Effect of fermentation on content,molecule weight distribution and viscosity of β-glucans in oat sourdough

This study investigated the effect of fermentation on the physicochemical properties of β-glucans in oat sourdough. Sourdoughs were produced from oat using homo-fermentative lactic acid bacteria, Lactobacillus plantarum 22134. The contents of total β-glucan and soluble β-glucan, the molecular weight (MW) of β-glucan and the viscosity of the extracted β-glucans were determined at 0, 4, 8, 10 and 12 h of fermentation. The total β-glucan content decreased from 4.89% to 4.23% after 12 h of fermentation. The soluble β-glucan concentration increased from 1.89% to 2.18% and then decreased to 1.97% after 8 h of fermentation. The content of β-glucans with MW > 10⁵ decreased from 0 to 4 h of fermentation, followed by an increase and then a decrease after 8 h. The oat sourdough fermented for 8 h had high viscosity, which could be more beneficial for health and bread texture quality, especially for gluten-free breads.     

Optimization of ingredients and baking process for improved wholemeal oat bread quality

Baking technology for tasty bread with high wholemeal oat content and good texture was developed. Bread was baked with a straight baking process using whole grain oat (51/100 g flour) and white wheat (49/100 g four). The effects of gluten and water content, dough mixing time, proofing temperature and time, and baking conditions on bread quality were investigated using response surface methodology with a central composite design. Response variables measured were specific volume, instrumental crumb hardness, and sensory texture, mouthfeel, and flavour. The concentration and molecular weight distribution of β-glucan were analysed both from the flours and the bread. Light microscopy was used to locate β-glucan in the bread. Proofing conditions, gluten, and water content had a major effect on specific volume and hardness of the oat bread. The sensory crumb properties were mainly affected by ingredients, whereas processing conditions exhibited their main effects on crust properties and richness of the crumb flavour. β-glucan content of oat bread was 1.3/100 g bread. The proportion of the highest molecular weight fraction of β-glucan was decreased as compared with the original β-glucan content of oat/wheat flour. A great part of β-glucan in bread was located in the large bran pieces.     

Acrylamide–asparagine relationship in baked/toasted wheat and rye breads

Acrylamide in baked and toasted wheat and rye bread was studied in relation to levels of asparagine in flour, dough, bread and toasts. Asparagine was consumed during bread preparation resulting in reduced acrylamide content in the products. In wheat bread, 12% of the asparagine initially present in the flour (0.14 g kg^?1) remained after yeast fermentation and baking; for rye bread, 82% of asparagine remained after sourdough fermentation and baking. Asparagine present in untoasted wheat bread had totally reacted after hard toasting. Toasted wheat and rye bread slices contained 11–161 and 27–205 µg kg^?1 acrylamide, respectively, compared to untoasted wheat and rye bread with <5 and 7–23 µg kg^?1 acrylamide, respectively. The dietary intake of acrylamide from bread (untoasted) of 2 µg day^?1 is relatively low; however, acrylamide exposure from bread increases several fold for people eating toasted bread.     

Probabilistic methodology for assessing changes in the level and molecular weight of barley β-glucan during bread baking

The objective of this study was to create a probabilistic model to assess changes in the levels and molecular weight (Mw) of β-glucan during the bread baking process using Monte Carlo simulation techniques. Three different composite flours were formulated by substituting wheat flour (WF) with barley whole meal flour (BWMF), barley straight grade flour (BSGF) or barley fibre rich fraction (BFRF). The β-glucan level in the flour increased significantly (by approximately 10-fold) when barley was substituted for WF. The baking process resulted in approximately a 47–48% reduction in the β-glucan level in the baked bread (base-line model). The base-line model observed ∼25% and 7% reduction in high molecular weight (HMw) and medium molecular weight (MMw), respectively and a subsequent increase in low molecular weight (LMw). The analysis also showed the importance of various steps involved in bread baking, such as mixing time (Mt), fermentation time (Ft) and baking (BGloss), on the level and Mw of β-glucan in baked breads. A parallel experimental validation study provided confidence in model predictions of β-glucan levels. This study aids in optimising the various unit operations involved in the bread baking process to give a final product with increased nutritional qualities.     

