Waxy durum and fat differ in their actions as improvers of bread quality

Fat is commonly added to bakery products to improve eating qualities and extend shelf life. Flour milled from waxy durum grain was incorporated into bread formulations and its effects on crumb softness and loaf volume compared to those of added fat. Low levels of fat (0.1-0.3% of flour weight) softened the bread crumb and increased loaf volume. Most of the softening effects were evident in the crown of the loaves protruding above the tin and a high proportion of the reduction in compression was associated with increased volume. Loaves baked with waxy durum flour were softer than those baked with fat and the softening effects were evident both in the crown of the loaf and at its base where it had been confined within the tin. Waxy durum flour reduces compression independently of increased volume. It is suggested waxy durum flour acts by slowing the migration of water from the gluten phase to the starch phase so maintaining the level of mobile water in the gluten where it acts as a plasticiser. Independent organoleptic assessment of bread quality baked with combinations of waxy durum and fat confirmed the quality enhancing effects of waxy durum flour.     

Wheat Bread Quality as Influenced by the Substitution of Waxy and Regular Barley Flours in Their Native and Cooked Forms

The substitution of wheat flour with barley flours altered the bread loaf volume, colour and bread crumb firmness. These changes were found to be dependent on the barley cultivar, substitution level and flour treatment. In native form, Phoenix barley flour at 15% substitution produced breads with bigger loaf volume and softer crumb than Candle barley flour. However, when the barley flours were heat-treated (pan-cooked in excess water and then dried) before substitution, Candle barley flour produced better quality breads in terms of loaf volume, crumb firmness and crust colour than the Phoenix counterparts. The baking functionality of Candle flour was markedly improved when added after heat treatment.     

Suitability of tef varieties in mixed wheat flour bread matrices: A physico-chemical and nutritional approach

Wheat flour replacement from 0 to 40% by single tef flours from three Ethiopian varieties DZ-01-99 (brown grain tef), DZ-Cr-37 (white grain tef) and DZ-Cr-387 (Quncho, white grain tef) yielded a technologically viable ciabatta type composite bread with acceptable sensory properties and enhanced nutritional value, as compared to 100% refined wheat flour. Incorporation of tef flour from 30% to 40% imparted discreet negative effects in terms of decreased loaf volume and crumb resilience, and increase of crumb hardness in brown tef blended breads. Increment of crumb hardness on aging was in general much lower in tef blended breads compared to wheat bread counterparts, revealing slower firming kinetics, especially for brown tef blended breads. Blended breads with 40% white tef exhibited similar extent and variable rate of retrogradation kinetics along storage, while brown tef-blended breads retrograded slower but in higher extent than control wheat flour breads. Breads that contains 40% tef grain flour were found to contain five folds (DZ-01-99, DZ-Cr-387) to 10 folds (DZ-Cr-37) Fe, three folds Mn, twice Cu, Zn and Mg, and 1.5 times Ca, K, and P contents as compared to the contents found in 100% refined wheat grain flour breads. In addition, suitable dietary trends for lower rapidly digestible starch and starch digestion rate index were met from tef grain flour fortified breads.     

Wheat Bread Quality as Influenced by the Substitution of Waxy and Regular Barley Flours in Their Native and Extruded Forms

The substitution of wheat flour with barley flour (i.e. native or pretreated/extruded) reduced the loaf volume. Depending on the barley variety and flour pretreatments, the colour and firmness/texture of the bread loaves were altered. Amongst the barley breads prepared from native flours (at 15% barley flour substitution level), Phoenix had higher loaf volume and lower crumb firmness than Candle. However, amongst the barley breads prepared from extruded flours, CDC-Candle had higher loaf volume and lower crumb firmness than Phoenix. The lower loaf volume and firmer crumb texture of barley breads as compared with wheat bread may be attributed to gluten dilution. Also, the physicochemical properties of barley flour components, especially that of β-glucan, can affect bread volume and texture. β-glucan in barley flour, when added to wheat flour during bread making, could tightly bind to appreciable amounts of water in the dough, suppressing the availability of water for the development of the gluten network. An underdeveloped gluten network can lead to reduced loaf volume and increased bread firmness. Furthermore, in yeast leavened bread systems, in addition to CO₂, steam is an important leavening agent. Due to its high affinity for water, β-glucan could suppress the amount of steam generated, resulting in reduced loaf volume and greater firmness. In the present study, breads made with 15% HTHM CDC-Candle flour had highly acceptable properties (loaf volume, firmness and colour) and it indicated that the use of extruded barley flours would be an effective way to increase the dietary fibre content of barley breads.     

