김치의 연화현상을 방지하기 위해 배추에 존재하는 펙틴에스테라제(PE)와 폴리갈락투로나제(PG)의 특성을 이용하여 예비 열처리 조건을 구하고 예비 열처리한 배추로 김치통조림을 제조하여 6개월 간 저장한 후 경도를 살펴보았다. 최적 pH는 PE가 8.0, PG가 5.2이었으며 최적 NaCl농도는 PE가 0.25M, PG가 0.3M이었다. PE의 최적 $CaCl_2$농도는 0.02M이었으며 이 농도에서 PG는 저해되었다. 최적 온도는 PE가 $50^{circ}C$, PG가 $65^{circ}C$이었다. 예비 열처리는 $50^{circ}C$의 0.05M $CaCl_2$ 용액에서 1시간 30분 동안 열처리하는 것이 최적으로 나타났다. 예비 열처리법에 의해 제조한 김치통조림을 6개월간 저장했을 때 대조구에 비해 줄기와 잎사귀는 경도가 더 높았으며 연화가 현저히 방지됨을 알 수 있었다.
Polygalacturonase(PG) and pectinesterase(PE) were extracted from Chinese cabbage and physicochemical properties of the enzymes were characterized. The preheating conditions for maximum retention of Kimchi texture were also studied. The activity of PE was highest at $50^{circ}C$ and at 0.02M $CaCl_2$ but decreased in 0.2M $CaCl_2$, PG exhibited maximum activity at $65^{circ}C$ with 0.3mM $CaCl_2$ but was inhibited by $CaCl_2$ at 0.5mM. Both of the enzymes, however, exhibited the maximum activity with 0.25M NaCl. Optimum preheating treatment was determined for minimum PG activity and maximum PE activity. Thus a maximum crispness and firmness was obtained with preheating in 0.05M $CaCl_2$ solution at $50^{circ}C$ for 1.5hr results indicated that PE activity and calcium ion were very effective in preserving firmness.
