Changes of chemical composition and dough rheology in two fractions of sieve-classified Polish spring wheat flour

The study of chemical composition and dough rheology changes in sieve-classified two fractions (up to 60 and 60-240 microm particles) of wheat flour was the subject of this study. The straight grade flours were obtained by the milling of three Polish varieties of spring wheat, differing in particle size index (PSI) values. The flours were separated with the use of an SZ-1 laboratory sifter. The yield of fine fraction was in the range 50.0-55.7%. The obtained fractions were assayed for the content and composition of free lipids, gluten proteins, damaged starch, ash, water absorption and amylograph viscosity. Dough rheology (extrusion in OTMS cell, alveograph and farinograph tests) and baking trials were also performed. The content of free lipids, including the non-polar and phospholipids was lower and the content of glycolipids was higher in fine flours. Those fractions were more rich in linoleic acid but the lower content of oleic and linolenic acids resulted in a higher oxidizability index of free lipids. Fine flours contained less ash and significantly more damaged starch. At the same time, they were characterized by a higher content of wet gluten, water absorption, amylograph viscosity and better dough parameters. This was reflected in the bread volume, which was higher by 6.3-10.7%. The influence of the changes in composition and the content of free lipids upon the rheology of the dough after the 90 days flour storage has not been defined unambiguously and requires further research.     

Bread quality and dough rheology of enzyme-supplemented wheat flour

The enzymatic treatment of wheat flours is an interesting alternative for improving their functional properties. Since enzymes with different biochemical activities could induce synergistic effects on dough behaviour or product quality, the individual and combined use of a wide range of enzymes (transglutaminase, glucose oxidase, laccase, α-amylase, pentosanase and protease) applied nowadays in bread-making processes were investigated. The blend of enzymes resulted in an improvement in the rheological behaviour of doughs and the quality of the final product. The simultaneous presence of transglutaminase (TG) and glucose oxidase (GO), as well as TG and protease (PROT) led to a synergistic effect on alveograph parameters. Polysaccharide-degrading enzymes exercised a significant effect on rheology only when used in combination with other enzymes, mainly affecting consistograph parameters. Analysis of bread-making data revealed significant interactions between TG and all the other enzymes except laccase (LAC). Significant synergistic effect on bread quality was observed by the combined use of GO and LAC, GO and pentosanase (PP), amylase (AMYL) and LAC, AMYL and PROT, and PP and PROT. Bread quality parameters showed greater correlations with alveograph parameters than with consistograph properties of dough. Tenacity (P) and extensibility (L) proved to be acceptable predictors of the height/width ratio of loaves. The duration of the alveograph test enhanced the prediction of bread quality parameters. Conversely, none of the rheological properties studied showed a high correlation with the specific volume of loaves.     

Effect of buckwheat flour addition to wheat flour on acylglycerols and fatty acids composition and rheology properties

In this paper, the rheological properties and lipids composition with an emphasis on acylglycerols and fatty acids composition of dough with various portions of buckwheat flour (BWF) are investigated. The results show lipids from wheat-buckwheat flour mixture has higher ratio of total unsaturated to saturated fatty acids content (3.77-4.78 g/100 g) than those of wheat flour only (3.71 g/100 g). The value of dough water absorption (WA), development time (DT), dough stability (DSt), gelatinization temperature (T_max) and maximal pasta viscosity (η_max) increases when content of free fatty (FFA) acids increases, i.e. when buckwheat flour portion in flour mixtures increases, so FFA content has a proper influence on these dough properties. Dough with buckwheat flour has higher WA (54.3-56.0 ml/100 g), T_max (82.0-84.1 °C) and η_max (630-860 AU), longer Dst (0.7-4.6 min) and lower Dsf (82-90 FU) than dough with wheat flour only, whose appropriate values are 54.3 ml/100 g, 81.2 °C, 480 AU, 0.3 min and 90 FU, respectively. So, the flour mixture with buckwheat flour of at least 5 g/100 g can be considered good quality flour.     

