Affiliation:
1. Food Protection Research, Environmental Sanitation Program, National Center for Urban and Industrial Health, Public Health Service, Cincinnati, Ohio 45202
Abstract
The dry-heat resistance of
Bacillus subtilis
var.
niger
spores located in or on various materials was determined as
D
and
z
values in the range of 105 through 160 C. The systems tested included spores located on steel and paper strips, spores located between stainless-steel washers mated together under 150 inch-lb and 12 inch-lb of torque, and spores encapsulated in methylmethacrylate and epoxy plastics.
D
values for a given temperature varied with the test system. High
D
values were observed for the systems in which spores were encapsulated or under heavy torque, whereas lower
D
values were observed for the steel and paper strip systems and the lightly torqued system. Similar
z
values were obtained for the plastic and steel strip systems (
z
D
= 21 C), but an unusually low
z
for spores on paper (
z
D
= 12.9 C) and an unusually high
z
for spores on steel washers mated at 150 inch-lb of torque (
z
D
= 32 C) were observed. The effect of spore moisture content on the
D
value of spores encapsulated in water-impermeable plastic was determined, and maximal resistance was observed for spores with a water activity (
a
w
) of 0.2 to 0.4. Significantly decreased
D
values were observed for spores with moisture contents below
a
w
0.2 or above
a
w
0.4. The data indicate that the important factors to be considered when measuring the dry heat resistance of spores are (i) the initial moisture content of the spore, (ii) the rate of spore desiccation during heating, (iii) the water retention capacity of the material in or on which spores are located, and (iv) the relative humidity of the system at the test temperature.
Publisher
American Society for Microbiology
Subject
General Pharmacology, Toxicology and Pharmaceutics,General Immunology and Microbiology,General Biochemistry, Genetics and Molecular Biology,General Medicine
Reference19 articles.
1. American Public Health Association. 1966. Recommended methods for the microbiological examination of foods 2nd ed. American Public Health Association Inc. New York.
2. Bigelow W. D. G. S. Bohart A. C. Richardson and C. 0. Ball. 1920. Heat penetration in processing canned foods. Res. Lab. Bull. 16-L National Canners Association Washington D.C.
3. Permeability of bacterial spores. IV. Water content, uptake, and distribution;Black S. H.;J. Bacteriol.,1962
4. Permeability of dormant bacterial spores;Black S. H.;Nature,1960
5. Gerhardt P. and S. H. Black. 1961. Permeability of bacterial spores p. 218-228. In H. 0. Halvorson [ed.] Spores It. Burgess Publishing Co. Minneapolis.
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