Experimental approach to optimize the use of alpha-Amylases in breadmaking.

alpha-Amylases from different origins (wheat, malted barley, fungi, and bacteria) are used extensively to improve breadmaking. However, the enzyme activities, in addition to the differences associated with their origins, are strongly affected by the process conditions and the presence of other compounds in the medium. The activity of different alpha-amylases was tested under different conditions (pH and temperature), and in the presence of some bread ingredients (salt and sugar), some breadmaking additives (ascorbic acid and sodium propionate), and some metabolites (organic acids and saccharides) generated during the fermentation step, to envisage the behavior of these alpha-amylases during the breadmaking process. The alpha-amylase activities were affected to a different extent by the addition of these compounds depending on the enzyme origin. In general, the alpha-amylases from cereals (wheat and malted barley) were less sensitive to the presence of some ingredients, additives, and metabolites. These results show the great variation of the alpha-amylase activity with the process conditions and the importance of its knowledge in the selection of the appropriate alpha-amylase for a specific breadmaking process.     

Changes in Phytate Content in Whole Meal Wheat Dough and Bread Fermented with Phytase‐Active Yeasts

The degradation of inositol hexakisphosphate (IP6) was evaluated in whole meal wheat dough fermented with baker's yeast without phytase activity, different strains of Saccharomyces cerevisiae (L1.12 or L6.06), or Pichia kudriavzevii with extracellular phytase activity to see if the degradation of IP6 in whole meal dough and the corresponding bread could be increased by fermentation with phytase‐active yeasts. The IP6 degradation was measured after the dough was mixed for 19 min, after the completion of fermentation, and in bread after baking. Around 60–70% of the initial value of IP6 in the flour (10.02 mg/g) was reduced in the dough already after mixing, and additionally 10–20% was reduced after fermentation. The highest degradation of IP6 was seen in dough fermented with the phytase‐active yeast strains S. cerevisiae L1.12 and P. kudriavzevii L3.04. Activity of wheat phytase in whole meal wheat dough seems to be the primary source of phytate degradation, and the degradation is considerably higher in this study with a mixing time of 19 min compared with earlier studies. The additional degradation of IP6 by phytase‐active yeasts was not related to their extracellular phytase activities, suggesting that phytases from the yeasts are inhibited differently. Therefore, the highest degradation of IP6 and expected highest mineral bioavailability in whole meal wheat bread can be achieved by use of a phytase‐active yeast strain with less inhibition. The strain S. cerevisiae L1.12 is suitable for this because it was the most effective yeast strain in reducing the amount of IP6 in dough during a short fermentation time.     

Moderate decrease of pH by sourdough fermentation is sufficient to reduce phytate content of whole wheat flour through endogenous phytase activity

Whole wheat bread is an important source of minerals but also contains considerable amounts of phytic acid, which is known to impair their absorption. An in vitro trial was performed to assess the effect of a moderate drop of the dough pH (around 5.5) by way of sourdough fermentation or by exogenous organic acid addition on phytate hydrolysis. It was shown that a slight acidification of the dough (pH 5.5) with either sourdough or lactic acid addition allowed a significant phytate breakdown (70% of the initial flour content compared to 40% without any leavening agent or acidification). This result highlights the predominance of wheat phytase activity over sourdough microflora phytase activity during moderate sourdough fermentation and shows that a slight drop of the pH (pH value around 5.5) is sufficient to reduce significantly the phytate content of a wholemeal flour. Mg "bioaccessibility"of whole wheat dough was improved by direct solubilization of the cation and by phytate hydrolysis.     