Cooperation of phosphatidylcholine with endogenous lipids of wheat flour for an increase in dough volume

Phosphatidylcholine (PC) increases the gas-retaining ability of dough, the dough volume on fermentation and the loaf volume of bread. The cooperation of wheat flour endogenous lipids with PC was examined. More than 90% of the total wheat flour lipids were extracted with chloroform, the extracted lipids comprising glycolipids (33 wt%), non-polar lipids (56 wt%), and phospholipids (11 wt%). The increase in the specific volume of dough with delipidated wheat flour by the addition of PC was smaller than the increase in the specific volume of dough with native wheat flour. The addition of the extracted lipids to delipidated wheat flour restored the increase in dough volume by the addition of PC. The glycolipid fraction of the extracted lipids was most effective for enhancing the action of PC. The results suggest that interaction of PC with wheat flour glycolipids may synergistically increase foam stability to enhance the gas-retaining stability of dough.     

Effect of an enzyme preparation on wheat flour and dough color, mixing, and test baking

Bleaching flours with natural rather than chemical extracts is attractive because it reduces risks upon exposure and appeals to natural food consumers. This paper reports effects of a commercial proprietary blend of ‘natural’ bleaching enzymes on wheat flour and dough color, mixing behavior and test bake performance. Enzyme preparation did not improve whiteness (L*) and yellowness (b*) of flour system, but benzoyl peroxide sharply reduced b*. For whole wheat flour dough, L* increased for enzyme-treated dough after 2-h resting, ending higher than benzoyl peroxide and control dough. Yellowness increased in enzyme-treated dough. When enzyme application was during milling, resulting whole wheat flour dough had much higher L*. Mixograms of flours with increasing enzyme concentration showed severe dough weakness and rapid breakdown. Dialysis of the enzyme preparation in 3500 molecular weight cutoff (MWCO) tubes and freeze-drying prior to flour application recovered dough strength. l-cysteine in the enzyme mix was thought to adversely affect dough strength, and dialysis helped recover dough strength. However, pup loaf baking with dialyzed enzyme showed some loss of baking characteristics (loaf volume, loaf weight, and proof height) over the control. Although the natural enzyme extract addition enhanced whiteness for whole wheat dough, its effects on dough and baking properties were not favorable.     

小麦粉在不同粒度下其面团及馒头品质

为研究小麦粉在不同粒度下其面团及馒头品质的变化,通过控制研磨条件得到基本组分相同而粒度不同的6种粒度不同的小麦粉（分别全部穿过150 μm、137 μm、123 μm、112 μm、100 μm、88 μm,以下简称S150、S137、S123、S112、S100、S88）,对其色泽、基本理化特性、面团水分分布、发酵特性及馒头各项指标进行分析,从而探究粒度对面团特性及馒头品质的影响。结果表明：当小麦粉粒度减小时,其水分在粒度S112时较低,灰分、脂肪含量无显著性（p＜0.05）变化,粒度组成中D50从120.84 μm降至73.64 μm、湿面筋含量显著性（p＜0.05）降低,L*值、破损淀粉含量显著性（p＜0.05）增加;面团内深层结合水和自由水含量逐渐降低而弱结合水含量逐渐增加。在粒度为S123时,面团最大膨胀高度、漏气时间、产气量和持气率达到最大。随着小麦粉粒度减小,馒头的比容、L*值、弹性、内聚性、回复性整体呈先增加后降低趋势,硬度、胶着性、咀嚼性呈先降低后升高,宽高比在粒度为S112时最小。综上所述,粒度在S123～S112小麦粉适合制作馒头。     

Fatty acids composition and rheology properties of wheat and wheat and white or brown rice flour mixture

