Dry heat destruction of spores on metal surfaces and on potatoes during baking

Heat destruction characteristics of the normal microflora on potatoes and of Bacillus subtillis var. niger spores deposited on potatoes were determined during heating in an air oven at 175 C. These results were compared to the heat destruction characteristics of B. subtilis var. niger deposited in metal cups heated at several temperatures in the same oven. The results of this study indicate that; (a) B. subtilis var. niger spores in tin cups have a D(150 C) of 0.92 min, and a z-value of 21.8 C, (b) B. subtilis var. niger spores on potato surfaces are more resistant to dry-heat destruction than when they are on metal surfaces, and (c) the normal microorganisms on potatoes are less heat resistant than B. subtilis spores on potato surfaces. Results of this study suggest that the normal flora of a potato are not eliminated during baking and that a spore population inoculated by chance onto a potato also will likely survive the baking process.