韧化处理对3种晶型淀粉消化特性的影响

比较玉米淀粉(A型)、马铃薯淀粉(B型)和锥栗淀粉(C型)韧化处理前后的颗粒形貌、结晶特性和热特性变化,探究韧化处理对3种晶型淀粉消化特性的作用机理。SEM图片显示,韧化处理后玉米淀粉表面出现凹坑,马铃薯淀粉表面出现少许裂痕,锥栗淀粉表面变得光滑,褶皱消失;XRD和FTIR分析表明,3种淀粉经韧化后晶型未有改变,但结晶度均显著提高,分子短程有序性增加,晶体结构更趋稳定;DSC分析表明,韧化处理后3种晶型淀粉的糊化温度显著升高,热焓值无显著变化;韧化处理对不同晶型淀粉消化特性的影响存在差异,3种淀粉经韧化后RS含量均显著增加,水解指数HI和血糖指数GI显著降低;玉米淀粉韧化后RDS含量显著增加,SDS含量显著减少,水解平衡浓度由84.81%降至76.79%;马铃薯淀粉中SDS和RDS含量均显著减少,水解平衡浓度由30.59%降至21.84%;韧化处理对锥栗淀粉的RS、SDS、RDS含量及水解平衡浓度变化影响较小。     

韧化温度和时间对不同直链淀粉质量分数玉米淀粉物化性质的影响

为进一步探讨韧化处理对淀粉性质的作用机理,通过测定糊化性质、热特性、膨胀力、结晶特性及观察偏光十字现象和微观结构,研究了不同韧化温度和时间对不同直链淀粉质量分数玉米淀粉（普通玉米淀粉（normal corn starch,NCS）和蜡质玉米淀粉（waxy corn starch,WCS））物化性质的影响。结果表明,韧化处理主要作用于NCS和WCS淀粉颗粒的无定形区,对淀粉结晶类型没有影响;但韧化处理能够明显增强NCS和WCS的热稳定性和抗剪切能力,抑制淀粉老化和糊化,显著降低峰值黏度和膨胀力（P＜0.05）。韧化温度升高至60 ℃时韧化效果更加明显,糊化焓和相对结晶度明显降低,颗粒表面被明显破坏。但延长韧化时间对NCS和WCS老化的抑制效果和对糊化焓、膨胀力、颗粒形貌等的影响不明显。     

高温处理对玉米淀粉应用性质变化的影响

探讨在100℃以上的高温处理后,玉米淀粉应用性质的变化,本实验对玉米淀粉进行蒸煮、焙烤、油炸的高温处理,并对高温处理后的淀粉颗粒形态、淀粉糊黏度、糊化温度及淀粉糊性质等进行检测和对比分析。结果说明,玉米淀粉经过蒸煮、焙烤和油炸处理后,淀粉颗粒形态发生很大变化;蒸煮和焙烤的玉米淀粉的溶解度和膨胀度都低于原淀粉,随温度升高而增加的趋势变缓;峰值粘度降低,粘度稳定性增加,冻融稳定性变化不大,淀粉糊透明度好于原淀粉。玉米淀粉油炸处理后,淀粉粒结构变化程度大,应用性质不及蒸煮、焙烤淀粉和原淀粉。     

韧化处理对板栗淀粉特性的影响

以燕山板栗淀粉为材料,在30、40和50℃分别进行韧化处理。采用扫描电子显微镜(SEM)、X-射线衍射分析(XRD)、差示扫描量热分析(DSC)及体外消化法等方法,研究了韧化处理对板栗淀粉颗粒结构、理化特性和体外消化性的影响。研究表明:与原淀粉相比,韧化处理后2种板栗淀粉的直链淀粉含量降低,淀粉颗粒破损率增大,但淀粉仍为C型晶体。随着韧化温度的升高,淀粉颗粒表面出现凹坑和损伤越显著,膨胀度随着处理温度的升高而降低。DSC分析表明,韧化处理使淀粉的糊化温度升高,热焓变化不大。不同的韧化处理温度对板栗淀粉体外消化性有不同的影响,韧化处理使淀粉的快消化淀粉(RDS)含量减少,慢消化淀粉(SDS)含量增大。     

