Bread Dough Fermentation Research Articles

Composition of Polysaccharides in Hull-Less Barley Sourdough Bread and Their Impact on Physical Properties of Bread.

The complex of polysaccharides of the grain transforms during processing and modifies the physical and chemical characteristics of bread. The aim of the research was to characterize the changes of glucans, mannans and fructans in hull-less barley and wholegrain wheat breads fermented with spontaneous hull-less barley sourdough, germinated hull-less barley sourdough and yeast, as well as to analyze the impact of polysaccharides on the physical parameters of bread. By using the barley sourdoughs for wholegrain wheat bread dough fermentation, the specific volume and porosity was reduced; the hardness was not significantly increased, but the content of β-glucans was doubled. Principal component analysis indicates a higher content of β-glucans and a lower content of starch, total glucans, fructans and mannans for hull-less barley breads, but wholegrain wheat breads fermented with sourdoughs have a higher amount of starch, total glucans, fructans and mannans, and a lower content of β-glucans. The composition of polysaccharides was affected by the type of flour and fermentation method used.

Pesticides and gas production by baker's yeast in bread dough

SummaryPesticide residues might delay food fermentation. The aim of this study was to determine the effect of thirty‐one commercial pesticides (fourteen fungicides; eleven herbicides; one growth regulator; five insecticides) on the fermentative activity of baker's yeast in bread dough and sugared water. Yeast gas production after 3 h at 38 °C in dough or water was slightly inhibited by 10 mg kg−1 of a herbicide containing glufosinate‐ammonium and 100 mg kg−1 of fungicides with tebuconazole or metconazole. At the highest level assayed, 1000 mg kg−1, more than one‐third of the thirty‐one pesticides assayed did not impair baker's yeast gas production. Yeast cells were not inhibited by 300 mg active ingredients kg−1 in a mix of the pesticides, a concentration unlikely to be present in dough considering existing application rates in the field. Dough protected baker's yeast from pesticide residues. In sugared water, sub‐inhibitory concentrations of pesticides stimulated yeast fermentative activity. We conclude that it is unlikely that pesticide residues would impair baker's yeast gas production during bread dough fermentation.

Effect of Nitrogen Source on Growth Endophytic Yeast from Salacca edulis Reinw. and Bread Quality Analysis

east biomass is often used in the fermentation of bread dough. Dough fermentation can be maximized by adding a nitrogen source. This study used yeast isolates from salak pondoh (YIS-3, YIS-4, and YIS-7). The purpose of this study was to determine the effect of nitrogen addition on yeast growth and bread quality. This study used an experimental approach. The results of the growth study showed that all isolates treated with 0.05% urea produced higher biomass and cell counts than those treated with control. The highest biomass was produced by YIS-7, which was 3.81 g/300mL, while the highest number of cells was produced by YIS-3, which was 29.02x106 cells/mL. The percentage of proofing results showed that all yeast isolates treated with 0.05% urea needed a longer time to achieve the highest proofing. However, the volume of bread after baking showed better results than those treated with control. The largest volume of bread produced by YIS-3, was 972.14 cm3. The results of the organoleptic test showed that P<5%, which means that all treatments had a significant effect on the taste, aroma, color, and texture of the bread. Overall, the panelists gave good acceptance of the bread fermented by YIS-3 with 0.05% urea treatment. So it can be concluded that the addition of urea with a concentration of 0.05% in YIS-3 gave the best effect on the yeast growth and bread quality.

Biotechnological Importance of Torulaspora delbrueckii: From the Obscurity to the Spotlight

Torulaspora delbrueckii has attracted interest in recent years, especially due to its biotechnological potential, arising from its flavor- and aroma-enhancing properties when used in wine, beer or bread dough fermentation, as well as from its remarkable resistance to osmotic and freezing stresses. In the present review, genomic, biochemical, and phenotypic features of T. delbrueckii are described, comparing them with other species, particularly with the biotechnologically well-established yeast, Saccharomyces cerevisiae. We conclude about the aspects that make this yeast a promising biotechnological model to be exploited in a wide range of industries, particularly in wine and bakery. A phylogenetic analysis was also performed, using the core proteome of T. delbrueckii, to compare the number of homologous proteins relative to the most closely related species, understanding the phylogenetic placement of this species with robust support. Lastly, the genetic tools available for T. delbrueckii improvement are discussed, focusing on adaptive laboratorial evolution and its potential.

