Staphylococcus Carnosus CS 300 Grown Under Varying Conditions at 42°C as a Potential Surrogate for Correlation of Hepatitis A Virus Inactivation in Select Foods

Hepatitis A virus (HAV) is an epidemiologically relevant foodborne pathogen, more thermally resistant than most tested non-spore forming bacteria, that necessitates validation of its inactivation during food processing. Staphylococcus carnosus strain CS 300 has been evaluated as a potential HAV-surrogate. In this study, the thermal resistance of S. carnosus CS 300 grown in Tryptic Soy Broth (TSB) containing 4% NaCl, 5% NaCl, or 20% glycerol at 42°C and inoculated into spinach, macaroni and cheese, and pasta salad after growth in TSB with 20% glycerol was compared to HAV, by the linear and Weibull models. In buffer, linear model D-values of CS 300 grown in 4% NaCl ranged from 14.39±1.51 to 3.12±0.78 min for 56 to 64°C, for 5% NaCl ranged from 23.82±3.82 to 0.90±0.15 min, and for 20% glycerol ranged from 27.35±3.17 to 0.90±0.18 min at 56 to 68°C, respectively. Weibull model td=1 values in 4% NaCl ranged from 16.68±5.79 to 2.48±1.50 min for 56 to 64°C; in 5% NaCl at 56 to 68°C was 22.74±7.64 to 0.96±0.45 min; while in 20% glycerol ranged from 28.84±5.51 to 0.68±0.03 min. Increased D-values of CS 300 in spinach that ranged from 69.44±8.02 to 1.24±0.10 min for 58 to 68oC, while td=1 values of 75.63±20.87 to 0.87±0.46 min were obtained. Similarly, D-values in pasta salad ranged from 29.96±1.86 to 0.91±0.13 min for CS 300 compared to 9.67±0.41 to 1.33±0.09 min for HAV, with td=1 of 29.37±7.51 to 1.29±0.13 min for CS 300 and 10.58±4.44 to 1.42±0.62 min for HAV at 56 to 64°C, respectively. D-values for macaroni and cheese were 62.02±1.73 and 9.96±0.66 min for CS 300 compared to 2.72±0.25 and 1.29±0.32 for HAV at 60 and 64°C, with higher td=1 values for both. Comparing models, over-processing was dependent on the temperature and food matrix. Overall, increased heat-resistant S. carnosus CS 300 grown in TSB with 20% glycerol appears suitable for validation of heat-inactivation of HAV at 56, 60, and 64°C in spinach, macaroni and cheese, and pasta salad, though it loses its thermal resistance at the higher temperatures tested by both the linear and Weibull models.

Chapter 2 to be submitted to the Journal of Food Science