Wheat Sourdough Research Articles

Rheological Changes in Wheat Sourdough During Controlled and Spontaneous Fermentation

ABSTRACTThe changing rheological characteristics of wheat doughs during fermentation at 30°C for 72 hr were measured using a controlled stress rheometer. Dynamic oscillation tests were performed at frequencies ranging from 0.01 to 10 Hz. Wheat sourdoughs (dough yield 200) were prepared with a mixed starter culture containing typical hetero‐ and homofermentative sourdough lactic acid bacteria. Results from the controlled fermentation process were compared to results from spontaneous fermentation. Maximum phase angle values, especially at low frequencies, were closely related to total gas production in the doughs. Complex viscosity decreased during fermentation and reached lower final values for doughs without starter culture. Heating characteristics of doughs after various fermentation times were measured at temperatures ranging from 30 to 80°C. The highest values for complex viscosity were found at ≈65°C. When heated, fermented doughs produced weaker gels than fresh doughs. The temperatures at which these maxima occurred increased significantly with fermentation time for spontaneously fermented dough.

Flavour of sourdough wheat bread crumb

This study investigates the effect of adding sourdough to wheat bread dough on the production of flavour compounds in wheat bread crumb. The sourdoughs were fermented with starter cultures of lactic acid bacteria alone and in combination with sourdough yeasts. The volatile compounds in the bread crumb were isolated by a dynamic headspace technique and extraction analysis, analysed by gas chromatography (GC), and identified on the basis of GC retention times for reference compounds and mass spectrometry (MS). The chemical analyses were combined with sensory evaluation. The volume of the loaves increased significantly when the doughs had 5–20% sourdough added compared with the control bread (bread without sourdough). In the sourdough bread, the content of acetic acid, 2-methylpropanoic acid, and 3-methylbutanoic acid was generally higher, and loaves made with the addition of sourdoughs fermented withLactobacillus plantarum, L. delbrueckii, orL. sanfrancisco had a higher content of 2- or 3-methyl-1-butanol than control bread. Interactions were seen between the starter cultures and the sourdough yeasts, and the production of the following compounds was increased depending on the starter culture used and on the sourdough yeast: ethanol, 2-methylpropanol, 2/3-methyl-1-butanol, 2-phenylethanol, benzyl alcohol, acetic acid, 2-methylpropanoic acid, and 3-methylpropanoic acid. Bread made with an addition of 5% to 15% sourdough fermented withL. sanfrancisco had a pleasant, mild and sour odour and taste.L. plantarum bread had a strong, sour and unpleasant odour and a metallic sour taste with a sour aftertaste, but when the sourdough was also supplemented with the sourdough yeastSaccharomyces cerevisiae, the bread attained a more aromatic wheat bread flavour, which may be caused, in part, by a higher content of 2/3-methyl-1-butanol, 2-methylpropanoic acid, 3-methylbutanoic acid and 2-phenylethanol.

The sourdough microflora Microbiological, biochemical and breadmaking characteristics of doughs fermented with freeze-dried mixed starters, freeze-dried wheat sourdough and mixed fresh-cell starters

Freeze-dried mixed starters, freeze-dried wheat sourdough and mixed fresh-cell starters made withLactobacillus sanfrancisco CBI,L. plantarum DC400 andSaccharomyces cerevisiae 141 and/orS. exiguus M14 were used for leavening wheat doughs, and their microbiological, biochemical and breadmaking characteristics were compared with those of Italian traditional doughs produced by baker's yeast. All the doughs fermented with starters had more balanced microbiological and biochemical characteristics than dough started with baker's yeast in which alcoholic fermentation end-products largely predominated. By using starters, the greatest lactic acid bacteria cell number and acetic acid production, were achieved, along with more complete profiles of volatile compounds and greater structural stability of fermented doughs. Fresh-cell starters showed higher microbial functionality and represented the only way to enrich the doughs withS. exiguus M14, some of which survived the freeze-drying process. No differences were detected between the two different types of freeze-dried starters and the subsequent use (10 times) of doughs initially produced with freezedried starters eliminated initial differences in the microbial functionality with respect to fresh-cell starters.

