Physical properties of enzyme-supplemented doughs and relationship with bread quality parameters

 The textural properties of wheat doughs made with different commercial amylases, xylanases/pentosanases, lipases and glucose-oxidase, singly and in mixed combinations, were investigated. Parameters from the texture profile analysis (TPA) and measurement of stickiness (Chen and Hoseney test) were determined after mixing the dough and after it had rested for 3.5 h. Resting of doughs led to softer and less cohesive doughs, with higher adhesive properties. Enzymes acted quickly and induced significant changes in the textural properties of doughs immediately after mixing. The influence of enzymes continued during resting. Xylanases/pentosanases substantially reduced dough consistency and increased stickiness, while addition of glucose-oxidase and specific lipases overcame these effects. Strong correlations could be established between different TPA parameters and stickiness and bread quality characteristics (i.e. volume, density and texture). Bread quality could be described by a single or multiple linear combination of textural variables. Received: 21 May 1997 / Revised version: 10 July 1997     

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     

Texture properties of formulated wheat doughs Relationships with dough and bread technological quality

Texture properties of wheat doughs were determined with a texturometer by using texture profile analysis (TPA) as well as Chen and Hoseney methodologies. The time elapsed between two compressions and strain were optimized so that meaningful values were obtained for TPA. Single effects and interactions between flour type, the breadmaking process and anti-staling additives (i.?e. monoglycerides, diacetyl tartaric ester of monoglycerides, sodium stearoyl lactylate, carboxymethylcellulose and hydroxypropylmethylcellulose) on dough texture properties (i.?e. springiness, resilience, hardness, cohesiveness, adhesiveness, chewiness, gumminess and stickiness) were estimated. The breadmaking process and addition of hydrocolloids had the most important effects and interactions on TPA. Hydrocolloids and α-amylase increased dough stickiness. Dough cohesiveness was a good predictive parameter of bread quality. Water content, acidity values and gluten quality were the main factors determining the texture properties of dough.     

Effect of β-Glucan Concentrate on the Water Uptake,Rheological and Textural Properties of Wheat Flour Dough

The effects of the addition of β-glucan concentrate (2.5–10 g/100 g flour) and water (58–70 mL/100 g flour) on the rheological and textural properties of wheat flour doughs were studied. Various empirical (farinograph, extensograph, dough inflation, and dough stickiness) and fundamental rheological tests (oscillatory and creep-recovery) were employed to investigate composite dough structure and an attempt was made to correlate the data obtained from different instrumental measurements. The water absorption increased with the addition of β-glucan concentrate into wheat flour. An increase in mixing time and stability were recorded upon addition of β-glucan concentrate (≤ 5 g/100 g flour), and the extensibility decreased at similar condition. The composite dough exhibited predominating solid-like behavior. The mechanical strength, dough stickiness, the peak dough inflation pressure decreased with increasing water content but those parameters increased with β-glucan concentrate incorporation within the studied concentration range. Creep-recovery tests for 5 g β-glucan concentrate/100 g flour doughs recorded less resistance to deformation with an increase in water level and data were well described by the Burger model. Thermal scanning of doughs revealed that the protein denaturation peak was significantly influenced by water content, and the values were ranged between 110 and 124°C. Significant relationships between empirical and fundamental rheological testing methods were found.     

Influence of yeast and frozen storage on rheological, structural and microbial quality of frozen sweet dough

The aim of the present study was to investigate the effect of yeast content and frozen storage (9 weeks at −40 °C) on the structural and rheological parameters, and fermentative activity of frozen sweet dough. Two types of dough were studied (to estimate dough shelf life): simple yeasted dough (SY) and double yeasted dough (DY). Fermentative activity (yeast viability, gassing power, and dough volume), rheological and textural parameters were assessed for frozen sweet doughs.These effects were explored by different and complementary methods: Fourier transform infrared (FTIR), dynamic rheology, texture profile analysis (TPA) and differential scanning calorimetry (DSC).The data showed that the longer the frozen storage time at −40 °C, the higher the decreased of frozen sweet dough quality. The rheological attributes such as hardness, ΔS, springiness, tan δ and yeast activity declined significantly during frozen storage. This modification led to lower specific volume of frozen sweet dough during proofing.The observed changes of the frozen sweet doughs rheological properties after thawing may be attributed to the damage on the gluten cross-linking, mainly produced by the ice crystallization during frozen storage. The storage effect was particularly concentrated in the first 27 days of storage.     