Small Differences in SUC Gene Sequences Impact Saccharomyces cerevisiae Invertase Activity and Specificity toward Fructans with Different Chain Lengths.

Saccharomyces cerevisiae (S. cerevisiae)invertase is encoded by a family of closely related SUC genes. To identify and understand the molecular basis for differences in substrate specificity, we examined 29 SUC alleles from industrialS. cerevisiaestrains and cloned alleles with small sequence differences into an invertase-negative strain. Our study showed that an F102Y substitution in Suc-enzymes lowers yeast invertase activity toward fructo-oligosaccharides (FOS) by 36% and the specificity factor by 43%. By contrast, an A409P substitution in Suc-enzymes resulted in an increased capacity of the yeast to hydrolyze FOS and Fibruline by 17 and 41%, respectively, likely because of a change in the loop conformation resulting in a wider active site. Bread dough fermentation experiments revealed that sucrose and fructan hydrolysis during fermentation is influenced by this natural variation in SUC sequences. Our research thus opens the door for the selection or engineering of yeasts and Suc-enzymes with specific activities that may ultimately allow controlling fructan hydrolysis.

Changes in structure and solubility of wheat arabinoxylan during the breadmaking process

Arabinoxylans (AXs) are the major nonstarch polysaccharides of wheat. AX functionality is essential for many wheat flour-based products, including pan bread. Regarding the quality of pan bread, the primary focus has been on protein content and quality. However, AX may play an important role in the end-product quality of pan bread. To understand the role that AX plays in the quality of pan bread, the chemical and structural changes of AX during bread preparation and dough fermentation were studied. Flour from three wheat varieties (Bolles, Glenn, and Elgin-ND) was used, and samples were taken at seven stages during the breadmaking process. Changes in AX solubility, AX substitution rate, and fine structure of AX were evaluated. The solubility of AX increased significantly (P < 0.05) during mixing and fermentation, but was significantly (P < 0.05) lower in the bread. The degree of xylose substitution also changed significantly (P < 0.05) during mixing and/or fermentation. There were also changes to the substitution pattern that indicated structural changes to AX during the fermentation process. Flour properties, such as xylanase activity and the initial structural and functional properties of AX, could impact changes to AX occurring during the fermentation and baking process. The flour samples used in this study had similar protein contents, but differed in dough properties and AX structure. Overall, there were substantial changes in the AX of wheat flour during bread processing. The changes to AX could have a great impact on dough functionality and the end-product quality of pan bread.

Enhanced iron absorption from lactic acid fermented bread (an in vivo/ex vivo study)

Dietary modification to increase iron bioavailability is an effective strategy to compensate nutritional iron deficiency. In this study, we investigated the effect of lactic acid fermentation of bread dough on iron absorption in Caco-2 cells and serum ferritin in rat. Four types of bread were prepared: ordinary bread; bread + iron; bread + iron + Lactobacillus acidophilus (L. acidophilus) and finally, bread + L. acidophilus. For in vivo study, 24 rats were divided into four groups and fed with each type of bread. Serum ferritin level was measured after 30 days. For ex-vivo study, each type of bread was digested and added to the Caco2 cells and ferritin formation in the cells was assessed. The results were showed that by adding L. acidophilus to the dough, ferritin formation increased significantly compared to controls in the intestinal cells (in vitro) and animal serum (in vivo). According to the results, iron absorption from iron fortified lactic acid fermented bread could be increased and due to that iron fortified lactic acid fermented bread, possibly being a simple and low cost supplement for iron deficiency anaemic patients.

Investigating the impact of α-amylase, α-glucosidase and glucoamylase action on yeast-mediated bread dough fermentation and bread sugar levels

Wheat flour is generally supplemented with α-amylases to increase maltose levels in bread dough and increase loaf volume. While the preference of yeast for glucose and fructose over maltose as substrate for fermentation is well documented, the impact of maltose versus glucose producing enzymes on bread dough fermentation kinetics and bread sugar levels is ill documented. Hence the impact of α-amylase, α-glucosidase and glucoamylase action on both aspects was investigated. Glucoamylase and α-amylase increase the total fermentable sugar content of dough, while α-glucosidase only affects the glucose/maltose ratio. Due to their effect on total fermentable sugar levels, addition of α-amylase or glucoamylase prolongs the total productive fermentation time, while this is not the case for α-glucosidase. In contrast to α-amylase, both glucoamylase and α-glucosidase supplementation leads to higher CO2 production rates during the initial stages of fermentation. In the final bread product, different sugar levels are observed depending on the dosage and type of starch-degrading enzyme. The results of this study imply that long and short fermentation processes benefit from α-amylase and α-glucosidase addition, respectively, while glucoamylase supplementation is suitable for both long and short fermentation times.