A Modelling Approach to Estimate the Level and Molecular Weight Distribution of β-Glucan During the Baking of an Oat-Based Bread

Oat and oat products containing β-glucans are associated with many health claims. Both the level and molecular weight of β-glucans play an important role in determining the physiological efficacy of β-glucan in terms of health benefits, including reducing blood cholesterol levels. The objective of this study was to develop a probabilistic model to investigate the effect of various process stages in bread making on the level of β-glucan (BG) and its molecular weight (Mw) distribution using Monte Carlo simulation techniques. Various composite flours were formulated by substituting wheat flour (WF) with oat whole flour (OWF), oat refined flour (ORF), oat bran (OB) or rolled oats (RO). The baseline model predicted an overall mean reduction of 49% in BG in baked bread. The mean Mw of β-glucan in all composite flours was reduced following processing and baking from 1.22 to 0.77 × 10⁶ (g/mol) for OWF + WF, 1.07 to 0.68 × 10⁶ (g/mol) for ORF + WF, 1.17 to 0.75 × 10⁶ (g/mol) for OB + WF and 1.25 to 0.80 × 10⁶ (g/mol) for RO + WF. In all formulated breads, high molecular weight β-glucan was observed to be more susceptible to degradation compared with medium molecular weight and to lower molecular weight. A sensitivity analysis highlighted the negative influence of WF on β-glucan content and the BG reduction with fermentation time. The scenario analysis showed a positive influence on the level of BG with increase addition of oat flour in all formulated breads. The model was validated with experimental data and values were found to be within the confidence interval of predicted BG levels. This model facilitates the optimisation of various steps in the bread making process and highlights the potential for oat flour to improve the nutritional quality of baked bread.     

Application of Bifidobacteria as Starter Culture in Whole Wheat Sourdough Breadmaking

This investigation is aimed at developing a new cereal-based product, with increased nutritional quality, by using Bifidobacterium pseudocatenulatum ATCC 27919 as starter in whole wheat sourdough fermentation and evaluating its performance. Four different sourdough levels (5%, 10%, 15%, and 20% on flour basis) in bread dough formulation were analysed. The effects of the use of bifidobacteria in sourdough bread were comparatively evaluated with controls (yeast and/or chemically acidified sourdough with antibiotics). The sourdough and dough fermentative parameters analysed were pH, total titratable acidity, d/l-lactic and acetic acids. Bread performance was evaluated by specific volume, slice shape, crumb structure and firmness, crust and crumb colour, pH, total titratable acidity, and d/l-lactic and acetic acids, phytate, and lower myo-inositol phosphate contents. The sourdough breads showed similar technological quality to the control sample, with the exception of specific bread volume (decreased from 2.46 to 2.22 mL/g) and crumb firmness (increased from 2.61 to 3.18 N). Sourdough inoculated with bifidobacteria significantly increased the levels of organic acids in fermented dough and bread. The Bifidobacterium strain contributed to the fermentation process, increasing phytate hydrolysis during fermentation owing to the activation of endogenous cereal phytase and its own phytase, resulting in bread with significantly lower phytate levels (from 7.62 to 1.45 μmol/g of bread in dry matter). The inclusion of sourdough inoculated with bifidobacteria made possible the formulation of whole wheat bread with positive changes in starch thermal properties and a delay and decrease in amylopectin retrogradation.     

Expression and characterization of β-1,3-1,4-glucanase of Aspergillus usamii in Escherichia coli and its application in sourdough bread making