Effect of Thermal Treatment on Selected Cereals and Millets Flour Doughs and Their Baking Quality

Selected cereals (rice and sorghum) and millets (finger millet and pearl millet) were steamed for 20 min at ambient pressure. The rheological properties of doughs, made from these steamed as well raw grain flours, were characterized in addition to examining their baking quality. The two-cycle compression test was employed and instrumental values were correlated with sensory attributes (color, aroma, taste, stickiness, chewiness, tearing strength, cohesiveness, and rollability) using principal component analysis (PCA). Rice doughs made from both raw as well as thermally treated flour imparted maximum hardness (96.6–99.3 N) and least cohesiveness (0.05–0.09) with highest stickiness values (105–110°) among all the dough samples at the same moisture content. Pearl millet and raw sorghum flour doughs possessed the least instrumental hardness, adhesiveness, and stickiness and were the easiest to flatten. The PCA biplot showed that sensory and instrumental cohesiveness formed a cluster on the left side on the x axis while shear force, and sensory attributes like tearing strength, chewiness, stickiness, and rollability formed another cluster on the other side of the axis. Raw rice and finger millet doughs were associated with the high extent of instrumental and sensory stickiness. Thermally treated pearl millet and sorghum doughs were the best followed by treated rice and finger millet samples to give the desirable dough characteristics, and were quite close to wheat chapathi in texture.     

A COMPARISON OF THE FARINOGRAPH AND A MODIFIED SHEAR-PRESS FOR MEASURING THE RHEOLOGICAL PROPERTIES OF DOUGH AND ITS FINISHED PRODUCTS1

The development of a single texture testing instrument for determining the complicated properties of dough and the textural characteristics of the final product of dough will eliminate the need for a series of specialized instruments. The farinograph and a modified shear-press were used to determine the rheological properties of doughs made from 15 mixtures of all purpose wheat flour, hard wheat flour and 6% soy fortified wheat flour adjusted with 54.7, 58.0, 61.1, 64.6 and 67.9% water absorptions. The shear-press was also used to determine the textural characteristics of the finished products. The shear-press was found to be equal to the farinograph in providing information on certain rheological properties of dough, and high correlations were obtained between these ‘texturegrams’ and farinogram parameters. For instance, the correlation between “viscoelasticity” per texturegram and “maximum consistency” per farinogram was 0.982; between “viscoelasticity” per texturegram and “elasticity” per farinogram was 0.969; and the correlation between “stability of viscoelasticity” per texturegram and “twenty minute drop” per farinogram was 0.941. The adhesive and cohesive properties of dough obtained from shear-press texturegrams explained 88.4% of the variance of the hardness of the end-products. The consistency and elasticity of dough obtained from farinograms explained 90.6% of the variance of the hardness of the end-products. If the method of water absorption and mixing of flour could be standardized, the shear-press could be utilized both for predicting rheological properties of bakery products from determinations on doughs as well as direct evaluations of the finished products.     

Origin and practical significance of the sticky dough factor in 1BL/1RS wheats

When translocated into wheat, the short arm of the 1R chromosome of rye carries with it linked resistance genes to powdery mildew, stripe rust, leaf rust and stem rust. The translocation is also reported to increase yield potential of hard wheats. However, many doughs made from some 1BL/1RS hard wheats are unacceptable for breadmaking purposes because of excessive stickiness and mixing intolerance. 1BL/1RS wheats may be sticky because of: the inheritance of secalin proteins from rye and absence of key glutenin subunits; higher amounts and/or differences in the composition of cell wall polysaccharides, β‐glucans and pentosans; and/or the presence of a ferulic acid ester moiety residing with the water‐soluble fraction of 1BL/1RS flours. None of these hypotheses has been proven or disproven, to date, as a cause of excessive stickiness. Investigators have found that 1BL/1RS doughs are not uniformly sticky and are in some instances less sticky than non‐1BL/1RS doughs. Significant genotype–environment interactions have been reported for dough stickiness and flour quality characteristics of 1BL/1RS wheats. Investigators have generally failed to find significant differences in the breadmaking performance of 1BL/1RS and non‐1BL/1RS hard wheats despite a report that 1BL/1RS doughs break down and soften during high‐speed mixing. The 1BL/1RS translocation has been shown to reduce cookie spread of soft wheat flours but has no deleterious effects on cake volume or texture. © 2002 Society of Chemical Industry     