Influence of puroindoline alleles on milling performance and qualities of Chinese noodles,steamed bread and pan bread in spring wheats

Two trials with a total of 75 spring bread wheat cultivars and advanced lines, were used to evaluate single kernel characterization system hardness, puroindoline alleles, milling yield, flour ash content, flour colour, and end-use qualities for Chinese noodles, steamed bread and pan bread. The results indicated that all International Maize and Wheat Improvement Center hard wheat lines surveyed were Pina-D1b genotype, whereas Pinb-D1b was the most common allele in the remaining cultivars. Genotypes with Pinb-D1b possess significantly lower flour ash content and higher milling yield than those of genotypes with Pina-D1b. For steamed bread, mean scores for loaf volume, crumb colour, width, structure and total score of Pinb-D1b genotypes were significantly higher than those of genotypes with Pina-D1b and wild type. For Chinese fresh white noodles, means for noodle a*, colour score, viscoelasticity and total score with Pinb-D1b were significantly higher than those of Pina-D1b and wild type. Means of loaf volume, texture and total score for Pinb-D1b genotypes were significantly higher than those of Pina-D1b genotypes. This study further illustrated the superiority of the Pinb-D1b allele on milling and processing qualities for various end products and provides useful information for wheat quality improvement.     

Waxy durum acts as a unique form of crumb softener in bread

Flour milled from waxy durum grain was incorporated into bread formulations and its effects on crumb softness and loaf volume compared to those of added fats and emulsifiers. Waxy durum had a small effect on increasing loaf volume, and little of this effect could be explained by dough height or oven spring; effects of most other additives were closely related to dough height or oven spring. For all additives, the relationship between crumb softness and loaf volume fitted a power law relationship. Waxy durum and some of the additives had a greater softening effect than predicted from their effect on volume while others produced a much firmer crumb. With only one exception, when combined with other additives waxy durum reduced compression of the crumb more than predicted on the basis of the effects on loaf volume of the additives alone. In common with some of the added lipids, during compression analysis, crumb prepared with waxy durum flour had similar levels of structural damage as crumb baked from the standard formulation; other lipids and emulsifiers produced more fragile crumb. Waxy durum flour appears to have unique effects on crumb softness.     

Low moisture milling of wheat for quality testing of wholegrain flour

The objective of this study was to produce wholegrain wheat flour on a laboratory-scale with particle size distributions similar to commercially-milled samples without re-milling the bran. The moisture contents of four hard winter wheat cultivars were adjusted to 7.29–7.98% (by drying), 9.00–10.6% (“as is”), and 15.6% (by tempering) prior to milling into wholegrain flour. The moisture treatments appeared to affect the partitioning of wholegrain flour particles into each of three categories: fine (<600 μm), medium (600–849 μm) and coarse (≥850 μm). When the distributions of particles were grouped into these categories, wholegrain flours made from dried and “as is” wheat fell within the values for commercial wholegrain flours, while that from tempered wheat contained more coarse particles than even the coarsest commercial wholegrain flour. Loaf volumes and crumb firmness were not significantly different between bread made from wholegrain flour that had been produced from dried or “as is” wheat, but loaf volume was significantly lower and bread crumb firmness was significantly higher when wholegrain flour from tempered wheat was used. These results show that wheat may be milled without tempering to produce wholegrain flour with particle size similar to some commercially-milled flours without needing to re-grind the bran.     

