玉米淀粉高压糊化动力学的初步探讨

通过计算玉米淀粉高压糊化的动力学参数认为，作为能独立改变物质状态的两种因素—压力和热，它们使淀粉糊化的反应同属一级反应，由此根据已有的热糊化动力学理论提出了保压时间与淀粉糊化度的动力学关系式，解释了高压淀粉糊化机理和影响糊化速度的因素     

玉米高压糊化淀粉的老化特性和变色性质

研究了玉米淀粉高压糊化后的冻融稳定性和色泽变化，并和热糊化淀粉的老化特性和色泽变化做了比较。高压完全糊化淀粉糊没有与热加工糊化淀粉糊相同的老化现象。同时，高压不象热加工使玉米淀粉的颜色变黄。     

几种淀粉的糊化特性及力学稳定性(简报)

为探索淀粉糊化的力学稳定性,以不同来源淀粉为原料,采用快速黏度分析仪于不同搅拌速度下,研究外力作用对淀粉糊化特性的影响,为淀粉质食品的品质控制提供依据。结果表明,不同来源淀粉的黏度曲线及其力学稳定性有差异。以小麦淀粉的糊化温度最低;马铃薯淀粉糊的黏度和温度稳定性最大;马铃薯和莲子淀粉的峰值黏度较高,冷糊稳定性好;莲子淀粉的热糊稳定性差;玉米淀粉糊易于老化。外力作用对淀粉糊的黏度曲线有影响。较强的外力作用后,会导致淀粉糊的强度、黏度和糊化温度降低,改善热糊稳定性和冷糊稳定性。淀粉糊化的力学稳定性与其颗粒强度有关,较大颗粒强度的淀粉的力学稳定性较好。     

高压处理玉米淀粉的X射线衍射图谱分析

采用Ｘ射线衍射仪研究了高压处理玉米淀粉的结晶度。研究结果表明：随压力和含水量的增加，高压处理玉米淀粉的Ｘ射线衍射图谱的峰值下降，峰形逐渐消失，结晶度下降，糊化度增加。在７００ＭＰａ时处理干淀粉，未能使淀粉晶体结构破坏，说明高压处理玉米淀粉糊化的本质也是通过水合作用来实现的。     

影响甜玉米羹罐头质量因素的分析

为保证甜玉米羹罐头具有良好质量，加工时，要选用普通型甜玉米，并在其乳熟前期及时采收。若甜玉米采收之后不能及时加工，需要将其在０℃冷藏或－１５℃以下低温速冻保藏。在加工中需要注意罐头内容物的配料组成，添加淀粉量为０．３％～０．６％，并且在内容物预煮糊化时尽可能利用高温（１１５～１２５℃）短时间（２０～３０ｍｉｎ）处理，在杀菌过程中尽可能缩短内容物受热的时间。     

玉米高压淀粉糊流变特性的研究

高压玉米淀粉糊的流变特性为：随含水量提高剪切模量、动态粘度和耗损角都提高；在小于９０Ｈｚ低频波作用下，高压淀粉糊的剪切模量和动态粘度因保压时间延长而增大；在１００Ｈｚ的剪切波作用下，高压淀粉糊的上述特征值则因保压时间延长而减小。     

玉米淀粉微晶结构在加热和高压作用下的变化

对照研究了玉米淀粉微晶结构在高压和加热单独作用下的变化。玉米淀粉加压或加热后，在偏振光显微镜下均有偏光十字消失现象，说明玉米淀粉的微晶结构发生了相同的变化，且均已被破坏，即加热和加压均可使淀粉糊化     

微波的热与非热效应对淀粉性质的影响

微波是波长微小的电磁波,具有很强的介质穿透能力,可实现物料内外的同时升温。在利用微波熟化淀粉类食品时,具有热效率高、可控性强、设备占地小等优点。本文介绍了淀粉升温糊化过程中微波热效应和非热效应;总结了研究微波非热效应的几种新手段;比较了微波处理与热传导处理在淀粉升温糊化过程中,淀粉颗粒表观特征、晶体结构和分子结构的变化以及热学特性的差异;论述了微波处理淀粉乳中水的响应。本文为后续深入研究微波处理对食物中淀粉糊化的影响与微波糊化淀粉特性的开发利用提供了参考。     