Effects of formulation and processing conditions on easily extractable lipid and nitrogen components of wheat sourdoughs

SummaryThe changes in free lipid (neutral lipids, glycolipids, and phospholipids) and extractable nitrogen (amino acids, peptides, and proteins) components of unyeasted and yeasted wheat sourdoughs started with Lactobacillus plantarum B‐39 were investigated in samples under different processing conditions. A central composite surface response design was used with factor analysis to investigate the effect of flour extraction rate (ash content), added water, presence or absence of yeast, and fermentation temperature on readily extractable lipid and nitrogen components. Absolute values for extractable protein and non‐protein components were highly correlated with ash content of flour (factor 1); whereas phospholipids and neutral lipids were closely connected with added water (factor 2). Sixty sourdoughs were classified into three groups: 1) high‐ash fermented sourdoughs produced high (>350 mg kg−1) total non‐protein amino nitrogen and medium (<3 mg g−1) lipid levels; mid‐ash flour doughs had lower levels of both components; 2) low‐ash fermented sourdoughs produced low (<300 mg kg−1) levels of amino acids and peptides and medium lipids levels, and 3) unfermented sourdoughs had low (<250 mg kg−1) levels of non‐protein nitrogen components and most made with lowash flour had medium lipid levels; most made with medium and high‐ash flours had high (>4 mg g−1) neutral lipid levels and were largely separated from the low‐ash group. The most promising sourdoughs for bread were those with low added water, fermented from higher ash flour with maximum levels of extractable amino acids, peptides and proteins and medium to high polar and neutral lipid levels.

Volatile compound and organic acid productions by mixed wheat sour dough starters: influence of fermentation parameters and dynamics during baking

Lactobacillus brevis subsp. lindneri CB1, Lactobacillus plantarum DC400 and Saccharomyces cerevisiae 141 or Saccharomyces exiguus M14 were used as starters to produce wheat sour dough breads. Sour doughs with higher relative percentage of yeast fermentation products (1-propanol, 2-methyl-1-propanol, 3-methyl-1-butanol and ethanol) and with higher total peak area of volatile compounds, or with a more complete profile (higher amounts of ethylacetate and lactic and acetic acids, and the presence of carbonyl compounds) were produced by the associations between lactic acid bacteria (LAB) and S. cerevisiae 141 or S. exiguus M14, respectively. Low temperature (25°C) and sour dough firmness (dough yield 135) were appropriate for LAB souring activities but limited yeast metabolism. Raising the temperature to 30°C and semi-fluid sour doughs gave more complete volatile profiles. Flour ash content from 0·55–1% positively influenced the total amount of volatiles and lactic and acetic acid productions. While at 3 h the sour dough was mainly characterized by iso-alcohols, an increase of leavening time up to 9 h gave a total amount of volatiles about three times higher than that at 5 h and strengthened the LAB contribution. The additions of fructose and citrate to the dough enhanced the acetic acid and volatile synthesis by LAB, respectively. After baking, the ethanol disappeared, 2-methyl-1-propanal was synthetized, lactic and acetic acids remained constant, the total amount of volatiles was reduced to a level <12·5% of the initial and an increase in the relative percentage of iso-alcohols and aldehydes was detected. The differences attributed to the two mixed starters were maintained after baking. A comparison between amino acid and volatile profiles before and after baking showed the influence of amino acids on the formation of volatiles during baking.

Volatile compound and organic acid productions by mixed wheat sour dough starters: influence of fermentation parameters and dynamics during baking

Lactobacillus brevis subsp. lindneri CB1, Lactobacillus plantarum DC400 and Saccharomyces cerevisiae 141 or Saccharomyces exiguus M14 were used as starters to produce wheat sour dough breads. Sour doughs with higher relative percentage of yeast fermentation products (1-propanol, 2-methyl-1-propanol, 3-methyl-1-butanol and ethanol) and with higher total peak area of volatile compounds, or with a more complete profile (higher amounts of ethylacetate and lactic and acetic acids, and the presence of carbonyl compounds) were produced by the associations between lactic acid bacteria (LAB) and S. cerevisiae 141 or S. exiguus M14, respectively. Low temperature (25°C) and sour dough firmness (dough yield 135) were appropriate for LAB souring activities but limited yeast metabolism. Raising the temperature to 30°C and semi-fluid sour doughs gave more complete volatile profiles. Flour ash content from 0·55–1% positively influenced the total amount of volatiles and lactic and acetic acid productions. While at 3 h the sour dough was mainly characterized by iso-alcohols, an increase of leavening time up to 9 h gave a total amount of volatiles about three times higher than that at 5 h and strengthened the LAB contribution. The additions of fructose and citrate to the dough enhanced the acetic acid and volatile synthesis by LAB, respectively. After baking, the ethanol disappeared, 2-methyl-1-propanal was synthetized, lactic and acetic acids remained constant, the total amount of volatiles was reduced to a level

