Thermal resistance variations due to post‐harvest treatments in Bacillus subtilis spores

Abstract
Spores of Bacillus subtilis NCTC 10073 were produced using three different methods on solid and liquid defined media. Thermal resistance at 90d̀C was examined in relation to the effects of cleaning procedures such as number of washings, speed and temperature of centrifugation on the spores. Ion‐exchange spore forms (hydrogen and calcium) and coat‐defective forms (urea‐mercaptoethanol and urea‐dithiothreitol‐sodium dodecyl sulphate) were prepared from spores produced by the different spore production methods and compared for thermal resistance. The resistance patterns observed are discussed in terms of the spore properties of germinability. colony formation, dipicolinic acid and calcium contents.