韧化处理条件下缓慢消化玉米淀粉的形成机理

探讨韧化处理条件下,缓慢消化玉米淀粉的形成过程。分别采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、差示扫描量热仪(DSC)研究韧化处理前后玉米淀粉颗粒形貌、结晶特性、热焓特性的变化情况。结果表明,韧化处理对玉米淀粉的颗粒形貌基本无影响,处理后基本保持原来的A型结晶结构,但结晶结合更为紧密,韧化玉米淀粉和去除快速消化玉米淀粉(RDS)的韧化玉米淀粉相比,DSC图谱的To、Tp、Tc以及Tc－To均较原玉米淀粉有所提高。这表明,韧化处理过程促进缓慢消化玉米淀粉的形成主要是通过调整玉米淀粉的结晶结构,使其结合更为紧密,从而对酶的抵抗作用增强而实现的。     

玉米淀粉退火处理及其性质变化

采用扫描电子显微镜(SEM)、激光粒度分析仪(LPA)、X射线粉末衍射仪(XRD)和差示扫描量热仪(DSC)研究退火处理对玉米淀粉颗粒形貌、粒径大小、晶体结构和热力学性质的影响。结果显示:退火处理会改变玉米淀粉颗粒的外貌,使其微孔增多,孔径增大;退火处理会增加玉米淀粉颗粒粒径;退火处理不涉及玉米淀粉晶体结构的变化;退火处理会使玉米淀粉糊化温度显著增高,糊化温度范围变窄;原玉米淀粉(NC)和退火处理玉米淀粉(AC)的溶解度和膨胀率都随着温度的升高而增大,在相同温度条件下,退火处理玉米淀粉(AC)溶解度和膨胀率均小于原玉米淀粉(NC)。     

韧化处理对甘薯淀粉糊化特性的影响

本文采用差示扫描量热分析、快速粘度分析等现代仪器分析方法研究了不同韧化时间、韧化温度和含水量等韧化处理方法对甘薯淀粉糊化特性的影响。结果表明,不同韧化温度处理后,甘薯淀粉的起始糊化温度、峰值糊化温度和终止糊化温度均呈升高趋势,其中起始糊化温度升高趋势明显,由甘薯淀粉的62.47℃升高到70.37℃,糊化温度范围变窄,糊化热焓值增加;其峰值黏度呈下降趋势,55℃时为1342 cp比甘薯淀粉下降了321 cp,破损值降低、回生值升高。不同韧化时间处理后,甘薯淀粉To升高,糊化温度范围变窄,由甘薯淀粉的21.35℃减少到60 h的15.09℃,回生值上升了29.89%。不同水分含量韧化处理后,85%时糊化热焓值提高了36.20%,峰值黏度比甘薯淀粉下降了378 cp。甘薯淀粉经韧化处理后糊化温度、热焓值升高,黏度下降,回生值增加。     

重复韧化对普通玉米淀粉消化、理化性质和结构特性的影响

通过体外消化、快速黏度分析、X射线衍射、傅里叶红外光谱、扫描电子显微镜观察等方法,探究重复韧化处理(55℃,24 h)1～3次对普通玉米淀粉消化、糊化性质及淀粉颗粒结构等的影响。结果表明,重复韧化3次可以降低普通玉米淀粉的膨胀力、快速消化淀粉和慢速消化淀粉含量,降低衰减值和回生值,提高抗性淀粉含量和凝胶硬度,相对结晶度增加4.1%,糊化温度升高2.3℃,淀粉颗粒微观表面的孔洞和缝隙增多,但没有破坏结晶结构。重复韧化处理通过促进淀粉分子链间的相互作用,使淀粉易于形成完美晶体结构,提高淀粉颗粒的热稳定性。     