UNIAXIAL COMPRESSIBILITY OF BLACKGRAM DOUGHS BLENDED WITH CEREAL FLOURS

The uniaxial compression characteristics of papad dough (moisture content 62%, dry basis), made from blackgram flour as well as after incorporation of different types of cereal (rice, sorghum and wheat) flours at different levels (20 and 40%), were determined. The stress-strain data can be interrelated by a power law type equation. The sensory attributes (stickiness, firmness, elasticity and ease of flattening/rolling) were correlated with the energy for compression, deformability modulus and apparent biaxial elongational viscosity. Inelastic doughs resulted from the blackgram dough; doughs with 20% rice or wheat blends were also inelastic but sorghum samples were elastic. The deformability modulus for sorghum doughs were extremely high. The blackgram dough as well as the wheat blended doughs were the easiest doughs to roll/flatten. Blended dough consisting of wheat flour (at 20 and 40% level) or rice flour up to 20% level was suitable for making cereal-blended papad doughs.     

Ultrasonic Investigation of the Effect of Vegetable Shortening and Mixing Time on the Mechanical Properties of Bread Dough

ABSTRACT:  Mixing is a critical stage in breadmaking since it controls gluten development and nucleation of gas bubbles in the dough. Bubbles affect the rheology of the dough and largely govern the quality of the final product. This study used ultrasound (at a frequency where it is sensitive to the presence of bubbles) to nondestructively examine dough properties as a function of mixing time in doughs prepared from strong red spring wheat flour with various amounts of shortening (0%, 2%, 4%, 8% flour weight basis). The doughs were mixed for various times at atmospheric pressure or under vacuum (to minimize bubble nucleation). Ultrasonic velocity and attenuation (nominally at 50 kHz) were measured in the dough, and dough density was measured independently from specific gravity determinations. Ultrasonic velocity decreased substantially as mixing time increased (and more bubbles were entrained) for all doughs mixed in air; for example, in doughs made without shortening, velocity decreased from 165 to 105 ms⁻¹, although superimposed on this overall decrease was a peak in velocity at optimum mixing time. Changes in attenuation coefficient due to the addition of shortening were evident in both air-mixed and vacuum-mixed doughs, suggesting that ultrasound was sensitive to changes in the properties of the dough matrix during dough development and to plasticization of the gluten polymers by the shortening. Due to its ability to probe the effect of mixing times and ingredients on dough properties, ultrasound has the potential to be deployed as an online quality control tool in the baking industry.     

RHEOLOGICAL PROPERTIES OF ENZYME SUPPLEMENTED DOUGHS

The rheological behaviour of doughs made with different commercial amylases, xylanases, lipases, and glucose-oxidase, singly and in mixed combinations was investigated. All doughs showed similar trends when subjected to frequency and strain sweep tests. The elastic and viscous moduli increased with frequency, and showed a nonlinear behaviour for strains between 0.2 and 3%. Phase angle presented a maximum at 5 hz in the frequency plot. Resting of doughs decreased complex modulus and increased loss tangent. Enzyme supplementation resulted in softening and weakening of doughs immediately after mixing, and further effects during resting. Pentosan degrading enzymes caused the main changes, and pure lipase preparations the least significant, when compared with unsupplemented doughs. Glucose-oxidase reduced the softening effect of polysaccharide hydrolysing enzymes.     

