魔芋葡甘聚糖对冷冻小麦面团面筋蛋白结构和功能特性的影响

为研究魔芋葡甘聚糖（konjac glucomannan,KGM）对冷冻小麦面团面筋蛋白分子质量、游离巯基、二级结构和微观结构及持水性、流变性、热特性的功能特性影响,从小麦粉中提取面筋蛋白,运用十二烷基硫酸钠-聚丙烯酰氨凝胶电泳、流变仪、差示扫描量热仪、紫外分光光度计、傅里叶变换红外光谱和扫描电子显微镜对冷冻小麦面团面筋蛋白结构和功能特性进行分析。结果表明,与对照相比,KGM显著增强了面筋蛋白的持水性,提高了面筋蛋白黏弹特性、变性温度（Tp）和变性焓（ΔH）。在KGM存在的情况下,面筋二级结构α-螺旋和β-折叠结构占比增加,β-转角结构和无规卷曲结构减少,使其在冷冻环境下更加稳定。扫描电子显微镜图像分析表明KGM取代度为1.5%时,面筋蛋白微观结构具有明显的海绵状结构和更大的孔隙。KGM对冷冻小麦面团中的面筋蛋白特性有显著影响,对面筋蛋白起到冷冻保护作用。     

Aggregative and structural properties of wheat gluten during post-harvest maturation

Wheat post-harvest maturation induced baking and technological quality improvement through a series of biochemical and colloidal changes. Weak-, middle-, and strong-gluten wheat displayed varying gluten network structures that determined the flour ingredient formulations and processing conditions. However, the aggregation and structural properties of wheat with different gluten strengths post-harvest remain largely unexplored. In this study, we investigated changes in the aggregative properties of gluten protein, gluten composition, S–S content, network structure, and secondary structures of weak-, middle-, and strong-gluten wheat during post-harvest maturation. The results indicated that the macromolecular aggregation of gluten proteins was impaired in weak-gluten wheat, while it was enhanced for middle- and strong-gluten wheat during storage. Post-harvest maturation resulted in an increase in glutenin content and a decline in the gliadin and gliadin/glutenin ratio in middle- and strong-gluten wheat as well as a decreased glutenin content in weak-gluten wheat. Moreover, additional gluten subunits were observed in middle- and strong-gluten wheat, but no substantial change was observed in weak-gluten wheat with long storage times. The disulfide bond content of gluten protein for middle-gluten and strong-gluten gradually increased but declined for weak-gluten wheat. Secondary structure analysis of gluten indicated that post-harvest maturation caused the conversion of α-helix to random coil for weak-gluten wheat, β-turn and random coil to α-helix for middle-gluten wheat, and β-turns to α-helix for strong-gluten wheat, which led to a disordered structure for weak gluten and an ordered stable gluten network for middle- and strong-gluten. Thus, the increased S–S and α-helix content induced by post-harvest maturation enhanced the aggregation of gluten proteins for middle- and strong-gluten wheat, resulting in a denser network structure. Conversely, the decrease in the content of α-helix resulted in the existence of a looser gluten network structure for weak-gluten wheat during post-harvest maturation.     

发酵时间对馒头品质及面筋蛋白结构的影响

利用体积仪、质构仪和傅里叶变换红外光谱分别测定馒头比容、质构特性与面筋蛋白二级结构,探究发酵时间对馒头品质及面筋蛋白结构的影响。结果表明：馒头中醇溶蛋白与麦谷蛋白中β-折叠含量均为最高。随着发酵时间的不断延长,醇溶蛋白中β-折叠、α-螺旋相对含量无显著性变化,无规则卷曲逐渐减少,而β-转角则逐渐增加;羟基吸收带逐渐增强,醇溶蛋白的水合作用增强。麦谷蛋白中α-螺旋与无规则卷曲相对含量变化不大,β-折叠相对含量先上升后下降,而β-转角相对含量则是先下降后上升;羟基带强度逐渐减弱;当发酵时间延长到80?min时,麦谷蛋白红外光谱位于1?082?cm－1与1?155?cm－1处的峰消失,可能是蛋白质环状结构的C—C振动减弱。     

冻藏时间对麦谷蛋白和麦醇溶蛋白二级结构及面团性能的影响研究

分别对小麦醇溶蛋白和麦谷蛋白在-18℃下冻藏0²8d后其巯基和二硫键含量以及二级结构的变化情况进行研究,并分析了变化可能的内在机理;进一步探讨了冻藏导致的面团质构变化与两种面筋蛋白结构变化的对应关系。结果表明:冻藏处理使麦醇溶蛋白和麦谷蛋白中巯基含量增加、二硫键含量减少,α-螺旋和β-转角结构含量下降,β-折叠结构含量升高;其中,冻藏处理对麦谷蛋白二级结构的影响程度要明显大于麦醇溶蛋白。质构研究结果表明:两种蛋白质中二硫键、α-螺旋和β-转角结构含量的减少,对冻藏后面团粘性、弹性、硬度的降低有着重要影响。      

