Interacting Effects of pH and NaCl on Heat Resistance of Bacterial Spores

Authors

  • MICKI T. HUTTON,

    1. The authors are affiliated with the Campbell Institute for Research and Technology, Campbell Soup Company, Campbell Place, Camden, NJ 08103-1799.
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  • MARY ANN KOSKINEN,

    1. The authors are affiliated with the Campbell Institute for Research and Technology, Campbell Soup Company, Campbell Place, Camden, NJ 08103-1799.
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  • JOHN H. HANLIN

    1. The authors are affiliated with the Campbell Institute for Research and Technology, Campbell Soup Company, Campbell Place, Camden, NJ 08103-1799.
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  • The authors are indebted to Mr. George Evancho for helpful discussions and to Ms. Carol Middleton for assistance in graphics and manuscript preparation.

ABSTRACT

Spores of PA3679 (C. sporogenes) and Clostridium botulinum 213B were less heat resistant when heated in a menstruum of decreasing pH. The D value of the spore population decreased by 50% when heated in pH 5.0 buffer compared to pH 7.0 buffer. Addition of NaCl to the recovery medium reduced the number of colony forming units in a population of heated spores. Presence of NaCl at 2.0% in the recovery medium decreased the spore D-value by 20-40% irrespective of pH of the heating menstruum. Combined effects of pH and NaCl could be illustrated by three-dimensional histograms.

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