Thermal Resistance of Listeria Monocytogenes At Low Water Activity: Effect of Humectants Wang, Peng The thermal resistance of L. monocytogenes Scott A was examined in glycerol solutions, sucrose solutions, and peanut butters at different water activities (aw) from 0.27-0.99. The analysis of D-values in glycerol and sucrose solutions shown L. monocytogenes has greater thermal resistance in sucrose solutions at each same water activity level (0.85 and 0.80). The calculated D-values were 13.80 ± 0.31, 6.38 ± 0.73, 3.02 ± 0.10 min in sucrose solution (aw = 0.80), and 9.39 ± 0.22, 4.86 ± 0.29, 2.40 ± 0.19 min in sucrose solution (aw = 0.85), compared to D-values of 1.20 ± 0.04, 0.36 ± 0.03, 0.12 ± 0.01 sec in glycerol solution (aw = 0.80), and 9.60 ± 0.20, 4.20 ± 0.26, 1.80 ± 0.10 sec in glycerol solution (aw = 0.85) at 72, 75 and 78◦C. In each menstrum the thermal resistance of Listeria increased significantly as compared to phosphate buffer. However, the comparison of D-values in glycerol and sucrose solutions failed to reflect a linear relationship between water activities and thermal resistance of L. monocytogenes. In peanut butter samples, the D-values were 16.53 ± 0.31, 9.06 ± 0.75, 7.13 ± 0.27 min and 35.36 ± 2.14, 23.10 ± 1.31, 17.73 ± 1.96 min for 3.13% and 9.38% sugar concentration respectively at temperatures of 80, 90, 100◦C. The Z-values were 56.08 ± 4.87◦C and 67.18 ± 8.44◦C in peanut butter with 9.38% and 3.13% sugar concentration. These results indicate increases of thermal resistance of Listeria with increased sugar concentration in a pure solution. The same protection effect of sugar did not appear to play a role in much increased thermal resistance of Listeria in peanut butter. M.S. in Food Safety and Technology Zhang, Wei 2012-04-25 2012-05 Thesis application/pdf islandora:7538 http://hdl.handle.net/10560/2815 BIOL / Biology Illinois Institute of Technology en In Copyright http://rightsstatements.org/page/InC/1.0/ Restricted Access