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。     

Effects of cultivar and soil fertility on grain protein yield,grain protein content,flour yield and breadmaking quality of wheat

Grain protein content affects the flour yield and breadmaking characteristics of wheat (Triticum aestivum L). In this study, grain protein yield, grain protein content, flour yield and loaf volume were quantified for four wheat cultivars (Inia, Carina, Kariega and SST 86) grown under six different soil fertility regimes in a long-term fertilisation and irrigation experiment at the University of Pretoria. The experimental design was a randomised complete block replicated four times, with fertility as the main plots and cultivars as the subplot treatments. Grain protein yield, flour yield, loaf volume and mixograph dough peak mixing time varied among cultivars and soil fertility situations. Grain protein content differed among cultivars, but mixograph water absorption and dough characteristics did not differ. The highest grain protein yield was 873 kg ha⁻¹ for Carina and the lowest 527 kg ha⁻¹ for SST 86. Grain protein content averaged 131 g kg⁻¹ for Carina and 122 g kg⁻¹ for Kariega. Breadmaking performance showed that in a well-balanced soil fertility situation, Kariega produced 1025 cm³ of loaf volume while Inia averaged 950 cm³. Grain protein yield increased with increasing soil fertility, but grain protein content, flour yield, loaf volume, water absorption and mixograph peak mixing time varied with soil fertility. The interaction between cultivar and soil fertility was significant for grain protein yield, grain protein content, flour yield, loaf volume and water absorption but not dough peak mixing time. The results indicate cultivar differences in breadmaking quality characteristics and that soil fertility status affects grain protein yield, grain protein content, flour yield, loaf volume potential and water absorption but not mixograph peak mixing time and dough characteristics. © 1999 Society of Chemical Industry     

Responses of breadmaking quality to sulphur in three wheat varieties

Field experiments were carried out at three sites in England to investigate the effects of S fertilisation on breadmaking quality of three winter wheat varieties (Hereward, Rialto and Spark) in the 1996–1997 season. The soils at the three sites differed in extractable S contents. Depending on site, either 180 and 230 kg ha⁻¹ N or 230 and 280 kg ha⁻¹ N treatments were factorially combined with three S treatments (0, 20 and 100 kg ha⁻¹ S). Addition of S increased loaf volume significantly at two sites where grain S concentration was also significantly increased and grain N:S ratio decreased. Application of the extra 50 kg ha⁻¹ N increased grain protein concentration but did not increase loaf volume at any of the sites. Loaf volume was found to correlate more closely with grain S than with grain protein concentration. Addition of S generally decreased the elastic modulus of gel protein and dough resistance but increased dough extensibility. Despite considerable differences in their dough rheology, the responses in rheology and loaf volume to S were similar in all three varieties. Selected flour samples of Rialto from the Bridgets site were also analysed for the glutenin subunit distribution, showing that S addition increased the relative proportion of low-molecular-weight subunits at the expense of high-molecular-weight subunits of glutenin. This study therefore shows that the beneficial effects of S on breadmaking quality are associated with decreased dough elasticity and increased extensibility resulting from effects on the amount and composition of the glutenin polymers. The results also indicate that S fertilisation is required in some areas of England to maintain breadmaking quality. © 1999 Society of Chemical Industry     

Effect of soybean addition on the rheological properties and breadmaking quality of wheat flour

The effects of enzyme‐active full‐fat (EAFFSF), heat‐treated full‐fat (HTFFSF) and enzyme‐active defatted (EADSF) soy flours and commercial soy protein isolates (SPIs) on mixing properties and extensibility of dough, gluten formation, gas production and retention properties of dough and bread quality were studied. The soy products utilised in this study presented values of urease activity, nitrogen solubility index (NSI) and enthalpies of protein denaturation according to their previous heat processing. Soy products interfered in gluten formation, weakened dough strength and decreased dough gas retention capacity. Bread quality was negatively affected by soy product addition. The negative effects were exacerbated by an increase in soy/wheat ratio. Soybean protein state was identified as an important factor in determining dough and bread properties. Copyright © 2005 Society of Chemical Industry     

Hearth bread baking quality of durum wheat varying in protein composition and physical dough properties