Effect of physicochemical and empirical rheological wheat flour properties on quality parameters of bread made from pre-fermented frozen dough

The objective of this study was to examine the influence of flour quality on the properties of bread made from pre-fermented frozen dough. The physicochemical parameters of 8 different wheat flours were determined, especially the protein quality was analysed in detail by a RP-HPLC procedure. A standardized baking experiment was performed with frozen storage periods from 1 to 168 days. Baked bread was characterised for specific loaf volume, crumb firmness and crumb elasticity. The results were compared to none frozen control breads. Duration of frozen storage significantly affected specific loaf volume and crumb firmness. The reduction of specific loaf volume was different among the used flours and its behaviour and intensity was highly influenced by flour properties. For control breads wet gluten, flourgraph E7 maximum resistance and RVA peak viscosity were positively correlated with specific loaf volume. However, after 1–28 days of frozen storage, wet gluten content was not significantly influencing specific loaf volume, while other parameters were still significantly correlated with the final bread properties. After 168 days of frozen storage all breads showed low volume and high crumb firmness, thus no significant correlations between flour properties and bread quality were found. Findings suggest that flours with strong gluten networks, which show high resistance to extension, are most suitable for frozen dough production. Furthermore, starch pasting characteristics were also affecting bread quality in pre-fermented frozen dough.     

Low moisture milling of wheat for quality testing of wholegrain flour

The objective of this study was to produce wholegrain wheat flour on a laboratory-scale with particle size distributions similar to commercially-milled samples without re-milling the bran. The moisture contents of four hard winter wheat cultivars were adjusted to 7.29–7.98% (by drying), 9.00–10.6% (“as is”), and 15.6% (by tempering) prior to milling into wholegrain flour. The moisture treatments appeared to affect the partitioning of wholegrain flour particles into each of three categories: fine (<600 μm), medium (600–849 μm) and coarse (≥850 μm). When the distributions of particles were grouped into these categories, wholegrain flours made from dried and “as is” wheat fell within the values for commercial wholegrain flours, while that from tempered wheat contained more coarse particles than even the coarsest commercial wholegrain flour. Loaf volumes and crumb firmness were not significantly different between bread made from wholegrain flour that had been produced from dried or “as is” wheat, but loaf volume was significantly lower and bread crumb firmness was significantly higher when wholegrain flour from tempered wheat was used. These results show that wheat may be milled without tempering to produce wholegrain flour with particle size similar to some commercially-milled flours without needing to re-grind the bran.     

Grain of high digestible,high lysine (HDHL) sorghum contains kafirins which enhance the protein network of composite dough and bread

The aim of this study was to determine whether protein body-free kafirins in high digestibility, high-lysine (HDHL) sorghum flour can participate as viscoelastic proteins in sorghum-wheat composite dough and bread. Dough extensibility tests revealed that maximum resistance to extension (g) and time to dough breakage (sec) at 35 °C for HDHL sorghum-wheat composite doughs were substantially greater (p < 0.01) than for normal sorghum-wheat composite doughs at 30 and 60% substitution levels. Functional changes in HDHL kafirin occurred upon exceeding its T_g. Normal sorghum showed a clear decrease in strain hardening at 60% substitution, whereas HDHL sorghum maintained a level similar to wheat dough. Significantly higher loaf volumes resulted for HDHL sorghum-wheat composites compared to normal sorghum-wheat composites at substitution levels above 30% and up to 56%, with the largest difference at 42%. HDHL sorghum-wheat composite bread exhibited lower hardness values, lower compressibility and higher springiness than normal sorghum-wheat composite bread. Finally, HDHL sorghum flour mixed with 18% vital wheat gluten produced viscoelastic dough while normal sorghum did not. These results clearly show that kafirin in HDHL sorghum flour contributes to the formation of an improved protein network with viscoelastic properties that leads to better quality composite doughs and breads.     