Establishing the relative importance of damaged starch and fructan as sources of fermentable sugars in wheat flour and whole meal bread dough fermentations

It is generally believed that maltose drives yeast-mediated bread dough fermentation. The relative importance of fructose and glucose, released from wheat fructan and sucrose by invertase, compared to maltose is, however, not documented. This is surprising given the preference of yeast for glucose and fructose over maltose. This study revealed that, after 2h fermentation of wheat flour dough, about 44% of the sugars consumed were generated by invertase-mediated degradation of fructan, raffinose and sucrose. The other 56% were generated by amylases. In whole meal dough, 70% of the sugars consumed were released by invertase activity. Invertase-mediated sugar release seems to be crucial during the first hour of fermentation, while amylase-mediated sugar release was predominant in the later stages of fermentation, which explains why higher amylolytic activity prolonged the productive fermentation time only. These results illustrate the importance of wheat fructan and sucrose content and their degradation for dough fermentations.

Gluten weight in ancient and modern wheat and the reactivity of epitopes towards R5 and G12 monoclonal antibodies

SummaryDifferences in the level of coeliac‐active gluten epitopes in wheat might have some significance for individuals reporting noncoeliac gluten sensitivity. The aim of this study was to compare the reactivity of epitopes towards ELISA R5 and G12 monoclonal antibodies in ancient (emmer; Khorasan wheat; spelt) and modern wheat (common bread wheat; durum), and to check whether the bread‐making process leads to the degradation of epitopes. Data from ELISA R5 and G12 did not match gluten dry weight in wheat. Bread dough fermentation and extensive baking did not change the reactivity of coeliac‐active epitopes towards monoclonal antibodies. Compared to hexaploid bread‐type wheat (spelt; common bread wheat), ancient and modern pasta‐type tetraploid wheat (emmer; Khorasan; durum) had less epitopes reactive towards ELISA R5 and G12 and might be preferable for wheat‐sensitive individuals looking for food with reduced coeliac‐active epitopes.

Metabolite Analysis Allows Insight into the Differences in Functionality of 25 Saccharomyces cerevisiae Strains in Bread Dough Fermentation

During dough fermentation, yeast (Saccharomyces cerevisiae) changes the physical properties of the dough matrix. In this study, we investigate if different yeast strains have an impact on dough rheology and on the gas holding capacity of fermenting dough. Furthermore, we analyze whether observed differences are linked to the metabolite profiles of the yeast strains. More specifically, the impact of 25 yeast strains on dough spread, dough fermentation properties, and dough metabolite profile was analyzed. Our results demonstrate large differences in the fermentation ability and metabolite profile of the 25 strains. Analysis of metabolites in fermented dough confirmed that acetic acid and succinic acid are likely responsible for the lowering of dough pH during fermentation and that the onset of CO2 release from dough is related to dough pH rather than to the volume of CO2 within the dough. Our results further suggest that the spread test is an inadequate tool to quantify rheological differences observed for strains with different fermentation profiles.

Glycerol production by fermenting yeast cells is essential for optimal bread dough fermentation.

Glycerol is the main compatible solute in yeast Saccharomyces cerevisiae. When faced with osmotic stress, for example during semi-solid state bread dough fermentation, yeast cells produce and accumulate glycerol in order to prevent dehydration by balancing the intracellular osmolarity with that of the environment. However, increased glycerol production also results in decreased CO2 production, which may reduce dough leavening. We investigated the effect of yeast glycerol production level on bread dough fermentation capacity of a commercial bakery strain and a laboratory strain. We find that Δgpd1 mutants that show decreased glycerol production show impaired dough fermentation. In contrast, overexpression of GPD1 in the laboratory strain results in increased fermentation rates in high-sugar dough and improved gas retention in the fermenting bread dough. Together, our results reveal the crucial role of glycerol production level by fermenting yeast cells in dough fermentation efficiency as well as gas retention in dough, thereby opening up new routes for the selection of improved commercial bakery yeasts.

