Use of gaseous ozone for reduction of ochratoxin A and fungal populations on sultanas

Abstract

Background and Aims: Contaminated dried vine fruits including sultanas are regarded as an important source of ochra-toxin A (OTA), a fungal secondary toxic metabolite, in human diets. Management of fungal contamination and OTA in the dried vine fruit industry includes prevention, regulation and decontamination. The purpose of this study was to evaluate the efficacy of gaseous ozone on the degradation of OTA on spiked sultanas. The effect of ozonation on indigenous fungal populations and the concentration of phenolic substances was also evaluated on non-spiked portions of the sultana sample. Methods and Results: Sultanas were exposed to a continuous stream of gaseous ozone at 12.8 mg/L for up to 240 min in a treatment chamber at ambient laboratory conditions. The initial OTA level on spiked sultanas, determined as 16.7 μg/kg, was reduced by 60.2 and 82.5% after 120 and 240 min of ozone exposure, respectively. Exposure to gaseous ozone for 120 min yielded more than 2.2 log reduction in the fungal population naturally present on sultanas. Ozonation for up to 120 min did not cause a significant (P > 0.05) change in the concentration of phenolic substances of sultanas. Conclusions: Greater than the 60% reduction in the concentration of OTA on superficially contaminated sultanas can be achieved by gaseous ozone treatment without causing a significant decrease in the concentration of phenolic substances. Significance of the Study: Gaseous ozone has potential to degrade OTA and reduce fungal viability on sultanas.