A β-1,3-1,4-glucanase gene (Auglu12A) from Aspergillus usamii was successfully expressed in Escherichia coli BL21(DE3). The recombinant enzyme, reAuglu12A was efficiently purified using the one-step nickel-nitrilotriacetic acid affinity chromatography. The specific activity of reAuglu12A was 694.8 U/mg, with an optimal temperature of 55°C and pH of 5.0. The reAuglu12A exhibited stability at temperatures up to 60°C and within the pH range of 4.0–5.5. The reAuglu12A hydrolytic activity was increased in the presence of metal ions, especially K⁺ and Na⁺, whereas it exhibited a K_m and V_max of 8.35 mg/mL and 1254.02 µmol/min/mg, respectively, toward barley β-glucan at pH 5.0 and 55°C. The addition of reAuglu12A significantly increased the specific volume (p < 0.05) and reduced crumb firmness and chewiness (p < 0.05) of wheat–barley sourdough bread during a 7-day storage period compared to the control. Overall, the quality of wheat–barley sourdough bread was improved after incorporation of reAuglu12A (especially at 3000 U/300 g). These changes were attributed to the synergistic effect of acidification by sourdough and its metabolites which provided a conducive environment for the optimal action of reAuglu12A in the degradation of β-glucans of barley flour in sourdough. This stabilized the dough structure, thereby enhancing the quality, texture, and shelf life of the bread. These findings suggest that reAuglu12A holds promise as a candidate for β-glucanase application in the baking industry.     

Effects of two barley β-glucan isolates on wheat flour dough and bread properties

The effects of wheat flour fortification with two different molecular weight barley β-glucan isolates (1.00 × 10⁵, BG-100 and 2.03 × 10⁵, BG-200) on the rheological properties of dough and bread characteristics, using flours from two wheat cultivars that differ in their breadmaking quality, have been examined. The farinograph water absorption of doughs and the moisture content and water activity of the breads increased with increasing β-glucan content; the β-glucan isolate with the higher molecular weight (BG-200) exerted a greater effect than did BG-100. The addition of β-glucans to the dough formula increased the development time, the stability, the resistance to deformation and the extensibility of the poor breadmaking quality doughs, as well as the specific volumes of the respective breads, exceeding even that of the good breadmaking cultivar. Furthermore, the colour of the bread crumbs got darker and their structure became coarser, whereas the bread crumb firmness decreased with increasing level of β-glucan addition. Generally, the BG-200 was more effective in increasing the specific bread volume and reducing the crumb firmness, especially when used to fortify the poor breadmaking quality flour. The results further indicate a requirement for optimisation of the fortified doughs (level and molecular size of the β-glucan) to maximise bread quality attributes (loaf volume, texture, and staling events).     

Optimization of sourdough process for improved sensory profile and texture of wheat bread

The aim of the study was to determine optimum sourdough process conditions for improved flavour and texture of wheat bread. The influence of process conditions and the starter culture on the characteristics of wheat sourdough bread was established by using response surface methodology. Influence of fermentation temperature (16-32 °C), ash content of flour (0.6-1.8 g/100 g), and fermentation time (6-20 h) were considered as independent factors and their effects were studied in sourdough bread fermented with Lactobacillus plantarum, Lactobacillus brevis, Saccharomyces cerevisiae or with a combination of yeast and lactic acid bacteria. Intensity of sensory attributes, specific volume and bread hardness were considered as the main responses. Ash content of flour and fermentation time were the main factors determining the intensity of sensory attributes. The possibility to enhance intensity of overall flavour, aftertaste and roasted flavour without excessive pungent flavour and without reduced fresh flavour in wheat bread containing 20 g sourdough/100 g of wheat dough was demonstrated by choosing e.g. Lb. brevis for a starter and by utilization of high ash content of flour, long fermentation time and reduced temperature. Bread specific volume was improved 0.2-0.5 ml/g and hardness was reduced (after 4 days of storage) up to 260 g by using low ash content of flour and by optimizing fermentation time according to the microbial strain. Lactic acid fermentation had more profound influence on both desired and undesired flavour attributes, as well as textural features of bread in comparison with yeast fermentation.     