韧化处理对大米淀粉性质的影响

为韧化处理在大米淀粉改性中的应用提供理论依据,作者以余赤早籼米为原料,在不同温度（50～70℃）和水分质量分数（45%～65%）条件下对大米进行韧化处理,然后提取韧化处理后大米中的淀粉,以未经韧化处理提取的大米淀粉为对照,研究韧化处理对大米淀粉溶解度、膨润力、糊化特性、消化特性和冻融稳定性的影响。研究结果表明：与对照组相比,经韧化处理的大米淀粉溶解度和膨润力降低;峰值黏度、最终黏度、谷值黏度、回生值和衰减值均有所降低,糊化温度升高,不同韧化处理温度对衰减值的影响差异显著;淀粉中RDS（快消化淀粉）质量分数升高,RS（抗性淀粉）质量分数减少,SDS（慢消化淀粉）质量分数随着韧化处理条件的不同而不同,说明韧化处理提高了大米淀粉的消化性,也使大米淀粉冻融稳定性下降。     

湿热处理对不同晶型淀粉理化性质及消化性的影响

采用三种不同晶型淀粉即玉米淀粉(A型)、马铃薯淀粉(B型)、豌豆淀粉(C型)为原料,在水分含量为25%、温度120℃条件下湿热处理13 h,研究湿热处理对不同晶型淀粉的理化性质及消化性的影响。研究表明,与原淀粉相比,经湿热处理的三种淀粉的结晶结构均发生了改变,玉米淀粉由A型变为了A+V型,马铃薯淀粉和豌豆淀粉分别由B型和C型变为了A型;三种淀粉颗粒表面均出现了不同程度的破损;三种淀粉的部分颗粒的偏光十字的中心强度有所减弱;三种淀粉样品的糊化温度均升高,但A型和B型淀粉的焓值降低,而C型淀粉的焓值升高;三种淀粉的抗性组分含量均有所升高,抗消化性显著增强,其中C型淀粉变化最明显。     

Effect of Ultrasonic Treatment on the Physicochemical Properties of Maize Starches Differing in Amylose Content

Normal maize, waxy maize and amylomaize V starches were treated at a moisture content of 70% by ultrasonic treatment. The results showed that the surface of normal and waxy maize starches was porous after treatment and a fissure could be clearly observed in the surface of amylomaize V starch. Ultrasonic treatment did not change the X‐ray pattern of the three maize starches. The swelling power (amylomaize V (B‐type) > normal maize > waxy maize (A‐type)) and solubility (amylomaize V > normal maize > waxy maize), the syneresis of amylomaize V starch and the gelatinization transition temperatures of the three starches increased on this treatment. Ultrasonic treatment decreased the syneresis of normal and waxy maize starches, the enthalpy of gelatinization (amylomaize V > waxy maize ≈︂ normal maize) and the gelatinization temperature range (amylomaize V > normal maize ≈︂ waxy maize) of all starches. A drop in viscosity of all three starches was observed and the viscosity patterns of three starches remained unchanged after ultrasonic treatment. The data showed that ultrasonic treatment degraded preferentially the amorphous regions and more easily attacked linear amylose than highly branched amylopectin.     

