Changes in the Factors Associated with Decrease of Pungency in ‘Kagdugi’ during Fermentation

깍두기 숙성중 매운맛 감소에 관련된 인자들의 변화

Studies were carried out on the factors responsible for the change of pungency in 'Kagdugi'. During fermentation, the pH in 'Kagdugi' decreased to around to 4, while acidity increased continuously. In accordance with the decrease of pungency, the content of 4-methylthio-3-butenyl isothiocyanate (MTB-NCS) in the homogenate of 'Kagdugi' decreased gradually and on 3rd day, the optimum period for good flavor, below 5% of that in the homogenate of fresh radish. The decrease of MTB-NCS formation was accompanied by the gradual loss of 4-methylthio-3-butenyl glucosinolate (MTB-glucosinolate), which was found to disappear more rapidly than total glucosinolate. Also, the ascorbic acid-dependent myrosinase activity was observed to decline gradually with the fermentation time, although the ascorbic acid content varied above the concentration required for maximal enzyme activity. Thus, it was suggested that the decline of MTB-NCS may be related to the gradual losses of MTB-glucosinolate content and myrosinase activity which are both susceptible to the effect of acidic pH.

깍두기 숙성중 일반적 특성변화로는, 숙성이 진행됨에 따라 pH는 낮아져 3일 후에는 pH 4 이하로 감소되었으며, 산도는 증가하였다. 아스코르브산의 함량은 숙성적기에 약간 증가된 후 다시 감소되었으나 숙성기간동안 최저 1 mM 정도를 유지하였다. 깍두기 숙성중 매운맛이 감소되는 정도를 RP-HPLC에 의해 정량적으로 평가한 결과, 마쇄시 생성되는 MTB-NCS는 숙성이 진행됨에 따라 감소하여 숙성 1일에 81%, 2일에 18%, 2일에 8%, 4일에 3%로 되어 관능검사 결과와 일치하였다. 따라서, 깍두기 숙성중 매운맛의 감소는 MTB-NCS의 생성 감소에 기인된 것이었으며, MTB-NCS의 감소원인은 숙성에 따른 pH 저하로 인한 myrosinase 활성도 감소와 기질인 MTB-glucosinolate의 분해에 의한 것으로 나타났으며, 특히 숙성 3일을 중심으로 이러한 변화가 현저히 관찰되었다.