不同链淀粉含量玉米微晶淀粉理化性质研究

分别以蜡质玉米淀粉、玉米淀粉及高直链玉米淀粉为原料,在酸醇介质中制备不同水解率微晶淀粉,测定不同微晶淀粉水解性能并研究其颗粒形貌、结晶结构、溶解度及消化性。结果表明:淀粉颗粒内部结构致密性依次减弱,支链淀粉含量高的淀粉较易被试剂进攻;经酸醇处理后,三种微晶淀粉均保留原来晶型,颗粒形态没明显变化,没破碎和膨胀出现,但颗粒表面变粗糙;随直链淀粉含量增加,相似条件(水解率和温度)淀粉溶解度逐渐降低;in-vitro消化体系中三种淀粉及其微晶淀粉消化速度依次降低。     

淀粉颗粒结构体系

该文就淀粉分子、微晶和淀粉颗粒结构组成及其相互间关系进行论述。由支链淀粉分子形成无定形层和结晶层构成微晶,当低分支或链长较短分子存在于微晶时会形成缺陷微晶,常态微晶组成淀粉颗粒中硬质骨架,而缺陷微晶组成软质骨架,微晶还原端朝向颗粒脐点;依据常态微晶和缺陷微晶排列,淀粉颗粒分为同型骨架和异型骨架两种类型。     

玉米、木薯及马铃薯淀粉颗粒微晶结构及性质的研究

运用广角X射线衍射分析方法对玉米、木薯及马铃薯淀粉颗粒结晶结构及常温下水的溶胀作用对淀粉颗粒不同微晶结构的影响进行了系统研究,提出了在淀粉颗粒中存在着大量的介于微晶和非晶之间的亚微晶结构,并提供了在一条X射线衍射曲线图中确定微晶、亚微晶和非晶区域的方法。     

捏合淀粉颗粒形貌和结晶结构的研究

利用扫描电子显微、偏光显微、X-射线衍射等现代分析技术,研究了经捏合作用后淀粉颗粒形貌和结晶结构的变化。结果表明,与HylonV玉米淀粉相比,捏合后淀粉颗粒形貌和结晶结构都受到不同程度的破坏,尤其导致了结晶形态由B型向V型转变,由此引起淀粉的消化性能发生改变,为淀粉的改性提供了一种“绿色”深加工技术。     

捏合淀粉颗粒形貌和结晶结构的研究

利用扫描电子显微、偏光显微、X-射线衍射等现代分析技术,研究了经捏合作用后淀粉颗粒形貌和结晶结构的变化。结果表明,与HylonV玉米淀粉相比,捏合后淀粉颗粒形貌和结晶结构都受到不同程度的破坏,尤其导致了结晶形态由B型向V型转变,由此引起淀粉的消化性能发生改变,为淀粉的改性提供了一种“绿色”深加工技术。      

淀粉结晶结构对淀粉水解过程的影响

本文采用广角Ｘ射线衍射分析技术研究了玉米原淀粉以及超声波，电场，磁场作用后的玉米淀粉微晶的组成，性质及其变化规律，测试了玉米淀粉在不同物理场作用下基本晶体参数，研究了不同物理场对淀粉结晶结构的影响情况。     

不同热处理方式对绿豆淀粉颗粒特性影响研究

湿热处理前后绿豆淀粉的颗粒形貌基本未发生变化。随着热处理温度的提高,淀粉的结晶结构发生一定程度的变化,表现为特征峰部分融合、峰强度下降以及结晶度降低。但处理前后的X射线图谱表明,处理后的绿豆淀粉基本保持了原有的A型结晶结构。与原淀粉相比,湿热处理后玉米淀粉的结晶结构变化幅度不大。压热处理后绿豆淀粉,其颗粒形貌已经完全发生了变化,颗粒破裂重组,不同淀粉颗粒中的链淀粉相互形成氢键,从而改变了原淀粉的结晶结构,从X射线衍射图谱我们可以看出,处理后淀粉有新结晶峰的形成。     

微波改性高链玉米淀粉颗粒的抗消化性能与结晶结构的关系

通过控制不同的微波作用条件,获得了不同抗消化性能的微波改性高链玉米淀粉颗粒.并采用偏光显微和X射线衍射技术对不同抗消化性能的微波改性高链玉米淀粉颗粒的结晶结构进行了研究.结果表明,经微波改性后,高链玉米淀粉偏光十字和结晶形态都发生了改变,随着抗消化性能的提高,其偏光十字明显减弱,结晶形态从B型向V型转变.     

