A comparison of the spore heat resistance of dairy isolates of Geobacillus stearothermophilus obtained using a CDC biofilm reactor and a sporulating medium

Abstract

In this study we compared a heat resistance of spores of Geobacillus stearothermophilus A1, D1, P3 and ATCC 12980 obtained using a milk biofilm system under continuous flow with previously reported values obtained by a sporulating medium. The average decimal reduction times of A1, D1, P3 and ATCC 12980 were 4.2, 4.9, 4.1 and 7.9 min, respectively, and were not significantly different (p < 0.05) from the heat resistance of spores obtained by a sporulating medium. In addition, the total calcium content of spores of A1, D1, P3 and ATCC 12980 were 1.9, 2.0, 2.5 and 5.1 ppm, respectively. The dipicolinic acid (DPA) content of spores of A1, D1, P3 and ATCC 12980 were 0.19, 0.26, 0.33, 1.38 pg per spore, respectively. The findings presented here provide new insights which can be used in the design of thermal processing steps in the dairy industry.