Impact of microbial transglutaminase on the viscoelastic profile of formulated bread doughs

The effects of microbial transglutaminase (TGM) on the viscoelastic profile of wheat flour doughs when added singly and in combination with hydrocolloids—hydroxypropylmethylcellulose (HPMC) and a high ester pectin (GENU pectin type BIG, or BIG)—, amylolytic (-amylase) and non amylolytic enzymes (xylanase) and an emulsifier [diacetyl tartaric acid ester of mono-diglycerides (DATEM)] have been investigated by applying response surface analysis to a Draper-Lin small composite design of formulated dough samples. In spite of the major effects on mixing, textural, extensional and viscometric parameters, which were provided by hydrocolloid/surfactant combinations, incorporation of TGM into dough formulas improved some viscoelastic properties. TGM, when added to DATEM and/or HPMC-containing doughs, induced synergistic effects on mixing parameters, resulting in increased water absorption, development time and stability. Highly cohesive doughs with improved water holding capacity and gluten strength during mixing and fermentation, and suitable pasting behaviour during cooking were achieved using TGM/BIG/DATEM mixtures, mainly associated with suitable interactions of the pairs TGM/DATEM and DATEM/BIG.     

Effect of hydroxypropyl methylcellulose,whey protein concentrate and soy protein isolate enrichment on characteristics of gluten‐free rice dough and bread

Due to a lack of gluten, rice dough needed some additives to improve its properties. This study aimed to investigate effect of hydroxypropyl methylcellulose (HPMC), whey protein concentrate (WPC) and soy protein isolate (SPI) on rice dough and bread. HPMC increased water absorption of the rice dough (P ≤ 0.05). Adding SPI (2–4 g per 100 g flour) together with HPMC tended to increase stability time and reduce tolerance index. During fermentation, HPMC increased maximum dough height, while SPI increased final dough height (P ≤ 0.05). All addition improved tan δ (G″/G′) to be comparable to the wheat dough, but it could not improve gas production and retention. Therefore, specific volume, springiness, cohesiveness and chewiness of rice bread were lower than those of wheat bread (P ≤ 0.05). Percentage of small pores in rice bread was reduced to be comparable to wheat bread, by adding WPC. All addition could improve porosity of the rice bread.     

Effect of modified celluloses on dough rheology and microstructure

The effect of different modified celluloses on dough microstructure and rheological characteristics was studied. Microcrystalline cellulose (MCC), carboxymethylcellulose (CMC) and two different types of hydroxypropylmethylcellulose (HPMC F4M and HPMC F50) were tested in a range of concentration from 0.25% to 1.5% (flour basis). Doughs were formulated without and with salt (2%w/w flour basis). Farinographic water absorption increased when hydrocolloids were incorporated and the highest values were obtained in mixtures without NaCl and when HPMCs were added. A linear relationship between the percentage increment in water absorption and the hydrocolloid level was observed within the assayed range of concentrations. The development time was markedly increased when CMC was added. CMC and HPMC did affect or not dough stability depending on the presence or absence of salt whereas the stability was not modified by MCC. Texture attributes and the rheometric parameter tan δ were analyzed through Principal Component Analysis (PCA). Two factors described the 88.9% of total variation, one of them composed by hardness, consistency, adhesiveness and tan δ and the other composed by resilience and cohesiveness. Hydrocolloids addition softened the dough, particularly when salt was absent. Samples with salt and with hydrocolloids exhibited more cohesive and less resilient characteristics. Rheological results were in agreement with the characteristics of gluten network studied by SEM since a diminished stability and softer dough could be associated with a more disrupted matrix.     

Effect of glutens of different quality on dough characteristics and breadmaking performance

Glutens of different quality were extracted from commercial flours of distinct breadmaking performance and employed as improvers at a level of 1 g/100 g. The same flours used as a source of gluten were employed for testing the gluten effect. Flours were characterized by farinographic and alveographic assays and their protein profile was determined by SDS-PAGE. Rheology of each dough without and with gluten addition was studied by empirical and fundamental assays. Breadmaking performance was evaluated by loaf volume measurements and crumb texture.Though protein content was similar for all flours (11 g/100 g), dough exhibited different breadmaking characteristics which could be related to a different gliadin/glutenin proportion and a different protein profile. The weakest flour lacked two glutenin subunits (83 and 64.5 kDa) and showed a lower number of bands of gliadins respect to the other ones. Adding any of the three types of gluten to the weakest flour resulted in an increase of farinographic stability. The medium and inferior quality flours showed an increase in dough elasticity when the strongest gluten was added. In breadmaking assays the medium quality flour and its mixtures with gluten showed the highest specific volumes.     

