Effect of Sodium Chloride and pH on Initiation of Growth by Heat-Damaged Spores of Clostridium Botulinum

Abstract

Spores of Clostridium botulinum strains 13983B and 62A were heated at pH 6.0, 6.5 or 7.0 in M/15 phosphate buffer at 110 C (230F) to Fo=0.01, 0.1, 0.3, and 0.6. The spores that survived were enumerated in media of the same pH as the buffer in which they were heated: the media contained 0 — 6% salt (sodium chloride). In general, the more severe the heating, the more inhibited were the survivors by salt. However, the amount of inhibition by salt following a specific heat treatment depended on the pH of the medium used for enumeration of survivors: at pH 6.0 salt in the range of 2 — 5% was generally less inhibitory than at pH 7.0. After heating to Fo 0.01 and 0.1, more spores of strain 13983B grew at pH 6.0 in medium with 2 – 4% salt than in medium without salt: a similar, but reduced effect was obtained with strain 62A after heating to Fo 0.01, but not after heating to Fo 0.1.