Heat Injury of Bacillus subtilis Spores at Ultrahigh Temperatures1

Abstract

The following three criteria indicated that Bacillus subtilis A spores were injured, but not completely inactivated, by ultrahigh temperature treatment. (i) Significant reductions in survivors were observed when spores were enumerated with a standard medium but not when the medium contained added CaCl2 and sodium dipicolinate. (ii) After a damaging heat treatment, more survivors were enumerated with the standard medium after incubation at 32 C than at 45 C, which was opposite to the result with untreated or slightly heated spores. (iii) Apparent numbers of survivors increased during the initial period of 3 C storage when enumerated with the standard medium at 45 C. No injury was evident when survivors were enumerated at either incubation temperature with the medium containing added CaCl2 and sodium dipicolinate. Heat activation of the spores did not significantly influence the appearance of heat injury. The data suggested that the heat injury occurred in a germination system which was required in the absence of CaCI2 and sodium dipicolinate.

The Effect of Incubation Temperature on the Recovery of Spores of Bacillus subtilis 8057

“…Untreated spores gave similar recoveries with incubation temperatures from 16-50" whereas spores heat treated for 70 min showed an optimum recovery in the range 24-32". Edwards et al (1965) found that severely heat,ed spores of B. subtilis gave greater recovery a t 32" than a t 45"; this agrees with the results presented here. However, with untreated spores they found the converse to be true, which was not the case in the present study.…”

“…However, with untreated spores they found the converse to be true, which was not the case in the present study. This might be because the unheated spores used in the present work were less affected by incubation temperature than those used by Edwards et al (1965).…”

(Symposium on Bacterial Spores: Paper VII). Recovering Spores Damaged by Heat, Ionizing Radiations or Ethylene Oxide

“…subtilis spores had been damaged a t ultrahigh temperatures, more survivors were evident in a standard medium at 32" than a t 45", whereas the opposite was true of unheated or lightly heated spores (Edwards, Busta & Speck, 1965b) ; no such temperature effect was evident with medium supplemented with CaDPA (see Section 3(b) (iii)).…”

“…A parallel experiment with B. subtilis failed to show the same response. Edwards, Busta & Speck (1965b) reported that apparent counts of B. subtilis spores surviving 113.3-131.1" increased after storage at 3" by up to 10-fold, and counts of C1. botulinum spores increased after storage a t 22" for 2 weeks (Mazokhina-Porshnyakova & Ladukhina, 1967), again by a factor of the order of 10-fold.…”

A Model System for Testing the Microbiological Stability of Foods Processed in Laminated Flexible Pouches

“…Incubation temperature may, however, affect the recovery of heat treated bacterial spores, some species recovering better at temperatures below the optimum for that of unheated spores. Thus Edwards et al (1965) found that B. subtilus spores subjected to 'ultra high temperature' treatment (150 OC/2 s) showed greater recovery at 32 OC than at 45 "C, whereas the reverse was obtained with unheated spores. Prentice & Clegg (1974) found an optimum recovery temperature of ca.…”