促进玉米直链淀粉回生的甘薯淀粉晶种的筛选及表征

通过向四次回生的玉米直链淀粉中添加草酸侵蚀的四次回生的甘薯淀粉、甘薯直链和甘薯支链淀粉晶种(质量分数:1%),研究甘薯淀粉晶种对玉米直链淀粉回生的影响。结果表明,甘薯淀粉晶种明显促进了玉米直链淀粉回生长晶,其中甘薯直链淀粉晶种使得玉米直链淀粉回生率达到59.5%,比不添加晶种提高了19.3%。可见吸收光谱研究表明,甘薯淀粉晶种及长晶后的玉米直链淀粉均保持了双螺旋结构。X-射线研究表明草酸侵蚀后甘薯淀粉、甘薯直链淀粉、甘薯支链淀粉均为A+B型。将其分别添加到玉米直链淀粉中并长晶后的样品,结构均为B型。DSC研究表明,甘薯支链淀粉晶种具有最高的吸热焓,说明其晶体含量最高。三种晶种分别促进玉米直链淀粉长晶后的结构较为相似,晶体含量也较相近。该研究为提高淀粉的回生率、研究回生淀粉结晶结构提供良好的技术支持。     

差示扫描量热法分析麦谷蛋白抑制小麦淀粉回生的机理

为了深入探索麦谷蛋白抑制小麦淀粉回生的机理,以小麦谷蛋白、小麦原淀粉和小麦回生淀粉中分子量分布范围较窄的直链和支链淀粉为原料,对比淀粉混合蛋白回生前后热学性质的变化,分析小麦谷蛋白抑制小麦淀粉回生的机理。结果表明,小麦谷蛋白的添加在回生前使小麦原淀粉、直链淀粉的峰值温度升高,使小麦支链淀粉的峰值温度降低,使3种淀粉的熔化吸热焓从225.0、238.0、241.8 J/g分别降低为134.2、96.5和93.5 J/g。回生后含谷蛋白的直链淀粉峰值温度下降,回生过程使含有谷蛋白的3种淀粉的熔化吸热焓均明显升高。小麦谷蛋白的添加使3种小麦淀粉均出现第2个峰值温度(220~230℃),说明蛋白和淀粉混合相互作用形成了新物质,该物质的形成阻碍了淀粉分子相互作用,抑制了淀粉的回生。     

麦芽糖转葡糖基酶修饰对普通玉米淀粉分子结构与消化性能的影响

主要探讨了不同浓度麦芽糖转葡糖基酶(简称4αGT)修饰对玉米淀粉精细结构与消化性能的影响。结果表明,当酶浓度增加时,改性淀粉中慢消化淀粉(SDS)含量增加,分子质量下降,直链淀粉含量也有所下降。当酶作用量为20 U/g淀粉时,与原淀粉相比,改性淀粉中SDS含量由9.4%增加至21.68%,直链淀粉含量由32.8%下降为25.3%,分子量也有所下降。链结构分析结果显示,其短链淀粉含量(DP<13)和长链淀粉含量(DP>30)相较于原淀粉均有所增加。4αGT作用于淀粉后合成了具有慢消化功能的新型结构。     

发酵过程中原花青素对大米淀粉多尺度结构及体外消化特性的调控

为了调控发酵米制品的消化性能,采用小角X射线散射、凝胶渗透色谱及体外模拟消化等多种现代分析技术,系统考察原花青素在大米淀粉发酵过程中对淀粉结构和消化性能的影响。研究表明,在发酵过程中原花青素与淀粉分子间存在相互作用,进而提高大米淀粉颗粒的抗消化性能,且在原花青素的添加量为8%时RS含量可达66.85%。在原花青素协同微生物发酵过程中,原花青素抑制微生物胞外酶活性并降低了淀粉分子被降解及聚集态结构无序化的程度;原花青素与淀粉分子形成淀粉分子-原花青素-淀粉分子的复合结构,促使淀粉半结晶层状结构中半结晶层厚度增大、无定型层厚度降低及聚集态结构紧密程度和表面短程有序化结构比例增加,且其在消化过程中释放原花青素并抑制淀粉酶活性,最终显著降低淀粉的消化性能。研究结果为发酵米制品消化性能的调控提供了依据。     