高温高湿处理对小麦中蛋白质性质的影响

目的：探索高温高湿工艺对小麦及其制品蛋白质性质的影响。方法：分析了经高温高湿工艺处理后小麦粉及其制品的面筋蛋白、麦谷蛋白及麦醇溶蛋白的理化性质、分子性质和超微结构。结果：小麦粉和挂面中蛋白质的水溶性随处理时间的延长而降低;挂面面筋蛋白的持水力优于小麦粉,其中麦谷蛋白的持水能力占主要作用;随着处理时间的延长,小麦蛋白质中相对分子量较大的麦谷蛋白含量增多,而分子量较小的麦醇溶蛋白含量减少。SEM分析发现,热变性使谷蛋白由原来的膜状结构逐渐变成多孔结构,此结构使面筋网络中的孔隙变大,孔隙变大可以更好地包裹淀粉颗粒。结论：高温高湿处理工艺对小麦和面条中的蛋白质性质影响具有差异。小麦粉中的蛋白质持水能力经处理后基本没有变化,而水溶能力则呈下降趋势;面条经高温高湿处理后持水力与水溶力均提高。     

不同面筋蛋白组分对小麦淀粉消化特性的影响机理

分别将面筋蛋白、谷蛋白及醇溶蛋白与淀粉按一定质量比（14∶86）混合,运用流变仪、热重分析仪及激光共聚焦显微镜等手段分析不同面筋蛋白组分与淀粉/α-淀粉酶之间的相互作用,以明确面筋蛋白及其不同组分对淀粉消化特性的影响及潜在机理。结果表明：与纯小麦淀粉相比,添加面筋蛋白、谷蛋白及醇溶蛋白使酶解120 min的淀粉消化率分别下降了39.93%、49.48%及26.61%。淀粉与不同面筋蛋白组分之间通过氢键相互作用形成了更稳定的复合物,提高了样品的热稳定性。与面筋蛋白和醇溶蛋白相比,添加谷蛋白在淀粉基质周围形成了更加致密的物理性屏障,更大程度地抑制了酶对淀粉的水解。此外,谷蛋白对α-淀粉酶的抑制率最高（约79%）,激光共聚焦观察到的结果也证实了谷蛋白和α-淀粉酶之间的结合程度更高。研究结果有助于丰富典型蛋白质组分调控食品体系中淀粉消化的机理,为低血糖指数食品的开发提供一定理论指导。     

Role of gluten and its components in influencing durum wheat dough properties and spaghetti cooking quality

Protein is an important component of grain which affects the technological properties of durum wheat. It is known that the amount and composition of protein can influence dough rheology and pasta quality but the influence of the major classes of protein is not well documented. The influence of the various gluten components on dough and pasta properties was investigated. The protein composition of durum semolina was altered by either adding gluten fractions to a base semolina or preparing reconstituted flours with varying protein composition. The effects on semolina dough rheology and spaghetti texture were measured. Published methods to isolate relatively pure quantities (gram amounts) of glutenin, gliadin, high molecular and low molecular weight glutenin subunits were evaluated and modified procedures were adopted. Reconstituted flours with additional glutenin increased dough strength while additional gliadin and LMW‐GS decreased strength. These changes did not impact on spaghetti texture. Results from using the addition of protein fractions to a base semolina showed that gluten and glutenin addition increased the dough strength of a weak base semolina while gliadin addition weakened the base dough further. Addition of HMW‐GS greatly increased dough strength of the base while addition of LMW‐GS greatly reduced dough strength. Again, these affects were not translated into firmer pasta. Copyright © 2007 Society of Chemical Industry     