玉米抗性淀粉形成过程的研究

研究了水解-压热法制备玉米抗性淀粉的形成过程,通过扫描电子显微镜、X射线衍射及差示扫描量热法对玉米抗性淀粉形成过程中颗粒结构、结晶结构和热特性的变化进行了分析。实验分别从不同角度揭示了水解和压热处理对淀粉结构的破坏方式和程度,得出玉米抗性淀粉在形成过程中失去了原淀粉的结晶结构,形成了新的结晶结构。      

玉米抗性淀粉形成过程的研究

研究了水解-压热法制备玉米抗性淀粉的形成过程,通过扫描电子显微镜、X射线衍射及差示扫描量热法对玉米抗性淀粉形成过程中颗粒结构、结晶结构和热特性的变化进行了分析。实验分别从不同角度揭示了水解和压热处理对淀粉结构的破坏方式和程度,得出玉米抗性淀粉在形成过程中失去了原淀粉的结晶结构,形成了新的结晶结构。     

微晶淀粉的制备及影响微晶晶型的因素研究

玉米淀粉经过酸、酶等催化水解后,再经过溶解、过滤、结晶、洗涤及干燥等步骤,可得到微晶淀粉。X-射线衍射分析表明,随着结晶温度的升高、结晶浓度的增大,微晶的晶型从B型向A型转化;短链淀粉有利于形成A型结构,而长链淀粉倾向于形成B型结构。     

淀粉老化检测技术研究进展

淀粉老化是被破坏的淀粉分子链重新结合成有序结构的过程,其机制十分复杂,因此需要多种方法相结合才能全面、准确地分析老化过程中淀粉特性的变化。由于淀粉老化在很大程度上影响米面制品的货架期和感官品质,因此,对比分析淀粉老化检测技术无论对淀粉理论的发展,还是对米面制品的品质改良都具有重要的意义。本文对淀粉老化目前应用范围最广的技术检测方法进行阐述,分别从形变测试、光谱法、热分析法和微观结构角度总结各个技术的检测原理,深入分析不同检测方法针对样品的主要测量属性和对结晶结构的表征形式,为淀粉老化检测方法的选择提供参考。     

二甲基亚砜/水溶液体系中氢键对静电纺淀粉纤维的影响

为探究氢键对静电纺淀粉纤维膜的影响,以二甲基亚砜/水为溶剂体系对淀粉进行溶解制备静电纺纤维膜。通过调节二甲基亚砜/水体系中含水量,诱导水分子与淀粉分子链上的羟基结合形成氢键,研究氢键对淀粉溶解及淀粉纤维成型的影响。通过扫描电子显微镜、红外光谱、差热分析、X线衍射及拉伸实验等对静电纺淀粉纤维的表面形貌、结构和力学性能进行表征。结果表明：二甲基亚砜破坏了淀粉分子中的氢键,有利于淀粉的溶解;随着二甲基亚砜/水体系中含水量的增加,水与淀粉分子链中的羟基形成了氢键。氢键的形成会对淀粉纤维产生影响,一方面,氢键的形成使得淀粉纺丝液的可纺性变差,纤维形貌变得不均一;另一方面,对于静电纺纤维膜而言,过多的水会与淀粉分子形成氢键,抑制分子链的自由移动,导致纤维膜的断裂强度提高,断裂伸长率下降。     

超高压处理对玉米淀粉结构及糊化特性的影响

利用光学显微、X-射线衍射、差示扫描量热、快速黏度分析技术研究了超高压处理对玉米淀粉结构及糊化性质的影响。结果显示,超高压处理能使玉米淀粉糊化,处理压力为500 MPa及600 MPa时完全糊化所需保压时间分别为15 min和5 min,但400 MPa超高压处理30 min也不会使淀粉糊化。超高压糊化过程中,淀粉颗粒结构逐渐破坏膨胀,结晶结构由A型向V型转化,RVA黏度曲线峰值黏度逐渐消失。适宜条件的超高压处理对淀粉颗粒同时具有韧化和晶体破坏作用。其中,400 MPa超高压处理5~10 min时,淀粉颗粒内部韧化作用占优,因而表现为相对结晶度、糊化温度(T_o,T_p)及糊化焓增加,而RVA曲线峰值黏度降低。     

水分含量对小麦淀粉颗粒结晶度的影响

应用X射线衍射方法对不同水分含量的小麦淀粉颗粒的结晶度进行了研究.结果表明:随着水分含量的增加,样品的结晶度逐渐增加,并达到一个平衡值(约45%).室温下,当w(水)＜11.27%时,小麦淀粉颗粒中的无定型区域处于玻璃态,衍射图形显示的是微晶区域和无定型区域两部分的衍射图形的综合;由于塑化作用的影响,增大含水量会导致更多的微晶结构的形成.当w(水)＞19.4%时,淀粉颗粒中的无定型区域处于橡胶态,其X射线衍射图形仅由微晶区域形成;再增大水分含量,会导致微晶片层和剩余的无定型片层的同时分解.     