Effects of aleurone-rich fraction on the hydration and rheological properties attributes of wheat dough

This study aimed to evaluate the effects of incorporation of aleurone-rich fraction (ALF) on the hydration and rheological properties of wheat dough. Incorporation of ALF significantly increased water absorption (P < 0.05) and competition for water in dough was observed. Peak viscosity, through viscosity, and final viscosity decreased with the amount of ALF added (P < 0.05), whereas 20% ALF had stronger gel ability than whole-wheat flour. Dynamic rheological experiments revealed ALF blend dough were more stable than whole-wheat dough, which was in accord with the higher dough stability and strength observed in Mixolab. Scanning electron microscopy showed that disruption of gluten network with ALF incorporation, whereas 20% ALF showed better stability dough structure than the whole-wheat dough. Considering those influences on dough properties, the 20% ALF seems to be a promising substitute for whole-wheat flour to producing dietary fibre-rich products.     

马铃薯全粉在面条中的应用研究

将马铃薯全粉添加到小麦粉中,并辅助添加谷朊粉,制成马铃薯全粉面条。从质构特性、微观结构和面条的理化性质三个层面对三个不同马铃薯全粉添加比例的面条组别进行研究,发现马铃薯全粉对面团的力学性质,面筋网络的形成和构造以及面条的蒸煮参数和外观都会产生一定的影响。结果表明：马铃薯全粉添加量为20%（g/g）,谷朊粉添加为0.03%（g/g）时,总体指标最好;马铃薯全粉对面团的作用具有双向性,马铃薯淀粉对面团的影响偏负向,但是其中的多糖和蛋白质可能对面团和面筋网络有正向影响,同时谷朊粉的添加对面团的稳定性和面条的质量有改善作用。     

Effect of butter content and baking condition on characteristics of the gluten‐free dough and bread

This study aimed to investigate effect of butter content (0–30 g/100 g flour) and baking conditions hot air baking (HA), microwave baking (MW) and hot air‐microwave baking (HA‐MW) on quality of the rice flour dough and bread. The increased butter (up to 15 g butter/100 g flour) enhanced elastic modulus (G′) and viscous modulus (G″) of dough and specific volume of bread. Additionally, the increased butter improved crust colour and reduced hardness of the bread. The HA‐MW and MW conditions were useful for the gluten‐free bread by reducing baking time and predicted glycemic index (GI), regardless of butter content. However, enthalpy of retrogradation and crystallinity in the HA‐MW and MW bread stored at 4 °C for 7 days were increased and higher than those of the HA bread, indicating a faster staling. The predicted GI of both MW and HA‐MW bread remained at a medium level during storage.     

Effects of wheat sourdough process on the quality of mixed oat-wheat bread

The aim of this work was to study the effects of sourdough fermentation of wheat flour with Lactobacillus plantarum, on the quality attributes of mixed oat-wheat bread (51 g whole grain oat flour and 49 g/100 g white wheat flour). Emphasis was laid both on β-glucan stability as well as bread structure and sensory quality. The variables of the sourdough process were: dough yield (DY), fermentation time, fermentation temperature, and amount of sourdough added to the bread dough. The sourdough process was shown to be a feasible method for mixed oat-wheat bread, and, when optimized, provided bread quality equal to straight dough baking. A small amount (10g/100 g dough) of slack sourdough fermented at high temperature for a long time resulted in the most optimal sourdough bread with the highest specific volume (3.5 cm³/g), the lowest firmness after 3 days storage (0.31 kg), and low sensory sourness with high intensity of the crumb flavour. Wheat sourdough parameters did not affect the content of oat β-glucan in the bread. Additionally, both straight dough and sourdough bread contained 1.4-1.6 g β-glucan/100 g fresh bread. The average molecular weight of β-glucan was 5.5 × 10⁵ in both types of bread, while that of oat flour was 10 × 10⁵. This indicates that a slight degradation of β-glucan occurred during proofing and baking, and it was not affected by variation in the acidity of the bread between pH 4.9-5.8.     

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。     

Effects of endogenous flour lipids on the quality of short‐dough biscuits

Fractionation and reconstitution techniques were used to study the contribution of endogenous flour lipids to the quality of short‐dough (shortcake type) biscuits. Biscuit flour was defatted with chloroform and baked with bakery fat, but without endogenous lipid. Short‐dough biscuits baked from defatted flour had smaller diameters, and were flatter, denser and harder than control biscuits. Defatted flour shortcake doughs exhibited different rheological behaviour from the control samples, showing higher storage and loss moduli (G′ and G″ values), ie higher viscoelasticity. Functionality was restored when total non‐starch flour lipids were added back to defatted flour. The polar lipid fraction had a positive effect in restoring flour quality whereas the non‐polar lipid fraction had no effect. Both fractions were needed for complete restoration of both biscuit quality and dough rheological characteristics. A study of the microstructure of defatted biscuits revealed that their gluten protein was more hydrated and developed than the gluten of the control biscuits. This conclusion was supported by the higher water absorption of the defatted gluten. Copyright © 2004 Society of Chemical Industry