青稞和小麦醇溶蛋白和谷蛋白结构性质的比较研究

采用Osbron法分别提取青稞和小麦中的醇溶蛋白和谷蛋白,对这4 种蛋白质进行十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE）分析和红外光谱分析,并测定其表面疏水性、热稳定性、总巯基和二硫键含量。结果表明：醇溶蛋白在青稞蛋白质中的含量为16.96%,低于其在小麦蛋白质中的含量;谷蛋白在青稞蛋白质中的含量为47.83%,高于其在小麦蛋白质中的含量,但经SDSPAGE分析发现青稞中高分子质量谷蛋白亚基（high molecular weight glutenin subunit,HMW-GS）含量远低于小麦中的。青稞醇溶蛋白和谷蛋白中的二硫键和总巯基含量均低于小麦中的。4 种蛋白的表面疏水性差异不大。青稞谷蛋白的热稳定性高于小麦谷蛋白,不利于其吸收水分和部分展开。红外光谱分析发现小麦醇溶蛋白和青稞醇溶蛋白的二级结构主要由β-转角和β-折叠组成,而小麦醇溶蛋白中的β-转角所占比例更高;青稞谷蛋白和小麦谷蛋白的二级结构主要以β-折叠为主。     

Effects of japonica rice flour on the mesoscopic and microscopic properties of wheat dough protein

The aim of this study was to study the effects of twelve varieties of japonica rice flour on the gluten protein composition and structure of wheat dough. Experimental results indicated that the addition of japonica rice flour significantly decreased the α-helix structure in the gluten protein sample, but increased the random coil content, indicating that the protein secondary structure became more disordered. The ratio of α-helix/β-sheet structures in the dough supplemented with different varieties of japonica rice flour was decreased, contributing to improved dough stability. Increasing the proportion of japonica rice flour from 10% to 40% significantly decreased the sulfhydryl content of the mixed flour dough. However, the total sulfhydryl content was only positively correlated with the amount of Longdao 19 japonica rice flour, reaching a maximum of 25.34 mol g⁻¹ at 40% japonica rice flour. The gluten structure of mixed flour dough typically forms a porous three-dimensional network, with the Longdao 19, 20, 23 and 25, Longjing 31 and Mudanjiang 31 japonica rice flours leading to improved gluten protein networks. In summary, the supplementation of standard wheat flour with japonica rice flour can alter dough properties and gluten structure.     

Relationship between gluten degradation by Aelia spp and Eurygaster spp and protein structure

Gluten from wheat damaged by heteropterous insects loses its functionality after a short period of resting. In this study the properties of the gluten from damaged wheat are compared with that from sound wheat in order to understand the changes produced during incubation at 37 °C. The amounts of free thiol and amino groups were quantified, obtaining a marked increase of those groups during incubation of the damaged wheat. The thermal characterization of the damaged gluten showed a decrease in the denaturation temperature and a pronounced increase in the protein denaturation enthalpy after a short incubation, although the value of that enthalpy greatly dropped with a longer incubation period. The high‐molecular‐weight glutenin subunits (HMW‐GS) were rapidly hydrolysed while the low‐molecular‐weight glutenin subunits (LMW‐GS) showed a slower degradation. It seems that the HMW‐GS backbone was first hydrolysed, leading to a protein structure with higher thermal stability but, as the hydrolysis proceeded, a deeper degradation of the structure yielded a protein structure with lower denaturation enthalpy. The loss of gluten functionality results from complex changes in the gluten structure at the first and second level of the protein organization structure. Copyright © 2005 Society of Chemical Industry     

小麦面筋蛋白组成、结构和功能特性

小麦面筋蛋白(俗称谷朊粉)主要由麦醇溶蛋白和麦谷蛋白组成,其蛋白组成和结构是影响小麦面团特性和烘焙品质重要因素。该文对小麦面筋蛋白组成、结构进行综述,以更清楚了解其结构对功能性影响。     

水分对冷冻小麦面团质构及面筋蛋白二级结构的影响

应用质构分析仪和傅里叶变换红外光谱仪测定小麦面团质构特性和微观结构(面筋蛋白二级结构),分析不同加水量对冷冻和未冷冻面团品质的影响。结果表明:加水量和冷冻对小麦面团的质构特性和面筋蛋白二级结构影响显著。随着加水量的增加,冷冻后小麦面团与未冷冻相比硬度增加、黏性升高、内聚性下降、弹性降低,而对面团的回复性影响很小。经冷冻后面团面筋蛋白的二级结构β-折叠和α-螺旋的相对含量增加,β-转角的相对含量降低,使面筋蛋白的网状结构趋于稳定。以上结果可以说明水分可能是影响冷冻面团品质的一个重要因素,也为进一步揭示加水量在小麦冷冻面团中的作用机理提供了重要的研究参考。     

