Crosslinking of wheat dough proteins by glucose oxidase and the resulting effects on bread and croissants

The crosslinking of wheat flour proteins results in significant improvements in the functional properties of baked products. In this research, the enzyme glucose oxidase was investigated for its crosslinking effect on the dough proteins of bread and croissants. The macroscopic effects resulting from the addition of glucose oxidase to the dough formulation were compared to changes seen at the molecular level in individual protein fractions. Treatment with glucose oxidase produced slight improvements in crumb properties but no increase in product volume. At the molecular level, crosslinking occurred mainly in the water-soluble (albumin and globulin) fraction and was demonstrated to involve both disulfide and non-disulfide linkages. The SDS-soluble and -insoluble glutenins, which make up much of the gluten network, were crosslinked to a much lesser extent, with mainly non-disulfide linkages. These findings corroborate our theories on the relationship of wheat protein crosslinking and functional properties. Specifically, we conclude that (i) crosslinking of albumin and globulin proteins enhances crumb properties and (ii) changes in croissant volume require crosslinking of the glutenin fraction of wheat proteins.     

Rebuilding gluten network of damaged wheat by means of glucose oxidase treatment

The disrupted gluten structure of infested wheat flours leads to low‐quality doughs unusable in bread‐making processes. Enzymes are replacing chemical treatments in the food industry as a tool to treat weak flours. Glucose oxidase is one of the most promising oxidative enzymes, although its efficiency compared with the alcohol‐soluble fraction of gluten proteins has not yet been demonstrated. If this enzyme could restore the broken covalent bonds between glutenin subunits, the gluten network of damaged wheat flour would recover its native structure and functionality. This treatment would allow bakers to use damaged flour, reducing the economic losses caused by this plague around Europe and North Africa. Electrophoretic studies demonstrated the formation of high‐molecular‐weight aggregates in the glutenin fraction, which had a characteristic thermal stability depending on enzyme dosage. Those molecular studies agreed with the bread‐making assays made with maximum enzyme dosage and microstructure determination. Overall results showed that glucose oxidase is a real alternative to traditionally used chemical oxidants. It acted specifically on the high‐molecular‐weight glutenin subunits of damaged wheat, forming dityrosine crosslinks between the wheat proteins, which reinforced the gluten network and gave away the dough functionality. Copyright © 2007 Society of Chemical Industry     

IMPROVEMENT OF THE WHEAT AND CORN BRAN BREAD QUALITY BY USING GLUCOSE OXIDASE AND HEXOSE OXIDASE

The effects of addition of wheat (10, 20 and 30%) and corn bran (10 and 20%) on rheological and bread making properties of flour were examined. To improve dough and bread properties, glucose oxidase (GO) and hexose oxidase (HO) (15–30 and 45 mg/kg) were used separately in each bran-wheat flour formula with L-ascorbic acid at 75 mg/kg, glucose at 0.5% and vital gluten at 9.2%. Water absorption and development time increased as the amount of wheat and corn bran increased, while dough stability, maximum resistance to extension, extensibility, energy and loaf volume decreased. Corn bran was found to be more detrimental to dough rheology and bread characteristics than wheat bran. Corn bran and wheat bran could be used at bread making up to levels of 10 and 20%, respectively. Addition of 30 mg/kg of HO in combination with constant additives was most effective in improving dough and bread characteristics and GO with its 15 mg/kg usage level followed it. Further increasing of enzyme levels led to over oxidizing of doughs and breads.

PRACTICAL APPLICATIONS

Corn bran up to 10% and wheat bran up to 20% levels can be used in bread making. To improve dough and bread quality, besides L-ascorbic acid (75 mg/kg) and vital gluten (as a percentage of added bran weight), GO (15 mg/kg) or HO (30 mg/kg) could be incorporated into wheat flour-bran mixtures. However, the amount of enzyme should be carefully chosen because when they are used above the mentioned levels, they cause overoxidation of doughs and small loaf volumes are obtained. As a conclusion; by using the corn bran, which is a by-product of the starch industry, not only could it be possible to offer healthy alternative breads which contain high amounts of dietary fiber to consumers, but it could also be possible to obtain economical value by evaluating such a by-product in the bread industry.     

