A Pulsed NMR Study of Some Aspects of Starch Gelatinization

Spin-spin relaxation times of protons in starch suspensions are reported. Values were found to change markedly upon gelatinization. This behaviour is attributed to an increase in the mobility and hydration of polymer chains. It is suggested that the change in relaxation time reflects the properties of a small number of protons in the system and that the bulk of the water is not bound in any fundamental sense.     

淀粉的回生机理及其测定方法

从分子结构上对淀粉的短期回生和长期回生机理进行了阐述,并对淀粉分子结构、系统水分和温度、淀粉酶和脂类等因素对淀粉回生的影响进行了系统论述。在此基础上对流变法、差示扫描量热法、X射线衍射法等方法检测淀粉的短期回生和长期回生进行了分析比较。     

Retrogradation of Sweetpotato Starch

Hardness and the percentage of leaked water of sweetpotato starch gels after storage were investigated as indexes of starch retrogradation. Starches of some varieties of sweetpotato were retrograded rapidly, but those of others were not retrograded during storage for one week. After one month of storage, starches of all varieties were highly retrograded, but the varietal order of hardness and the percentage of leaked water were almost the same as that after storage for one week. The study of chain length distribution by gel permeation chromatography after debranching by isoamylase showed that the hardness and the percentage of leaked water from the gel were positively correlated with amylose content and the proportion of Fr 1, the fraction of the highest molecular weight, containing amylose and extremely long chains of amylopectin, and negatively correlated with the proportion of Fr 3, the fraction with the lowest molecular weight, containing shorter chains of amylopectin. In addition, it was demonstrated by high performance anion exchange chromatography that the proportion of extra‐short chains (around DP 10) of amylopectin after isoamylase treatment was negatively correlated with the retrogradation index of starch. These results suggest that retrogradation of sweetpotato starch was promoted by amylose and extremely long chains of amylopectin and was inhibited by extra‐short chains (around DP 10) of amylopectin.     

淀粉的老化机理及抗老化研究

对谷物淀粉的理化特性进行了研究,分析了淀粉的老化机理及老化模型.根据淀粉的特性,选用酶制剂、乳化剂和胶体等作为抗老化剂用于谷物食品保鲜,能有效延长食品的货架期.     

米饭回生研究(I)脉冲核磁共振法测定谷物及淀粉糊化度与回生度方法的建立

脉冲核磁共振法（ＰＮＭＲ） 测定谷物及淀粉糊化度与回生度,具有快速准确,对样品无损伤,且可测定完形谷物颗粒等优点。简要叙述了ＰＮＭＲ的工作原理,并以标准曲线法确定了ＰＮＭＲ测定值Ｓ’与米粉及米淀粉糊化度（ＤＧ）间的关系。结果表明：选择适宜的仪器参数ｆｓ ,可使Ｓ’—ＤＧ标准曲线具备良好的线性（ｒ２ ＞ ０．９９） ,同时,在米淀粉与米粉的Ｓ’—ＤＧ标准曲线之间存在着紧密的联系     

Retrogradation of Some Starch Mixtures

Retrogradation tendencies of starch from local materials at two storage temperatures (10 and 30°C) were investigated. The kinetics of the crystallization process were studied using the Avrami equation. The values for the Avrami exponent and rate constant differ greatly at the two storage temperatures and for the various starches. The behavior of 50:50 (w/w) binary mixtures of starch on retrogradation was also investigated. The starches when combined were found not to behave independently of each other; rather, an interaction between the two starches combined was observed.     

大米淀粉胶凝和回生机理的研究

利用差示扫描量热仪和动态流变仪对 3种不同大米淀粉的胶凝和回生过程进行了研究。实验结果表明 :在淀粉糊化后的冷却胶凝过程中 ,在 95～ 80℃会有大量淀粉分子通过氢键交联聚合 ,直链淀粉含量越高 ,交联聚合越多 ,这些氢键的形成使得凝胶的硬度和弹性增大 ;在后期储藏过程中 ,主要是支链淀粉的重结晶随时间延长而逐步增大 ,而直链淀粉和脂类的复合物以及直链间的聚合变化则不明显 ,但直链淀粉的存在加速了支链淀粉的重结晶 ,支链淀粉的重结晶是后期凝胶硬度增大的主要因素。     

影响板栗淀粉回生的因素研究

研究了pH、温度、蔗糖和氯化钠对板栗淀粉回生的影响.pH为4和6,板栗淀粉易回生,pH为3和8,抑制回生;在选择的温度范围内,温度升高抑制淀粉回生;在选择的浓度范围内,蔗糖和食盐都可抑制回生,但浓度和抑制效果无明显关系.     

