小麦-卵穗山羊草1Mg异附加系蛋白质品质形成解析

为了突破小麦品质育种瓶颈,从小麦的近缘属种中挖掘优质蛋白亚基,并解析优质亚基的品质效应,本研究选取中国春(CS)及CS与卵穗山羊草1Mg异附加系(CS-1Mg)作为试验材料,研究其亚基组成、籽粒发育过程中的谷蛋白聚合体动态积累、面筋蛋白的微观结构与二级结构、面团的混揉特性等以解析异源染色体的加入对面团品质形成的影响。结果表明,与CS相比,CS-1Mg中出现了新型HMW-GS,使其在籽粒发育过程中UPP快速积累,面筋蛋白呈现出更好的二级结构分布,微观结构上蛋白质交织更紧密,流变学特性及混揉特性增强,品质显著提高。CS-1Mg所携带的新型HMW-GS可以作为优质基因源用于优质小麦育种,CS-1Mg可作为中间材料应用于小麦品质改良的生产实践中。     

Aggregation behavior of wheat gluten during carboxylic acid deamidation upon hydrothermal treatment

Changes of aggregation behavior of wheat gluten during carboxylic acid deamidation upon hydrothermal treatment were investigated to test the influences of deamidation on the aggregation extent of wheat gluten. Hydrothermal treatment induced that the size of soluble wheat gluten aggregate progressively increased by cross-linking of gliadins and slowly cleaved glutenins. But significant changes in molecular weight distribution, solubility under six denaturing agents’ treatment and Zeta potential of wheat gluten aggregates were observed at 6 min heating time and distinct shift of intra-/inter-molecular interactions of wheat gluten aggregates occurred before and after 6 min heating treatment respectively. Moreover, as heating time increased, the island-like aggregates decreased markedly and the striped aggregates increased notably. To explain the aggregation behavior in this case, we postulated that the extent of aggregation of wheat gluten depended on the balance between intra-/inter-molecular electrostatic repulsion, the non-covalent and disulfide bonds formation in the system. Hence, a scheme was drawn, which appeared to be the mechanism responsible for the aggregation of wheat gluten through thermal cross-linking and opening up of the network structure of wheat gluten aggregates by deamidation.     

Thermal,rheological properties and microstructure of hydrated gluten as influenced by antifreeze protein from oat (Avena sativa L.)

This study examined the thermal, rheological properties and microstructure of hydrated gluten as influenced by oat antifreeze protein (AsAFP). The thermal properties of fresh hydrated gluten, including the melting temperature, freezing temperature, freezable water content and glass transition temperature, were determined. For hydrated gluten samples after freeze-thaw treatment, the change in melting performance and freezable water content were analyzed. The results showed that the addition of AsAFP increased the glass transition temperature and decrease the melting enthalpy and freezable water content of fresh hydrated gluten. The supplementation of AsAFP also influenced the melting performance of hydrated gluten after freeze-thaw treatment. The rheological properties showed that the addition of AsAFP inhibited the deterioration of the rheological properties of hydrated gluten. The secondary structure of the gluten proteins changed significantly, α-helix decreased and β-sheet increased. The microstructure of the hydrated gluten demonstrated that supplementation with AsAFP may protect the gluten matrix from disruption during freeze-thaw cycles.     

Endogenous redox agents and enzymes that affect protein network formation during breadmaking – A review

During breadmaking, wheat gluten proteins form a continuous network which is stabilized by disulfide bonds and modified by thiol/disulfide interchange reactions. This gluten network results in visco-elastic dough that holds together the other dough components and assists in retaining carbon dioxide. Wheat flour contains several components, enzyme co-factors and enzymes which can affect the formation and properties of the gluten network and, hence, the dough and bread characteristics. We present a brief overview of our current knowledge of the fate of gluten proteins during breadmaking, and how they are affected by endogenous wheat components (e.g. glutathione, cysteine and NAD(P)(H)) and enzyme systems (e.g. tyrosinase, peroxidase, the NADP-dependent thioredoxin and glutathione enzyme systems, protein disulfide isomerase, lipoxygenase, catalase and dehydrogenases).     