碱性盐对小麦粉面筋特性和面条蛋白质组分的影响

为研究碱性盐（Na2CO3+K2CO3）对小麦粉和其面条品质变化的影响,以3种不同筋力的小麦品种为试验材料,结合SDS-PAGE电泳法,探讨了Na2CO3和K2CO3复配比例和碱性盐添加量对其小麦粉面筋特性和面条中蛋白质组分及分子量变化的影响,并结合SDS-PAGE电泳法考察了碱性盐对面条中蛋白质分子量分布变化的影响。结果表明：添加碱性盐后,3种小麦粉的湿面筋和干面筋含量减少而面筋指数增加,其中西农979湿面筋含量由36.04%逐渐下降至26.58%,干面筋含量由12.22%下降至7.74%。碱性盐使得3种小麦面条粉中的清蛋白和盐溶蛋白含量整体上显著增加而球蛋白和面筋蛋白含量整体上显著减少,GMP含量变化不显著但醇溶蛋白与谷蛋白含量减少,其中由矮抗58制得的面条中醇溶蛋白含量随着碱性盐添加量的增加由4.12%降至1.69%,而谷蛋白含量则由4.44%降至2.77%,研究结果可以为面条的工业化生产提供理论依据。     

花青素与小麦蛋白相互作用及对蛋白质结构的影响

利用荧光光谱法和傅里叶变换红外光谱法,研究中性条件下黑豆皮中的花青素（矢车菊素-3-O-葡糖苷（cyanidin-3-O-glucoside,C3G））与小麦蛋白麦醇溶蛋白（gliadin,Gli）及麦谷蛋白（glutenin,Glu）的相互作用。荧光结果表明：C3G对Gli、Glu均有较强的荧光猝灭作用,对Glu的荧光猝灭机制属于静态猝灭,而与Gli的猝灭方式为动态猝灭和静态猝灭的结合,C3G与Gli和Glu的结合常数（KA）分别为20.827×104、14.690×104 L/mol,结合位点（n）分别为1.263和1.159（298 K）,说明与Gli作用较强。热力学研究表明：C3G与Gli主要通过疏水作用结合;与Glu作用主要通过范德华力和氢键作用结合。同步荧光光谱分析表明：C3G与Gli的结合位点更接近色氨酸残基,而与Glu的结合位点更接近酪氨酸残基。傅里叶变换红外光谱表明：C3G能够与Gli、Glu结合并相互作用,使蛋白构象发生变化。     

Effect of citric acid deamidation on in vitro digestibility and antioxidant properties of wheat gluten

The effects of citric acid deamidation on the physiochemical properties of wheat gluten were investigated. In vitro digestion was carried out to determine changes of molecular weight distribution, amino acids composition and antioxidant efficacy of wheat gluten hydrolysates. Results indicated that citric acid deamidation significantly increased gluten solubility and surface hydrophobicity, at a neutral pH. Deamidation induced molecular weight distribution change of gluten with little proteolysis. Results from FTIR indicated that the α-helix and β-turn of deamidated gluten increased accompanied by a decrease of the β-sheet structure. After deamidation, in vitro pepsin digestibility of wheat gluten decreased, while in vitro pancreatin digestibility increased. The oxygen radical absorbance capacity (ORAC) activity of the in vitro digests decreased with increase of deamidation time. The high Lys and total essential AAs amounts in the final digests suggested that the nutritional values of wheat gluten after deamidation might be enhanced.     

小麦粉吸水速率与其蛋白组成特性的关系

蛋白质理化特性的差异会导致小麦粉吸水速率的不同。本文以不同吸水速率的小麦粉为研究对象,测定面粉中粗蛋白含量、面筋蛋白含量、湿面筋含量、面筋指数、沉降值、谷蛋白溶胀指数、氨基酸含量及观测面团内部微观网络结构。结果表明,当粗蛋白含量13.25%降低到6.98%时,小麦粉的吸水速率从0.17 g/s增大到3.87 g/s;当麦醇溶蛋白含量从4.02%下降到1.53%及麦谷蛋白含量从5.28%下降到2.77%时,因形成的面筋膜的质量下降使小麦粉的吸水速率增大。同时吸水速率随湿面筋含量的减小而显著性增大,面筋指数对吸水速率无显著性影响。沉降值从69.50m L降到32.50 mL,谷蛋白溶胀指数从5.24%下降到3.33%,均与吸水速率呈显著性负相关(p0.05)。半胱氨酸含量从0.14%降低到0.04%,导致二硫键含量下降,使蛋白质间的分子作用力下降。当面团内部面筋网络结构紧密时,面粉成团时的阻力越大,其吸水速率越小。本研究表明蛋白质性质与小麦粉吸水速率呈负相关。     