气流粉碎对玉米淀粉结构及理化性质的影响

为研究气流粉碎对玉米淀粉结构及理化性质的影响,该文以普通玉米淀粉为原料,通过流化床气流粉碎处理,采用扫描电子显微镜、偏光显微镜、粒度分析仪、X-射线衍射仪、红外光谱仪、差示扫描量热仪、快速黏度分析仪等分析手段研究经微细化处理前后玉米淀粉颗粒形貌、晶体结构、热力学特性、糊化特性、溶解度和膨胀度、冻融稳定性、持水能力等结构及性质的变化。结果表明,微细化处理后,淀粉颗粒形变的不规则,粒径明显减小,中位径(D50)由14.37μm减小到5.25μm,偏光十字减少,相对结晶度由33.43%降低至15.46%,淀粉颗粒结晶结构被破坏,由多晶态向无定形态转变,粉碎过程淀粉无新的基团产生;热焓值、糊化温度均降低,热糊稳定性好;溶解度、膨胀度均升高,持水能力增加,冻融稳定性好,产生较好的热糊稳定性和冷糊力学稳定性,该研究为玉米淀粉的深度加工与应用提供了理论依据及技术支撑。     

玉米淀粉黏结剂的黏结性能

基于水量、糊化温度、糊化剂及交联剂4个因素设计了正交试验L₉(3⁴)方案，制备糊化玉米淀粉黏结剂，以木材黏结压缩剪切强度评价黏结剂的黏结性能。对试验数据进行了极差分析，得出了影响淀粉黏结剂因素的优水平、主次因素及最优组合，最优组合即当普通玉米淀粉为10 g时，水量125 g，糊化温度B₂=75℃，糊化剂NaOH为0.10 g，交联剂Na₂B₄O₇·10H₂O为0.03 g。对最优组合进行了试验验证，得到木材黏结压缩剪切强度为1.425 MPa，其结果符合极差分析结果。并对试验数据进行方差分析，得出各因素对黏结剂黏结性能影响的显著程度。研究表明：水量因素和糊化温度因素对黏结性能影响显著，而糊化剂和交联剂因素对黏结性能影响不显著。该论文为进一步研究玉米淀粉黏结剂的特性和应用提供参考。     

Morphological Changes of Granules of Different Starches by Surface Gelatinization with Calcium Chloride

Native starch granules of 11 selected cultivars (potato, waxy potato, sweet potato, normal maize, high‐amylose maize, waxy maize, wheat, normal barley, high‐amylose barley, waxy barley, and rice) were treated with a calcium chloride solution (4M) for surface gelatinization. The surface‐gelatinized starch granules were investigated using light microscopy and scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). In general, those starches with larger granule sizes required longer treatment time to complete the gelatinization. The salt solution treatment of starch was monitored by light microscopy and stopped when the outer layer of the granule was gelatinized. The surface gelatinized starch granules were studied using scanning electron microscopy. On the basis of the gelatinization pattern from calcium chloride treatments, the starches could be divided into three groups: 1) starches with evenly gelatinized granule surface, such as normal potato, waxy potato, sweet potato, maize, and high‐amylose maize; 2) starches with salt gelatinization concentrated on specific sites of the granule (i.e., equatorial groove), such as wheat, barley, and high‐amylose barley; and 3) starches that, after surface gelatinization, can no longer be separated to individual granules for SEM studies, such as waxy barley, waxy maize, and normal rice. The morphology of the surface gelatinized starch resembled that of enzyme‐hydrolyzed starch granules.     