Wheat gluten: high molecular weight glutenin subunits--structure, genetics, and relation to dough elasticity

ABSTRACT:  Gluten proteins, representing the major protein fraction of the starchy endosperm, are predominantly responsible for the unique position of wheat amongst cereals. These form a continuous proteinaceous matrix in the cells of the mature dry grain and form a continuous viscoelastic network during the mixing process of dough development. These viscoelastic properties underline the utilization of wheat to prepare bread and other wheat flour based foodstuffs. One group of gluten proteins is glutenin, which consists of high molecular weight (HMW) and low molecular weight (LMW) subunits. The HMW glutenin subunits (HMW-GS) are particularly important for determining dough elasticity. The common wheat possesses 3 to 5 HMW subunits encoded at the Glu-1 loci on the long arms of group 1 chromosomes (1A, 1B, and 1D). The presence of certain HMW subunits is positively correlated with good bread-making quality. Glutamine-rich repetitive sequences that comprise the central part of the HMW subunits are actually responsible for the elastic properties due to extensive arrays of interchain hydrogen bonds. Genetic engineering can be used to manipulate the amount and composition of the HMW subunits, leading to either increased dough strength or more drastic changes in gluten structure and properties.     

Dough rheology and baking performance of wheat flour–lupin protein isolate blends

The impact of addition of two lupin protein isolates (LPI), enriched either in proteins belonging to globulin (LPI G) or to albumin (LPI A) fraction, on wheat flour dough and bread characteristics was investigated. LPI addition increased the dough development time and stability plus the resistance to deformation and the extensibility of the dough. The presence of LPI proteins in dough affected bread quality in terms of volume, internal structure and texture, while extra gluten addition to the blends to compensate for wheat gluten dilution, resulting from LPI addition, led to an improvement of bread quality characteristics. Generally, the incorporation of LP isolates to wheat flour delayed bread firming. The results obtained are discussed in terms of a possible action of LPI particles as a filler of the gluten network and partly in terms of possible interactions that take place between the gluten protein constituents and those of lupin.     

Effects of microencapsulated glucose oxidase on wheat flour dough properties and Chinese steamed bread quality

This study was to investigate the effects of microencapsulated glucose oxidase (MGO), in comparison with free glucose oxidase (GO), on wheat flour dough properties and Chinese steamed bread (CSB) quality. Effects on wet gluten (WG) content, farinograms and extensograms properties, dynamic rheological properties, microscopic structure, texture profile and sensory evaluation scores were studied. The results demonstrated that MGO catalysed the oxidation of dough at a much slower speed and exerted relatively great advantages in many aspects such as WG content, extensibility, G′ (Elastic modulus), G″ (viscous modulus), tan δ (equal to G′/G″), microstructure and texture properties and sensory evaluation scores of CSB, compared with free GO. The results suggested that slow oxidation of MGO was superior to free GO based on the improvements of wheat flour dough properties and subsequent CSB quality.     

Effect of Proline and Glutamine on the Functional Properties of Wheat Dough in Winter Wheat Varieties

ABSTRACT: Combinations of proline and glutamine significantly increased the functional properties of soft wheat that were unseen when added individually. To hard wheat, proline contributed more positively than glutamine on most dough and bread properties, which is different from the observations with soft wheat. Addition of glutamine to hard wheat increased the amount of gluten and glutenin after mixing, whereas proline hinders gluten formation despite the increase in glutenin. The ability of proline and glutamine to modify the functional properties of dough and bread appears to be interdependent. Addition of either proline or glutamine appears to have a protective effect on the retention of the other amino acid during breadmaking.     

Combined effects of wheat gluten and carboxymethylcellulose on dough rheological behaviours and gluten network of potato–wheat flour-based bread

Incorporating high level of potato flour into wheat flour enhances nutritional values of bread but induces a series of problems that lead to the decline of the bread quality. To overcome the barrier, wheat gluten and carboxymethylcellulose (CMC) were added into potato–wheat composite flour to improve dough machinability and bread quality. The rheological properties, thermo-mechanical properties and microstructures of dough were investigated. The results showed that the interaction between gluten and CMC mitigated the discontinuity of gluten matrix and gluten protein aggregation caused by the addition of potato flour, which yielded a more branched and compact gluten network. The compact three-dimensional viscoelastic structure induced improvements of gas retention capacity and dough stability, making it mimic the machinability properties of wheat flour dough. Bread qualities were apparently improved with the combined use of 4% gluten and 6% CMC, of which specific volume increased by 42.86%, and simultaneously, hardness reduced by 75.93%.     

Genetic Variation in Glutenin Protein Composition of Aestivum and Durum Wheat Cultivars and Its Relationship with Dough Quality

Genetic variability of high molecular weight glutenin subunits and low molecular weight glutenin subunits composition at the Glu-1 loci in Triticum aestivum L., and T. durum L., wheat was studied using sodium dodecyl sulfate polyacrylamide gel electrophoresis and polymerase chain reaction based markers. The end use quality of wheat is mainly influenced by the composition of glutenin protein. Aestivum cultivar GW-273 showed highest gluten index (94.4%) and sedimentation value (61 mL). GW-273 and GW-322 showed highest Glu-1 score of 10 out of 10, indicating superior dough quality for bread making. Results from glutenin protein separation using electrophoresis revealed that selected Indian wheat cultivars were abundant in high molecular weight glutenin subunits AxNull allele, which is responsible for poor quality. Gene specific polymerase chain reaction using high molecular weight glutenin subunits and low molecular weight glutenin subunits primers showed Dx5 and Dy10 in only two cultivars GW-273 and GW-322, which is responsible for good dough quality. Sequencing of high molecular weight glutenin subunits Dx5 gene fragment showed four cysteine at the N-terminal end. Cysteine residues are helpful in intermolecular disulfide bond formation among different glutenin and gliadins proteins leading to good elasticity of dough.     

