【作者】 张璐璐；

【导师】 金征宇；

【作者基本信息】 江南大学 ， 食品科学， 2011， 硕士

【摘要】 慢消化淀粉(SDS)是指在小肠中被完全消化吸收但酶解速率较慢的一类淀粉的统称。制备慢消化淀粉的主要方法有物理改性(湿热处理、压热处理)、酶脱支改性(普鲁兰酶脱支)、化学改性(环氧丙烷交联或糊精化)、复合变性(酶法-物理法、酯化-物理法等),此类方法或对设备要求高,或成本较高,或存在化学试剂污染为食品安全性带来隐患。因此,本课题拟采用变温结晶的方法制备质量分数较高的大米慢消化淀粉,该方法简便易行、无需添加任何化学试剂,具有良好的社会效益和经济利益。本文确定了沸水浴相比高压蒸煮,可以更显著提高慢消化淀粉质量分数。因此,本研究采用沸水浴处理糯米淀粉进行单因素试验和正交试验优化慢消化淀粉制备工艺参数,得出:淀粉干基与水的比例为1:2,变温温度为4/25℃,时间间隔为24 h,变温时间为7 d时可得到慢消化淀粉质量分数最高为51.62%。本文还研究了变温结晶对淀粉的体外消化性、热力学性质、结晶性、血糖(GI)指数和膨胀度(SF)的影响,结果表明:变温回生的糯米淀粉中SDS质量分数最高为51.62%,远高于粳米淀粉中SDS的最高质量分数(19.58%);变温回生的糯米淀粉具有较高的起始温度(To)以及较低的熔融温度范围(Tc-To)和焓变(ΔH);变温结晶处理7 d的糯米淀粉1047 cm-1/1022 cm-1最大为0.899;变温回生处理21 d的糯米淀粉GI指数最小为59;变温结晶的样品具有较低的膨胀度,膨胀度的降低使酶不易靠近淀粉链,从而引起其慢消化特性。最后,本文研究了变温结晶形成慢消化淀粉的机理。变温回生动力学特征分析发现:变温回生处理的糯米淀粉,Avrami指数n值小于1(0.8234),晶体成核为一次成核;变温条件下成核速率常数k值(0.785)大于恒温条件下的k值(0.725,0.0570)。分析残基表面结构发现:变温结晶使糯米淀粉的表面更光滑,内部支链淀粉排列更紧密,酶解后形成结构紧凑、互相分离的实心小块;通过分析SDS质量分数与Tc-To关系发现:SDS质量分数与Tc-To呈负相关。因此,变温回生形成慢消化淀粉的机理为:支链淀粉晶体在适宜温度下以较高的成核速率结晶,晶体一次成核形成大量不完美同质性晶体的过程。更多还原

【Abstract】 Slowly digestible starch is the portion that digested slowly by amylase from 20 to 120 min in small intestine, and has significant implications on human health, such as, cardiovascular diseases, non-insulin diabetes, obesity and providing sustained and stable energy for athletes. Recently, there are a number of techniques to prepare slowly digestible starch, such as pullulanase debranching, hydrothermal treatment, microwave heat treatment and a citric acid modification.The paper studied the influence of autoclaving and heat treatment on the digestibility of rice starch and found that waxy rice starch treated by heated gelatinization and temperature-cycled retrogradation was a new technique to prepare slowly digestible starch. The paper also studied the influence of cycled-temperature, cycled-time, cycled-time interval, moisture on the forming of slowly digestible starch, and determinated the optimal SDS content by orthogonal test. It was found that the maximum SDS content was 51.62%, when the starch: water was 1:2, stored under cycled-temperature 4/25°C for 7 days and cycled-time interval for 24 h.The results indicated that there was a higher onset temperature (To), a narrower melting temperature range (Tc-To), a lower enthalpy change and a higher ratio (1047 cm-1/1022 cm-1 was 0.899) of the slowly digestible starch products prepared under the temperature cycled condition than that under the isothermal retrogradation. Furthermore, it was evident that the in vitro glycemic index and swelling factors of slowly digestible starch products with temperature cycled retrogradation was reduced more than that with isothermal storage. Therefore, the waxy rice starch stored under cycled-temperature was more difficult to hydrolyzed by amylase than that under isothermal storage.At last, amylopectin of waxy rice starch recrystallized more quickly at 4/25°C (0.785) than at isothermal temperature (0.725, 0.0570) and its crystal nucleus formed once for all as same as that at 4°C while crystal nucleus at 25°C formed step by step . Meanwhile, our results showed the similar kinetics of crystallization characters in normal rice starch stored at 4°C, 25°C and 4/25°C. The results from the enzymatic hydrolysis procedure found that waxy rice starch stored under cycled temperature showed a more ordered and smooth surface, and a solid section appeared after hydrolysed for 120 min. Besides, the SDS content and melting temperature range was negative correlation. The mechanism of temperature-cycled retrogradation formed slowly digestible starch was that crystal nucleus formed once for all, and amylopectin recrystallised and a large amount of imperfect and homogeneous crystals formed.更多还原