Manufacturing of bread from rice flour only presents technological difficulty because the rice is gluten-free and gluten is the most important structure forming protein. By using wheat and rice flour mixture, this problem can be avoided, and end product is enriched by rice-oil constituents. In this paper fatty acids composition, with an emphasis on total saturated, and total unsaturated fatty acids, rheological and baking properties of wheat–rice flour mixture (70:30 w/w) were investigated. The results show that wheat–rice flour mixture has better fatty acids composition with higher content of stearic, arachidic, lignoceric, oleic, and phthalic acids compared to wheat flour. Also, wheat flour did not include myristic, arachidic, lignoceric and linolenic acids, so rice flour addition made fatty acids profile richer as number of constituents is higher, nine instead six. The content of total unsaturated fatty acids content was higher in wheat–brown rice flour mixture than in wheat flour and in wheat–white rice flour mixture. When rice flour was added to wheat flour the rheological properties were changed: flour mixture had less water absorption, less degree of softening, longer development time, higher gelatinization temperature, but better stability and finally, better quality number and group than wheat flour. So, the wheat and rice flour mixture can be considered as a good quality flour and can be used for making good quality wheat-rice bread and cake.     

Non-linear creep-recovery measurements as a tool for evaluating the viscoelastic properties of wheat flour dough

Creep-recovery measurements were used to analyze the non-linear viscoelastic properties of wheat flour. First the effect of creep time, recovery time and shear stress was investigated on the non-linear viscoelastic properties of Bussard dough. The Burgers model was fitted to the creep and recovery curves. A linear increase of maximum creep compliance was observed with increasing creep time. On the other hand, maximum recovery compliance remained constant but an increase of the retardation time was observed which indicates a slower recovery. A recovery time of 10 min seemed to be sufficient to obtain most of the recovery. Maximum creep compliance increased proportionally with increasing shear stress until a plateau was reached. Maximum recovery was constant between 100 and 500 Pa but the speed of the recovery increased as shear stress increased. Finally, the optimised creep-recovery methodology was used to analyze the non-linear viscoelastic properties of 17 pure wheat cultivars. By applying principal component analysis, it was possible to identify three groups of wheat cultivars with similar rheological properties and bread volumes.     

Relationship of polymeric proteins and empirical dough rheology with dynamic rheology of dough and gluten from different wheat varieties

Dynamic rheological properties of dough and gluten were studied and related to the empirical rheology (Farinograph) and the protein fractions of different wheat varieties. The relationship between high molecular weight-glutenin subunits (HMW-GS) and dough strength was evaluated. Dynamic rheology of under-, optimum- and over-mixed dough was also related to the farinograph characteristics and the protein fractions. The moduli (G′ and G″) of over- and optimally-mixed dough were significantly correlated with Farinograph characteristics and SDS-unextractable polymeric protein (UPP) content. The temperature-induced rheology of glutens revealed that the differences in G′ and G″ during heating as well as cooling were related to the UPP content. Principal component analysis revealed wide range of differences in the dynamic rheology among the wheat varieties mainly attributed to UPP.     

Energetical and rheological approaches of wheat flour dough mixing with a spiral mixer

Wheat flour dough was mixed in a spiral mixer for different operating conditions, at a speed ranging from 80 to 320 rpm, for a period of 7-15 min. The specific mechanical energy E_s delivered and the dough temperature T_d were continuously recorded and varied from 7 to 82 kJ/kg and T_d of 13.5 to 36 °C, respectively. E_s and T_d were strongly correlated because of viscous dissipation but variations of ingredients initial temperature allowed to uncouple them. The energy balance during mixing process was set through a simple model assuming constant heat transfer (h = 75 W/(m² °C)) which took into account thermal losses. Shear viscosity curves of the dough were determined by correlating volumic power to angular speed; by comparison to typical dough shear flow curve, a constant characteristic of the mixer geometry (K_s = 1.55) was determined like for models of mixer power consumption. The impact of mixing on small deformation rheological properties was assessed by DMA and the variations of the ratio, of maximum (75 °C) to minimum (50 °C) elastic modulus, was interpreted in relation with gluten network development.     