Microstructural and physicochemical properties of heat-moisture treated waxy and normal starches

Starches from normal rice (21.72% amylose), waxy rice (1.64% amylose), normal corn (25.19% amylose), waxy corn (2.06% amylose), normal potato (28.97% amylose) and waxy potato (3.92% amylose) were heat-treated at 100 °C for 16 h at a moisture content of 25%. The effect of heat-moisture treatment (HMT) on morphology, structure, and physicochemical properties of those starches was investigated. The HMT did not change the size, shape, and surface characteristics of corn and potato starch granules, while surface change/partial gelatinization was found on the granules of rice starches. The X-ray diffraction pattern of normal and waxy potato starches was shifted from B- to C-type by HMT. The crystallinity of the starch samples, except waxy potato starch decreased on HMT. The viscosity profiles changed significantly with HMT. The treated starches, except the waxy potato starch, had higher pasting temperature and lower viscosity. The differences in viscosity values before and after HMT were more pronounced in normal starches than in waxy starches, whereas changes in the pasting temperature showed the reverse (waxy > normal). Shifts of the gelatinization temperature to higher values and gelatinization enthalpy to lower values as well as biphasic endotherms were found in treated starches. HMT increased enzyme digestibility of treated starches (except waxy corn starch); i.e., rapidly and slowly digestible starches increased, but resistant starch decreased. Although there was no absolute consistency on the data obtained from the three pairs of waxy and normal starches, in most cases the effects of HMT on normal starches were more pronounced than the corresponding waxy starches.     

湿热处理对玉米淀粉性质的影响

研究了湿热处理对不同直链淀粉含量的普通玉米淀粉?高直链玉米淀粉和蜡质玉米淀粉性质的影响。试验证明,经湿热处理后,三种玉米淀粉的颗粒形状都没有发生明显的变化,偏光十字也没有消失,但表面出现一些裂纹;湿热处理不会改变三种玉米淀粉的晶型,但经湿热处理后玉米淀粉的晶体结构变强,糊化温度提高,糊黏度降低。     

天然淀粉的超高压糊化压力研究

在悬浮液浓度为5%(w/v),温度为(20±2)℃时,对8种不同淀粉进行高压处理5 min使淀粉发生糊化,采用X射线衍射测试技术得到了各种淀粉完全糊化的压力:小麦淀粉和木薯淀粉约为500 MPa,玉米淀粉、荸荠淀粉、糯小麦淀粉和糯米淀粉均为550 MPa,糯玉米淀粉约为650 MPa,马铃薯淀粉为750 MPa.     

Influence of moisture content on the degradation of waxy and normal corn starches acid-treated in methanol

Waxy and normal corn starches with different moisture contents, 5.1-16.9% and 4.8-15.9%, respectively, were prepared and treated in methanol containing 0.36% HCl at 45 °C for 1 h. Recovery of all the treated starches was found to be above 90%. Peak viscosity, gelatinization temperature and enthalpy change of gelatinization of waxy and normal corn starches decreased after treatment and this decrement was found to be more in treated starches having lower initial moisture content. The weight-average degree of polymerization and chain length (CL) of waxy and normal corn starches decreased upon acid-methanol treatment. The decrement ratio of molecular weight of modified starches was found to be negatively correlated with the initial moisture content of the starches. The decrement ratio of normal corn starch was higher than waxy corn starch with similar moisture content of starch. The content and CL of long chain fraction of amylopectin for waxy corn starch slightly decreased after treatment, while no obvious trend was found among starches with different moisture contents. CL of amylose for acid-methanol-treated normal corn starch decreased and this change was found to be higher in starches with lower initial moisture contents. Results demonstrated that the initial moisture content of starch granules strongly influenced the functional properties and degradation of starch treated by acid in methanol.     

Physicochemical Properties of Starch Isolated from Bracken (Pteridium aquilinim) Rhizome

Bracken (Pteridium aquilinum) is an important wild plant starch resource worldwide. In this work, starch was separated from bracken rhizome, and the physicochemical properties of this starch were systematically investigated and compared with 2 other common starches, that is, starches from waxy maize and potato. There were significant differences in shape, birefringence patterns, size distribution, and amylose content between bracken and the 2 other starches. X‐ray diffraction analysis revealed that bracken starch exhibited a typical C‐type crystalline structure. Bracken starch presented, respectively, lower and higher relative degree of crystallinity than waxy maize and potato starches. Ordered structures in particle surface differed among these 3 starches. The swelling power tendency of bracken starch in different temperature intervals was very similar to that of potato starch. The viscosity parameters during gelatinization were the lowest in waxy maize, followed by bracken and potato starches. The contents of 3 nutritional components, that is, rapidly digestible, slowly digestible, and resistant starches in native, gelatinized, and retrograded starch from bracken rhizome presented more similarities with potato starch than waxy maize starch. These finding indicated that physicochemical properties of bracken starch showed more similarities with potato starch than waxy maize starch.     