Dough Properties and Bread Quality of Wheat–Barley Composite Flour as Affected by β‐Glucanase

Barley is rich in nutritionally positive compounds, but the quality of bread made of wheat–barley composite flours is impaired when a high percentage of barley is used in the mixture. A number of enzymes have been reported to be useful additives in breadmaking. However, the effect of β‐glucanase on breadmaking has scarcely been investigated. In this paper, the influence of different levels (0.02, 0.04, 0.06, and 0.08%, based on composite flour) of β‐glucanase (100,000 U/g) on the properties of dough and bread from 70% wheat, 30% barley composite flour were studied. Although dough development time, dough stability, and protein weakening value decreased after β‐glucanase addition, dough properties such as softness and elasticity as well as bread microstructure were improved compared with the control dough. β‐Glucanase also significantly improved the volume, texture, and shelf life of wheat–barley composite breads. The use of an optimal enzyme concentration (0.04%) increased specific volume (57.5%) and springiness (21%), and it reduced crumb firmness (74%) and staling rate. Bread with added β‐glucanase had a better taste, softness, and overall acceptability of sensory characteristics compared with the control bread. Moreover, the quality of wheat–barley composite bread after addition of 0.04% β‐glucanase was nearly equal to the quality of pure wheat bread. These results indicate that dough rheological characteristics and bread quality of wheat–barley composite flour can be improved by adding a distinct level of β‐glucanase.     

Contribution of wheat endogenous and wheat kernel associated microbial endoxylanases to changes in the arabinoxylan population during breadmaking

Wheat kernel associated endoxylanases consist of a majority of microbial endoxylanases and a minority of endogenous endoxylanases. At least part of these enzymes can be expected to end up in wheat flour upon milling. In this study, the contribution of both types of these endoxylanases to changes in the arabinoxylan (AX) population during wheat flour breadmaking was assessed. To this end, wheat flour produced from two wheat varieties with different endoxylanase activity levels, both before and after sodium hypochlorite surface treatment of the wheat kernels, was used in a straight dough breadmaking procedure. Monitoring of the AX population during the breadmaking process showed that changes in AX are to a large extent caused by endogenous endoxylanases, whereas the contribution of microbial endoxylanases to these changes was generally very low. The latter points to a limited contamination of wheat flour with microbial enzymes during milling or to an extensive inactivation of these wheat flour associated microbial endoxylanases by endoxylanase inhibitors, present in wheat flour. When all wheat kernel associated microbial endoxylanases were first washed from the kernels and then added to the bread recipe, they drastically affected the AX population, suggesting that they can have a large impact on whole meal breadmaking.     

Partial Purification of a Water-Extractable Rye (Secale cereale) Protein Capable of Improving the Quality of Wheat Bread

Rye water-soluble extracts contain a protein fraction that, when added at low concentrations to a straight-dough breadmaking recipe, significantly increased bread volume. Enrichment of the active component is possible by anion-exchange fractionation with diethylaminoethyl-cellulose (DEAE), by ammonium sulfate precipitation, or by using rye bran or shorts milling fractions as the starting material. The active material was not bound to DEAE-cellulose. With ammonium sulfate precipitation, the fractions obtained at 30, 40, and 50% saturation were active in straightdough baking experiments. Iso-electric focusing revealed that fractions active in breadmaking invariably contained alkaline protein fractions (pI > 7.5). Inactivation of enzyme material by boiling the water-soluble extract from rye destroyed all breadmaking activity. The activity of the bread improver was additive to that of potassium bromate but not to that of ascorbic acid. It was not counteracted by catalase, showing that it does not work by a mechanism involving the production of hydrogen peroxide. The extract was not able to overcome the detrimental effect on bread quality resulting from mixing dough in a nitrogen atmosphere.     

Differential recovery of lupin proteins from the gluten matrix in lupin-wheat bread as revealed by mass spectrometry and two-dimensional electrophoresis

Bread made from a mixture of wheat and lupin flour possesses a number of health benefits. The addition of lupin flour to wheat flour during breadmaking has major effects on bread properties. The present study investigated the lupin and wheat flour protein interactions during the breadmaking process including dough formation and baking by using proteomics research technologies including MS/MS to identify the proteins. Results revealed that qualitatively most proteins from both lupin and wheat flour remained unchanged after baking as per electrophoretic behavior, whereas some were incorporated into the bread gluten matrix and became unextractable. Most of the lupin α-conglutins could be readily extracted from the lupin-wheat bread even at low salt and nonreducing/nondenaturing extraction conditions. In contrast, most of the β-conglutins lost extractability, suggesting that they were trapped in the bread gluten matrix. The higher thermal stability of α-conglutins compared to β-conglutins is speculated to account for this difference.     