Thirty durum wheat genotypes from ten countries of origin were grown in field plots for two consecutive years. Three of the genotypes were γ‐gliadin 42 types and the remainder were γ‐gliadin 45 types. Among the γ‐gliadin 45 types, six high‐molecular‐weight glutenin subunit (HMW‐GS) patterns were identified: 6 + 8, 7 + 8, 7 + 16, 14 + 15, 20 and 2*, 20. All the γ‐gliadin 42 genotypes contained low amounts of unextractable polymeric protein (UPP) and exhibited low gluten index values and weak gluten properties. The γ‐gliadin 45 genotypes exhibited a wide range of UPP, gluten index and dough strength. HMW‐GS 20 genotypes were generally weak, whereas HMW‐GS 6 + 8 and 7 + 8 genotypes were generally strong. When baked by a lean formulation, long‐fermentation straight‐dough hearth bread process, the durum wheat genotypes exhibited a wide range of baking quality. Loaf volume and bread attributes were strongly correlated with UPP and gluten index. Some of the genotypes exhibited bread attributes and loaf volume equal or slightly superior to those of a high‐quality bread wheat flour. However, even the strongest durum wheat genotypes exhibited inferior fermentation tolerance to the bread wheat flour, as seen by a requirement for lower baking absorption during dough handling and more fragile dough properties when entering the oven. Among the HMW‐GS groups, HMW‐GS 7 + 8 and 6 + 8 exhibited the best and HMW‐GS 20 the poorest baking quality. Farinograph, alveograph and small‐scale extensigraph properties demonstrated that a combination of dough elasticity and extensibility was needed for superior durum wheat baking performance. Copyright © 2007 Society of Chemical Industry     

Dough properties and breadmaking qualities of whole waxy wheat flour and effects of additional enzymes

BACKGROUND: Waxy wheat, a new kind of genetically back‐crossed wheat, was applied to make whole bread in this study. Dough properties and bread quality of the whole waxy wheat flour, which was milled from 100% whole grains containing bran and germ, were determined. RESULTS: Whole waxy wheat had lower protein and lipid contents but higher dietary fiber content than whole regular wheat flour. Pasting temperature and viscosity of the whole waxy wheat flour were significantly lower than those of the whole regular wheat. However, the white wheat flour milled from wheat grains with 48% recovery had significantly higher peak viscosity than the whole waxy wheat. Bread made from the whole waxy wheat flour was significantly softer than that from the whole regular wheat flour during storage. However, bread made from whole waxy wheat had significantly lower specific volume than that from the white waxy flour because of the high amount of dietary fiber. Addition of cellulase increased paste viscosity, lowered dough mixing properties and reduced the firmness of the bread. The addition of pentosanase also increased paste viscosity, lowered dough mixing properties, improved loaf volume of bread but increased the firmness of breadcrumbs, while the addition of α‐amylase only increased final viscosity of flour and did not affect dough properties and bread qualities of whole waxy wheat flour. CONCLUSION: As a result, waxy wheat shows superior properties for making whole breads. Additional enzymes are also necessary to improve bread quality and nutritive values of whole waxy bread. Copyright © 2007 Society of Chemical Industry     

Blocked thiols in glutenin and protein quality

It has already been suggested that when glutenin chains are synthesised, two cysteine residues on each chain preferentially form interchain disulphide bonds (SS) resulting in linear arrays of polypeptide chains. Presumably steric factors stop the growth of a molecule eventually, leaving each terminal chain with a free SH group. It is now postulated that the free SH groups later react with low molecular weight (mol. wt) thiols and SS compounds, which also break some interchain bonds by SS interchange so reducing the average mol. wt of the glutenin. Terminal SH groups and the halves of each broken SS become blocked by low mol. wt compounds. Therefore, if the quantity of glutenin-bound low mol. wt thiols (end-blockers) bound to glutenin could be measured it would enable the number of glutenin molecules to be calculated and hence a number-average mol. wt. When six wheats spanning the normal range of baking quality were tested, glutenin-bound half-cystine and glutathione residues were eventually found, but no SH groups could be detected. The number-average number of chains per glutenin molecule (proportional to mol. wt) was correlated with intrinsic viscosity of glutenin and with loaf volume per gram of loaf protein, thus supporting the hypothesis. It is suggested that the main aim of reducing the native thiol content of flour with improvers is to limit degradation of glutenin molecules. If the hypothesis should be confirmed it may be advantageous to breed wheats with low contents of thiols and active disulphides in the grain, since their quantities may largely account for glutenin mol. wt and, in turn, protein quality.     

