Influence of Koji Molds on the Production of Aflatoxins by Aspergillus flavus in Rice

Aspergillus flavus에 의한 쌀에서의 Aflatoxin 생성에 미치는 고오지 곰팡이의 영향

Aflatoxin accumulation by Aspergillus flavus in rice was inhibited by A. kawachii and A. Shirousamii so that the rate of toxin accumulation and the maximum concentration of accumulated aflatoxins were considerablly reduced, although the initiation of aflatoxin accumulation was not affected. The maximal accumulated aflatoxin $B_1$ in rice by A. flavus at $28^{\circ}C$ and 85% RH was $40{\mu}g/50g$ rice after 35 days. Under the same condition but the additional inoculation of A. kawachii, $25{\mu}g\;of\;aflatoxin\;B_1$ was accumulated maximally in 50g rice after 45 days. When A. shirousamii was inoculated simultaneously with A. flavus on rice, however, only trace levels of aflatoxins were detected throughout 60 days of storage. Aflatoxins added to rice were reduced by 97% with A. kawachii and by 98% with A. shirousamii after 7 days during rife koji preparation. They were also reduced after 48 Hours of incubation by 30-67%, with A. kawachii koji and by 16-75% with A. shirousamii koji.

Aspergillus kawachii 혹은 A. shirousamii는 저장 중인 쌀에서 A. flavus에 의한 aflatoxin의 시발생성시기에는 영향을 주지 못하였으나 생성속도와 생성량은 현저하게 감소시키었다. 백미를 A. flavus로 접종하여 상대습도 85%, $28^{\circ}C$에서 저장하는 동안 aflatoxin $B_1$은 35일 후에 최고 $40{\mu}g/50g$ 생성되었다. 같은 조건에서 A. kawachii 동시접종한 경우에는 45일 후 최고 $25{\mu}g/50g$ 생성되었으나 A. shirousamii를 동시접종한 경우에는 60일 동안 흔적 정도만이 검출되었다. Aflatoxin을 첨가한 쌀에 A. kawachii 및 A. shirousamii를 7일간 키우면 각각 97% 및 98%의 aflatoxin이 감소되었다. 또한 aflatoxin을 첨가한 쌀을 A. kawachii 및 A. shirousamii로 만든 쌀 고오지로 48시간 당화시키는 동안 각각 30-67% 및 16-57%의 aflatoxin이 감소되었다.