Effect of processing conditions on acidification properties of wheat sour doughs

The pH, total titratable acidity (TTA) and lactic and acetic acids production have been investigated for wheat sour doughs with and without yeast addition, inoculated with two strains of Lactobacillus plantarum (B33, B39). To study the effect of flour extraction rate (0.54, 11.11 and 1.68% ash content), dough yield (DY) (160, 200 and 240 of sour dough/100 g flour), and fermentation temperature (25, 30 and 35°C) a response surface regression, factor analysis and K-means clustering analysis were used. • Results from factor analysis point out that the extraction rate of flour governs TTA and acetic acid content; this factor accounts for the 53% of variability of the data. Dough yield is highly correlated with lactic acid content, explaining 27% of the total variance. Finally, temperature explains the remaining 16% of variation, but it is not related to any analytical variable. From K-means clustering analysis, flour extraction rate of 1.68% ash content leads to the highest TTA and acetic acid values, whereas DY of 240 g sour dough/100 g flour gives the greatest lactic acid content, and DY of 160 leads to the lowest levels of TTA and organic acids .

Influence of Wheat Flour Type on the Production of Flavour Compounds in Wheat Sourdoughs

Abstract The influence of wheat flour type on the production of flavour compounds in wheat sourdoughs was investigated in sourdoughs fermented with four strains of lactic acid bacteria. The acidification of the sourdoughs and the production of lactic acid were influenced mainly by the flour type, with most lactic acid produced in sourdoughs made from low-grade flour and wholemeal flours. The production of volatile flavour compounds, including acetic acid, in the sourdoughs depended primarily on the starter culture used. An interaction between the starter culture and the flour type was observed for some of the flavour compounds, however. The flour type had a significant effect on the production of ethyl acetate and ethanol in sourdoughs fermented with heterofermentative cultures, with the highest amounts detected in sourdoughs made from wholemeal flour and low-grade flour.

Volatile compounds in wheat sourdoughs produced by lactic acid bacteria and sourdough yeasts

The content of volatile compounds in wheat sourdoughs fermented with four different starter cultures of the genusLactobacillus was compared with those in chemically acidified doughs. Sourdoughs as well as chemically acidified doughs were also combined with four different sourdough yeasts to investigate the effect of adding yeasts on the production of volatiles. The volatile compounds in the doughs were isolated by a dynamic headspace technique, analysed by gas chromatography (GC), and identified on the basis of GC retention times for reference compounds and mass spectrometry. Few volatile compounds were identified in the chemically acidified doughs compared to the sourdoughs. The content of volatile compounds in the sourdoughs varied with the starter culture used. Ethanol and ethyl acetate were produced in the highest amounts in sourdoughs fermented with heterofermentative cultures, especiallyL. sanfrancisco. Apart from ethanol,n-hexanol was the dominating alcohol in all the sourdoughs. The content of other compounds was low. When sourdough yeasts were added to the sourdoughs, the number and amount of volatile compounds increased. The content of ethanol, 2-methyl-propanol and 2/3-methyl-1-butanol was highest in the sourdoughs with addedSaccharomyces cerevisiae, whereas the ethyl acetate content was highest in the sourdoughs with added strain A. The content of esters other than ethyl acetate was low. The carbonyls acetoin and diacetyl were produced in small amounts in the sourdoughs with the addition of strain A.

Effect of processing conditions on oligosaccharide profile of wheat sourdoughs

Oligosaccharide profiles in yeasted and unyeasted wheat sourdoughs inoculated withLactobacillus plantarum have been investigated. A surface response design (central composite design structure) has been used to study the effect of flour extraction rate (0.54, 1.11 and 1.68% ash content), dough yield (160, 200, and 240) and fermentation temperature (25, 30 and 35°C). Unfermented and 20 h fermented doughs were evaluated. Multivariate data analysis was used to analyse the data. Unfermented doughs contained variable amounts of glucose, fructose and maltose, but oligosaccharides with a degree of polymerization (DP) over 3 were not detected. The greatest levels of monosaccharides corresponded to yeasted sourdoughs from brown flours prepared at 30 and 35°C. Factor analysis of fermented sourdoughs showed three factors explaining 83% variability of the data. The first factor (43% variance explained) was directly related to oligosaccharides with a DP above 5, and inversely related to maltose content. Factor two (27%) was related to DP 3 and DP 4, and the third factor (16%) to glucose and fructose levels. The greatest quantities of maltose corresponded to white unyeasted sourdoughs, and the highest amounts of monosaccharides corresponded to brown unyeasted samples. On the other hand, yeasted sourdoughs contained higher amounts of oligosaccharides with DP 3 to DP 5. Samples of white flour, low consistency, yeasted and fermented at ≧30°C showed the biggest content of DP 6 and DP 7.