Effect of NaCl on rheological properties of dough and noodle quality

To assess the effect of NaCl on processing properties of different varieties of wheat flour and noodle quality, the rheological properties of dough, and the quality of white salted noodles made from three different varieties of wheat flour were evaluated. The results showed that the addition of NaCl had different effects on the rheological properties of different varieties of wheat flour. As NaCl concentration increased, the stability time of both intermediate-gluten and weak-gluten wheat flour increased, while that of strong-gluten wheat flour increased initially and then remained stable. The developing time of strong-gluten wheat flour increased, while those of both intermediate-gluten and weak-gluten wheat flour did not change significantly. The energy values of intermediate- and weak-gluten wheat flour did not change significantly while that of strong-gluten wheat flour increased. NaCl had no apparent effects on the hardness, springiness, gumminess, chewiness and resilience of noodles. The cooking loss of fresh noodles increased positively with increasing NaCl concentration. Microstructure of noodles showed that gluten network structure of noodles became more and more dense with increasing NaCl concentration. The effect of NaCl on gluten protein contributed to the change of rheological properties and noodle quality.     

Thermoplastic films from wheat proteins

We show that the wheat proteins gluten, gliadin and glutenin can be compression molded into thermoplastic films with good tensile strength and water stability. Wheat gluten is inexpensive, abundantly available, derived from renewable resource and therefore widely studied for potential thermoplastic applications. However, previous reports on developing thermoplastics from wheat proteins have used high amounts of glycerol (30-40%) and low molding temperature (90-120 °C) resulting in thermoplastics with poor tensile properties and water stability making them unsuitable for most thermoplastic applications. In this research, we have developed thermoplastic films from wheat gluten, gliadin and glutenin using low glycerol concentration (15%) but high molding temperatures (100-150 °C). Our research shows that wheat protein films with good tensile strength (up to 6.7 MPa) and films that were stable in water can be obtained by choosing appropriate compression molding conditions. Among the wheat proteins, wheat gluten has high strength and elongation whereas glutenin with and without starch had high strength and modulus but relatively low elongation. Gliadin imparts good extensibility but decreased the water stability of gluten films. Gliadin films had strength of 2.2 MPa and good elongation of 46% but the films were unstable in water. Although the tensile properties of wheat protein films are inferior compared to synthetic thermoplastic films, the type of wheat proteins and compression molding conditions can be chosen to obtain wheat protein films with properties suitable for various applications.     

面筋蛋白对小麦粉理化性质及面包烘焙品质的影响

为明确不同类型小麦的面粉改良方案,为我国优质面包专用粉的生产提供理论与技术支持,以三个筋力不同的小麦品种宁麦13、扬麦16和郑麦9023为材料,通过洗面筋法提取各供试材料的湿面筋,将其冷冻干燥后按照7%、8%、9%、10%、11%的添加比例与各自面粉进行配比,对配粉的面包烘焙品质、面粉理化性质和面团流变学特性进行了测定分析。结果发现,随着面筋蛋白添加量的提高,配粉的蛋白质、湿面筋、谷蛋白大聚体(GMP)含量和沉降值逐步上升;粘度参数和面团弱化度有所下降;糊化温度和糊化时间呈上升趋势。在同一添加量下,强筋小麦的烘焙品质和面粉理化性质始终优于中筋小麦和弱筋小麦。随着面筋蛋白添加量的提高,面包体积、弹性、回复性、内聚力增大,而硬度、咀嚼性减小,感官品质得到改善。面筋蛋白添加量超过一定范围(宁麦13、扬麦16添加9%,郑麦9023添加8%),面包品质改良效果变缓,且色泽不断加深。综上所述,适量添加面筋蛋白可改变面粉的理化性质,提高其面包烘焙品质;配粉的蛋白质含量为18%左右是最经济的面包烘焙品质改良方案。     