Retrogradation of Starch in Cooked Wheat

Retrogradation phenomenon in cooked wheat grain was investigated by means of Differential Scanning Calorimetry (DSC) and mechanical compression tests. The extent of starch retrogradation as measured by endotherm increased with time. More importantly, the onset, peak and conclusion temperatures are dependent on the storage temperature and are significantly lower for grain stored at lower temperatures. The firmness of the grain due to starch crystallization as indicated by the elastic modulus also increased with time and was higher at lower storage temperatures. Lowered storage temperature not only accelerates starch recrystallization and thus firming process of the cooked grain, but also seems to generate a different organization in the ordering of the starch.     

提高甘薯淀粉中抗消化淀粉含量的技术研究

抗消化淀粉是一种具有保健功能作用的淀粉,老化淀粉是制备抗消化淀粉最主要的方法.本文研究了酶水解预处理和冷冻解冻循环处理对甘薯老化淀粉中抗消化淀粉形成的影响,得到了提高甘薯淀粉中抗消化淀粉含量的适宜的工艺路线和参数,即：先用300U/g淀粉的普鲁兰酶水解2h,再用10U/g淀粉的α-淀粉酶水解0.5h,浓度为12%的酶处理淀粉胶在4℃条件下老化20h后,再经冷冻（-20℃,2h）-解冻（50℃,30min）-老化（4℃,6h）循环处理3次,淀粉中RS含量可达31.21%.实验结果表明,甘薯淀粉通过普鲁兰酶和α-淀粉酶复合水解处理和冷冻解冻循环处理能明显提高老化淀粉中抗消化淀粉的含量.     

酵母菌发酵生淀粉提高马铃薯淀粉回生率机理研究

以马铃薯淀粉为原料,淀粉回生率为考察指标,研究酵母菌发酵对马铃薯淀粉回生率的影响。通过对比发酵前后马铃薯回生淀粉的可见和红外吸收曲线,分析了酵母菌发酵提高马铃薯淀粉回生率的机理。结果表明,纤细酵母菌发酵马铃薯淀粉可使马铃薯淀粉回生率由12%提高到39.4%,提高了2.28倍。发酵后马铃薯回生淀粉中直链淀粉的最大可见吸收波长为587.8 nm,大于发酵前的569.6 nm。酵母菌发酵马铃薯淀粉提高其回生率的原因有两方面:一是发酵过程产生的酶使马铃薯支链淀粉脱支生成直链淀粉,增加了参与回生直链淀粉的量;二是发酵过程使马铃薯淀粉中醛基部分转变为伯醇基,进而生成糖苷键,增加直链淀粉链长,有利于淀粉回生过程晶体长大。     

大米淀粉老化特性的研究进展

概述了近几年国内外对大米淀粉老化特性的研究。简要阐述了大米淀粉的老化机理,表明大米淀粉的老化可以划分为短期老化(short-term retrogradation)和长期老化(long-term retrogradation)两个阶段。然后介绍了直、支链淀粉、糖类、蛋白质、脂质、水分含量及温度等影响因素对大米淀粉老化的作用原理,其中重点介绍了直链淀粉含量的多少、支链淀粉结构及蔗糖、魔芋葡甘露聚糖(KGM)、β-葡聚糖、β-环糊精等糖类的食品添加剂对大米淀粉老化的影响机理。最后展望了大米淀粉老化性质未来的研究和应用方向。     

非晶颗粒态玉米淀粉老化特性

实验通过非晶颗粒态玉米淀粉不同环境下黏度变化分析其老化特性及其影响因素.结果表明:非晶颗粒态玉米淀粉糊静置贮藏过程中会发生老化现象,在4℃下老化比常温下快:非晶颗粒态玉米淀粉乳的临界浓度小于10%,13%～14%的淀粉乳,老化作用明显;加入葡萄糖和蔗糖均能促进非晶颗粒态玉米淀粉老化,浓度越大,老化效果越明显,老化后期高浓度蔗糖又抑制淀粉乳的老化;在偏酸或者偏碱的环境或无机盐存在,抑制非晶颗粒态玉米淀粉的老化.     