Effects of dough mixing and oxidising improvers on free reduced and free oxidised glutathione and protein-glutathione mixed disulphides of wheat flour

Changes in free reduced glutathione (GSH), free oxidised glutathione (GSSG) and protein-glutathione mixed disulphides (PSSG) during dough mixing were monitored. After a rapid decrease in the GSH content and an increase in the GSSG content, the contents of both GSH and GSSG decreased progressively, whereas the PSSG content increased, as a simple flour-water dough was mixed. Total glutathione (GSH plus GSSG plus PSSG) levels in simple flour-water doughs and doughs treated with ascorbic acid or potassium bromate remained essentially constant during dough mixing, indicating that the reactions in which glutathione is involved are simple oxidations of sulphydryl (SH) groups to disulphide (SS) bonds and SH/SS interchange reactions. Yeast contributed high levels of GSH and GSSG to doughs, but analysis of dough aqueous phases (liquors) and the similarity of the PSSG contents of simple and yeasted flour-water doughs suggested that the yeast GSH and GSSG were largely unavailable to react with flour proteins. The GSH content of ascorbic-acid-treated and yeasted dough decreased rapidly on wetting the flour, the magnitude of the decrease indicating that the ascorbate oxidation system oxidised the yeast intracellular GSH as well as the flour GSH. With further mixing, the GSH content of the ascorbate dough remained constant at low levels similar to those of the simple flour-water dough. The GSSG content of the ascorbate dough increased rapidly on wetting the flour, but declined as dough mixing continued. The PSSG content of the doughs increased markedly as dough mixing proceeded to the optimum and then stabilised. The increase in the PSSG content lagged behind the rapid oxidation of GSH to GSSG. Potassium bromate caused a pattern of changes similar to those observed for ascorbate, but the changes in GSH and PSSG contents were smaller in magnitude. The results indicate that the changes in the different glutathione pools and the effects of oxidising bread improvers are rather more complex than envisaged previously, particularly the effects on PSSG.     

Effect of flour heating on dough rheology

Heating soft wheat flour at 80°C for 15 min has already been shown to improve its bread-making potential. In this study, flour was fractionated to determine the specific effect of heating on its constituents (gluten, starch, lipid, water-soluble). While gluten was easier to extract and its texture was slacker after heating, it significantly increased dough-mixing stability and development time (P<0.01). Heated water-soluble fraction containing pentosans partly decreased stability (P=0.06).     

Impact of endogenous constituents from different flour milling streams on dough rheology and semi-sweet biscuit making potential by partial substitution of a commercial soft wheat flour

A flour fractionation-reconstitution procedure was used to study the substitution of a commercial soft wheat flour with gluten, water extractables, prime starch and starch tailing fractions isolated from patent and clear flour streams on dough rheology and semi-sweet biscuit characteristics. Substitution of soft wheat flour with increasing levels of the native patent and clear flour streams raised the dough consistency, hardness and elastic properties as well as the biscuit textural attributes (density, hardness). The dough stickiness of the base flour was also reduced and the biscuits were free of cracks. Gluten isolated from the patent flour had a greater impact on dough consistency, hardness and elastic properties than gluten obtained from the clear flour, likely due to the superior protein quality of the former. Additionally, with increasing gluten levels in the fortified flour there were moderate increases in biscuit density, hardness, and lower crunchiness. The addition of starch tailings produced the largest impact on consistency and hardness of the dough. This fraction also exerted a pronounced effect on biscuit density and hardness, while it lowered crunchiness, presumably due to its higher pentosan content. Overall, the dough rheological properties and biscuit characteristics were controlled by the amount-nature of the fractions added; i.e., besides gluten (amount and quality), other constituents such as pentosans and the overall composition of the flour blends can largely affect the quality of the semi-sweet biscuits.     

