紫米吸水特性及其動力學之研究

Abstract

Black rice is widely preferred by consumers because of its dark purple (red) color and abundant amounts of nutrients and special flavor and odor. Soaking is an important step in the processing of rice products. This study examines the effects of soaking temperature (30, 40, 50 and 60℃) on the water absorption properties of black rice and the estimation of its kinetic properties. The research results showed that there was an increasing trend in the rate of water absorption of black rice along with an increase in soaking time and temperature. The increase of the temperatures can increase the rate of water absorption from 30℃, 7.30×10^(-3) (min^(-1)) to 60℃, 4.2×10^(-2) (min^(-1)) (r^2>0.98). The activation energy was 47.08 kJ/mole. Moreover, there was an increasing trend in the rate of solid loss along with an increase in the temperatures and time. There was a decreasing trend in the hardness of the rice particles. The research results showed that the relationship between water absorption of black rice and soaking temperatures and time was found to be t=2×10^6T^(-2.517) (t: soaking time, T: soaking temperature) (r^2=0.98). This temperature can be used to calculate the soaking time at different soaking time.紫米外觀呈誘人紫黑（紅）色，富含豐富營養及特殊香氣、風味，深受消費者喜歡。浸漬是米食加工之重要步驟，本實驗探討浸漬溫度(30、40、50、60℃)對紫米吸水特性影響及評估其吸水動力學，實驗結果如下：紫米之吸水率隨浸漬時間延長及溫度提高呈增加趨勢，提高溫度能增加吸水速率常數，由30℃、7.30×10^(-3)(min^(-1))提高至60℃、4.2×10^(-2)(min^(-1))(r^2>0.98)，其吸水活化能為47.08kJ/mole。另固形物溶出率隨溫度提高及時間延長呈增加變化，米粒硬度則呈下降趨勢。實驗結果可求出浸漬過程中，水分的吸收在浸漬時間及溫度呈一函數關係：t=2×10^6T^(-2.517)（t：浸漬時間；T：浸漬溫度）(r^2=0.98)可供推算紫米在不同溫度浸漬時，所需之浸漬時間