The effect of sodium chloride on gluten network formation and rheology

Gluten samples were obtained from two wheat flours with different levels of total protein in the presence or absence of sodium chloride (2% flour base). The dynamic oscillation rheology, large extensional deformation, confocal laser scanning microscopy (CLSM), transmission electron microscopy (TEM) and chemical analysis of disulfide bond linkages and the ratio of polymeric glutenins and monomeric gliadins were used to investigate the effect of salt on the structure and rheological properties of gluten. CLSM and TEM images showed that NaCl caused the gluten to form fibrous structure. The presence of NaCl increased non-covalent interactions and β-sheet structure, measured by FTIR, in gluten proteins. The gluten matrix formed with salt resulted in higher tan δ values corresponding to a less elastic network when measured using oscillatory rheometry. Large deformation extensional measurements showed that the maximum force to fracture were lower for the gluten samples prepared in the presence of NaCl. The results from this study indicate that changes in the solvent quality due to the presence of NaCl during dough mixing result in different molecular conformation and network structure of gluten proteins which contributed to the differences in the rheological properties.     

Accelerated ageing of wheat grains: Part II-influence on thermal characteristics of wheat starch and FTIR spectroscopy of gluten

Wheat quality characteristics are influenced by different factors such as moisture content, storage time and temperature. In this study accelerated ageing of wheat grains was carried out by increasing moisture content (16, 18 and 20%) and keeping the samples in different temperatures (30, 40 and 50 °C) for different periods (2, 5 and 8 days). After milling, the thermal properties of starch and structure of gluten were investigated using Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR); respectively. The experimental set up was designed using response surface methodology and the three distinct factors were combined by central composite design. Results showed that increasing moisture content caused a decrease in onset, peak and end set temperatures of gelatinization while increasing storage time and temperature increased these parameters. By progressing storage time the band intensity of thiol groups decreased while that of disulfide groups of gluten increased indicating an improvement in gluten quality. Increasing moisture content from 16 to 20% and higher storage temperature (50 °C) decreased intensity of disulfide bands.     

Influence of high solid concentrations on enzymatic wheat gluten hydrolysis and resulting functional properties

Enzymatic hydrolysis at increased solid concentrations is beneficial with regard to energy and water consumption. This study examines the influence of the solid concentration on the enzymatic hydrolysis of wheat gluten and the resulting functional properties of the hydrolysate. Wheat gluten was mildly hydrolyzed at a solid concentration varying from 10% to 60% to degrees of hydrolysis (DH%) ranging from 3.2% to 10.2%. The gluten was susceptible to hydrolysis at all solid concentrations but the hydrolysis rate was influenced by increasing solid concentrations. Size-exclusion high-performance liquid chromatography revealed an increase in the ratio of peptides with a molecular mass >25 kDa for solid concentrations of 40% and 60%. The water solubility increased on hydrolysis and was independent of the solid concentration during proteolysis. The foam stability was not influenced by the solid concentration at low DH%. At DH% higher than 8%, high solid concentrations increased the foam stability, which might be related to the presence of more peptides with a molecular mass >25 kDa. In addition, we found increased reactor productivity. The results show the potential of hydrolyzing wheat gluten at high solid concentrations, which could lead to large savings for water and energy when applied industrially.     

富含11S大豆分离蛋白中试规模提取及其在冰淇淋和面制品中的应用

11S球蛋白是大豆蛋白中的主要成分,具有优良的加工特性.本文报道了中试水平上提取富含11S组分大豆分离蛋白技术,及其添加到冰淇淋和面粉中对产品特性的影响.试验结果表明,中试生产所得到的富含11S组分分离蛋白中,11S组分的含量达81.3%(占总蛋白含量).添加6%左右的富含11S组分大豆分离蛋白代替冰淇淋原料中的脱脂奶粉可提高冰淇淋的膨胀率,并具有良好的风味;在中等筋度的小麦粉中添加3%的富含11S组分分离蛋白,可提高面团吸水率、面团形成时间和面团稳定性,粉质评价值得到提高.     