Fermented Sorghum as a Functional Ingredient in Composite Breads

Whole sorghum flour was fermented (a five‐day natural lactic acid fermentation) and dried under forced draught at 60°C, and evaluated for its effect on sorghum and wheat composite bread quality. In comparison with unfermented sorghum flour, fermentation decreased the flour pH from 6.2 to 3.4, decreased total starch and water‐soluble proteins, and increased enzyme‐susceptible starch, total protein, and the in vitro protein digestibility (IVPD). Fermentation and drying did not decrease the pasting temperature of sorghum flour, but slightly increased its peak and final viscosity. In comparison with composite bread dough containing unfermented sorghum flour, fermented and dried sorghum flour decreased the pH of the dough from 5.8 to 4.9, increased bread volume by ≈4%, improved crumb structure, and slightly decreased crumb firmness. IVPD of the composite bread was also improved. Mixing wet fermented sorghum flour directly with wheat flour (sourdough‐type process) further increased loaf volume and weight and reduced crumb firmness, and simplified the breadmaking process. It appears that the low pH of fermented sorghum flour inactivated amylases and increased the viscosity of sorghum flour, thus improving the gas‐holding capacity of sorghum and wheat composite dough. Fermentation of sorghum flour, particularly in a sourdough breadmaking process, appears to have considerable potential for increasing sorghum utilization in bread.     

Effect of cyclodextrin glycosyl transferase [corrected] on dough rheology and bread quality from rice flour

Gluten-free breads are usually characterized by deficient quality characteristics as compared to wheat breads. Problems related to volume and crumb texture are associated with gluten-free breads even when rice flour is used, which seems to be the best raw material for this type of bread. The potential use of cyclodextrin glycosyl transferase (CGTase) as a rice bread improver is presented. The effect of CGTase addition to rice flour on dough rheology and bread quality was investigated. In addition, an experimental design was developed to optimize the levels of CGTase, hydroxypropylmethylcellulose (HPMC), and oil. The addition of CGTase produced a reduction in the dough consistency and also in the elastic modulus. With regard to the rice bread quality, better specific volume, shape index, and crumb texture were obtained. The amount of cyclodextrins in the bread crumb was quantified to explain the action of this enzyme. The data indicate that the improving effect of the CGTase results from a combination of its hydrolyzing and cyclizing activities, the latter being responsible for the release of cyclodextrins, which have the ability to form complexes with lipids and proteins.     

Effect of Puroindolines on the Breadmaking Properties of Wheat Flour

The role of lipid-binding proteins from wheat seed (puroindolines) on the breadmaking properties of wheat flour was investigated by determining the relationship between breadmaking quality and puroindoline content in samples of 32 wheat cultivars. An inverse relationship was mainly explained by the link between hardness and puroindoline contents. This link is in agreement with previous results which have shown a close structural identity between basic friabilins and puroindolines. Next, the effect of puroindolines in breadmaking was investigated by performing reconstitution experiments with two puroindoline-free hard cultivars of opposite quality (Florence Aurore and Ecrin) as indicated in the screened wheat sample. Addition of 0.1% puroindolines to these flours drastically modified both the rheological properties of doughs and the structure of the bread crumb. Puroindolines are essential to the foaming properties of dough liquor, and a close relationship was found between the fine grain crumb provided by reconstituted flours with puroindolines and the fine structure of corresponding dough liquor foams. The effect of puroindolines on bread volume was mainly related to the rheological properties of wheat doughs.     