Amino Acid Profiles of Fermenting Wheat Sour Doughs

ABSTRACTThe free amino acid patterns of unfermented and fermented wheat sour doughs started with Lactobacillus plantarum were related by factor analysis to dough yield, ash content of flour, fermentation temperature and presence/absence of yeast, from data corresponding to a central composite design of samples. Individual levels of hydrophobic, acid and basic amino acids as well as total amino acid content positively correlated with extraction rate of flours. The presence of yeast promoted metabolism of histidine, aspartic acid and asparagine, particularly in samples made with whole and wholemeal flours. Proliferation of predominant amino acids by enzymatic release was more notable at higher fermentation temperatures and wholemeal samples. Sour doughs with maximum levels of hydrophobic and basic amino acids were started with no yeast bacterial cultures, made with whole and wholemeal flours and fermented at 35°C.

Biochemical characteristics and breadmaking performance of freeze-dried wheat sour dough starters

Four mixtures (I–IV) of pure yeasts (Sacharomyces cerevisiae, S.fructuum andCandida boidinii) and/or lactobacilli (Lactobacillus brevis andL.plantarum) were inoculated into wheat sourdoughs, which after 18 h fermentation time were freeze-dried and used as starters (DS). Before their addition to wheat doughs they were rehydrated and reactivated. Besides DS (20% flour basis), bread dough contained instant active dry yeast (0.6%). Biochemical characteristics (production of organic acids, evolution of sugars and headspace composition), and breadmaking performance (fermentative and rheological properties and bread quality) of these doughs were investigated and compared with control doughs (C) without DS. Doughs with DS showed lower gassing power, and pH, and higher total titratable acidity (TTA) than C. The dough level in the maturogram reached maximum values for C and DS (IV) with only lactic acid bacteria. Doughs with DS (IV) also led to lower values for extensibility, and higher resistance to extension in the extensigram. The dynamics of glucose and fructose were faster during fermentation of doughs with DS than for C. The lactic and acetic acid levels were higher in DS-containing doughs, but ethanol and ethyl acetate contents were greater for C. Some bread characteristics (volume, density, pH, TTA, organic acids and sugar contents) were similar for all DS samples, and, except for sugars, significantly differed from those of C. Generally, sensory bread scores were higher for DS breads than for C, mainly for loaf shape, volume, edibility and overall acceptance. Starters I and IV, with the same composition of lactobacilli, showed a similar performance over starters II, III, and C.

Controlled production of acetic acid in wheat sour doughs

Sour doughs are characterized by their pH value, their total amount of titratable acidity (TTA) and their fermentation quotient (FQ=mol ratio lactic acid/acetic acid). At comparable TTA, the FQ may evidently affect the sensory properties and the shelf life of breads. Therefore, attention should be directed to controlling FQ by enhancing or suppressing the production of acetic acid. Over a limited range, this is possible by setting to appropriate levels the process parameters temperature and dough yield. Alteration the availability of the hydrogen acceptor (via fructose or invert sugar supply) is another way of influencing the FQ directly by shifting the heterolactic pathway from the ethanol to the acetate branch and vice versa. The objective of this investigation was to combine the effects of dough yield and temperature with those of fructose supply in order to improve the control of FQ. The central composite design was used to arrange the experiments to quantify the effects of temperature (25–40° C), dough yield (180–320) and fructose supply (0–10 g/100 g flour) on fermentations of sour dough started withLactobacillus brevis 25 a. In this way, it was possible to modulate the FQ levels between 0.9 and 4.5. The results indicate, that temperature has no significant effect, and that fructose is more efficient in influencing the FQ than dough yield. No interactive effects were detected.

Evolution of biochemical and rheological characteristics and breadmaking quality during a multistage wheat sour dough process

The evolution of some biochemical (acetic and lactic acid contents, fermentation quotient and changes in mono-, di-, and trisaccharides), rheological and fermentative characteristics (extensigram, maturogram and impulsogram) and bread quality (volume, density, texture, and degree of acidification) during a multistage wheat sour dough process have been investigated. Acetic acid contents of sour doughs (SD), bread doughs (BD) and breads (B) increased with the increase in number of processing stages. Lactic acid followed similar trends in SD, but in BD and B it reached maximum levels during the third stage. SD contained higher amounts of acids than BD and B. Dynamics of sugars followed patterns according to the fermentative activity and microflora evolution in the different steps. An improvement as the number of SD stages increased was observed in rheological and fermentative properties of BD, such as in oven spring. A positive effect on B characteristics (volume, density, texture, and acidity) was also observed. The last stage of the SD process led to the best final product, with noticable differences in relation to those occurring with a smaller number of stages.

Microbiological aspects of wheat sour-dough

Microbiological aspects of wheat sour-dough