Contribution of the tricarboxylic acid (TCA) cycle and the glyoxylate shunt in Saccharomyces cerevisiae to succinic acid production during dough fermentation

Succinic acid produced by yeast during bread dough fermentation can significantly affect the rheological properties of the dough. By introducing mutations in the model S288C yeast strain, we show that the oxidative pathway of the TCA cycle and the glyoxylate shunt contribute significantly to succinic acid production during dough fermentation. More specifically, deletion of ACO1 and double deletion of ACO1 and ICL1 resulted in a 36 and 77% decrease in succinic acid levels in fermented dough, respectively. Similarly, double deletion of IDH1 and IDP1 decreased succinic acid production by 85%, while also affecting the fermentation rate. By contrast, double deletion of SDH1 and SDH2 resulted in a two-fold higher succinic acid accumulation compared to the wild-type. Deletion of fumarate reductase activity (FRD1 and OSM1) in the reductive pathway of the TCA cycle did not affect the fermentation rate and succinic acid production. The changes in the levels of succinic acid produced by mutants Δidh1Δidp1 (low level) and Δsdh1Δsdh2 (high level) in fermented dough only resulted in small pH differences, reflecting the buffering capacity of dough at a pH of around 5.1. Moreover, Rheofermentometer analysis using these mutants revealed no difference in maximum dough height and gas retention capacity with the dough prepared with S288C. The impact of the changed succinic acid profile on the organoleptic or antimicrobial properties of bread remains to be demonstrated.

Critical assessment of the formation of hydrogen peroxide in dough by fermenting yeast cells

Fermentation of bread dough leads to strengthening of the dough matrix. This effect has previously been ascribed to the action of hydrogen peroxide (H2O2) produced by yeast in dough. In this study, we re-evaluate the production of H2O2 by yeast in dough and aqueous fermentation broth. Results show that the previously reported high levels of H2O2 in fermenting dough were most probably due to the lack of specificity of the potassium dichromate/acetic acid-based method used. Using the chemiluminescent HyPerBlu assay, no yeast H2O2 production could be detected in fermented dough or broth. Even though the formation of low levels of H2O2 cannot be ruled out due to the presence of catalase in flour and the fast reaction of H2O2 with gluten proteins, our results suggest that the changes in dough matrix rheological properties upon fermentation are not due to production of H2O2 by yeast.

Formation of Melatonin and Its Isomer during Bread Dough Fermentation and Effect of Baking

Melatonin is produced mainly by the pineal gland in vertebrates. Also, melatonin and its isomer are found in foods. Investigating the formation of melatonin and its isomer is of importance during bread dough fermentation and its degradation during baking since bread is widely consumed in high amounts. Formation of melatonin was not significant during dough fermentation. The melatonin isomer content of nonfermented dough was found to be 4.02 ng/g and increased up to 16.71 ng/g during fermentation. Lower amounts of isomer in crumb and crust than dough showed that the thermal process caused a remarkable degree of degradation in melatonin isomer. At the end of the 180 min fermentation Trp decreased by 58%. The results revealed for the first time the formation of a melatonin isomer in bread dough during yeast fermentation.

Continuous monitoring of bread dough fermentation using a 3D vision Structured Light technique

Fermentation of the dough is an important phase in the bread-making process which is affected by several important factors related to raw materials and processing. Changes in fermentation affect parameters in the final product, such as texture, palatability and general quality. For this reason, it is important to develop dynamic methods to study this phase. In this work, a 3D vision system based on Structured Light (SL) was used to monitor the fermentation phase. The evolution of the dough was studied employing 10 wheat flours with non-physicochemical and rheological differences. However, differences in dough behaviors during fermentation were found based on SL method parameters. When the variation of the total transversal area was related to the maximum height at each fermentation time a set of peaks and valleys appeared. These sets were directly related to the fermentation capacity. Specifically, a lower number of peaks during the main fermentation time (100min) is related to wheat flours with high fermentation capacity. Consequently, the proposed SL Technique could be used as a method to check the fermentation capacity of wheat flours according to their fermentation behavior.

