IngentaConnect Inactivation Kinetics of Avirulent Bacillus anthracis Spores in M...

Authors: Xu, Sa¹; Labuza, Theodore P.¹; Diez-Gonzalez, Francisco¹

Source: Journal of Food Protection®, Volume 71, Number 2, February 2008 , pp. 333-338(6)

Publisher: International Association for Food Protection

Abstract:

The combined effect of heat and hydrogen peroxide (HP) on the inactivation of avirulent Bacillus anthracis spores (Sterne strain 7702; strain ANR-1, an avirulent Ames derivative lacking the pXO2 plasmid; and strain 9131, a plasmid-less Sterne strain) was evaluated in milk. The study temperature ranged from 90 to 95°C, and the concentration of added HP varied from 0.05 to 0.5%. Decimal reduction times (D-values) were determined using a sealed capillary tube technique. The mean D- and z-values of hydrated freeze-dried spores of all three strains in milk ranged from 550 s at 90°C to 180 s at 94°C and from 8.6 to 9.0°C, respectively. When 0.05% HP was added to the milk, the D-values were decreased at least threefold, and at 0.5% HP the D-values ranged from 1 to 10 s. At 90°C, all three strains had similar D-values when 0.05% HP was added. Increasing the concentration of HP to 0.5% had a greater reducing effect on the D-value for strain 7702 than on the values for strains ANR-1 and 9131. The rate of inactivation of each strain followed first-order reaction kinetics at each temperature-peroxide combination. Equations in the form of D = Constant × (HP concentration)ⁿ had R² values greater than 0.97 for strains ANR-1 and 7702 and of at least 0.7 for strain 9131. This study suggests that a combination of high temperature (from 90 to 95°C) and HP could be used for inactivation of B. anthracis spores in the event of deliberate contamination of milk such that the contaminated milk could be disposed of safely.

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Inactivation Kinetics of Avirulent Bacillus anthracis Spores in Milk with a Combination of Heat and Hydrogen Peroxide