Synergistic effect of oregano essential oil fumigation combined with infrared heating on the inactivation of Aspergillus flavus

Abstract

This study was aimed to evaluate the fungicidal effects of oregano essential oil (OEO) fumigation combined with intermediate-wave infrared (IWIR) heating on Aspergillus flavus (A. flavus) in peanuts, and investigate the synergistic mechanism of the combined treatment (OEO-IWIR). Vitro experiments results indicated that OEO fumigation completely inhibited the A. flavus mycelium growth and aflatoxin production at a dose of 135 mg/L for 6 h. Meanwhile, the sterilization efficacy was assessed by inoculating peanuts with 6 log10 CFU/g A. flavus spores. OEO-IWIR exhibited synergistic effects and reached the 5-log reduction requirement by OEO fumigation at 135 mg/L for 6 h combined with IWIR heating at 65 °C for 1 h. Next, cultivability and spore viability tests of A. flavus were assayed. IWIR heating caused culturable sublethal spores, while the OEO-IWIR exhibited complete inactivation. Finally, the mechanism study confirmed that OEO-IWIR caused a higher degree of cell membrane permeabilization (from 17.0% to 65.6%), more significant alteration of cellular ultrastructure, and higher inhibition of ATPase activity than single treatments.