Combined effect of sourdough lactic acid bacteria and additives on bread firmness and staling

The effect of various sourdoughs and additives on bread firmness and staling was studied. Compared to the bread produced with Saccharomyces cerevisiae 141, the chemical acidification of dough fermented by S. cerevisiae 141 or the use of sourdoughs increased the volume of the breads. Only sourdough fermentation was effective in delaying starch retrogradation. The effect depended on the level of acidification and on the lactic acid bacteria strain. The effect of sourdough made of S. cerevisiae 141-Lactobacillus sanfranciscensis 57-Lactobacillus plantarum 13 was improved when fungal alpha-amylase or amylolytic strains such as L. amylovorus CNBL1008 or engineered L. sanfranciscensis CB1 Amy were added. When pentosans or pentosans, endoxylanase enzyme, and L. hilgardii S32 were added to the same sourdough, a greater delay of the bread firmness and staling was found. When pentosans were in part hydrolyzed by the endoxylanase enzyme, the bread also had the highest titratable acidity, due to the fermentation of pentoses by L. hilgardii S32. The addition of the bacterial protease to the sourdough increased the bread firmness and staling.     

Effect of the Coenzymes NAD(P)(H) in Straight‐Dough Breadmaking on Protein Properties and Loaf Volume

The nicotinamide adenine dinucleotide coenzymes [NAD(P)(H)] are strong redox agents naturally present in wheat flour, and are indispensable cofactors in many redox reactions. Hence, it is not inconceivable that they affect gluten cross‐linking during breadmaking. We investigated the effect of increasing concentrations of NAD(P)(H) on gluten cross‐linking, dough properties, and bread volume using two flours of different breadmaking quality. Separate addition of the four nicotinamide coenzymes did not significantly affect mixograph properties. While addition of NAD⁺ hardly affected bread volume, supplementation with NADP(H) and NADH significantly decreased loaf volumes of breads made using flour of high breadmaking quality. Wheat flour incubation with NAD(P)H under anaerobic conditions increased wheat flour thiol content, while NAD(P)⁺ increased the extractability in SDS‐containing medium of the protein of the strong breadmaking flour. Based on the results, it was hypothesized that at least three reactions, competing for NAD(P)(H), occur during breadmaking that determine the final effect on protein, dough, and loaf properties. Next to coenzyme hydrolysis, the experiments pointed to coenzyme oxidation and NAD(P)(H) dependent redox reactions affecting protein properties.     

Application of Pregerminated Brown Rice for Breadmaking

Pregerminated brown rice (PGBR) prepared by immersing in water was used for breadmaking, and effects on the dough properties and bread qualities were studied to compare with the ungerminated brown rice (BR). The substitution of BR or PGBR for wheat flour produced smaller specific volume in bread than in the control bread without BR or PGBR along with the increasing amount of substitution. However, the bread samples containing BR or PGBR suppressed staling during storage. The improving effect was especially obvious for substitutions of 10 and 20% PGBR as compared with BR. PGBR made viscous dough and retarded the staleness of bread compared with BR. γ‐Aminobutyric acid and oryzanol did not contain in the final BR and PGBR substituted bread, and phytic acid was decomposed ≈54 and 45% for 30% BR and 30% PGBR substituted breads, respectively. But ferulic acid was quite stable in the final baked product. As a result, substitution of PGBR for wheat flour improved the bread quality.     

麦麸酚基木聚糖对发酵面团特性和馒头品质的影响

为了提高麦麸的附加值、馒头的品质以及增强馒头的营养价值,该试验以小麦粉为原料,采用2个分子量的麦麸酚基木聚糖（820、581 kD）,研究不同添加量（0.25%、0.5%、1.0%、2.0%）对发酵面团特性以及馒头品质的影响。结果表明：随着麦麸酚基木聚糖添加量的增加,发酵面团的弹性模量、质子密度A22先增加后下降,黏性模量、质子密度A23增加,弛豫时间T22下降;馒头的亮度下降,红度和黄度增加,比容、黏聚性、回复性先增加后下降,硬度、咀嚼性先下降后上升,黏附性下降,馒头的感官得分先上升后下降。高分子量的麦麸酚基木聚糖,其发酵面团的弹性模量和黏性模量变幅较大,弛豫时间T22、T23较大、质子密度A21较小,低分子量的麦麸酚基木聚糖,其馒头比容和弹性较大,但馒头硬度和咀嚼性相对也较大。麦麸酚基木聚糖添加量在0.5%时,对发酵面团以及馒头品质改善效果最好。添加量在1.0%内,发酵面团特性以及馒头品质均可接受。高分子量的酚基木聚糖对发酵面团以及馒头品质改善效果高于低分子量的酚基木聚糖。研究结果为麦麸酚基木聚糖广泛应用于馒头中,提高馒头品质及营养价值提供理论依据。     