糯米粉储藏过程中的消化性能

研究糯米淀粉的消化性能,与玉米淀粉、马铃薯淀粉和豌豆淀粉进行对比,研究发现,经过糊化后的淀粉比天然淀粉中的快消化淀粉(RDS)含量增加50%左右,而原先品种不同淀粉的慢消化淀粉(SDS)和抗性淀粉(RS)含量均会减少至10%左右,并且基本没有差异性。糊化后,糯米淀粉的RDS上升到最大,说明淀粉糊化后的消化性能和支链淀粉的含量呈负相关的关系。在短期储藏中,多数淀粉体系中的SDS和RS含量上升幅度均在5%左右,而RDS的含量下降幅度在10%。但糯米淀粉较特殊,因为在储藏早期影响淀粉消化性能的主要是直链淀粉,糯米淀粉主要含的是支链淀粉,支链淀粉的重结晶发生缓慢。所以,在储藏早期其对糯米淀粉消化性能的影响非常小,RDS、SDS和RS含量基本没有变化。     

不同直链/ 支链比的玉米淀粉分子质量及其构象

采用凝胶渗透色谱(GPC)和十八角度激光光散射(MALLS)技术,以二甲基亚砜为流动相测定蜡质玉米淀粉、普通玉米淀粉、直链/ 支链比1:1 的高直链玉米淀粉(G50)、直链/ 支链比4:1 的高直链玉米淀粉(G80)的分子质量及其分布以及在二甲基亚砜(DMSO)溶液中的均方根旋转半径和构象。结果表明：分子质量最大的是蜡质玉米淀粉,其重均分子质量达到了1.416 × 108g/mol,其次是普通玉米淀粉2.744 × 107g/mol 与G50 1.026 × 107g/mol,最小的是G80 的3.992 × 106g/mol;均方根旋转半径也是随着直链淀粉含量的增加依次减小;蜡质玉米淀粉在DMSO 溶液中的构象是较为紧密的无规则卷曲型,其他3 种玉米淀粉的构象均为球型。     

葡萄籽乙醇提取物对玉米淀粉微观结构及回生性质的影响

为研究葡萄籽乙醇提取物(Ethanol Extract of Grape Seed,EEGS)对玉米淀粉回生性质的影响,采用扫描电镜(SEM)测定其微观结构,红外光谱测定1047/1022的比值,X-射线衍射仪(XRD)测定其结晶结构,差式扫描量热仪(DSC)测定其热力学性质,并综合评价EEGS对玉米淀粉回生的抑制作用,同时测定EEGS对玉米淀粉体外消化性能的影响。结果表明:与对照组相比,EEGS的添加促使玉米淀粉表面微观结构趋于平滑,多孔结构减少。当EEGS的添加量为2.5%时,玉米淀粉的1047/1022的比值、相对结晶度、熔融焓值下降程度最大,玉米淀粉的回生受到明显抑制。此外,随着EEGS的添加量增加,玉米淀粉中RDS含量逐渐下降,而SDS和RS的含量随之增加。EEGS可作为玉米淀粉回生抑制剂、抗性淀粉生产的添加剂的潜在来源,在食品加工中被开发利用。     

6种不同种类直支链淀粉相互混合对其回生的影响

目的 研究6种不同种类直支链淀粉相互混合对其回生的影响。方法 将玉米淀粉、甘薯淀粉、木薯淀粉、马铃薯淀粉、糯米淀粉、小麦淀粉等6种不同种类直支链淀粉分离出来, 然后两两混合, 研究不同直支链混合对其回生率的影响。 结果 马铃薯支链淀粉与甘薯支链淀粉以2:8(m:m)混合回生率最低, 为60.0%, 玉米支链淀粉与木薯支链淀粉以8:2(m:m)混合回生率最低为52.6%, 小麦支链淀粉与糯米支链淀粉以8:2(m:m)混合回生率最低为51.2%, 甘薯支链淀粉与小麦支链淀粉以1:1(m:m)混合回生率最低为53.7%。木薯支链淀粉与小麦直链淀粉以1:1(m:m)混合时所得淀粉回生率最大, 达到了92.0%, 混合淀粉回生后X射线晶型为B型。结论 不同种类直支链淀粉混合对其回生率影响很大, 食品加工中尽量不要混合使用木薯支链淀粉与小麦直链淀粉。     