Application of response surface methodology for the optimization of oxidants in wheat flour

The objective of this study was to apply the statistical technique known as response surface methodology (RSM) to optimize the proportion between three oxidant compounds compromising lipoxygenase enzymes (x₁), benzoyl peroxide (x₂) and ascorbic acid (x₃) on wheat flour colour and some rheological characteristics of the dough. P, L and W parameters were obtained using a “Chopin” alveograph. Flour colour, characterized by brightness (Lc) and hue (b), was measured using a HunterLab colorimeter and was ranked visually by selected judges. Three regression models were fitted to the dependent variables P, L and Lc and showed non-significant lack of fit (p > 0.114) with an elevated determination coefficient (0.92, 0.84 and 0.94, respectively). A mixture containing 0.27% of x₁, 4.80 ppm of x₂ and 325 ppm of x₃ was obtained from the regression optimization and used for validating the models. These results suggest that, instead of the empirical methods, RSM can be applied to determine the optimal proportion between oxidant compounds normally used to improve colour and rheological parameters in wheat flour.     

Differences in content and composition of free lipids and carotenoids in flour of spring and winter wheat cultivated in Poland

The work presents the content and composition of free lipids and carotenoids in spring and winter classes of wheat flour. It discusses genetical and physiological aspects of their synthesis and accumulation in wheat kernels and also indicates how methodological differences explain differences in results presented in the literature. It has been reported that spring wheat flours are richer in free lipids, especially in the non-polar fraction. The content of glycolipids ranged from 134 to 215 mg/100 g flour and was more stable within the winter wheat class. The percentages of the two main fractions, namely DGDG and MGDG, were similar in both wheat classes and reached ca. 77%. Phospholipids constituted the smallest fraction of the flour free lipids in both wheat classes; however, spring wheat flours were richer in these compounds, which is likely associated with a greater content of spherosomes in the endosperm of this wheat class. The free lipids of spring wheat flour contained more oleic and slightly less linoleic and linolenic acids. Spring wheat flour was also richer in carotenoids, although there were varieties in both classes that deviated from this. The main carotenoid was lutein, whose total percentage in the form of different isomers ranged from 71.3% to 83.3% and was slightly lower for spring wheat flour. Lutein, in the form of a trans-isomer, constituted about 62% and 70% of all carotenoids in spring and winter wheat flours, respectively.     

Interactive effects of flour, starter and enzyme on bread dough machinability

 Dough machinability of samples formulated with the enzyme principles glucose-oxidase, lipase, amylase and pentosanase/hemicellulase, and fermented with different microbial starters, was assessed by texture profile analysis and dough stickiness measurements. The individual and interactive effects of flour, enzyme and starter on the primary and secondary mechanical and surface-related parameters were evaluated, and the suitability of enzyme mixtures added to started doughs to improve dough handling characteristics and minimize adhesiveness and stickiness in flours was established. The general improving effect of the mixture of α-amylase, pentosanase and hemicellulase on most dough texture properties is particularly relevant when high-grade and/or sourer-started systems are used, because of their strong effect in decreasing hardness and adhesiveness respectively. Individual additions of glucose-oxidase and lipase cancelled out the excessive stickiness/adhesiveness of started and enzyme-supplemented doughs while the simultaneous presence of glucose-oxidase and lipase improved cohesiveness, chewiness and gumminess. The extent of the effects of this binary combination on dough mechanical characteristics was comparable to that obtained with the ternary mixture of α-amylase, pentosanase and hemicellulase, but avoided the deleterious effect of the latter enzyme combination on stickiness. In well-defined flour-starter systems, the enzyme supplementation of doughs constitutes a useful alternative to chemical improvers for enhancement of dough plasticity. Reveived: 16 February 1998     

