Influence of guar gum on the thermal stability of Listeria innocua, Listeria monocytogenes, and gamma-glutamyl transpeptidase during high-temperature short-time pasteurization of bovine milk.

摘要

Mathematical models describing the thermal inactivation of gamma-glutamyl transpeptidase (TP) and L. innocua in milk during HTST pasteurization were validated with data from TP, L. innocua and L. monocytogenes trials in guar gum-milk blend. Holdingtube times were determined for turbulent flow using water, and for laminar flow using a guar gum (0.27% w/w)-sucrose (5.3% w/w)-water mixture. Inactivation of TP and L. innocua was lower in a solution of guar gum (0.25% w/w) in whole milk than was predicted by models derived from studies with whole milk alone. Use of laminar flow timings improved model fit but did not completely account for the observed protective effect. L. monocytogenes survival was close to that predicted by the L. innocua model, although some protection was afforded this pathogen under laminar flow. Considerable inter-trial variability was noted for L. monocytogenes. Risk analysis simulations were used to account for inter-trial variability. Simulated log10 %reductions consistentlyunder-predicted experimental L. monocytogenes survival (fail-safe), thus the L. innocua model derived in milk is suitable for estimating L. monocytogenes survival in viscous products. Increased thermal tolerance during laminar flow may be attributed tothe protective effect of stabilizer.