欧李原花青素对马铃薯淀粉消化的影响

向马铃薯(青薯9号)中添加不同比例的欧李果实原花青素，通过体外模拟消化实验，研究分析了欧李原花青素与马铃薯淀粉复合后的消化特性，并通过扫描电子显微镜(scanning electron microscope, SEM)、X-射线衍射(X-ray diffraction, XRD)、傅里叶变换红外光谱(Fourier transform infrared spectroscopy, FTIR)和AutoDock Vina软件等探究欧李原花青素抑制马铃薯中淀粉消化的机理。结果表明，随着欧李原花青素添加量的增加马铃薯中慢消化淀粉(readily digestible starch, RDS)含量显著降低，慢消化淀粉(slowly digestible starch, SDS)和抗性淀粉(resistant starch, RS)含量升高。FTIR和XRD结果说明，欧李原花青素可能以氢键等非共价作用力与马铃薯中的淀粉结合。另外利用AutoDock Vina软件对欧李原花青素与α-淀粉酶进行分子模拟对接处理。结果表明，对接位点位于淀粉酶蛋白结构的疏水空腔内，且欧李原花青素通过共价结合和非共价作用...     

蒸煮条件及回生处理对方便米饭消化特性的影响

考察蒸煮方式及回生处理对方便米饭体外消化率的影响。实验利用不同蒸煮条件及回生时间处理低直链淀粉含量和高直链淀粉含量的不同品种大米,制备得到具有不同性质的方便米饭,并研究了方便米饭快消化淀粉(RDS)、慢消化淀粉(SDS)和抗性淀粉(RS)的含量差异及其体外消化率。结果表明,相对于电饭锅蒸煮,采用常规方式蒸煮,即控制米水比为1∶1,86℃蒸煮28 min制备的方便米饭RDS含量得到极大的降低,SDS含量明显的升高(P0.05)。回生处理可以显著的降低方便米饭RDS含量。与此同时,实验发现低直链淀粉含量品种的米饭含有较低的RDS含量、较高的SDS和RS含量,高直链淀粉含量品种的米饭则含有较低的SDS和较高的RS含量。通过控制蒸煮和回生条件,可以得到淀粉消化率低的方便米饭,对肥胖及高血糖人群健康有积极作用。     

直链淀粉晶种对淀粉回生的影响机制

由于淀粉回生影响因素复杂和研究手段局限,基于直链淀粉主导的短期回生阶段和支链淀粉主导的长期回生阶段关联性的回生共性机制未得到系统阐述。基于此,该研究制备短期回生的直链淀粉晶种,采用FTIR、¹³C CP/MAS NMR等手段,研究其诱导大米淀粉的长期回生过程与规律,揭示短期回生与长期回生关联性。结果表明,所制备的直链淀粉晶种粒度分布在200～450 nm,添加晶种导致淀粉短程有序度由0. 670最高提高至0. 887,双螺旋含量由14. 86%最高提高到了22. 80%。回生淀粉的短程有序度、双螺旋含量显著提高,表明所制备直链淀粉晶种显著促进淀粉长期回生过程,这种晶体协同增长效应,丰富了淀粉回生共性机制。     

Structural characterizations and digestibility of debranched high-amylose maize starch complexed with lauric acid