Enzymatic Hydrolysis of Barley Starch Lipids

The efficiency of phospholipase and lipase preparations in the hydrolysis of lysophospholipids of native and gelatinized barley starch was examined. The degree of hydrolysis was analyzed by determination of the amount of released fatty acids by an enzymatic method. Thermal and structural properties of the enzyme-treated starch were studied by differential scanning calorimetry and light microscopy. Lysophospholipids of the gelatinized barley starch were easily hydrolyzed, in contrast to the lipids of the granular starch. The maximum degree of hydrolysis achieved for the gelatinized starch was 80% and for the native starch ≈20%. Gelatinization enthalpies and micrographs indicated that even though the amount of the released fatty acids from the native starch was small, formation of free fatty acids inhibited swelling and gelatinization of starch granules.     

机械活化玉米淀粉的微生物降解性能

为了提高玉米淀粉的微生物降解反应活性,采用搅拌球磨机对玉米淀粉进行机械活化,以活化时间为60 min的玉米淀粉和原淀粉为原料,酒曲为降解试剂进行微生物降解反应,并以降解产物的葡萄糖值（Dextrose Equivalent,DE）为评价指标,分别研究了糊化温度、pH值、淀粉浓度、降解时间、降解温度、酒曲培养液用量等因素对降解产物中葡萄糖值的影响,并采用扫描电镜对淀粉降解过程中的颗粒进行形貌观察。结果表明,机械活化预处理能提高玉米淀粉微生物降解反应液中葡萄糖的含量,且活化淀粉未经糊化就能直接被微生物降解,降解60 min时的DE值为36.76%,与原淀粉相比,提高了27.80个百分点。说明机械活化作用破坏玉米淀粉紧密的颗粒表面和结晶结构,有效地提高了微生物降解反应活性。     

Water dynamics and retrogradation of ultrahigh pressurized wheat starch

The water dynamics and retrogradation kinetics behavior of gelatinized wheat starch by either ultrahigh pressure (UHP) processing or heat are investigated. Wheat starch completely gelatinized in the condition of 90, 000 psi at 25 degrees C for 30 min (pressurized gel) or 100 degrees C for 30 min (heated gel). The physical properties of the wheat starches were characterized in terms of proton relaxation times (T2 times) measured using time-domain nuclear magnetic resonance spectroscopy and evaluated using commercially available continuous distribution modeling software. Different T2 distributions in both micro- and millisecond ranges between pressurized and heated wheat starch gels suggest distinctively different water dynamics between pressurized and heated wheat starch gels. Smaller water self-diffusion coefficients were observed for pressurized wheat starch gels and are indicative of more restricted translational proton mobility than is observed with heated wheat starch gels. The physical characteristics associated with changes taking place during retrogradation were evaluated using melting curves obtained with differential scanning calorimetry. Less retrogradation was observed in pressurized wheat starch, and it may be related to a smaller quantity of freezable water in pressurized wheat starch. Starches comprise a major constituent of many foods proposed for commercial potential using UHP, and the present results furnish insight into the effect of UHP on starch gelatinization and the mechanism of retrogradation during storage.     

Association of Starch Granule Proteins with Starch Ghosts and Remnants Revealed by Confocal Laser Scanning Microscopy

Starch suspensions (0.25%) were gelatinized to 70 and 100°C, and starch ghosts (defined as gelatinized starch granule envelopes after the majority of internal starch polymers have been released) and remnants were collected by centrifugation and washed with water. Protein was revealed in isolated gelatinized normal starch ghosts using confocal laser scanning microscopy and a protein‐specific dye that fluoresces only after reaction with primary amines in protein. This technique eliminates background interference from residual dye. Observation of fluorescent‐labeled protein in the starch ghosts at different optical depths of field revealed that protein was concentrated in the envelopes of swollen, gelatinized potato, maize, and wheat starch ghosts. Only traces of protein were found in gelatinized starch granule remnants of waxy maize and amylose‐free potato starches after they were heated to 100°C, indicating that the proteins observed in gelatinized normal maize starch were largely granule‐bound starch synthase (GBSS). Moreover, fragility of the gelatinized waxy and amylose‐free starch granule remnants might be caused in part by the lack of GBSS. Gel electrophoresis of proteins in starch ghosts confirmed that GBSS in potato and maize was tightly associated with the starch ghosts. The study provides a structural explanation for a role of granule‐associated proteins in maintaining the integrity of starch ghosts and remnant structures, and their consequent effect on paste rheology.     

