Abstract
Large amount of aflatoxin $B_1(AFB_1)$ is disappeared in the presence of L-ascorbic acid(AA) in buffer solution at pH values from 1 to 7 during 5 days of Incubation at $37^{\circ}C$. $AFB_1$ was quite stable at pH's between 5 and 7 when AA was absent(control), however, $50{\sim}60%$ of APB, was degraded in its presence after 5 days. The rate of disappearance of $AFB_1$ increased with a decreasing of pH in the presence of AA, even though $AFB_1$ in the control degraded increasingly with the decrease in $pH(pH{\leq}4)$. The level of $AFB_1$, decreased as the reaction temperature increased when $AFB_1$ reacted with AA. The aflatoxin could not be detected at all after 3 days when the reaction occurred at $60^{\circ}C$, while the aflatoxin was stable at $5^{\circ}C$ thoughout the reaction period. $90{\sim}96%$ of $AFB_1$ was found to be degraded in a far when $AFB_1$ reacted with AA plus different concentrations of $CuSO_4{\cdot}5H_{2}O$, showing remarkably faster rate than the control; however, different concentrations of L-cysteine instead of $CuSO_4\;5H_{2}O$ protected the degradation of aflatoxin and no $AFB_1$ was degraded for a day and resulted in less $AFB_1$ disappeared than the control. The degradation of $AFB_1$ was dependent on AA concentration and the rate of disappearance as the concentration of AA decrease, but $AFB_1$ concentration did not influence the rate. The product formed when $AFB_1$ reacted with AA was identified to $AFB_{2a}$ by using HPLC chromatographic examinations, and by UV spectrum of $AFB_1$ reacted with AA. The disappearance of $AFB_1$ was correlated well in the appearance of $AFB_2a$. From the results, the degradation of $AFB_1$ in the presence of AA is probably due to one or more of the oxidative products of AA which was produced during the AA oxidation.
$AFB_1$과 아스콜빈산(AA)이 산성 $pH(pH1{\sim}7)$에서 반응하는 동안 ($37^{\circ}C$에서 5일간) 상당량의 $AFB_1$가 파괴되었다. 반응기간 중 $AFB_1$은 $pH5{\sim}7$ 사이에서 대조군의 경우 거의 파괴되지 않았는데 AA 존재할 때 5일 후 $50{\sim}60%$가 파괴되었다. pH4 이하에서는 대조군 자체에서도 pH가 낮아지면서 $AFB_1$의 파괴가 증가되었지만 AA 존재하에서는 그 파괴량도 증가되었을 뿐 아니라, pH가 떨어질수록 속도도 증가했다. $AFB_1$이 AA와 반응했을 때 온도가 증가함에 따라 $AFB_1$량이 점차 감소하여 $60^{\circ}C$에서 반응할 때는 3일 후에 전혀 $AFB_1$을 발견하지 못했지만 $5^{\circ}C$에서는 반응기간 중 $AFB_1$은 안정 했다. $AFB_1$이 산화제$(CuSO_4{\cdot}5H_2O)$가 첨가된 AA와 반응했을 때 그 반응속도는 급격히 증가되어 $90{\sim}96%$ 의 $AFB_1$이 파괴되었으며, 대조군의 4%만이 파괴된 것과는 대조적이었다. 환원제 L-cysteine을 첨가했을 때 하루 동안 $AFB_1$의 파괴는 거의 없었으며 반응기간 중 대조군보다 소량의 $AFB_1$이 파괴되었다. $AFB_1$의 파괴는 AA의 농도에 따라 달랐는데 AA농도가 감소할수록 파괴 속도가 감소했지만 $AFB_1$의 농도는 이 파괴 반응에 영향을 주지 못했다. $AFB_1$과 AA가 반응하여 새로이 생성된 반응물은 TLC, RPLC 및 UV spectrophotometer를 이용하였을 때 $AFB_2a$로 동정되었으며, $AFB_1$의 분해와 더불어 $AFB_2a$의 생성이 확인되었다. 이 실험 결과에 비추어 AA 존재시 $AFB_1$의 파괴는 AA 산화기간 중 생성된 산화 생성물에 의한 것으로 추정된다.
(Department of Food Science and Nutrition, Pusan National University)
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