Structural characterizations and digestibility of debranched high-amylose maize starch complexed with lauric acid (LA) were studied. The cooked starch was debranched by using pullulanase and then complexed. Light microscopy showed that the lipids complexed starches had irregularly-shaped particles with strong birefringence. Gel-permeation chromatograms revealed that amylopectin degraded to smaller molecules during increasing debranching time, and the debranch reaction was completed at 12 h. Debranching pretreatment and prolonged debranching time (from 2 h to 24 h) could improve the formation of starch lipids complex. X-ray diffraction pattern of the amylose–lipid complexes changed from V-type to a mixture of B- and V-type polymorphs and relative crystallinity increased as the debranching time increased from 0 to 24 h. In DSC thermograms, complexes from debranched starch displayed three separated endotherms: the melting of the free lauric acid, starch–lipid complexes and retrograded amylose, respectively. The melting temperature and enthalpy changes of starch–lipid complex were gradually enhanced with the increasing of debranching time. However, no significant enthalpy changes were observed from retrograded amylose during the starch–lipid complex formation. Rapidly digestible starch (RDS) content decreased and resistant starch (RS) content increased with the increasing of debranching time, while the highest slowly digestible starch (SDS) content was founded at less debranching time of 2 h. The crystalline structures with dense aggregation of helices from amylose-LA complex and retrograded amylose could be RS, while SDS mostly consisted of imperfect packing of helices between amylopectin residue and amylose or LA.     

Effect of maize type and extrusion‐cooking conditions on starch digestibility profiles

This study aimed at evaluating the influence of screw speed (250–600 rpm), barrel temperature (100–160 °C) and water content (16.4–22.5%) on rapidly digestible (RDS), slowly digestible (SDS) and resistant (RS) starch levels of waxy, normal and high‐amylose maize starches. In native starches, an increase in amylose content was correlated with lower SDS content. After extrusion, this trend was reversed. Both waxy and normal maize starches became rapidly digested. However, for normal maize starch, some SDS fraction remained. In contrast, the high‐amylose maize starch showed a significant increase in digestibility and an increase in SDS content from 20.4% in the native starch up to 27.5% after extrusion. This high level of SDS may be attributed to the presence of some remaining granular structures and formation of crystalline orders, which have slow digestion properties.     

Effect of retrogradation,pancreatin digestion and amylose/amylopectin ratio on the fermentation of starch by Clostridium butyricum (NCIMB 7423)

Using three different maize starches (maize, waxy maize and high amylose maize, containing 25%, 1% and 52% amylose, respectively) the influence of amylose/amylopectin content and of retrogradation on fermentation by the porcine caecal anaerobe Clostridium butyricum was assessed. Small intestine digestion was simulated using pancreatin before the starches were exposed to bacterial fermentation. It was found that retrogradation appeared to alter the extent of the fermentation and hence the amount of short-chain fatty acids produced, while pancreatin digestion appeared to alter the way in which the organism fermented the starch and hence the acetate/butyrate ratio. The amylose/amylopectin ratio seemed to have more influence on the way the starch was fermented by the bacteria after the starch had been subjected to digestion with pancreatic enzymes, but had less influence when the starch had been retrograded. © 1998 SCI.     

Starch gelatinization using sodium silicate: FTIR,DSC, XRPD,and NMR studies

The chemical and physical modifications of native maize starch subjected to treatment with aqueous Na silicate have been investigated. The application of FTIR, DSC, XRPD, and NMR analysis is discussed herein with respect to the interaction of Na silicate with starch in relation to gelatinization. XRPD results indicate that Na silicate, in the ionized form, disrupts the molecular structure of starch in a manner similar to thermally induced starch gelatinization. In addition, Na silicate forms new CO–O–SiO₂Na moieties with the amylopectin starch component. This was ascertained by the detection of the in‐plane vibration of the –Si–O as a distinctive FTIR band at 580–600 cm⁻¹ and the appearance of a new carboxyl group (–COOH) NMR chemical shift at 168 ppm for the amylopectin/Na silicate system. DSC analysis showed two adjacent endothermic transitions at 192 and 198°C for starch/amylopectin treated with Na silicate whereas amylose treated with Na silicate did not show any new endothermic/or exothermic transitions.     

