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Journal of Food Technology

Year: 2012  |  Volume: 10  |  Issue: 2  |  Page No.: 17 - 23

Thermodynamics of Heat Inactivation of Listeria monocytogenes in Soymilk of Varying Initial pH and Sugar Values

M.A. Igyor, C.C. Ariahu and C.U. Inyang

Abstract

The thermodynamics of heat destruction of Listeria monocytogenes in soymilk of varying initial pH (6.0-6.8) and sugar contents (0.5-10% w/v) were studied using kinetic parameters generated via the classical thermobacteriology assumption of a log-linear relationship between Listeria monocytogenes survivors and heating time (0.5-30 min at 50-65°C). The activation enthalpy (ΔH+), entropy (ΔS+), Energy (Ea) and frequency factor (k0) for the heat inactivation ranged, respectively, from about 275-302, 612-705 J/mol deg., 277-305 kJ/mol and 2.9x1043-2.0x1048 min-1 increasing with increases in initial sugar contents and acidity of soymilk. A kinetic compensation effect was observed for both ΔS+/ΔH+ and ln k0/Ea relationships with isokinetic temperature of 32.16x0.13°C and isokinetic destruction rate constant of 9.21x10-5 min-1 for the microbe in soymilk.

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