谷朊粉对高含量荞麦面团的影响及其作用机理

本文全面研究了不同添加量谷朊粉(5%、10%和15%)对高含量(50%小麦粉替代率)荞麦面团流变学特性及馒头品质的影响,并以添加10%谷朊粉的混合面团和参照组(纯小麦粉)面团为基础,通过扫描电镜,红外光谱及分析面团中的化学作用力等分析手段,进一步探讨了谷朊粉对改善混合面团流变学性质及馒头品质方面的作用机理。结果表明,添加10%的谷朊粉能够增加荞麦-小麦混合面团中二硫键的含量,改变面团中的化学作用力(离子键、氢键含量和疏水作用力),进而改变面团中面筋蛋白的构象,改善面团的微观结构,从而改善混合粉的糊化特性及面团的粉质和拉伸特性,提高馒头的比容和弹性,改善馒头芯的孔隙结构,但仍达不到参照组馒头的品质,表明添加高含量荞麦全粉不仅仅是稀释面筋蛋白。     

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     

Enzymes Action on Wheat–Soy Dough Properties and Bread Quality

High levels of soy flour added to wheat bread produce negative effects on gluten network formation, dough properties, and on bread final quality. The objective of this study was to assess the influence of three enzymes, transglutaminase (TG), glucose oxidase (GOX), and endoxylanase (XYL), on dough properties and final quality of high-protein breads. The addition of TG and GOX increased the mixing stability and maximum resistance of dough, decreased its extensibility, and produced stronger and more consistent dough samples. XYL incorporation produced opposite results. XYL addition and the lowest GOX dose increased bread volume significantly and decreased initial crumb firmness, while high doses of TG (0.3%) produced detrimental effects on bread volume and crumb firmness. In conclusion, XYL and GOX 0.001% addition improved the final quality of soy-fortified breads, but XYL was the best additive to improve dough properties, bread volume, and quality.     

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     

麦胚对面包质量影响的研究

研究了全脂麦胚和脱脂麦胚对面团的流变学特性和面包质量的影响。结果表明,面团的筋力随麦胚量的增加而降低;脱脂麦胚比全脂麦胚的面包质量较好;脱脂麦胚的适宜加量为8％;麦胚能改善面包的皮色、风味和营养价值。     

葡萄糖氧化酶和谷氨酰胺转氨酶对发酵麦麸面团加工品质的影响

本研究旨在探讨葡萄糖氧化酶和谷氨酰胺转氨酶对发酵麦麸面团加工品质的改良效果及改良机制,为改善全麦发酵食品食用品质提供应用参考。在全麦粉中分别添加1.0、3.0和6.0 U/g的葡萄糖氧化酶或谷氨酰胺转氨酶,分析测定了全麦粉粉质特性、发酵面团质构特性以及面筋的持水率、蛋白质组成和游离巯基含量的变化情况。研究结果表明:两种酶制剂的添加对全麦粉粉质特性有显著改善作用(p<0.05),面团稳定时间延长,弱化度减小;随酶制剂添加量的增加,发酵面团的弹性和凝聚性均显著增加,面筋蛋白中谷蛋白大聚合体(GMP)含量显著升高,游离巯基的含量显著减少(p<0.05),但高添加量的谷氨酰胺转氨酶(6.0 U/g)引起面筋蛋白持水率下降。谷氨酰胺转氨酶对麦麸面团品质的改良效果显著优于葡萄糖氧化酶(p<0.05),其适宜添加量为3.0 U/g,可使麦麸面团的稳定时间由5.3 min延长至9.3 min。     