Mechanism of gliadin–glutenin cross-linking during hydrothermal treatment

The gluten proteins, gliadin and glutenin, are important for wheat flour functionality and they undergo changes during heat treatment involving sulfhydryl (SH) groups. To change the level of SH-groups during hydrothermal treatment, the oxidant, potassium iodate (2.1 μmol/g protein) and the reducing agent dithiothreitol (DTT, 6.1 μmol/g protein) were added to 20% (w/w) gluten-in-water suspensions at room temperature, at 90 °C and after 15 min at 95 °C, and the viscosity was measured by the Rapid Visco Analyser (RVA). Protein extractabilities after hydrothermal treatment were determined by size-exclusion and reversed-phase HPLC. DTT decreased maximal RVA viscosity and the levels of extractable α- and γ-gliadin and this decrease was independent of the time of addition during hydrothermal treatment. In contrast, potassium iodate increased the levels of extractable α- and γ-gliadin. Its impact was less when added at later times during RVA analysis. A SH-blocking agent (N-ethylmaleimide, 8.0 μmol/g protein), added at room temperature to the gluten suspension, decreased RVA viscosity at 95 °C and increased the extractabilities of glutenin and α- and γ-gliadin after hydrothermal treatment. Subsequent addition, at 90 °C, of a reducing agent (glutathione, 3.1 and 6.2 μmol/g protein) recovered the control RVA profile and restored the control protein extractabilities after RVA analysis. This shows the importance of heat-induced gliadin–glutenin reactions for gluten viscosity and of the presence of free SH-groups for the polymerization of gluten proteins. A model explaining gliadin–glutenin polymerization through a sulfhydryl-disulfide exchange mechanism and demonstrating the effects of redox agents is put forward.     

Characterization of hydrolysates derived from enzymatic hydrolysis of wheat gluten

ABSTRACT:  The aim of this study is to investigate the characteristics of wheat gluten hydrolysates. Enzymatic hydrolysis was performed using a papain (food-grade enzyme) in the present study. The gluten proteins were hydrolyzed for 8 h. During enzymatic hydrolysis, average peptide chain length in the hydrolysate decreased rapidly. Increasing proteolysis resulted in the increase in the contents of the soluble forms of nitrogen. However, the content of peptide nitrogen increased within the 1st 6 h, and then began to decrease. The percentage of the released peptides with molecular weight (MW) of over 15 kD decreased with extending enzymatic hydrolysis, while those with MW below 5 kD increased significantly ( P < 0.05). The peptides with MW 10 to 15 kD and those having the MW 5 to 10 kD had different changes. The polymeric glutenin and monomeric gliadin in gluten complex showed different behavior after enzymatic hydrolysis. The monomeric protein (gliadin) and soluble glutenin were prone to enzymatic hydrolysis, while insoluble glutenin was resistance to enzymatic hydrolysis.     

面筋蛋白与面条品质关系研究

通过分离添加方法研究面筋蛋白、麦谷蛋白、麦醇溶蛋白对面条质构品质影响。结果表明:添加不同量面筋蛋白、麦谷蛋白后,面条硬度、咀嚼性、粘合性增大,而添加麦醇溶蛋白却减小;麦醇溶蛋白赋予面条粘附性;麦谷蛋白能增强熟面条内部强度即耐煮性;面筋蛋白对拉伸特性影响最大。     

酶解魔芋葡甘聚糖对冷冻面团拉伸特性的影响

将魔芋葡甘聚糖(KGM)及其酶解产物(KGM Ⅰ、KGM Ⅱ、KGM Ⅲ)加入冷冻面团中,通过高效液相色谱法、电子扫描显微镜、核磁共振技术以及质构分析仪等研究魔芋葡甘聚糖及其酶解产物对冷冻面团拉伸特性的影响。结果表明:随着冻融循环时间由0 d延长至60 d,未添加KGM及其酶解产物的面团中游离巯基含量由7.81 μmol/L上升至9.65 μmol/L,面筋蛋白分子量由1.98×10⁵ Da下降至1.39×10⁵ Da,β-折叠含量降低,自由水所占比例增加了3.96%,且面团内部孔洞增多,面筋网络破坏严重,拉伸能力明显降低。冻融循环时间达60 d的面团加入2.0%的KGM Ⅱ后,面筋蛋白中游离巯基含量则由9.65 μmol/L下降至5.38 μmol/L,面筋蛋白分子量由1.39×10⁵ Da增大至2.11×10⁵ Da,自由水所占比例下降,面筋蛋白包裹淀粉颗粒的能力逐渐上升,面团拉伸能力回升,而KGM、KGM Ⅰ和KGM Ⅲ的加入对冷冻面团性质的影响较KGM Ⅱ小,表明添加2.0%的KGM Ⅱ能够明显抑制二硫键的断裂和二级结构的变化,防止面团的水分散失,维持面团的拉伸能力。