Restoration of Breadmaking Properties to Frozen Dough by Addition of Sugar and Yeast and Subsequent Processing

We prepared bread dough A (a mixture of wheat flour, sugar, salt, and water), bread dough B (a mixture of bread dough A and yeast), and bread dough C (first‐proofed, molded, and second‐proofed bread dough B) and froze them at –20°C for six days. They were thawed at 4°C for 16 hr and subjected to their breadmaking processes. The results indicated that breadmaking properties (bread height [mm] and specific volume [cm³/g]) after bread dough A and B processes were the same as those of control bread dough (unfrozen dough). However, in the case of bread dough C, the resulting bread showed depression of the properties. The amount of centrifuged liquid from thawed bread dough C increased. Sugar was added to thawed bread dough C (bread dough C‐1), and then yeast was further added to bread dough C‐1 (bread dough C‐2), and they were subjected to the breadmaking process. The results showed that the breadmaking properties of bread dough C‐2 were the same as those of the control. It was further found that when the first proof step in the bread dough C‐2 process was omitted, the breadmaking properties were depressed. Frozen and thawed bread dough C was packed into a plastic tube, and extension of the dough was compared with that of control dough under reduced pressure. Bread dough C extended to 50 mm, compared with 70 mm for control dough. First proof, mold, and second proof steps of dough C‐2 caused it to extend to the same height as control dough. It was concluded that the increased amount of the separated liquid in thawed dough C caused depression of breadmaking properties resulting from lack of water in the appropriate places to provide the expected properties, but these properties could be restored to the levels of control bread dough by the addition of sugar and yeast following the first proof, mold, and second proof steps.     

Variations in Amino Acid and Protein Contents of Wheat During Milling and Northern‐Style Steamed Breadmaking

To determine the variations of amino acid and protein during milling and steamed breadmaking, two types of wheat cultivars belonging to soft and hard wheat types were used. The results showed that losses occurred in 17 amino acids during milling. The mean loss of threonine (18.0%) was the highest, which was followed by proline (15.5%), methionine (15.1%), and histidine (15.1%). The losses of tyrosine and lysine were the lowest (8.1 and 9.7%, respectively). Losses were also found for 17 amino acids during steamed breadmaking. The highest loss was observed in alanine (17.1%), with tyrosine (12.5%) close behind, and leucine (4.3%) exhibiting the lowest loss. The mean protein contents for whole‐wheat meal, flour, and steamed bread prepared from the test materials were 15.25, 14.27, and 14.33%, respectively. This meant that protein content decreased during milling; however, a slight increase was observed during steamed breadmaking. Amino acid scores of lysine in whole‐wheat meal, flour, and steamed bread prepared from the test materials were 45.4, 41.0, and 38.2, respectively. The general trend in the variations of protein and amino acids was similar in the two wheat cultivars tested.     

Use of Two Endoxylanases with Different Substrate Selectivity for Understanding Arabinoxylan Functionality in Wheat Flour Breadmaking

A Bacillus subtilis endoxylanase (XBS) with a strong selectivity for hydrolysis of water‐unextractable arabinoxylan (WU‐AX) and an Aspergillus aculeatus endoxylanase (XAA) with a strong selectivity for hydrolysis of water‐extractable arabinoxylan (WE‐AX) were used in straight‐dough breadmaking with two European wheat flours. Dough, fermented dough, and bread characteristics with different levels of enzyme addition were evaluated with a strong emphasis on the arabinoxylan (AX) population. The WU‐AX solubilized by XBS during breadmaking were mainly released during mixing and had higher molecular weight, in contrast to their counterparts solubilized by XAA, which were mainly released during fermentation and had lower molecular weight. This coincided with increased loaf volume with XBS and a negative to positive loaf volume response with XAA. Bread firmness and dough extract viscosity also were affected by endoxylanase addition. Results confirmed that WU‐AX are detrimental for breadmaking, while WE‐AX and solubilized AX with medium to high molecular weight have a positive impact on loaf volume.     