Interplay between starch and proteins in waxy wheat

Most of the unique properties of waxy wheat have been associated with the lack of amylose, that in turn may affect the mutual interactions between starch and proteins. To address this particular aspect, we carried out molecular, rheological, and calorimetric studies on flours from two waxy wheat lines that were compared with a non-waxy one. Dough thermal properties and water binding capacity were investigated by Differential Scanning Calorimetry (DSC) and by thermogravimetric analysis, respectively. Protein solvation, aggregation, and thiol accessibility were also investigated, together with dough mixing properties and stickiness. Proteins in waxy wheat samples needed more water to complete solvation, likely because of the water-retaining capacity of waxy wheat starch. In waxy wheat dough, water was tightly bound to starch, and DSC studies indicated an increase in gelatinization temperature. Moreover, the low water mobility in waxy wheat resulted in low and retarded gluten hydration and in high stickiness. In samples with the highest stickiness, protein aggregates were stabilized mainly by hydrophobic interactions. Differences between waxy wheat lines may be attributed to a different structural organization of components within each class of biopolymers.     

Wheat flour enriched with oat β-glucan: A study of hydration,rheological and fermentation properties of dough

The objective of this study was to evaluate the effects of the incorporation of oat β-glucan (OβG) on the hydration, rheological and fermentation properties of wheat flour dough. Wheat flour was substituted with OβG at levels varying from 1 g/100 g–5 g/100 g. The addition of OβG significantly increased water absorption and dough development time. The dilution effect of OβG, competing for water and interaction between OβG and gluten proteins, deteriorated the gluten network structure and reduced the stability of dough. Rheological evaluation revealed an increasing tendency to solid-like behavior with increasing addition of OβG. Regarding dough fermentation properties, OβG had no effect on yeast activity but reduced the gas retention capacity of dough. Our findings indicate that OβG is a key component that determines the properties of dough, and excess OβG exhibited poorer processing characteristics compared with control.     

超绿活性茶粉对不同筋度小麦粉面团流变学特性的影响

将超绿活性茶粉(Ultra-green Active Tea Powder,UGA-TP)添加到低筋粉、中筋粉、高筋粉中,加水形成小麦粉面团,利用粉质仪、拉伸仪测定含超绿活性茶粉的不同筋度小麦粉面团流变学特性。研究结果表明:超绿活性茶粉的添加可以提高小麦粉面团吸水率、面团形成时间和面团稳定时间,含茶低筋粉和中筋粉面团与空白面团样品相比,在醒发时间45、90、135 min时,拉伸曲线面积、拉伸阻力、拉伸比例显著增加,延伸度显著下降;其中超绿活性茶粉对低筋粉的影响最大,主要表现为添加超绿活性茶粉后,低筋粉面团吸水率显著增大2.9%,面团形成时间显著增加8.7 min,面团稳定时间显著增加19.2 min;以醒发45 min为例,拉伸曲线面积从76 cm2显著增大到134 cm2,拉伸阻力从300 BU显著增大到645 BU,拉伸比例从2.1显著增大到4.9,延伸度从142显著下降到131。综合得出超绿活性茶粉的添加对不同筋度小麦粉的加工性能均有改善效果,其中对低筋小麦粉改善的效果最大。     

Phytate negatively influences wheat dough and bread characteristics by interfering with cross-linking of glutenin molecules

The influence of added phytate on dough properties and bread baking quality was studied to determine the role of phytate in the impaired functional properties of whole grain wheat flour for baking bread. Phytate addition to refined flour at a 1% level substantially increased mixograph mixing time, generally increased mixograph water absorption, and reduced the SDS-unextractable protein content of dough before and after fermentation as well as the loaf volume of bread. The added phytate also shifted unextractable glutenins toward a lower molecular weight form and increased the iron-chelating activity of dough. It appears that phytate negatively affects gluten development and loaf volume by chelating iron and/or binding glutenins, and consequently interfering with the oxidative cross-linking of glutenin molecules during dough mixing. Phytate could be at least partially responsible for the weak gluten network and decreased loaf volume of whole wheat flour bread as compared to refined flour bread.     