Relationship between glutenin subunit composition and gluten strength measurements in durum wheat

Durum breeders use a range of techniques in the development of new cultivars. An important selection criterion is the rheological properties of semolina dough and durum wheat breeders use this criterion in the development of new cultivars using a range of techniques. Because of the need to process large numbers of genotypes encountered in breeding programs, methods that are inexpensive, rapid, require small amounts of sample and that correlate with semolina quality are desirable. Using breeding material, this study investigated the relationship between the glutenin subunit composition and two traditional tests of gluten strength, gluten index (GI) and mixograph. Two sample sets of durum wheat breeding lines and cultivars, one grown in Canada (n = 229) and the other grown in Australia (n = 139) were analysed for GI, mixograph and both high molecular weight (HMW) and low molecular weight (LMW) glutenin subunits by SDS‐PAGE. Nine different HMW and 14 different LMW allelic combinations were found. In the Canadian set, the most frequent LMW alleles were aaa, bba, caa and cfa while in the Australian set, caa was predominant. For the HMW subunits, the most common allelic groups were Glu‐A1c/Glu‐B1d (null, 6 + 8) and Glu‐A1c/Glu‐B1b (null, 7 + 8) with fewer numbers of Glu‐A1c/Glu‐B1e (null, 20) in both sample sets. LMW subunits were more important contributors to gluten strength than HMW subunits with the rank for higher GI according to the LMW allele (Canadian set) being caa = aaa > bba and aaa > cfa while HMW subunits 6 + 8 = 7 + 8 > 20. Similarly, using the mixograph, strength ranking for the LMW alleles was aaa > cfa = bba and HMW subunit 20 gave poorer rheological properties. For some samples with a good LMW allelic group a low GI was observed and vice versa. Further characterisation of the protein composition in these samples showed the GI results could be explained by polymeric/monomeric (P/M), glutenin/gliadin (Glu/Gli) and HMW/LMW ratios or the proportion of unextractable polymeric protein. © Crown in the right of the State of New South Wales, Australia; and for the Department of Agriculture and Agri‐Food, Government of Canada, © Minister of Public Works and Government Services Canada 2005. Published for SCI by John Wiley & Sons, Ltd.     

The HMW glutenin subunit composition of Canadian wheat cultivars and their association with bread-making quality

The proteins of 70 Canadian-grown wheat cultivars were fractionated by SDS-PAGE to determine their HMW glutenin subunit composition. On the basis of previously established relationships between individual subunits and measures of bread-making quality, Glu-1 scores were calculated for 67 cultivars. The three cuhivars Chinook, Cypress and Supreza were found to contain novel HMW glutenin subunits previously uncatalogued. The Glu-1 scores accounted for 59–69% of the variation in bread-making quality of these cultivars whereas flour ash accounted for none. The implications of these results to wheat breeding programmes are discussed.     

Biotechnology of Wheat Quality

Wheat gluten proteins are largely responsible for the visco-elastic properties that allow doughs to be processed into bread and various other food products including cakes, biscuits (cookies), pasta and noodles. Detailed biochemical and biophysical studies are revealing details of the molecular structures and interactions of the individual gluten proteins, and their roles in determining the functional properties of gluten. In particular, one group of gluten proteins, the high molecular weight (HMW) subunits of glutenin, have been studied in detail because of their role in determining the strength (elasticity) of doughs. The development of robust transformation systems for bread wheat is now allowing the role of the HMW subunits to be explored experimentally, by manipulating their amount and composition in transgenic plants. Such studies should lead to improvement of the processing properties of wheat for traditional end uses and the development of novel end uses in food processing or as raw material for other industries. © 1997 SCI.     

蕨麻对面包制品品质特性的影响

主要研究面粉中添加1％～9％的蕨麻粉对面团粉质特性以及面包品质的影响。结果表明．随着蕨麻粉添加量的增加,面团的吸水率逐渐增高,面团的形成时间和稳定时间延长,弱化度降低;随着蕨麻粉添加比例的增加,面包硬度增加,面包的感官评分总体上呈现降低趋势,但是当蕨麻添加量大于5％时,面包体积急剧减少,面包纹理结构变差,质地和口感都明显下降,因此,蕨麻粉在面包粉中的合理添加比例为5％。     

The relationship between HMW glutenin subunit composition and the bread-making quality of British-grown wheat varieties

