| Thermal resistance of bacterial endospores was evaluated at different temperature regimes using wet-heat inactivation process. This was with the view to determining
the thermal inactivation characteristics of bacterial spores recovered from selected packaged fruit juices. The bacterial strains recovered were Bacillus subtilis K16, Bacillus coagulans B74, Bacillus cereus Y28B, Clostridium perfingens T20 and Clostridium sporogenes A63. The success of the inactivation process was determined by the ability of the inactivated spores to germinate and form colonies. The decimal reduction times (D - values) for spores from strains K16, B74, Y28B, T20 and A63 were 2.20, 1.78, 2.32, 2.16 and 2.0 minutes at 65
0C, 75
0C, 85
0C and 95
0C
respectively. The Z values were 7.4
0C, 8.5
0C, 6.8
0C, 7.6
0C and 8.7
0C respectively. There were high variations in the heat resistance amongst the five spore crops studied, in the order B74>T20> A63>K16>Y28B. There was a perfect correlation between the process temperature and the D-values with high correlation coefficients. The linear regression analysis of the data for all the strains fitted into the linear model Y=a + b x. More than 75.0% of the spores from Y28B were inactivated within 30 minutes of heat treatment at 65
0C. Spores from other strains exhibited marked heat resistance at the different temperature regimes tested. Surviving sub population of spores were observed after heat treatment for 30 minutes at all temperatures tested. Therefore, temperature higher than 950C may be
required to inactivate bacterial spores in fruit juices |