米粒組成與加熱條件對米粒糊化速率之影響

Effects of Rice Compositions and Heating Conditions on the Gelatinization Rate of Rice Grains

賴嗚鳳(Vivian M.-F. Lai) ； 林穎聖(Ying-Sheng Lin) ； 盧訓(Shin Lu) ； 呂政義(Cheng-Yi Lii)

《臺灣農業化學與食品科學》 42卷4期 (2004/08) Pp. 280-292

https://doi.org/10.6578/TJACFS.2004.037

摘要

本研究旨在探討八種稻米粒在100℃烘箱加熱及電鍋烹煮過程中糊化速率之差異性，並解析化學組成、糊化性質與加熱溫度等影響因素以及比較糊化動力學模式參數。以10g米粒/鋁杯、水/米比(w/r)=2.3(w/w)為樣品組，樣品在100℃烘箱加熱的升溫速率約為電鍋烹煮的1/4。烘箱加熱時八種米粒糊化程度(DG)為溫度比值(T(下標 h)-T(下標 o))/(T(下標 c)-T(下標 o))的指數函數(其中T(下標 h)為樣品加熱溫度，T(下標 o)及T(下標 c)分別為米榖粉的糊化起始及結束溫度)。以1n(1-α)=－kt(上標 n)(α=DG/100，k=反應速率，t=加熱時間，n=常數)描述DG隨時間變化時，採n＝1及不固定(分別為first order及pseudo-first order 反應模式)所得之糊化速率參數分別與樣品的糊化尖峰溫度(T(下標 p))或T(下標 c)及溫度範圍(GT)呈顯著負相關，皆與化學組成無顯著相關。在電鍋烹煮方面，以臺中在來一號(TCN1)、臺稉九號(TG9)及臺中糯七十號(TCW 70)為代表樣品、w/r=2.3(w/w)及較適w/r(分別為1.6、1.4及1.2w/w)下，加熱前期的DG值與澱粉中直鏈澱粉含量(amylose content, AC)呈反比：三米種在r(下標 AP)^*(T(下標 h)-T(下標 o))/(T(下標 c)-T(下標 o))=1.5-1.8(其中r(下標 AP)=1－AC/100)時皆達DG≈100%；pseudo-first order 反應模式所得log k值亦隨AC增加呈線性降低趨勢。故電鍋烹煮時米粒DG變化受(T(下標 h)-T(下標 o))/(T(下標 c)-T(下標 o))及AC共同左右。

關鍵字

米粒 ； 糊化速率 ； 動力學 ； 溫度比值 ； 直鏈澱粉含量

並列摘要

The differences in gelatinization rate of eight varieties of rice grains during heating in a 100℃-oven and cooking in a rice cooker were investigated, with respect to rice chemical composition, gelatinization property, and heating temperature. The results of different kinetic models were compared as well. Using 10 g of rice grains in an aluminum cup and at a water/rice grain ratio (w/r)=2.3 w/w as samples, the heating rate of the samples in a 100℃-oven was approximately one fourth of those cooked in a rice cooker. In the oven the degree of gelatinization (DG) of eight rice grains increased exponentially with the temperature ratio (T(subscript h)-T(subscript o))/(T(subscript c)-T(subscript o)) (where T(subscript h)= the heating temperature of sample, T(subscript o) and T(subscript c)= the onset and conclusion gelatinization temperatures of rice flours, respectively). Using ln (1-α)=-kt(superscript n) (where α=DG/100, k= the gelatinization rate, t=the heating time, n= the constant) to describe the DG changes with heating time, the kinetic parameters obtained by fixing n = 1 and varying n (i.e. first-order and pseudo-first-order models, respectively) were significantly and negatively correlated with the gelatinization peak temperature (T(subscript p)) or T(subscript c) and gelatinization temperature range (GT), respectively. They did not show any significant correlations with the chemical composition of the samples. In the case of cooking in a rice cooker, Taichung native 1 (TCN 1), Taigung 9 (TG 9) and Taichung waxy 70 (TCW 70) rice were representatively examined at a w/r=2.3 and optimal water amount (w/r=1.6, 1.4, and 1.2 w/w, respectively). The DG during early-stage cooking was inversely proportional to the amylose content in starch (AC). Three varieties of rice reached DG≈100% at r(subscript AP ^*) (T(subscript h)-T(subscript o))/(T(subscript c)-T(subscript o))＝1.5-1.8 (where r(subscript r(subscript AP)= 1－AC/100). The n and log k values based on pseudo-first-order kinetics also changed quite linearly with AC. These results suggest that the DG changes of rice during cooking were concomitantly governed by (T(subscript h)-T(subscript o))/(T(subscript c)-T(subscript o)) and AC.

並列關鍵字

Rice grain ； Gelatinization rate ； Kinetics ； Temperature ratio ； Amylose content