Pasting Properties of Potato Starch and Waxy Maize Starch Mixtures

The pasting viscosity, morphological properties, and swelling properties of potato starch and waxy maize starch mixtures at different ratios were investigated. Pasting analysis of the starch mixtures (7% solids in water, w/w) using a Rapid Visco Analyser showed linear changes in peak viscosity and pasting temperature according to the mixing ratios of both starches, but not in breakdown and setback. The pasting profile revealed that the starches rendered mutual effects during pasting, more significantly when the amounts of potato and waxy maize starches were similar. The volume fraction of swollen granules and the presence of amylose appeared to be important parameters in the mutual effects of both starched during pasting. Under a light microscope, the swelling of potato starch granules was delayed by the presence of waxy maize starch. Overall results indicate that new pasting properties can be generated by mixing starches of different botanical sources.     

Physicochemical Properties of Waxy and Normal Maize Starches Irradiated at Various pH and Salt Concentrations

Waxy and normal maize starches of various pH values and salt contents were prepared, irradiated with gamma rays (5–20 kGy) and their molecular structure, pasting viscosity and rheological properties determined. Average molar mass and size of both waxy and normal maize starches decreased considerably by irradiation from >338.0×10⁶ to <39.4×10⁶ g/mol and from >237.5 to <125.2 nm, respectively. Adjustments of pH had little influence on the average molar mass and size of irradiated starch, whereas incorporation of salt greatly reduced the molar mass and size of irradiated waxy and normal maize starches. As the pH increased from 4 to 8, the pasting viscosity of the irradiated starches decreased from 1032 to 279 mPa s in waxy and from 699 to 381 mPa s in normal starches. Pasting viscosity of both irradiated waxy and normal starch decreased from 689 to 358 mPa s and from 327 to 184 mPa s as the salt concentration increased from 1 to 5%. The G′ of gels, determined during cooling from 90 to 10°C or storage for 8 h, decreased in irradiated waxy and normal starches by pre‐conditioning at pH 8 and in irradiated waxy starches by pre‐conditioning at 5% NaCl. With 5% NaCl, G′ of irradiated normal maize starch during cooling increased up to the irradiation level of 10 kGy, and increased during storage for 8 h at all levels of irradiation. Incorporated salt prior to irradiation appears to induce incremental modifications in the molecular structure, rheological and retrogradation properties of starch by boosting the degradation of molecules.     

Preparation of Nonfragmented,Completely Amorphous,Pregelatinized Maize Starches and Determination of the Effects of Fragmentation on the Adhesiveness of Their Pastes

The objective of this research was to prepare pregelatinized maize starches that were both completely amorphous (no crystalline structure) and unfragmented, and to apply the same method to partially depolymerized maize starches to determine the effect of fragmentation on the degree of stickiness (tackiness, adhesiveness). Amorphous pregelatinized normal maize starch could be prepared by precipitation of a paste with acetone. Precipitation with a polar organic solvent was not applicable for the preparation of amorphous, pregelatinized waxy maize starch, because a sticky, cohesive and adhesive mass was produced. Therefore, freeze drying was used to prepare amorphous pregelatinized waxy maize starch. Limited acid‐catalyzed hydrolysis of normal maize starch before pregelatinization increased stickiness up to a maximum, after which the degree of stickiness decreased. In all aspects of this research, it was clear that the behavior of waxy maize starch was rather different than that of normal maize starch.