添加挤压苦荞粉对纯苦荞挂面加工及面条品质的影响

为提高纯苦荞挂面的加工适应性及面条品质,将挤压处理后的苦荞粉与生苦荞粉混合后制作纯苦荞挂面,将挤压苦荞粉的添加量及和面加水量结合探究其对纯苦荞挂面加工品质及面条品质的影响。通过面带的质构品质、面条的蒸煮及质构特性评价纯苦荞挂面的加工性能和食用品质。结果表明,随着挤压苦荞粉添加量的增加,面带的表面黏附力和抗拉伸力及面条的蒸煮损失率显著(P<0.05)增加;随着和面加水量的增加,面带的表面黏附力显著(P<0.05)增加,抗拉伸力下降,面条的硬度、咀嚼性和蒸煮损失率均显著(P<0.05)增加,当挤压苦荞粉的添加量为30%,加水量为34%时,面带的表面黏附力最低,抗拉伸力适中,蒸煮损失率最小,质构品质较好,综合评价最高。     

Effect of mixing method on the rheological characteristics of biscuit dough and the quality of biscuits

 The effect of different mixing methods on the rheological characteristics of biscuit dough and the quality of biscuits was studied. The amount of water required to prepare the desired consistency of dough varied considerably depending on the mixing method: 16% for the creaming method (CM) and the sugar solution method (SSM), 20% for the blending method (BM), 24% for the all-in-one method (AOM), and 25% for the creaming followed by water and flour addition method (CWFM). Although the extrusion time, compliance, apparent biaxial extensional viscosity and hardness values of doughs made by different mixing methods were similar, the other rheological characteristics differed significantly. Elastic recovery, which is indicative of gluten development, was lower in the case of doughs mixed by the CM and the SSM and higher for the AOM and the CWFM. The CM produced dough with lower cohesiveness and adhesiveness, while the AOM produced dough with higher cohesiveness and adhesiveness. Biscuits produced by the CM and the SSM had lower thickness, higher spread and crisper texture. However, biscuits made by the other mixing methods had excessively higher thickness, porous crumb and hard texture. Received: 21 December 1998     

Effect of endoxylanases on dough properties and making performance of Chinese steamed bread

Two kinds of endoxylanase (XYL), one is a solid-phase enzyme (S-XYL) and the other a liquid-phase enzyme (L-XYL), were used to test their effect on the properties of dough and the quality of Chinese steamed bread (CSB). The textural properties of wheat dough made with the two enzymes were investigated. Parameters from the texture profile analysis (TPA) were determined after mixing the dough at 0th, 5th, 10th, 15th and 20th min, respectively. Both enzymes decreased farinograph parameters. They also influenced mixograms including decreasing time to peak and peak height. It was apparent that the decrease in hardness of the dough by adding S-XYL and L-XYL, respectively was more than that of the control sample and the sample with added yeast. It was found that the longer the time of fermentation, the lower the hardness of the dough. The mixing time was reduced by adding L-XYL by about 27.5%. The fermentation time was decreased by adding S-XYL or L-XYL. The addition of S-XYL and L-XYL on CSB resulted in increased specific volume, spread ratio and decreased crumb softness. A decreasing trend in L* value, a slightly increasing tendency in a* value and a slightly decreasing trend in b* value exist in crumb colour.     

THE RHEOLOGICAL BASIS OF DOUGH STICKINESS

Stickiness in wheat flour doughs was studied as a function of rheological and surface properties. Adhesion was measured using a modified peel test at various water additions, peel rates and peel layer thicknesses. Peeling energy gave a strong positive correlation with subjective bakery stickiness ratings. Peeling forces were highly rate dependent and showed transitions from sticky to nonsticky behvaiour with increasing rate of peeling. Dynamic storage modulus showed a negative correlation with stickiness ratings, suggesting stickiness is primarily a rheologically controlled process. Stress relaxation gradients were greater for sticky doughs and were very similar to peeling force vs. rate slopes, again indicating that adhesion is principally a function of the rheological properties of the dough. Surface tension measurements of sticky and nonsticky dough/liquor interfaces showed no significant differences and are typical of protein solutions. Calculated values of the interfacial surface energy between dough and interface were about 100 mJ/m², typical of secondary bonding interactions such as polar or van der Waals bonding.     