Improving the quality of nutrient-rich Teff (Eragrostis tef) breads by combination of enzymes in straight dough and sourdough breadmaking

The growing interest in the benefits of wholegrain products has resulted in the development of baked products incorporating less utilised and ancient grains such as, millet, quinoa, sorghum and teff. However, addition of wholegrains can have detrimental effects on textural and sensory bread product qualities.Enzymes can be utilised to improve breadmaking performance of wholegrain flours, which do not possess the same visco-elastic properties as refined wheat flour, in order to produce a healthy and consumer acceptable cereal product.The effects of Teff grain on dough and bread quality, selected nutritional properties and the impact of enzymes on physical, textural and sensory properties of straight dough and sourdough Teff breads were investigated.Teff breads were prepared with the replacement of white wheat flour with Teff flour at various levels (0%, 10%, 20%, and 30%) using straight dough and sourdough breadmaking. Different combinations of enzymes, including xylanase and amylase (X + A), amylase and glucose oxidase (A + GO), glucose oxidase and xylanase (GO + X), lipase and amylase (L + A) were used to improve the quality of the highest level Teff breads. A number of physical, textural and sensory properties of the finished products were studied. The nutritional value of breads was determined by measuring chemical composition for iron, total antioxidant capacity, protein, fibre and fat. The obtained results were used to estimates intakes of nutrients and to compare them with DRIs.The incorporation of Teff significantly (P < 0.05) improved dietary iron levels as 30% Teff breads contained more than double the amount of iron when compared to corresponding wheat bread (6 mg/100 g v 2 mg/100 g). Addition of Teff also significantly (P < 0.05) improved total antioxidant capacity from 1.4 mM TEAC/100 g to 2.4 mM TEAC/100 g. It was estimated that an average daily allowance of 200 g of Teff enriched bread would contribute to DRIs in the range of 42-81% for iron in females, 72-138% for iron in males; 38-39% for protein in males, 46-48% for protein in females; and 47-50% of fibre in adults.The major challenge was encountered in producing the highest level of Teff bread with good textural and sensory attributes. Increasing the level of Teff significantly (P < 0.05) increased dough development time, degree of softening, crumb firmness and bitter flavour whilst decreasing the dough stability, specific loaf volume and overall acceptability of the bread. Teff breads produced with the addition of enzyme combinations showed significant improvements (P < 0.05) in terms of loaf volume, crumb firmness, crumb structure, flavour and overall acceptability in both straight dough and sourdough breadmaking.     

Effects of Amylose/Amylopectin Ratio and Baking Conditions on Resistant Starch Formation and Glycaemic Indices

The possible improvement of the nutritional properties of starch in barley flour-based bread by using barley genotypes varying in amylose content (3–44%) was evaluated. Breads were made from 70% whole-meal barley flour and 30% white wheat flour. Test breads were baked from waxy barley (WB), ordinary barley (OB), ordinary Glacier barley (OGB) and high-amylose barley (HAB). Each bread was baked either at conventional baking conditions (45 min, 200 °C) or at pumpernickel conditions (20 h, 120 °C). A white wheat bread (WWB) was used as reference. The resistant starch (RS) content and rate of starch hydrolysis were measuredin vitro. The glycaemic index (GI) and the insulinaemic index (II) of the high-amylose breads were determined in healthy subjects. The amount of RS (total starch basis) varied from <1% (WB) to approximately 4% (HAB) in conventionally baked bread, and from about 2% to 10% in the corresponding long-time/low-temperature baked products. The long-time/low-temperature baked HAB displayed a significantly lower rate of starch hydrolysisin vitrocompared with WWB and reduced the incremental blood-glucose response in healthy subjects (GI=71). In contrast, the GI of the conventionally baked HAB was similar to that for WWB. It is concluded that a barley flour-based bread of low GI and high RS content can be obtained by choosing high-amylose barley and appropriate baking conditions.     

