Modelling the growth of Staphylococcus aureus with different levels of resistance to low temperatures in glutinous rice dough

When using predictive models to assess the risk posed by foodborne pathogens, certain strains exhibit resistance at low temperatures, which may affect the assessment result. To understand the influence of strain heterogeneity on growth dynamics, two Staphylococcus aureus strains, including comparatively low temperature tolerant BB-11 and sensitive BA-26, were inoculated into glutinous rice dough at temperatures ranging from 10 to 37 degrees C. The primary Gompertz model fit showed an obvious difference in the maximum specific growth (mu max) and duration of the lag phase (lambda) values at 10 degrees C (0.071/h and 28 h for BB-11 and 0.049/h and 34 h for BA-26, respectively). When Huang and Ratkowsky models were compared as secondary models, a log-linear relationship was demonstrated between mu max and lambda for both models. Ratkowsky's model fit was more accurate with a high R2 of 0.95. The predicted minimum growth temperatures were 4.8 degrees C and 6.3 degrees C for BB-11 and BA-26, respectively. The time for achieving a 4-log increase (t4.0) was 96 h for BB-11 at 10 degrees C, but only 2.4 log CFU/g increase was determined in BA-26 at 144 h. This study suggests that cold-tolerant strains should be considered when a pre-dictive model is used for risk assessment of foodborne pathogens.

Automated summary

When using predictive models to assess the risk posed by foodborne pathogens, it is important to consider strain heterogeneity, as certain strains exhibit resistance at low temperatures. This study investigated the growth dynamics of two Staphylococcus aureus strains in glutinous rice dough at different temperatures. The results showed significant differences in the maximum specific growth and duration of the lag phase between the cold-tolerant and sensitive strains. The findings suggest that predictive models should incorporate cold-tolerant strains for accurate risk assessment of foodborne pathogens.