淀粉细度测定方法的探讨

研究了淀粉细度的测定方法.探索了一种用标准检验筛筛分淀粉测定细度的方法,并将该方法和GB/T 12096-1989进行了比较.探讨了不同来源的淀粉、变性淀粉以及不同水分的淀粉运用该方法的可靠性.结果表明,用标准检验筛测定淀粉细度的条件为:金属丝编织筛网,孔径150 μm,频率1 420 r/min,振幅2-5 mm,时间10 min.     

抗性淀粉研究方法

抗性淀粉的研究分多个方面（１）空间结构的研究,（２）分子量分布的研究,（３）热力学研究,（４）含量的测定,本文对这些方面的研究作了综述。     

Retrogradation of Amylose in Solutions of Enzymatically Liquefied Starch

The retrogradation of amylose in solutions of enzymatically liquefied starch was investigated. The retrogradation is a very undesirable phenomenon in the first stage of enzymic starch liquefaction. The occurrence of retrogradation depends on the degree of starch hydrolysis and on the manner of solution preparation. Even at relatively high DE-values (20 – 30%) retrogradation could occur if the solution was obtained by liquefaction of starch at very low (below 5%) or at very high concentrations (more than 50%). In order to preclude the retrogradation it is necessary to liquefy the starch at an optimum concentration of 20–30% to reach a DE-value of more than 25%.     

电解法和微波法联合处理提高甘薯淀粉回生率

以甘薯淀粉为原料,采用电解、微波复合法制备回生抗性淀粉;以抗性淀粉制备率为考察指标,讨论微波、电解顺序对回生抗性淀粉制备产率的影响。最佳工艺为：淀粉→糊化→高压→微波→电解→老化→酶解→离心→干燥;最佳工艺参数：淀粉乳质量浓度50 g/L,高压温度120℃,高压时间30 min,糊化温度90℃,糊化时间30min,微波功率400 W,处理时间4 min,电解电压90 V,电解时间2 min,老化温度4℃,老化时间12 h。在此工艺条件下,甘薯回生抗性淀粉产率为24%,比空白组12%产率提高了1倍。     

不同添加剂对蕨根淀粉凝沉性的影响

凝沉特性是淀粉的重要性质,研究氯化钠、蔗糖、柠檬酸、明矾、海藻酸钠、单甘脂对蕨根淀粉凝沉性的影响。结果表明,不同添加剂对蕨根淀粉糊的凝沉性有改善作用;单甘脂、海藻酸钠、蔗糖对蕨根淀粉糊的凝沉性影响较显著;明矾添加一段时间后对其影响比较显著;氯化钠、柠檬酸对其影响较小。     

Studies on the Retrogradation of Starch in Starchy Foods. Part 3. Effect of the Addition of Sucrose Fatty Acid Ester on the Retrogradation of Corn Starch

A model of retrograded starch molecules was proposed in our previous paper. The effect of the addition of n-butyl alcohol or sucrose fatty acid on the retrogradation of starch was studied in this paper. The samples were prepared by repeating freeze-thaw cycles with or without addition of complex forming agents. The samples were treated with 16% sulfuric acid as by Nägeli amylodextrin preparation or a mixture of β-amylase-pullulanase. The residues of the acid or enzyme treatment were chromatographed. From the results of iodine titration, degree of gelatinization, X-ray diffraction, and chain length distribution, it is discussed how the helix forming angents react with fractions of starch and prevent the retrogradation. A schematic model of the retrograded starch with helix forming agents are also proposed.