Wheat Bread Quality as Influenced by the Substitution of Waxy and Regular Barley Flours in Their Native and Extruded Forms

The substitution of wheat flour with barley flour (i.e. native or pretreated/extruded) reduced the loaf volume. Depending on the barley variety and flour pretreatments, the colour and firmness/texture of the bread loaves were altered. Amongst the barley breads prepared from native flours (at 15% barley flour substitution level), Phoenix had higher loaf volume and lower crumb firmness than Candle. However, amongst the barley breads prepared from extruded flours, CDC-Candle had higher loaf volume and lower crumb firmness than Phoenix. The lower loaf volume and firmer crumb texture of barley breads as compared with wheat bread may be attributed to gluten dilution. Also, the physicochemical properties of barley flour components, especially that of β-glucan, can affect bread volume and texture. β-glucan in barley flour, when added to wheat flour during bread making, could tightly bind to appreciable amounts of water in the dough, suppressing the availability of water for the development of the gluten network. An underdeveloped gluten network can lead to reduced loaf volume and increased bread firmness. Furthermore, in yeast leavened bread systems, in addition to CO₂, steam is an important leavening agent. Due to its high affinity for water, β-glucan could suppress the amount of steam generated, resulting in reduced loaf volume and greater firmness. In the present study, breads made with 15% HTHM CDC-Candle flour had highly acceptable properties (loaf volume, firmness and colour) and it indicated that the use of extruded barley flours would be an effective way to increase the dietary fibre content of barley breads.     

Effect of gliadin/glutenin ratio on pasting,thermal, and structural properties of wheat starch

Gluten-starch interactions are of specific importance during the processing of cereal-based products. However, the mechanisms for gluten-starch interactions have not been illuminated. The effects of various gliadin/glutenin (gli-glu) ratios (0:10, 3:7, 5:5, 7:3, and 10:0) on the pasting, thermal, and structural properties of wheat gluten-starch mixtures were investigated. The peak, through, and final viscosities were obviously decreased, and the setback value initially increased and then decreased with increasing gli-glu ratios during the rapid viscosity analysis (RVA). Differential scanning calorimetry showed that the enthalpy changes increased with increasing gli-glu ratios. Thermogravimetric analysis showed a slight increase in the degradation temperature of the mixtures as the gli-glu ratio increased, although it was still lower than that of wheat flour. However, there was no significant difference in the weight loss among different gli-glu ratios. Rheometer-Fourier transform infrared (FTIR) spectroscopy showed that the C-6 peak at 996 cm⁻¹ for all the samples was displaced or disappeared due to the hydrogen bond fracture caused by water molecules entering the starch granules. It was also found that the absorption peak in amide II of gli-starch was more obvious than that of glu-starch. The CLSM obviously described the change structure of mixtures with different gli-glu ratio during starch gelatinizaton. By studying the changes in gluten protein components and how they affected the thermal and structural properties of starch, a simple model was proposed to describe the gelatinization process of the mixtures with different ratios of gli-glu and briefly describe the interactions between starch and wheat gluten components. Optimization of the proportion of protein components in wheat flour will enable greater control over the structural characteristics and elasticity of wheat food products.     