Scanning Electron Microscopic Study of Dough and Chapati from Gluten-reconstituted Good and Poor Quality Flour

Hard and soft wheat flours, which were used in the study, resulted in good and poor quality chapatis respectively. Gluten was isolated and interchanged among the two whole wheat flours and studied by scanning electron microscopy for its influence on structural characteristics of dough and its relation to chapati-making quality. Microscopic observations clearly indicated that larger gluten strands covered starch granules in hard wheat flour dough, while gluten was short and starch granules exposed in dough prepared from soft wheat flour. Greater film forming ability of gluten in hard wheat flour dough manifested in long and bulky starch strands interwoven with protein matrix in its chapati crumb. Higher moisture retention and starch gelatinization as a consequence of greater film forming ability of gluten in hard wheat flour resulted in pliable and soft textured chapati.     

Effect of arabinoxylans and laccase on batter rheology and quality of yeast-leavened gluten-free breads

The supplementation effects of maize fiber arabinoxylans (MFAX, 0%–6%), laccase (0–2 U/g flour) and water absorption level (90%–100%) on gluten-free (GF) batter rheology and bread quality were analyzed. From viscoamylograph analysis, lower starch amount in GF flour due to MFAX addition decreased peak viscosity and retrogradation. Surface response plots showed that laccase did not have significant effect on GF batter rheology and bread quality, whilst water was the most important variable. Higher levels of water absorption benefited bread texture. Higher water level (>100 mL/100 g flour) was needed in the experimental design to evaluate correctly the effect of 6% MFAX replacement on GF bread quality. Further analyses were carried in order to adjust water absorption of batters according to their consistency index (K ≈ 100 Pa sⁿ), resulting an optimal water absorptions of 95%, 100% and 105% for control flour and flours supplemented with 3% or 6% MFAX, respectively. Thus, MFAX addition enhanced water-binding capacity of flour and yielded GF breads with higher specific volume and softer crumb texture. These quality parameters were best rated with 6% MFAX addition to flours. This research demonstrated the potential of MFAX to develop GF breads with improved quality, when optimal water level is used.     

Quality characteristics of northern-style Chinese steamed bread prepared from soft red winter wheat flours with waxy wheat flour substitution

Quality characteristics of northern-style Chinese steamed bread (CSB) prepared from two soft red winter (SRW) wheat flours blended with 0–30% waxy wheat flour (WWF) were analyzed to estimate the influence of starch amylose content. The increased proportion of WWF in blends raised mixograph absorption with insignificant changes in protein content and dough strength-related parameters. WWF incorporation generally increased specific volume and crumb softness of CSB. The analysis of covariance revealed that CSB quality attributes were little affected by protein content and dough strength-related parameters, indicating that starch amylose content was largely responsible for the changes in CSB quality. Flour blends with 5–10% WWF, of which starch amylose content was 22.4–24.7%, produced CSB with superior crumb structure compared to other blends, but insignificant changes in surface smoothness, stress relaxation and total score compared to the respective control wheat flours. Flour blends with 15% WWF to produce a starch amylose content of 21.4–22.7% exhibited reduced staling of CSB with total scores comparable to the respective control wheat flours. CSB prepared from blends with more than 10% WWF exhibited a higher soluble starch content, indicative of reduced starch retrogradation, than that prepared from wheat flours without WWF during storage for 3 days.     

Influence of Starch Granule Size Distribution on Bread Characteristics

The granule size distributions of starches isolated from eight bread wheat flours were determined. Breads were baked from the same flours by varying fermentation time, mixing speed and work input according to a central composite experimental design. Response surface equations were calculated for the bread characteristics loaf volume, weight, form ratio (height/width) and crumb firmness. Multivariate regression (PLS2) was used to relate the starch granule size distribution spectra to the coefficient matrices. The models obtained by PLS2 explained 55% and 48% of the total variance in the response surface coefficients for bread weight, and form ratio respectively, with correlation coefficients 0·74 and 0·69. No models were obtained for crumb firmness and loaf volume. The correlations obtained with the constant terms indicated that high weights and form ratios were promoted by small A-granules (size 12 μm). The effect of starch granule size distribution on the bread characteristics was modified by work input and mixing speed, while fermentation time had no effect.     