Interactive effects of flour, starter and enzyme on bread dough machinability

 Dough machinability of samples formulated with the enzyme principles glucose-oxidase, lipase, amylase and pentosanase/hemicellulase, and fermented with different microbial starters, was assessed by texture profile analysis and dough stickiness measurements. The individual and interactive effects of flour, enzyme and starter on the primary and secondary mechanical and surface-related parameters were evaluated, and the suitability of enzyme mixtures added to started doughs to improve dough handling characteristics and minimize adhesiveness and stickiness in flours was established. The general improving effect of the mixture of α-amylase, pentosanase and hemicellulase on most dough texture properties is particularly relevant when high-grade and/or sourer-started systems are used, because of their strong effect in decreasing hardness and adhesiveness respectively. Individual additions of glucose-oxidase and lipase cancelled out the excessive stickiness/adhesiveness of started and enzyme-supplemented doughs while the simultaneous presence of glucose-oxidase and lipase improved cohesiveness, chewiness and gumminess. The extent of the effects of this binary combination on dough mechanical characteristics was comparable to that obtained with the ternary mixture of α-amylase, pentosanase and hemicellulase, but avoided the deleterious effect of the latter enzyme combination on stickiness. In well-defined flour-starter systems, the enzyme supplementation of doughs constitutes a useful alternative to chemical improvers for enhancement of dough plasticity. Reveived: 16 February 1998     

Dynamic rheology of wheat flour dough. II. Assessment of dough strength and bread‐making quality

Controlled stress rheometry revealed that differences in wheat flour dough strengths could be observed by means of dynamic rheological measurements in the region of higher stress amplitude (ie >100 Pa). At lower stress amplitude (τ_o) the values of elastic modulus G′ for weak doughs were higher than those for strong doughs, but they decreased substantially beyond 100 Pa stress amplitude (τ_o), such that the G′ values for strong doughs crossed over the G′ values for weak doughs. Beyond a critical value of stress amplitude (ie 100 Pa), true differences in dough strengths could be seen on the basis of their elastic characteristics, because at large deformations protein–protein interactions played a more dominant role in the rheological behaviour of flour doughs. Dynamic rheological analysis demonstrated a very weak inverse relationship (R² = 0.16) between the G′ values of flour doughs and loaf volume data for 12 wheat cultivars of diverse bread‐making performance. However, the G′ values of glutens showed significant positive relationships with bread‐making performance, explaining 73% of the variation in loaf volume. © 2002 Society of Chemical Industry     

Dynamic rheology of wheat flour dough. I. Non‐linear viscoelastic behaviour

Controlled stress rheometry was used to investigate the effects of starch and gluten fractions on the non‐linearity of wheat flour dough. Flour–water dough showed non‐linear viscoelastic behaviour over all stress values in a cyclic stress sweep. The amplitude‐dependent behaviour of the starch and amplitude‐independent nature of the gluten revealed that starch is responsible for the non‐linearity of the flour–water dough system. Adding starch to gluten caused a substantial narrowing of its linear viscoelastic range. © 2002 Society of Chemical Industry     

Effect of steaming on the rheological characteristics of wheat flour dough

 The effect of steaming on the various rheological characteristics of wheat flour dough was studied. Steaming of flours at atmospheric pressure for 15 min completely denatured the gluten and reduced the water absorption capacity from 58.4% to 45.0%. Even steaming for just 5 min increased the resistance to extension considerably from 500 BU (Brabender Units) to 1000 BU and the ratio figure (resistance to extension/extensibility) from 4.2 to 27.4, indicating stiffening of the dough. The dough made from steamed flour had a higher hardness value of 91.1 N than the dough made from raw wheat flour which had a value of 51.1 N. The pasting characteristics of flour steamed for 15 min measured in a Rapid Visco Analyser showed increased peak viscosity from 218 rapid visco units (RVU) to 257 RVU as well as increased cold paste viscosity from 175 RVU to 200 RVU and increased hot paste viscosity from 94 RVU to 108 RVU for flour steamed for 15 min. Received: 4 August 1998 / Revised version: 23 October 1998