Characterization of Potato Starch and Its Monoglyceride Complexes

Native potato starch granules and those complexed below the gelatinization temperature with 1-(C₈ to C₁₈)-monoglycerides were compared for solubility, swelling power (SP), viscosity, heat stability and water binding capacity (WBC). X-ray diffraction analysis proved that complexes were true clathrates (inclusion) compounds. Clathrate stability was a function of monoglyceride chain length. The presence of clathrates in granules decreased solubility by up to 90% and SP up to 10-times, while WBC dropped from 0.39 to as low as 0.25 g water/g starch. Endotherm characteristics were given for gelatinization, most perfect crystallite, and clathrate fusions. Enthalpies per mole glucose units of 15.4 kcal/mole for native starch and 27.5 for clathrate were obtained irrespective of monoglyceride chain length.     

Internal Plasticization of Granular Rice Starch by Hydroxypropylation: Effects on Phase Transitions Associated with Gelatinization

The effects of hydroxypropylation on phase transitions associated with gelatinization of granular rice starch were studied by differential scanning calorimetry. At a 1:1 starch/water ratio, a progressive shift of the biphasic gelatinization endotherms to lower temperatures as well as a broadening and shortening of the G endotherm with increasing molar substitution were observed, indicating increased internal plasticization and destabilization of the amorphous regions of the starch granules. The overall enthalpy of gelatinization was also reduced. Hydroxypropyl groups, which are attached to starch molecules primarily in the amorphous regions of the starch granules, behave as flexible side chains. The motion of these side chains creates a large amount of free volume, thereby lowering the glass transition and crystallite melting temperatures associated with starch gelatinization. The modified starch granules may thus be viewed as internally plasticized polymer resins which are more easily gelatinized than the unmodified starch.     

The Effects of Citric Acid on the Properties of Thermoplastic Starch Plasticized by Glycerol

The effects of citric acid on the properties of glycerol‐plasticized thermoplastic starch (GPTPS) were studied. In the presence of citric acid and glycerol, native cornstarch granules are transferred to a continuous phase as shown by scanning electron microscopy (SEM). As shown by thermogravimetric analysis (TGA), the improvement in thermal stability confirms that the adhesion between citric acid, glycerol, water and starch in TPS was enhanced with the addition of citric acid. It was proven by Fourier transform infrared (FTIR) spectroscopy that citric acid can form stronger hydrogen‐bond interactions with starch than glycerol. Both FTIR spectroscopy and X‐ray diffractometry of citric acid‐modified GPTPS (CATPS) revealed that citric acid can effectively inhibit starch re‐crystallization (i.e. retrogradation), because of the strong hydrogen‐bond interaction between citric acid and starch. Rheology studies revealed that citric acid can obviously decrease the shear viscosity and improve the fluidity of TPS. Citric acid can also improve the elongation of GPTPS and ameliorate the water resistance of GPTPS at high relative humidities, but decreased the tensile stress.     

New insights into loss of swelling power and pasting profiles of acid hydrolyzed starch granules

The effect of acid hydrolysis on the swelling power of pea starch granules was studied by field emission SEM (FE‐SEM). The swelling power of the native starch granules (g water absorbed/g dry starch) was 13, and this decreased to less than 2 after 1 day of acid hydrolysis. The proportion of the starch that was soluble in hot water increased from 15% for native starch to 75% after 1 day of hydrolysis. The swelling power of the starch decreased further, and solubility increased, with more extended hydrolysis. The decrease in swelling power and increase in solubility were attributed mainly to the disruption of side chains of amylopectin. Observations with FE‐SEM indicated that starch granules were still able to melt and coalesce after 1 day of acid hydrolysis, but after 2 days solubilization of starch chains occurred predominantly rather than swelling when the granules were heated in excess water. The intactness of amylopectin is proposed to play a crucial role in the swelling power of starch granules and in the structure of granule ghosts.     

木薯淀粉- 黄原胶复配体系中淀粉糊化机理

采用光学显微镜(LM)及扫描电子显微镜(SEM)观察木薯淀粉、木薯淀粉- 黄原胶复配体系在糊化过程中淀粉颗粒形态的变化。淀粉糊化是淀粉与水分相互作用的过程,利用核磁共振仪(NMR)测定质子自旋- 自旋弛豫时间(T2),来反映体系糊化过程中黄原胶对水分运动性的影响;通过测定渗漏直链淀粉含量,反映黄原胶对木薯淀粉糊化过程中链段运动性的影响,从而探究木薯淀粉在黄原胶为连续相体系中的糊化机理。结果表明：黄原胶一定程度上可抑制升温过程中淀粉颗粒的膨胀,同时SEM图显示黄原胶包裹于木薯淀粉颗粒周围,形成空间位阻使得淀粉颗粒分散均匀,与淀粉糊具有良好的相容性;升温过程中质子自旋- 自旋弛豫时间(T2)的差异体现了糊化过程中水分分布及结合程度的变化,由于黄原胶的吸水及包裹作用使得淀粉糊化温度升高,热糊稳定性提高,表现为T2 先降后升的拐点由50℃升高至60℃及95℃较高的T2;黄原胶的加入使得体系中链段运动性降低,表现为直链淀粉渗漏量随着黄原胶配比增加而减少。