Harvesting yeast (Saccharomyces cerevisiae) at different physiological phases significantly affects its functionality in bread dough fermentation

Fermentation of sugars into CO2, ethanol and secondary metabolites by baker's yeast (Saccharomyces cerevisiae) during bread making leads to leavening of dough and changes in dough rheology. The aim of this study was to increase our understanding of the impact of yeast on dough related aspects by investigating the effect of harvesting yeast at seven different points of the growth profile on its fermentation performance, metabolite production, and the effect on critical dough fermentation parameters, such as gas retention potential. The yeast cells harvested during the diauxic shift and post-diauxic growth phase showed a higher fermentation rate and, consequently, higher maximum dough height than yeast cells harvested in the exponential or stationary growth phase. The results further demonstrate that the onset of CO2 loss from fermenting dough is correlated with the fermentation rate of yeast, but not with the amount of CO2 that accumulated up to the onset point. Analysis of the yeast metabolites produced in dough yielded a possible explanation for this observation, as they are produced in different levels depending on physiological phase and in concentrations that can influence dough matrix properties. Together, our results demonstrate a strong effect of yeast physiology at the time of harvest on subsequent dough fermentation performance, and hint at an important role of yeast metabolites on the subsequent gas holding capacity.

Dynamics of the Saccharomyces cerevisiae Transcriptome during Bread Dough Fermentation

The behavior of yeast cells during industrial processes such as the production of beer, wine, and bioethanol has been extensively studied. In contrast, our knowledge about yeast physiology during solid-state processes, such as bread dough, cheese, or cocoa fermentation, remains limited. We investigated changes in the transcriptomes of three genetically distinct Saccharomyces cerevisiae strains during bread dough fermentation. Our results show that regardless of the genetic background, all three strains exhibit similar changes in expression patterns. At the onset of fermentation, expression of glucose-regulated genes changes dramatically, and the osmotic stress response is activated. The middle fermentation phase is characterized by the induction of genes involved in amino acid metabolism. Finally, at the latest time point, cells suffer from nutrient depletion and activate pathways associated with starvation and stress responses. Further analysis shows that genes regulated by the high-osmolarity glycerol (HOG) pathway, the major pathway involved in the response to osmotic stress and glycerol homeostasis, are among the most differentially expressed genes at the onset of fermentation. More importantly, deletion of HOG1 and other genes of this pathway significantly reduces the fermentation capacity. Together, our results demonstrate that cells embedded in a solid matrix such as bread dough suffer severe osmotic stress and that a proper induction of the HOG pathway is critical for optimal fermentation.

English

Although starch is the main polysaccharide used in the fermentation of bread dough, wheat flour also contain some non-starch polysaccharides such as pentosans or hemicelluloses, which may contribute up to 3% of the total polysaccharide content of the flour. Despite being present in relatively low amounts, pentosans and hemicelluloses play an important role in dough rheology and bread properties. The aim of this work is to understand how the xylanases from Aspergillus niger and Trichoderma sp. influence dough rheology, such as elasticity, extensibility, strength and stability. When the extensograph parameters such as extensibility (E) and elasticity (R) were determined, it was possible to note that all dosages of xylanase from A. niger were capable of decreasing the dough elasticity in 21%. Depending on the dosage, the xylanase from Trichoderma sp. can decrease dough stability in the mixing and, consequently, the mixing time during the process. An increased dosage of Trichoderma xylanase decreased the elasticity in 32% and increased the extensibility by 8% following 45 min. It was also observed that raising dosages of Trichoderma xylanase in flour content affected the dough rheology more significantly than raising dosages of A. niger xylanase .

Sourdough Technology-A Traditional Way for Wholesome Foods: A Review

Abstract: In the present era, consumers wish to have a wide range of foods that are nutritious and flavorful and have long shelf life without added preservatives. Sourdough is an important modern fermentation of cereal flours and water based upon an earlier spontaneous process. The sourdough microflora is dominated by lactic acid bacteria and, along with yeast, they play a key role in the fermentation of bread dough. Factors that affect the quality of sourdough are dough yield, temperature, type of starter culture, acidity of the medium, and the substrate. Sourdough is classified into 3 types (Types I, II, and III); the most widely used for commercial production is Type III. The sourdough fermentation has a number of beneficial effects that include prolonged shelf life, accelerated volume gain, delayed staling, improved bread flavor, and good nutritional value. Sourdough also improves sensory characteristics such as loaf volume, evenness of baking, color, aroma, taste, and texture of breads. Sourdough has been reported to contribute to extended shelf life by inhibiting spoilage bacteria and mold growth.