Exploitation of buckwheat sourdough for the production of wheat bread

This study investigates the exploitation of buckwheat sourdough for the production of wheat bread. The fermentation induced extensive hydrolysis of buckwheat main storage proteins, but did not influence the total protein, starch and polyphenols content of buckwheat. Buckwheat sourdough was incorporated at 10 and 20?% (w/w) in wheat dough, and control doughs were produced with the addition of a chemically acidified (CA) buckwheat batter. The addition of buckwheat sourdough greatly affected the rheological properties of the dough, by inducing a strengthening of the gluten network and decrease in elasticity. The acidification of wheat dough also stimulated the baker’s yeast activity during proofing, resulting in higher release of CO₂ in shorter times (volume of CO₂ released (ml), control dough, 1,671.5; dough with 10?% sourdough, 2,600; dough with 10?% chemically acidified dough, 2,715.5). The properties of wheat bread were enhanced by the addition of 10?% buckwheat sourdough, which led to higher specific volume (control, 3.41?ml/g; bread with 10?% sourdough, 4.03?ml/g) and softer crumb (crumb hardness, control, 5.28?N; bread with 10?% sourdough, 3.93?N). On the other hand, the higher acidification level did not influence the bread volume, but slightly hardened the crumb (crumb hardness, bread with 20?% sourdough, 7.41?N; bread with 20?% chemically acidified dough, 6.48?N). The fermentation positively influenced the nutritional properties of buckwheat flour and wheat bread, in terms of polyphenols (control bread, 8.84?mg GAE/100?g; bread with 10 and 20?% sourdough, 17.83 and 18.20?mg GAE/100?g, respectively) and phytic acid contents. Incorporation of buckwheat sourdough also led to an extension in the shelf life of wheat bread, which became more evident for the higher addition level. Overall, the results of this study suggest that buckwheat sourdough represents a suitable tool for enhancing the overall quality and nutritional properties of wheat bread.     

From wheat sourdough to gluten‐free sourdough: a non‐conventional process for producing gluten‐free bread

Gluten‐free (GF) sourdough was prepared from wheat sourdough and analysed both in fresh (GFS) and dried forms (DGFS). The gluten content in each GF sourdough sample was <20 mg kg^?1. The dough leavening capacity and the properties of the bread samples were investigated and compared to those of bread prepared using bakery yeast (Saccharomyces cerevisiae). Two commercial rice‐based mixtures (different for the presence/absence of buckwheat flour) were used to prepare bread samples. In GFS, lactic acid bacteria (LAB) and yeasts were found in amounts corresponding to 10⁸ and 10⁷ CFU g^?1, respectively, whereas both LAB and yeasts were detected in lower amounts (about 10⁶ CFU g^?1) in DGFS. When used in bread‐making, both GFS types produced significant dough acidification and exhibited good dough development during proofing, resulting in loaves with specific volume values between 3.00 and 4.12 mL g^?1, values similar to those obtained for reference bread (3.05÷4.15 mL g^?1). The use of GFS was effective in lowering the bread staling rate during storage for up to 7 days.     

Dietary exposure assessment of β-glucan in a barley and oat based bread

The objective of this study was to develop a β-glucan human exposure assessment model for a barley and a oat based bread and to compare the resulting exposure to the current FDA recommendation for a health promoting effect (3 g β-glucan/day, 0.75 g/portion of β-glucan). Three formulated barley and oat based breads with 30% (S1), 50% (S2) and 70% (S3) substitution of wheat flour were used in the Monte Carlo simulation model to predict human consumption levels. The level of soluble β-glucan was found to reach 0.77 g/portion for some barley and oat based breads with a substitution level of S3. Under normal consumption patterns, consumption of barley based bread can meet up to 50% of the FDA recommended intake with S1, 70% with S2, and 100% with S3, whereas by consuming an oat based bread the FDA recommended intake is met 30% with S1, 50% with S2 and 70% with S3. The model predicted that total cholesterol (TC) lowered with an increase intake of β-glucan content from ?0.27 to ?0.30 mmol/l and ?0.18 to ?0.29 mmol/l from S1 to S3 for barley and oats based bread, respectively. No significant change was noted for the blood glucose level.     

