储存对大米糊化特性的影响研究

Study on the effects of storage on the gelatinization properties of rice

将糯米、粳米及籼米在4℃、25℃、36℃下分别储存0月、1月、3月及6月,应用快速黏度仪研究其糊化特性。大米是一个有机体,在储存过程中代谢活动仍在继续,加上脱支酶等引起的酶促反应,使其直链淀粉含量增加而支链淀粉含量减少,从而改变了直链淀粉/支链淀粉比例,因此,在加热-保持-冷却测试过程中反映出的峰值黏度、保持黏度、衰减值、最终黏度及回生值出现增加,同时,由于储存后水分子进入淀粉颗粒所需能量减少使得糊化温度与峰值时间有所降低。另外,由于储存引起大米组织结构的变化及大米淀粉微晶束的改变等物理过程,加上不同种类大米的蛋白质及淀粉等组分受储存温度与储存时间的影响不同,使其淀粉糊化特性上的各个特性指标表现出明显的时间与温度依赖性。

Glutinous rice, japonica rice and indica rice were stored at 4 ℃, 25 ℃ and 36℃for 0 month, 1 month, 3 months and 6 months respectively, which were subsequently used to study its pasting properties by RVA. In the storage process based on continuation of the metabolic activities of rice due to its being an organism plus the enzymatic reactions etc. caused by debranching enzyme, the content of amylose increases and of amylopectin decreases making the variation of ratio of amylase/amylopectin, thus eventually the peak viscosity, degradation value, holding viscosity, final viscosity and setback value rise from the gelatinization curves during the testing procedure of heating - keeping - cooling and at the same time the pasting temperature and peak time decrease a little owing to reduction of energy needed for penetration into the starch granules after storage. In addition, because of the physical process like the changes in the organization structure and of starch microcrystalline beam of rice caused by storage plus the different influences of the storage temperature and storage time on the protein and starch in different kinds of rice, the various properties of the starch gelatinization characteristics on the starch pasting properties show obvious dependence on temperature and time.