不同谷物麸皮对面团流变学特性及面筋蛋白结构的影响

本实验选用小麦麸皮、黑小麦麸皮、燕麦麸皮为原材料,探究在高添加量(质量分数30%)情况下不同谷物麸皮对面团流变学特性、面筋蛋白组成及结构的影响。结果表明,谷物麸皮含有丰富的膳食纤维,麸皮的加入使面团的吸水率、黏度崩解值显著增加,回生值显著降低,面团的形成时间、稳定时间虽与麸皮种类有关,但整体均呈上升趋势;添加麸皮的面筋蛋白中麦谷蛋白与麦醇溶蛋白比例增加了24.7%~73.0%、二硫键含量显著下降了26.0%~35.5%;面筋蛋白中的二级结构以β-折叠为主,小麦麸皮和黑小麦麸皮的加入使得面筋蛋白中的β-转角结构向β-折叠结构转化;扫描电子显微镜图显示麸皮的加入破坏了面筋蛋白原本均匀致密的微观结构。综上所述,谷物麸皮的加入改变了面筋蛋白的组成及二级结构,这些变化可能是导致面团流变学特性及面制品品质下降的原因。     

葡萄糖氧化酶对全麦面团及全麦馒头品质改良的影响

将葡萄糖氧化酶(glucose oxidase,GOD)应用于全麦馒头的制作,通过测定面团的流变、热机械、吹泡特性以及全麦馒头品质的相关指标,研究该酶对全麦面团及馒头品质的影响。实验结果表明,随着GOD添加量的增加(小于300 U/kg),全麦面团的稳定时间增加,但对全麦粉吸水率没有显著改变;峰值粘度(C3)、保持粘度(C4)增加,表示面团的糊化稳定性越好,面团稳定性增加;当GOD的添加量为300 U/kg时,全麦面团的弹性模量、粘性模量最大,tanδ 值最低,全麦面团固体特性增强,机械强度增大;面团P值、L值、W值增加,改善了面团的韧劲、延展性和持气性。与空白组对照可知,随着GOD添加量的增大(小于300 U/kg),馒头的比容呈现增加趋势并且硬度、咀嚼性以及黏附显著降低,品质得到改善,但是过量的GOD(500 U/kg)反而对其品质有负面的影响。因此添加GOD 300 U/kg时,可改善面团的网络结构,改良全麦馒头的品质。     

Effect of enzymatic crosslinking on the handling properties of dough as a function of NaCl levels for CWRS varieties,Pembina and Harvest

The effects of transglutaminase (TG) and glucose oxidase (GO) on the handling properties of model bread dough were examined at both normal (2% wt. by flour) and reduced (1% wt.) sodium chloride (NaCl) levels using two Canada Western Red Spring (CWRS) cultivars; Pembina and Harvest. The reduction of NaCl level had negative effects on dough rheology and stickiness, however, the inclusion of GO (0.001 and 0.01% by flour weight) or TG (only at the 0.5% by flour weight inclusion) was able to improve dough strength and reduce stickiness. GO appeared to be more effective than TG (at 0.01%) at equivalent concentrations for improving dough‐handling properties. Flour cultivar had significant effects; Harvest flour (weaker) was more impacted by salt reduction and enzyme inclusion compared to Pembina flour (stronger). Crosslinking assays showed significant differences in glutenin macropolymer (GMP) content in dough prepared with GO, and dough prepared with different flours. Additionally, significantly fewer free thiol groups were found in dough produced with GO compared to dough without any enzymes and those with TG. GO appears to have potential for use as a bread improver to reduce stickiness and improve the strength of bread dough produced at lower salt concentrations, especially for dough prepared with weaker flour cultivars.     

Comparative proteome analysis of glutenin synthesis and accumulation in developing grains between superior and poor quality bread wheat cultivars

BACKGROUND: Wheat glutenins are the major determinants of wheat quality. In this study, grains at the development stage from three wheat cultivars (Jimai 20, Jin 411 and Zhoumai 16) with different bread‐making quality were harvested based on thermal times from 150 °C_d to 750 °C_d, and were used to investigate glutenin accumulation patterns and their relationships with wheat quality. RESULTS: High and low molecular weight glutenin subunits (HMW‐GSs and LMW‐GSs) were synthesised concurrently. No obvious correlations between HMW/LMW glutenin ratios and dough property were observed. Accumulation levels of HMW‐GSs and LMW‐GSs as well as 1Bx13 + 1By16 and 1Dx4 + 1Dy12 subunits were higher in superior gluten quality cultivar Jimain 20 than in poor quality cultivar Jing 411 and Zhoumai 16. According to the results of two‐dimensional gel electrophoresis, six types of accumulation patterns in LMW‐GSs were identified and classified. The possible relationships between individual LMW‐GSs and gluten quality were established. CONCLUSION: The high accumulation level of HMW‐GSs and LMW‐GSs as well as 1Bx13 + 1By16 and 1Dx4 + 1Dy12 subunits contributed to the superior gluten quality of Jimai 20. Two highly expressed and 16 specifically expressed LMW glutenin subunits in Jimain 20 had positive effects on dough quality, while 17 specifically expressed subunits in Zhoumai 16 and Jing 411 appeared to have negative effects on gluten quality. Copyright © 2011 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