Release of free ferulic acid and changes in antioxidant properties during the wheat and rye bread making process

Changes in the free ferulic acid (FFA) contents and antioxidant properties during bread making processes were determined. Experimental breads were produced from whole meal and white wheat and rye flours, and fermented using either baker’s yeast or sourdough starter. Sourdough fermented bread contained the highest content of FFA. Release of occurred mainly during dough fermentation. A further increase in the ferulic acid content in the bread crumb and a decrease in the crust was observed. Total antioxidant properties of sourdough bread, defined as the sum of lipophilic and hydrophilic compound activities, were significantly (p<0.05) higher than for yeast bread. Sourdough bread contained more methanol soluble phenolic compounds, proteins, tocochromanols, and oxidized products of fatty acids than yeast bread. The equilibrium between the anti- and pro-oxidative compound contents resulted in similar antioxidant properties for bread using both types of fermentation, and to results observed for the flour used for baking.     

Influence of water and barley β-glucan addition on wheat dough viscoelasticity

The effects of the addition of two barley β-glucan isolates (0.2–1.0% of wheat flour), differing in molecular weight, and water (53–63% in a poor breadmaking wheat flour, cv. Dion, and 58–68% in a good breadmaking wheat flour, cv. Yekora) on the viscoelastic properties of wheat flour doughs were investigated. A response surface model (CCF) was used to evaluate the effects observed on the dynamic and creep-recovery parameters of the dough. The evaluation was done separately for each combination of β-glucan isolate (BG1 of ～10⁵ Da and BG2 of ～2 × 10⁵ Da) and flour type. Besides the contents of β-glucan and water, the molecular size of the polysaccharide and the flour quality were important determinants of the dough’s viscoelastic behavior. Compared to BG1, the higher molecular weight β-glucan (BG2) brought about major changes on all the rheological responses of the fortified doughs. The addition of appropriate levels of β-glucans and water in the poor breadmaking cultivar (Dion) doughs could yield similar viscoelastic responses to those observed by a non-fortified good breadmaking quality flour dough (Yekora).     

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

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

Fundamental study on the effect of hydrostatic pressure treatment on the bread-making performance of oat flour

The use of sourdough in wheat and rye breads has been extensively studied; however, little is known about its potential effect when baking oat bread. Consequently, the impact of sourdough on oat bread quality was investigated. Two different sourdoughs were prepared from wholegrain oat flour without the addition of starter cultures, by continuous propagation at 28 (SD 28) or 37 °C (SD 37) until the composition of the lactic acid bacteria remained stable. The dominant LAB were identified by sequence analysis of the 16S rDNA isolated from pure cultures. LAB from SD 28 belonged to the species Leuconostoc argentinum, Pedicoccus pentosaceus and Weissella cibaria, while Lactobacillus coryniformis dominated SD 37. The isolated LAB were further used as starter cultures for the production of oat sourdoughs. Fundamental rheology revealed softening of the sourdoughs compared to non-acidified and chemically acidified controls, which could not be attributed to proteolytic activity. Incorporation of oat sourdough into an oat bread recipe resulted in significantly increased loaf-specific volume as well as improved texture, independent of addition level or sourdough type. Overall, the results of this study show that sourdoughs containing lactic acid bacteria isolated from oats have the potential to enhance oat bread quality.     

Acrylamide-asparagine relationship in baked/toasted wheat and rye breads

Acrylamide in baked and toasted wheat and rye bread was studied in relation to levels of asparagine in flour, dough, bread and toasts. Asparagine was consumed during bread preparation resulting in reduced acrylamide content in the products. In wheat bread, 12% of the asparagine initially present in the flour (0.14 g kg(-1)) remained after yeast fermentation and baking; for rye bread, 82% of asparagine remained after sourdough fermentation and baking. Asparagine present in untoasted wheat bread had totally reacted after hard toasting. Toasted wheat and rye bread slices contained 11-161 and 27-205 microg kg(-1) acrylamide, respectively, compared to untoasted wheat and rye bread with <5 and 7-23 microg kg(-1) acrylamide, respectively. The dietary intake of acrylamide from bread (untoasted) of 2 microg day(-1) is relatively low; however, acrylamide exposure from bread increases several fold for people eating toasted bread.     

