Thermal destruction of Clostridium botulinum spores suspended in tomato juice in aluminum thermal death time tubes

Abstract

The heat destruction characteristics of Clostridium botulinum spores suspended in tomato juice and phosphate buffer were determined by the survivor curve method with aluminum thermal death time tubes. Two type A strains of C. botulinum and a type B strain were evaluated. Strains A16037 and B15580 were implicated in outbreaks of botulism involving home-canned tomato products. Strain A16037 had a higher heat resistance than either 62A or B15580. The mean thermal resistance (D-values) for A16037 in tomato juice (pH 4.2) were: 115.6 degrees C, 0.4 min; 110.0 degrees C, 1.6 min; and 104.4 degrees C, 6.0 min. The mean D-values for A16037 in Sorensen 0.067 M phosphate buffer (pH 7) were: 115.6 degrees C, 1.3 min; 110.0 degrees C, 4.4 min; and 104.4 degrees C, 17.6 min. At each test temperature, the D-values were approximately three times higher in buffer than in tomato juice. The z-value for C. botulinum A16037 spores in tomato juice was 9.4 degrees C, and in buffer the z-value was 9.9 degrees C. The use of aluminum thermal death time tubes in a miniature retort system makes it possible to determine survivor curves for C. botulinum spores at 121.1 degrees C. This is possible because the lag correction factor for the aluminum tubes is only about 0.2 min, making possible heating times as short as 0.5 min.