Studies on the baking properties of wheat: Pigeonpea flour blends

Pigeonpea flour was substituted at levels of 0, 5, 10, 15,20, 25% to wheat flour and whole wheat meal for bread andChapatti making, respectively. Blends were prepared up to50% for cookie making. Increasing levels of pigeonpeas inthe blends significantly increased the protein and mineralcontent of the baked products. The bread from 10%pigeonpea flour blend with 2–3% vital gluten and 0.5%SSL had high loaf volume and loaf quality. Blends containing 15% pigeonpea flour were acceptable for Chapatti and 30% pigeonpea flour with 0.25% SSL wereacceptable for cookie making.     

Lipids in bread making: Sources, interactions, and impact on bread quality

Lipids exhibit important functional properties in bread making, although they are present in lower levels than starch or protein. They originate from flour, in which they are endogenously present, or from added shortening and/or surfactants. This review discusses lipid sources and their interactions during the entire process of bread making from dough mixing to fermentation, proofing, baking and the stored product. The focus is on lipid interactions with starch and gluten proteins, their role in gas cell stabilisation and their impact on bread loaf volume, crumb structure and crumb firming. Widely accepted views on lipid functionality, although often opposing, are presented and critically discussed.     

The Role of Dextrins in the Stickiness of Bread Crumb made from Pre-Harvest Sprouted Wheat or Flour Containing ExogenousAlpha-Amylase

Dextrins were extracted in water from bread made from pre-harvest sprouted wheat or standard flour supplemented with exogenousalpha-amylases. The dextrins were separated by gel permeation chromatography and the dextrin content (% of crumb weight) determined for different degree of polymerisation (DP) size classes; DP 1–2, DP 3–10, DP 11–50, DP 51–200 and DP >200. There were significant correlations between the dextrin content in each size class and crumb stickiness (r=0·84–0·91, 22 df ). The most significant correlation (r=0·96) was between total dextrin content and crumb stickiness. Addition of dextrins of various DP ranges from various sources to standard flour produced bread with sticky crumb. Again, the degree of stickiness was generally related to the amount of total dextrin in the crumb and not to size distribution of dextrins. In this instance, extensive enzymic hydrolysis of starch was not necessary to produce sticky crumb; the dextrins caused crumb stickiness directly. Addition of dextrins to reconstituted gluten–starch flour produced bread with unexpectedly low dextrin levels and correspondingly low stickiness scores. It is concluded that, to produce sticky crumb, high levels of dextrin of any size are necessary in the crumb; a sticky mass is produced when dextrins dissolve in the excess «free» water that is normally «bound» to starch, gluten and other insoluble components of bread crumb.     

Rheological properties and baking performance of rye dough as affected by transglutaminase

Since protein aggregation and formation of a continuous protein matrix in rye dough is very limited, an enzyme-induced protein aggregation method to improve the baking properties was investigated. The effects of microbial transglutaminase (TG) on the properties of rye dough were studied by rheological tests, confocal laser scanning microscopy (CSLM), standard-scale baking tests and crumb texture profile analysis. Addition of TG in the range of 0-4000 Ukg⁻¹ rye flour modified the rheological properties of rye flour dough, resulting in a progressive increase of the complex shear modulus (|G∗|) and in a decrease of the loss factor (tan δ) due to protein cross-linking or aggregation. CLSM image analysis illustrated a TG-induced increase of the size of rye protein complexes. Standard baking tests showed positive effects on loaf volume and crumb texture of rye bread with TG applied up to 500 Ukg⁻¹ rye flour. Higher levels of TG (500 U ≤ TG ≤ 4000 U) had detrimental effects on loaf volume. Increasing TG concentration resulted in an increase of crumb springiness and hardness. In conclusion, the results of this work demonstrated that TG can be used to improve the bread making performance of rye dough by creating a continuous protein network.