Evaluation of Leuconostoc citreum HO12 and Weissella koreensis HO20 isolated from kimchi as a starter culture for whole wheat sourdough

Leuconostoc citreum HO12 and Weissella koreensis HO20 isolated from kimchi were evaluated as starter cultures in the making of whole wheat sourdough bread. After 24 h of fermentation at 25 °C, both lactobacilli grew to the final cell numbers of ca. 10⁹ cfu/g dough, and both doughs had similar pHs and total titratable acidities. In addition, the fermentation quotient of the dough with Lc. citreum HO12 was slightly lower than that of the dough with W. koreensis HO20 (1.6 versus 2.8). Sourdoughs and bread with 50% sourdough produced with the starter cultures exhibited consistent ability to retard the growth of bread spoilage fungi (Penicillium roqueforti and Aspergillus niger) and rope-forming bacterium (Bacillus subtilis). Sourdough breads underwent a significant reduction in bread firming during storage. It seems that both lactobacilli have the potential to improve the shelf-life of wheat bread. The results indicate that the selected lactobacilli have unique fermentation characteristics and produce sourdough breads with overall satisfactory quality.     

Effect of Lactobacillus brevis-based bioingredient and bran on microbiological,physico-chemical and textural quality of yeast-leavened bread during storage

The effects of wheat bran and of a Lactobacillus brevis-based bioingredient (LbBio), obtained after growth in flour-based medium, on quality of yeast-leavened wheat bread (WWB) were investigated. Bran was used in bread formulation by substituting a part (20 g/100 g) of white wheat flour (WBB), while LbBio was used instead of the water content (WWB + LbBio and WBB + LbBio). The use of LbBio in WWB resulted in the biological acidification of the dough due to lactic, phenyllactic and OH-phenyllactic acid contents determining a high fermentation quotient value and an improved bread texture and microbiological quality. Conversely, wheat bran reduced the specific volume and crumb hardness during storage at 25 °C, and affected the antibacterial ability of LbBio during 30 °C storage. Our findings demonstrated that LbBio counteracted the negative effects of bran and allowed to obtain an enriched fibre bread with specific volume and soft crumb comparable to bread without bran.Industrial relevanceBread is a perishable food with a short microbiological and physico-chemical shelf-life. The main microbiological alteration occurring into few days after baking is the “rope spoilage” caused by spore-forming bacteria originating from raw materials. This phenomenon, often misinterpreted as a sign of unsuccessful dough leavening and not visible from outside, is more common under industrial production conditions during the hot season causing large economic losses in the warm climates of Mediterranean countries, Africa and Australia. The use of sourdough often controls this alteration even if the industrial application of this traditional process is limited by the long leavening times. In this study, an innovative procedure for the preparation of yeast-leavened bread comprising the addition of a fermentation product from Lactobacillus brevis grown in a flour-based medium has been applied. The resulting fermentation product (LbBio bioingredient) acts as a sourdough acidifying the dough and improving the textural, physico-chemical and microbiological properties of the resulting bread. The application of bioingredient LbBio could represent an innovative strategy in industrial bread production to obtain acidified yeast-leavened products, thus, preventing the ropy spoilage and reducing the negative effects of bran addition.     

Influence of the addition of lupin sourdough with different lactobacilli on dough properties and bread quality

The aim of this research was to study the effects of solid‐state fermentation (SSF) with Lactobacillus sakei, Pediococcus pentosaceus and P. acidilactici on lupine sourdough parameters and lupine sourdough influence on the physical dough properties and wheat bread quality. The results showed that lactic acid bacteria (LAB) significantly reduced the pH and increased total titratable acidity (TTA) of SSF lupine. The highest protease activity in lupine is excreted by L. sakei (187.1 ± 8.6 PU g^?1), and the highest amylase activity, by P. pentosaceus (155.8 ± 7.5 AU g^?1). Lupine sourdough has a significant effect on the rheological properties of doughs, which affect the baking characteristics of the final product. In conclusion, it can be said that L. sakei, P. pentosaceus and P. acidilactici could be used for lupine SSF, and the addition of up to the 10% SSF lupine products increases the wheat–lupine bread quality.