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The effect of age on the thermal resistance of arthroconidia from Chrysosporium inops
Author(s) -
Kinderlerer J.L.
Publication year - 1996
Publication title -
letters in applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.698
H-Index - 110
eISSN - 1472-765X
pISSN - 0266-8254
DOI - 10.1111/j.1472-765x.1996.tb00208.x
Subject(s) - spore , d value , population , biology , incubation , incubation period , microbiology and biotechnology , food science , medicine , biochemistry , environmental health
J. L. KINDERLERER. 1996. Food‐borne members of the genus Chrysosporium have been isolated relatively infrequently. The heat resistance of arthroconidia of the xerophilic fungus, Chrysosporium inops Carmichael, was determined in 0.1% peptone at 66d̀C. The survival curve was sigmoid in shape. The initial lag period was due to the chains of arthroconidia. Thermal inactivation occurred when one viable conidium was left per chain. The presence of chains of arthroconidia was confirmed with the cryo scanning electron microscope. The decimal reduction times were obtained from the regression line of the linear death phase for the heat‐sensitive spores. The decimal reduction time (D 66 ) increased with increasing spore age. It was 1.67 min for 3‐week‐old spores, 1.95 min for 4‐week‐old spores and 5.49 min for 6‐week‐old spores. The older spores could recover from thermal death if they were given sufficient time. There was a significant increase in D 66 value for 6‐week‐old spores from 3.97 min to 5.49 when the counts were obtained after 14 d incubation (compared to counts after incubation for 10 d). This effect was not seen for the 3‐ and 4‐week‐old spores. There was a small population of heat‐resistant spores. The initial population of arthroconidia was greater than log 7 cfu ml ‐1 . After heating for 1 h at 66d̀C approximately log 2.2 cfu ml ‐1 survived. These survivors represented approximately 0.001% of the original population.