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EFFECT OF SORBATE ON GROWTH, SPORE VIABILITY AND MYCOTOXIN PRODUCTION OF SELECTED PENICILLIUM SPECIES
Abstract
Various effects of sorbate were studied on several Penicillium species. The minimum inhibitory concentration of sorbic acid (pH 4.7) to P. digitatum was between 0.02 and 0.025%. The minimum inhibitory concentration of sorbate (pH 5.5) to two strains of P. digitatum and one strain of P. italicum was between 0.06 and 0.08%. The minimum inhibitory concentration of sorbate (pH 5.5) to P. cyclopium was between 0.14 and 0.15%. Increasing levels of sorbate resulted in increasing growth suppression of all molds tested. Two approaches were used to determine if molds associated with citrus rot (P. digitatum and P. italicum) could develop increased tolerance to sorbate upon repeated exposure to subinhibitory levels of the inhibitor. In the first study, populations of P. digitatum were tested for increased tolerance to sorbic acid, and after 10 generations, none was found. In the second study, individual molds that started from the same parent stock colony were observed for increased tolerance to sorbate. In the case of two P. digitatum strains, no increase in tolerance was observed after 19 transfers of the molds in the presence of subinhibitory levels of sorbate. In the case of P. italicum, a slight increase in tolerance to sorbate was observed after being exposed to subinhibitory levels for 10 transfers. The ability of spores to survive prolonged exposure to high levels of sorbate showed that as the concentration of sorbate in the incubation media increased, the length of exposure time (days) to obtain fungicidal action decreased. When sorbate was present in growth media at 0.01 and 0.05%, ochratoxin A production by P. cyclopium was suppressed, yet growth was not significantly (P < 0.05) changed. The low level of 0.01% sorbate stimulated ochratoxin A production after 21 days incubation. The combined effects of heat plus sorbate in the heating menstrua caused injury and death to P. cyclopium spores. Spores heated in the presence of sorbate exhibited an increased sensitivity to the presence of NaCl and sorbate in the recovery media. After 21 days incubation, the interaction of heat plus sorbate in the heating menstrua was shown to have a significant (P < 0.0007) effect on ochratoxin A production and mycelial dry weight of P. cyclopium.
Subject Area
Food science|Microbiology
Recommended Citation
RAY-SCHROEDER, LISA LAVAUGHN, "EFFECT OF SORBATE ON GROWTH, SPORE VIABILITY AND MYCOTOXIN PRODUCTION OF SELECTED PENICILLIUM SPECIES" (1982). ETD collection for University of Nebraska-Lincoln. AAI8306508.
https://digitalcommons.unl.edu/dissertations/AAI8306508