Effect of humidity on Allyl isothiocyanate antimicrobial activity

It is well known that various kinds of essential oils, including Allyl isot hiocyanate (AIT), suppress the growth of microorganism. AIT, the main flavo ring component of wasabi and mustard. is reported to have strong antimicrob ial activity with wide spectrum. However, the strong pungent smell of AIT l imits applicable areas for food protection. To reduce the dose of AIT, we t ested its activity against fungi under different humidity, RH 100% and RH 3 4%. We used membrane filters inoculated with Cladosporium cladosporioides. Aspergillus niger and Penicillium citrinum and bean sprout seed inoculated with Penicillium citrinum. We also tested bean sprout seed naturally contam inated with fungi. They were exposed to AIT under RH 100% and RH 34% for 6- 72 hours, and then incubated on potato dextrose agar at 25 degreesC. AIT showed stronger antimicrobial activity under high humidity both on memb rane filters and bean sprout. This implies moisture plays an important role in AIT activity, suggesting that AIT gas is initially absorbed into water and then contacts fungi. The result showed that the effective concentration of AIT can be reduced under high humidity.