Based on previous work, which related individual HMW glutenin subunits to bread-making quality by genetical analysis, quality scores were assigned to each of the commonly occurring subunits. The grain proteins of 84 home-grown wheat varieties were fractionated by SDS—PAGE to determine their HMW glutenin subunit composition. The quality scores of each of the subunits were summed to create a Glu-1 quality score for each variety. The results indicated that 47-60% of the variation in the independently established bread-making qualities of this set of varieties could be accounted for by variation in HMW subunits of glutenin. The presence or absence in the varieties of a translocated chromosome, which consisted of the long arm of 1B and the short arm of 1R from rye, was also established because of its known association with poor bread-making quality. A correction factor was applied to the Glu-1 quality score of those varieties that contained the 1 BLURS chromosome. The variations in the rye-adjusted Glu-1 quality scores were compared with those of the bread-making qualities of the varieties, and the proportion of variation in quality accounted for was raised to 55-67%. The Glu-1 quality score and the biscuit-making qualities of the same set of varieties were negatively related. The results are discussed in relation to future strategies recommended to wheat breeders for developing new varieties with improved bread-making quality.     

Variation in type and relative amounts of the high molecular weight glutenin subunits in dutch wheat varieties

The high molecular weight glutenin (HMWg) subunit genotypes and amounts of the individual subunits of 38 Dutch wheat varieties were determined. In winter wheat varieties, HMWg subunit alleles that, in general, have been shown to be related to a poor bread-making quality predominated. In spring wheat varieties, ‘high-quality’ alleles were most frequent. When examining the published HMWg subunit genotypes of British and German varieties a similar difference was found in HMWg subunit genotype between spring and winter wheats. Because bread-making quality of spring wheat varieties is, in general, superior to that of winter wheats, probably also because of the lower protein content of the latter, the two groups should be taken separately when studying the relation between HMWg subunit genotype and bread-making quality. There was a considerable variation in relative amounts of allelic HMWg subunits and of subunits encoded by different genes (at the same or homeologous loci). Between varieties with the same HMWg subunit genotype, relative amounts of identical subunits differed only slightly. Some of these differences may reflect differences in gene expression, but it is not known to what extent differences in genetic background or differences in gene promoter are involved. There were differences in relative amounts of HMWg subunits encoded by alleles at the Glu-Bl locus. Here, an increase in relative amounts coincided with an increase in contribution to bread-making quality of an allele.     

Effect of preharvest applied herbicides on breadmaking quality of hard red spring wheat

Certain herbicides can be applied prior to harvest for weed control in wheat. Research was conducted to determine the effect of preharvest applications of glyphosate, paraquat and metsulfuron + 2, 4‐D on grain, flour and the breadmaking quality of hard red spring wheat. Herbicides were applied at soft dough (SD), ～500 g kg^?1 kernel moisture and hard dough (HD), ～350 g kg^?1 kernel moisture stages of ‘Parshall’ hard red spring wheat. Test weight was reduced 1.3 and 2.3 kg hl^?1, 1000 kernel weight was reduced 3.5 and 4.5 g, and large kernel content was reduced 230 and 280 g kg^?1 by glyphosate and paraquat respectively when applied at SD. Metsulfuron + 2, 4‐D did not affect physical grain quality. Glyphosate and paraquat applied at SD and HD increased gluten index two to eight units. Metsulfuron + 2, 4‐D reduced the gluten index four units when applied at SD. Dough mixing stability was increased 1.7 min by glyphosate applied at SD or HD, and by paraquat applied at SD. Dough mixing time during bread making was 0.5 min longer with flour from wheat treated with glyphosate and was 0.4 min shorter with flour from wheat treated with Metsulfuron + 2, 4‐D at SD. Loaf volume, symmetry and crumb score were not affected by herbicide treatments. Copyright © 2004 Society of Chemical Industry     

The glutenin fraction of wheat protein: The importance of genetic background on its quantity and quality

The influence of high-molecular-weight glutenin subunits on the properties of the gel-protein fraction of glutenin proteins in wheat was determined on 20 varieties grown in the 1989 UK Recommended List trials. Both the presence of subunit 1 (chromosome 1A) and the 1B/1R rye translocation were shown to influence gel-protein weight and breakdown rate during mixing. The gel-protein tests were correlated with CBP (Chorleywood Bread Process) loaf volume, but they did not add anything to the correlation between Glu-1 score and loaf volume. Both gel-protein tests indicated that phenotypic variation could be almost as large as genotypic variation. Breakdown rate was able to detect the abnormal properties of Pastiche (weak) and Fresco (extra-strong) that were not observed using established quality tests such as the sodium dodecylsulphate sedimentation volume.     