Wheat starch production,structure, functionality and applications—a review

Starch is the main component of wheat having a number of food and industrial applications. Thousands of cultivars/varieties of different wheat types and species differing in starch functionality (thermal, retrogradation, pasting and nutritional properties) are grown throughout the world. These properties are related to starch composition, morphology and structure, which vary with genetics, agronomic and environmental conditions. Starches from soft wheat contain high amounts of surface lipids and proteins and exhibit lower paste viscosity, whereas that from hard cultivars contain high proportion of small granules and amylose content but lower gelatinization temperature and enthalpy. Waxy starches exhibit higher‐percentage crystallinity, gelatinization temperatures, swelling power, paste viscosities and digestibility, but lower‐setback viscosity, rate of retrogradation and levels of starch lipids and proteins than normal and high‐amylose starches. Starches with high levels of lipids are less susceptible towards gelatinization, swelling and retrogradation and are good source of resistant starch, while that with high proportion of long amylopectin chains are more crystalline, gelatinize at high temperatures, increase paste viscosity, retrograde to a greater extent and decrease starch digestibility (high resistant and slowly digestible starch and low rapidly digestible starch).     

Localisation of Amylose and Amylopectin in Starch Granules Using Enzyme-Gold Labelling

The independent localisation of amylose and amylopectin in a range of dry and hydrated native starch granules with varying amylose content (0—70 %) has been indirectly visualised using enzyme-gold cytochemical markers. Increasing amylose content was clearly demonstrated to result in distinct changes in granule architecture. In the absence of amylose (waxy maize starch) a framework of closely packed concentric layers of amylopectin exists in the granules. Low amylose content (potato starch) results in alternating layers of densely packed amylopectin and amylose molecules. High amylose content (amylomaize starch) granules were shown to possess an amylopectin centre surrounded by an amylose periphery encapsulated by an amylopectin surface. Elongated granules without the amylopectin centre were also observed in high amylose starches suggesting a relationship between amylopectin, amylose and granule shape. A model of starch granule architecture is proposed where increased compartmentalisation of amylose and amylopectin is observed in granules containing increasing levels of amylose.     

Preparation and properties of RS III from waxy maize starch with pullulanase

Waxy maize starch was treated by pullulanase debranching and retrogradation at room temperature to produce resistant starch (RS). Physicochemical properties, crystalline structure and in-vitro digestibility of starch samples with different RS content were investigated. Compared with native starch, apparent amylose content of RS products increased. Based on Gel Permeation Chromatography (GPC) the Molecular Weight Distribution (MWD) of resistant starches significantly changed. Scanning Electron Microscopy (SEM) showed that upon pullulanase debranching and retrogradation treatment the granular structure of native starch was destroyed and all RS samples exhibited irregular shaped fragments. Crystal structure of samples changed from A–type to a mixture of B and V–type. The crystallinity of resistant starch also improved as compared with native starch. Moreover, samples with higher resistant starch showed higher relative crystallinity. Differential Scanning Calorimetry (DSC) determination showed that To、Tp、Tc and ΔH all increased which was in agreement with RS content. The resistance of waxy maize starch with Pullulanase treatment to α-amylase digestibility also increased, while the in-vitro digestibility of products decreased.     

Retrogradation of Potato Starch as Studied by Fourier Transform Infrared Spectroscopy

Retrogradation kinetics for a potato starch-water system (10% w/w gel) was monitored by Fourier Transform Infrared spectroscopy and compared with waxy maize starch. The spectra showed the C-C and C-O stretching region (1300-800 cm⁻¹) to be sensitive to the retrogradation process. A multi-stage process was observed during the retrogradation of potato starch and characterized as the formation of short- and long-range order. The first stage was characterized as the formation of helices and the fast formation of crystalline amylose regions. The second stage was described as the induction time for amylopectin helix aggregation. Stage three was described as the helix-helix aggregation and the crystallization of amylopectin. The overall-first order calculated rate constant of potato starch was (9.6±1.4) 10⁻ 3h⁻¹. The calculated rate constant were in agreement with the known difference in retrogradation kinetics of waxy maize and potato starch. The effects were explained by the differences in retrogradation rate of amylopectin and amylose. Potato starch consists of amylose as well as amylopectin. Whereas amylose crystallization occurs within a few hours, amylopectin crystallization is slow and takes a few weeks.