Effect of Starch Degradation Enzymes on the Retrogradation of a Korean Rice Cakes

떡노화에 대한 전분분해효소류의 효과

In this study, enzymes were investigated as an antistaling agent for a Korean rice cake. Thermograms by a DSC demonstrated that the gelatinization-onset temperature of the Korean rice cake was at its lowest temperature of 71.1$^{\circ}C$ with the GP (glucoamylase+pullulanase) treatment, followed by $\beta$-amylase and $\alpha$-amylase. The gelatinization peak temperature of the Korean rice cake with enzyme treatment was relatively lower compared to the control. Furthermore, the Korean rice cake with GP treatment showed the lowest peak temperature. Melting enthalpy of the Korean rice cake increased with the enzyme treatment, with $\beta$-amylase, followed by $\alpha$-amylase and GP. Melting enthalpy of the Korean rice cake with GP treatment was significantly lower compared to the $\beta$- and $\alpha$-amylase treatment. Recrystallinity in the case of GP treatment was also significantly lower than control. The range of Avrami exponent (n) was 0.90 ∼ 1.20 and the time constant of retrogradation (1/k) of the Korean rice cake crystalline decreased in the following order: GP, $\beta$-, $\alpha$ -amylase and control. Textural characteristics of the Korean rice cake with enzyme treatment differed greatly from that of control. The L＊ values of all the Korean rice cakes made without $\beta$-amylase decreased and the a＊ values were significantly different at p<0.05. The GP treatment altered the b＊ value toward blue color, whereas $\beta$-and $\alpha$-amylase changed to the direction to yellow color. In sensory evaluation, the Korean rice cake with enzyme treatment showed higher evaluation compared to control.

효소류의 떡 노화에 미치는 영향을 검토하였다. DSC 열특성의 검토에서 호화개시온도는 GP(glucoamylase+pullulanase)로 처리한 경우가 71.1$^{\circ}C$로 가장 낮고 그 다음이 $\beta$-amylase, $\alpha$-amylase 순이었다. 또 호화최대온도는 효소 처리한 것이 대조구에 비해서 대부분 낮은 편이었으며 그 중 GP처리한 것이 가장 낮은 것으로 나타났다. 또 떡의 용융 enthalpy는 GP, $\beta$-amylase, $\alpha$-amylase 순으로 증가하였으며 GP의 용융 enthalpy값이 다른 경우보다 많이 낮게 나타났다. 재결정도는 GP의 값이 크게 낮은 것으로 나타났다. Avrami exponent(n)는 0.90 ∼ 1.20 범위에 있었으며 노화속도의 시간상수 1/k은 GP, $\beta$-amylase, $\alpha$-amylase, Control의 순이었다. 효소류를 첨가한 떡의 조직감은 대조구에 비해서 차이를 보였으며 종류별 효과는 GP, $\beta$-, $\alpha$-amylase의 순으로 나타났다. L＊ 값은 $\beta$-amylase를 제외하고는 모두 감소하고 a＊ 값은 효소간 5% 수준에서 유의차를 나타내었다. b＊ 값의 경우는 GP는 청색 방향으로, $\beta$-, $\alpha$-amylase는 반대인 황색 방향으로 변하였다. 효소 처리한 떡의 관능검사는 효소 처리한 것이 대조구보다 다소 높은 값을 나타내어 좋은 관능성을 보여주었다.