Models of growing season weather impacts on breadmaking quality of spring wheat from producer fields in western Canada

BACKGROUND: The purpose of this study was to quantify growing season weather and wheat quality at individual producer fields to understand weather impacts and develop weather‐based models of spring wheat quality. RESULTS: Ninety‐six hard red spring wheat samples of two genotypes supplied by western Canadian producers in 2003 and 2004 underwent comprehensive analysis for breadmaking quality. For each individual field, daily rainfall, maximum and minimum air temperature were observed and used to calculate several measures of heat. Modeled water use, demand and stress were also calculated and all weather variables were accumulated over different phenological stages. Relationships between weather variables and wheat quality variables were determined by multivariate regression analysis separated into four steps, each adding more complex information into the models. There was substantial variation in weather conditions and wheat quality between years with generally higher quality and stronger dough in the warmer and drier year, 2003. The two genotypes displayed many differences in response to the environment. Prediction of wheat quality improved with increasing complexity of weather models and close to 50% of the variation in quality could be explained by multivariate models. CONCLUSIONS: Results showed that even for top‐grade milling wheat of similar protein content, significant differences exist in breadmaking quality of wheat from different farms. The improvement in r² when using modeled environmental variables indicates that crop water use and water stress are important for wheat quality. The development of Canada Western Red Spring quality prediction models for western Canada based on growing season weather shows promise. Copyright © 2008 Society of Chemical Industry     

Quantification of monomeric and polymeric wheat proteins and the relationship of protein fractions to wheat quality

Wheat protein composition is important for understanding the biochemical basis of wheat quality. The objective of this study was to design a simple protein fractionation protocol with low cross‐contamination and to show that these protein fractions were associated with wheat quality. The protocol consists of three sequential extractions from 100 mg of flour with 7.5% propan‐1‐ol and 0.3 M sodium iodide (monomeric‐rich protein), 50% propan‐1‐ol (soluble glutenin‐rich protein) and 40% propan‐1‐ol and 0.2% dithiothreitol (insoluble glutenin‐rich protein). Nitrogen content of protein solubility groups was determined from dry residues using an automated combustion nitrogen analyser. About 90% of the total protein in the flour was solubilised. Cross‐contamination of protein fractions was evaluated by SDS‐PAGE, SE‐HPLC and RP‐HPLC. Variation in nitrogen content of the protein solubility fractions was lowest for monomeric‐rich protein (<2%) and insoluble glutenin‐rich protein (<4%). Three wheats with similar high‐molecular‐weight (HMW) glutenin subunit composition, Alpha 16, Glenlea and Roblin, varied significantly (P ≤ 0.05) in the proportion of monomeric‐rich and insoluble glutenin‐rich protein in the flour. Dough rheological properties were directly related to the proportion of insoluble glutenin‐rich protein and inversely related to the proportion of monomeric‐rich protein. The protocol was validated using an expanded set of 11 wheats which also showed that inter‐cultivar differences in the proportion of monomeric‐rich, insoluble glutenin‐rich protein and glutenin‐to‐gliadin ratio in the flour governed dough rheological properties such as mixograph, farinograph and microextension tests. The protocol has merit for quality screening in wheat‐breeding programmes when the sample size is too small or when time constraints limit the ability to perform traditional rheological tests. For the Department of Agriculture and Agri‐Food, Government of Canada, Copyright © Minister of Public Works and Government Services Canada 2003. Published for SCI by John Wiley & Sons, Ltd.     

小麦谷蛋白亚基的组成及含量与谷蛋白聚合体大分子的关系及其对面包烘焙品质的影响

含有高分子量谷蛋白亚基(HMW-GS)5 10的生物型小麦与2 12的生物型小麦相比，前者谷蛋白具有更大的分子量分布。高低分子量谷蛋白亚基的比例对于谷蛋白聚合体分子量的大小起着重要的作用，谷蛋白聚合体的体积越大，含有的高低分子量谷蛋白亚基的比例越高。SDS非可溶性谷蛋白含有较高比例的高低分子量谷蛋白亚基，并且其分子量要比可溶性谷蛋白聚合体的大。谷蛋白聚合体分子量分布的差异是不同小麦品种面包烘焙品质存在差异的重要因素。