Formation of dityrosine cross-links during breadmaking

To establish its significance during commercial breadmaking, dityrosine formation was quantified in flours and doughs of six commercial wheat types at various stages of the Chorleywood Bread Process. Dityrosine was formed mainly during mixing and baking, at the levels of nmol/g dry weight. Good breadmaking flours tended to exhibit a higher dityrosine content in the final bread than low quality ones, but no relationship was found for dityrosine as a proportion of flour protein content, indicating that the latter was still a dominant factor in the analysis. There was no correlation between gluten yield of the six wheat types and their typical dityrosine concentrations, suggesting that dityrosine cross-links were not a determinant factor for gluten formation. Ascorbic acid was found to inhibit dityrosine formation during mixing and proving, and it has no significant effect on dityrosine in the final bread. Hydrogen peroxide promoted dityrosine formation, which suggests that a radical mechanism involving endogenous peroxidases might be responsible for dityrosine formation during breadmaking.     

Molecular Weight Distribution of Proteins in Hard Red Spring Wheat: Relationship to Quality Parameters and Intrasample Uniformity

Molecular weight distribution (MWD) of proteins extracted from hard red spring wheat was analyzed by size‐exclusion HPLC to investigate associations with wheat and breadmaking quality characteristics. Certain protein fractions were related to associations between wheat and breadmaking parameters, specifically when effect of quantitative variation of protein on those parameters was statistically eliminated by partial correlation analysis. SDS‐unextractable high molecular weight polymeric proteins had positive partial correlations with percent vitreous kernel content and breadmaking parameters, including mix time and bread loaf volume. SDS‐extractable protein fractions that were eluted before the primary gliadin peak had positive partial correlations with kernel hardness and water absorption parameters. The proportion of main gliadin fractions in total protein had a negative partial correlation with bread loaf volume and positive correlations with kernel hardness and water absorption parameters. Intrasample uniformity in protein MWD and kernel characteristics was estimated from three kernel subsamples that were separated according to single kernel protein content within individual wheat samples by a single‐kernel near‐infrared sorter. Wheat subsamples were significantly different in protein MWD. Intrasample uniformity in protein MWD did not differ greatly among wheat samples.     

Protein Allelic Composition,Dough Rheology,and Baking Characteristics of Flour Mill Streams from Wheat Cultivars with Known and Varied Baking Qualities

Flour mill streams obtained by milling grain of 10 bread wheat cultivars grown in the Skopje region of Macedonia were analyzed for rheological and breadmaking quality characteristics and for composition of gliadins and HMW‐GS. The objective of this study was to examine the relationships between the composition of gluten proteins and breadmaking quality, as well as to determine the importance of gluten proteins for technological quality of flour mill streams. The grain was milled in an experimental mill according to a standardized milling procedure, with three break and three reduction passages. The addition of two vibratory finishers in the milling scheme enabled better separation of bran. A small‐scale baking method for evaluation of the breadmaking properties was developed, and electrophoretic methods including acid‐PAGE and SDS‐PAGE were used to determine the composition of the gluten proteins. There were significant differences in the degree of dough softening of individual and total flour fractions of the flour mill streams for cultivars with different alleles from six loci, for farinograph water absorption from seven loci, and for bread loaf volume and crumb quality score from six loci. The Glu‐1 quality scores for the wheat cultivars investigated were 3–9 and proved to be a useful indicator of breadmaking quality. The novel feature of the investigation related to the breadmaking potential of the flour mill streams compared with straight‐run flours.