Effect of high pressure processing on wheat dough and bread characteristics

Microbial, physical and structural changes in high pressured wheat dough were studied as a function of pressure level (50-250 MPa) and holding time (1-4 min). Thereafter, selected conditions of high hydrostatic processing (HPP) were applied to bread dough and the technological quality of the obtained breads was studied. The effect of HPP on wheat dough was investigated by determining microbial population (total aerobic mesophilic bacteria, moulds and yeasts), color and mechanical and texture surface related dough parameters (cohesiveness, adhesiveness, hardness and stickiness). HPP reduced the endogenous microbial population of wheat dough from 10⁴ colony forming units/g (CFU) to levels of 10² CFU. HPP treatment significantly (P < 0.05) increased dough hardness and adhesiveness, whereas treatment time reduced its stickiness. Scanning electron micrographs suggested that proteins were affected when subjected to pressure levels higher than 50 MPa, but starch modification required higher pressure levels. HPP treated yeasted doughs led to wheat breads with different appearance and technological characteristics; crumb acquired brownish color and heterogeneous cell gas distribution with increased hardness due to new crumb structure. This study suggests that high hydrostatic processing in the range 50-200 MPa could be an alternative technique for obtaining novel textured cereal based products.     

Semi-Sweet Biscuits: 2. Alternatives to the Use of Sodium Metabisulphite in Semi-Sweet Biscuit Production

The influence of sodium metabisulphite (SMS) and other gluten-modifying agents on the performance of a commercial biscuit flour in the production of semi-sweet biscuits has been studied. Use of a proteolytic enzyme as a gluten-modifying agent resulted in a dough with a longer mixing time than other doughs, partly as a result of mixing to a higher temperature. The extrusion time of doughs containing the proteolytic enzyme was closest to the extrusion time of doughs containing SMS. Doughs containing SMS or proteolytic enzyme produced significantly shorter extrusion times than doughs containing l -cysteine hydrochloride. Dynamic oscillatory measurements showed that for doughs made at a constant water level the lowest elastic and viscous moduli were produced by doughs containing sodium metabisulphite. Doughs containing the other gluten-modifying agents produced stronger elastic properties than those containing SMS but weaker elastic properties than doughs containing no gluten-modifying agent. The hardness of the semi-sweet biscuits produced was found to be reduced by a weakening of the rheological properties of the dough. All gluten-modifying agents reduced dough piece contraction in length during processing, although SMS was the most effective. A decrease in dough piece length during processing caused an increase in dough piece thickness and width. Use of a proteolytic enzyme or the enzyme and l -cysteine hydrochloride in combination, as gluten-modifying agents, produced biscuits closest in quality to those produced from doughs containing SMS.     

Quality Indicators of Rice-Based Gluten-Free Bread-Like Products: Relationships Between Dough Rheology and Quality Characteristics

The design of gluten-free bread-like products involves the study of gluten-free dough rheology and the resulting baked product characteristics, but little information has been obtained connecting dough and baked product properties. The aim of this study was to determine quality predictors of gluten-free bread-like products at dough level by defining possible correlations between dough rheological properties and both instrumental parameters and sensory characteristics of those products. Diverse rice-based gluten-free doughs were defined and rheologically characterised at dough level, and the technological and sensorial quality of the resulting baked products was investigated. Dough Mixolab® parameters, bread-like quality parameters (moisture content, specific volume, water activity, colour and crumb texture) and chemical composition significantly (P?<?0.05) discriminated between the samples tested. In general, the highest correlation coefficients (r?>?0.70) were found when quality instrumental parameters of the baked products were correlated with the dough Mixolab® parameters, and lower correlation coefficients (r?<?0.70) were found when sensory characteristics were correlated with dough rheology or instrumental parameters. Dough consistency during mixing (C1), amplitude and dough consistency after cooling (C5) would be useful predictors of crumb hardness; and C5 would be also a predictor of perceived hardness of gluten-free bread-like products.