Abstract
The mechanisms of aflatoxin $B_1(AFB_1)$ degradation by ammonia and alkaline pH during the storage of Korean soy sauces were studied. In the 0.05%, 0.1% and 0.5% of ammonia solutions, almost all of $AFB_1$(96-100%) was degraded after 2 to 24 hrs of incubation at $30^{\circ}C$. Increased levels of ammonia in both home made soy sauce(HMSS) and commercial soy sauce(CSS) caused slow increases in pH. The pH change was higher in CSS than in HMSS. The degradations of $AFB_1$ were not observed in the samples of HMSS, CSS, distilled water and 20 % of NaCl solution during the storage, however, when the pHs of the samples were adjusted to 10, the toxin was completely removed in all samples. $AFB_1$ was stable at pH 5 and 7 in bath buffer solutions and buffer solutions+0.2% ammonia, however, $AFB_1$ was degraded completely at pHs more than 9. $AFB_1$ was not degraded even at high concentrations of ammonia(0.2-1.0%) when the pH was maintained at 7 in the buffer solution. It indicated that ammonia content in the system was not important but the higher pH was the reason to degrade $AFB_1$. When the pHs of HMSS, CSS, buffersolution and buffer solution + 0.2% ammonia were adjusted to 5 and then reacted with $AFB_1$ for 5 days, the toxin was stable in all samples. However, when the pHs of the samples were adjusted to 7, about 60-70 % of $AFB_1$ was degraded in HMSS and CSS after 5 days of incubation during which the pH was not changed, but $AFB_1$ in the buffer solution and buffer solution + 0.2% ammonia was not degraded at all in the same conditions.
간장저장중 암모니아와 pH가 Aflatoxin $B_1(AFB_1)$의 파괴에 미치는 영향을 검토하였다. $0.05{\sim}0.5%$의 암모니아 용액에서 $AFB_1$은 $30^{\circ}C$의 저장 하루만에 완전히 파괴되었으나 이때 이 용액들은 pH가 10-11정도로 증가 되었다. $NH_3$의 농도에 따라 간장의 pH는 증가 하였지만 간장내의 완충능 때문에 다소 완만하였다. 이때 양조간장은 재래간장에서 보다 그 pH증가 정도가 더 크게 일어났다. 간장시료들과 대조군의 증류수와 20% NaCl용액의 pH를 10으로 증가 시켰을 때 $AFB_1$은 $30^{\circ}C$에서 1일 반응 후 완전히 파괴되었다. pH 5, 7, 9, 10, 11의 완충용액에서 $AFB_1$의 파괴 효과는 pH 5와 7에서는 안정하였지만 pH 9 이상에서는 첨가한 $AFB_1$을 검출할 수 없었다. 여러농도의 $NH_3(0.2-1.0%)$를 함유한 pH 7의 완충용액 에서 $AFB_1$은 $NH_3$의 농도와는 관계없이 저장기간중 안정하였으나 pH 9에서는 파괴(100%)되었다. pH 5의 간장을 $30^{\circ}C$에서 5일간 반응시켰을 때 $AFB_1$은 상당히 안정하였지만 pH 7의 간장 시료에서는 60-70%의 $AFB_1$의 파괴가 일어났으며 이때 간장의 pH는 전혀 변화가 없었다. 그러나 $AFB_1$은 pH 7의 완충용액과 0.2% $NH_3$를 함유한 완충용액에서는 5일의 저장기간중 안정하였다.
(Dept. of Food Science and Nutrition, Pusan National University)
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