Comparison of Irradiation and Chemical Fumigation Used in Grain Disinfestation on Production of Ochratoxin A by Aspergillus alutaceus in Treated Barley

Abstract

Effects of irradiation and fumigation on ochratoxin A production by Aspergillus alutaceus in barley were compared. Ochratoxin A production was enhanced relative to untreated controls, if the toxigenic fungus was inoculated into the grain following irradiation or fumigation with either methyl bromide or phosphine. Ochratoxin A production was diminished, if the toxigenic fungus was inoculated into the grain prior to treatment by irradiation or fumigation. The results are consistent with the interpretation that the perturbative effects of irradiation and fumigation on ochratoxin A production by A. alutaceus in this system are very similar and are mediated by a common mechanism. This mechanism involves disturbance of the competition between the toxigenic inoculum and the endogenous microflora of the grain. Reduction or elimination of the competitive microflora, by whatever treatment, allows production of greater amounts of toxin than would occur in the presence of effective competition. These findings suggest that the potential hazard associated with the possible enhancement of ochratoxin A (and probably other mycotoxin) production in treated grain is similar for irradiation or fumigation treatment. Fumigation for purposes of insect disinfestation of grain has been used for decades, with no evidence of any significant hazard vis-a-vis enhanced mycotoxin production.