Identification of QTL Controlling Thermal Properties of Maize Starch

Starch has many uses and some of these uses would be facilitated by altering its thermal properties. Genetic manipulation of starch thermal properties will be facilitated by a better understanding of the genetic control of starch gelatinization. We used differential scanning calorimetry to characterize the gelatinization parameters of maize (Zea mays L.) kernel starch prepared from two populations of recombinant inbred lines, an intermated B73xMo17 population (IBM) and an F_6:7 Mo17xH99 population. The traits examined were the onset and peak temperatures of gelatinization and the enthalpy of gelatinization. These traits were measured for both native starch and for gelatinized starch allowed to recrystallize, a process called retrogradation. Substantial variation in these traits was found in spite of the narrow genetic base of the populations. We identified several quantitative trait loci (QTL) controlling traits of interest in each population. In the IBM population, a significant QTL for the peak temperature of gelatinization of retrograded starch co‐localized to a molecular marker in the Wx1 gene, which encodes a granule bound starch synthase. The major QTL identified in this study explain, on average, ≈15% of the variation for a given trait, underscoring the complexity of the genetic control of starch functional properties.     

A Maltose Biosensor for Determining Gelatinized Starch in Processed Cereal Foods

A reliable method for the quantitative determination of gelatinized starch in processed cereal foods was developed. It consists of an electrochemical biosensor based on amyloglucosidase and glucose oxidase enzymes co‐immobilized on a Pt electrode surface, and a third enzyme, α‐amylase, added in solution. Analytical parameters such as time, temperature, and enzyme units were optimized. The degree of starch gelatinization was determined in different processed cereal foods using the biosensor method and the results were commensurate to those obtained with the reference method. The biosensor methods showed good accuracy (r² = 0.9629; relative error <12%) and comparable precision (RSD <5%). This electrochemical system is rapid, reliable, inexpensive, user‐friendly for unskilled operators, and can be a valid alternative to the methods traditionally used for gelatinized starch analysis.     

Retrogradation of Maize Starch After Thermal Treatment Within and Above the Gelatinization Temperature Range

Studies of starch retrogradation have not considered the initial thermal treatment. In this article, we explore the effect of heating to temperatures within and above the gelatinization range on maize starch retrogradation. In the first experiment, 30% suspensions of waxy (wx) starch were initially heated to final temperatures ranging from 54 to 72°C and held for 20 min. On reheating in the differential scanning calorimeter immediately after cooling, the residual gelatinization endotherm peak temperature increased, the endotherm narrowed, and enthalpy decreased. Samples stored for seven days at 4°C showed additional amylopectin retrogradation endotherms. Retrogradation increased dramatically as initial holding temperature increased from 60 to 72°C. In a second experiment, wx starch was initially heated to final temperatures from 54 to 180°C and rapidly cooled, followed by immediate reheating or storage at 4°C. Maximum amylopectin retrogradation enthalpy after storage was observed for initial heating to 82°C. Above 82°C, retrogradation enthalpy decreased as initial heating temperature increased. A similar effect for ae wx starch was observed, except that retrogradation occurred more rapidly than for wx starch. These experiments show that heating to various temperatures above the range of gelatinization may profoundly affect amylopectin retrogradation, perhaps due to varying extents of residual molecular order in starch materials that are commonly presumed to be fully gelatinized. This article shows that studies of starch retrogradation should take into account the thermal history of the samples even for temperatures above the gelatinization temperature range.