Effect of curdlan on the quality of frozen-cooked noodles during frozen storage

Frozen-cooked noodles (FCN) and its components undergo quality changes during frozen storage, such as reduced textural and cooking qualities, weakened gluten network, and damaged starch properties; thus, storage condition is a critical factor affecting the final quality of FCN. In this study, in view of the thermoirreversible high-strength gel property (at ≥ 80 °C) of curdlan, strong hydrophilicity, and freeze-thawed stability of high-strength gel prepared from curdlan powder, the effect of curdlan on the quality of FCN during frozen storage was first evaluated. The results showed that curdlan was effective in reducing cooking loss, enhancing water absorption, and improving textural properties of FCN; the improving effect presented a trend of first increasing and then decreasing with the amount of increasing curdlan (0.1%–0.9%); and the addition of 0.5% curdlan was most effective in improving the quality of FCN. Thermal gravimetric analysis indicated that curdlan enhanced thermal stability of FCN, implying curdlan could strengthen the gluten network. Meanwhile, structural observations revealed that, during frozen storage, FCN with added curdlan exhibited a more continuous and compact gluten network accompanied with more uniform and smaller ice crystals. Thus, curdlan is desirable to be used as a novel gum in FCN to provide specific functionality and minimize the negative effect of frozen storage. This study provides new insights into the quality improvement of FCN and further expands the application potential of curdlan in food industry.     

Intrinsic influence of various plasticizers on functional properties and reactivity of wheat gluten thermoplastic materials

Various compounds, differing in their chemical functions, number of functional group and degree of hydrophobicity, were tested as wheat gluten plasticizers in a thermoplastic process. A low melting point and a moderate hydrophobicity were found to be critical characteristics of a good wheat gluten plasticizer. The influence of five selected plasticizers (water, glycerol, 1,4-butanediol, lactic and octanoic acids) on functional properties of the wheat gluten network was investigated. Dried gluten was used to avoid any plasticization due to hydration water (usually around 10% for commercial gluten). The influence of plasticizer properties and content was studied by dynamic mechanical thermal analysis, size exclusion-high performance liquid chromatography, tensile and water swelling tests. The plasticizing effect, at the same molar content, was found to be identical for water, glycerol and 1,4-butanediol. Lactic and octanoic acids were found to have higher and lower plasticizing effects, respectively. Mechanical properties were mainly related to the thermoplastic state of the materials. Water and lactic acid were found to confer smaller and larger extensibilities, respectively, to gluten materials. Thermo-mechanical reactivity also depended on plasticizer properties. Gluten aggregation, normally induced by heating, was prevented by the acidic environment produced by lactic acid. Water swelling behaviour was found to depend on the hydrophobicity of the plasticizer used, on the degree of gluten crosslinking and on the pH of the gluten-plasticizer blend.     

Hydration,polymerization and rheological properties of frozen gluten-water dough as influenced by thermostable ice structuring protein extract from Chinese privet (Ligustrum vulgare) leaves

The effects of thermostable ice structuring proteins (TSISPs) extracted from Chinese privet (Ligustrum vulgare) leaves on water molecular state, dehydration of gluten proteins, secondary structure of proteins, glutenin subunit of glutenin macropolymer (GMP) and rheological properties of gluten doughs during frozen storage were investigated by nuclear magnetic resonance (NMR), attenuated total reflectance-Fourier transform infrared reflectance (ATR-FTIR), reversed phase-high performance liquid chromatography (RP-HPLC) and dynamic rheometry. After frozen storage for 5 weeks, the control sample showed dehydration of gluten proteins and mobility of water molecules in gluten dough increased, significantly indicating ice formation and water redistribution. Secondary structure of gluten proteins changed significantly, α-helix decreased and β-sheet increased. Glutenin subunits depolymerized, indicated by the decrease in high molecular weight glutenins/low molecular weight-glutenins (HMW/LMW) ratio. The decrease in elastic moduli (G′) and viscous moduli (G′') showed the deterioration of rheological properties of gluten dough. The addition of TSISPs inhibited the dehydration of gluten proteins, decrease in α-helix, increase in β-sheet and HMW/LMW ratio, resulting in improved rheological properties of gluten dough.