktail of toxin-producing B. cereus strains was measured in freshly prepared paneer incubated at 5-55 °C and modelled using a one-step parameter estimation combined with bootstrap re-sampling to generate confidence intervals for model parameters. The pathogen grew in paneer between 10 and 50 °C and the developed model fit the observed data well (R² = 0.972, RMSE = 0.321 log₁₀ CFU/g). The cardinal parameters for B. cereus growth in paneer along with the 95% confidence intervals were: μ_opt 0.812 log₁₀ CFU/g/h (0.742, 0.917); T_opt is 44.177 °C (43.16, 45.49); T_min is 4.405 °C (3.973, 4.829); T_max is 50.676 °C (50.367, 51.144). The model developed can be used in food safety management plans and risk assessments to improve safety of paneer while also adding to limited information on B. cereus growth kinetics in dairy products.

Keywords: Bacillus cereus; Food safety; Growth kinetics; One-step modelling; Predictive microbiology; Soft cheese.