The microflora of sourdough. XVIII. The protein degrading capabilities of lactic acid bacteria in sourdough

Acidification of the dough by the use of sourdough or acidifiers is necessary not only for good baking quality of rye flour but it is also very important for development of the typical sensory characteristics of rye bread. We confirmed that the lactic acid bacteria of sour dough are proteolytic. Proteolytic effects are observed in the increase of the amino acid content during fermentation. A marked increase was found in the content of leucine, alanine, valine, isoleucine, glutamic acid, glutamine, arginine, lysine, methionine, phenylalanine, tyrosine and serine. Lactobacillus plantarum showed a higher proteolytic activity than L. brevis ssp. lindneri or L. fructivorans.     

Defined multi-species semi-liquid ready-to-use sourdough starter

This paper aimed at setting up a protocol for the manufacture of a defined multi-species semi-liquid ready-to-use sourdough starter consisting of lactic acid bacteria (LAB) selected on the basis of their capacity of rapid acidification and adaptation to several technological factors. Preliminarily, 56 strains of sourdough LAB were screened based on the acidification kinetics during sourdough fermentation. The influence of temperature (25-37 degrees C), NaCl (2%, w/w, of wheat flour), initial cell number (10(7)-10(9) cfu g(-1)), dough yield (150-180), substrate for cell cultivation (mMRS or SDB media) and phase of cell growth (exponential or stationary phases) on the kinetics of acidification was also determined. Lactobacillus casei DPPMA27, Weissella confusa DPPMA20 and Lactobacillus fructivorans DPPMA8 were selected and used to produce a defined multi-species semi-liquid sourdough starter. Fermentation was carried out in a 2l batch fermentation bioreactor (12 h at 37 degrees C), under controlled pH, by cultivating cells in a medium made of water (60%), flour and other nutrients (40%). The semi-liquid sourdough starter was stored for 30 days under different conditions and used for dough fermentation (dough yield 160). The microbial composition, acidifying activity and fermentation end-products were kept constant during 21 days of storage. The findings of this study may be useful to increase the use of sourdough in bakery industries.     

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.     

Comparison of the effect of exopolysaccharide-producing lactic acid bacteria from sourdough on dough characteristics and steamed bread quality

The use of exopolysaccharide (EPS)-producing lactic acid bacteria (LAB) is promising in sourdough fermentation. However, the knowledge of the effects of various species of LAB on steamed bread making remains limited. In this study, the effects of two LAB with high EPS-producing capacity, namely Weissella cibaria L32 and Lactobacillus brevis L17 on dough fermentation and steamed bread quality were estimated. The addition of these two LAB strains significantly increased the titratable acidity and protease activity during the dough fermentation, especially L. brevis L17. Although the in situ EPS synthesised by LAB could improve the steamed bread quality, excessive acidification of L. brevis L17 would still increase the protease activity and thus destroy its gluten network structure. As a result, the steamed bread fermented with L. brevis L17 had the lowest specific volume and hardest texture in comparison with the steamed bread fermented with W. cibaria L32 and with added EPS produced by W. cibaria L32 and L. brevis L17. These results indicated that different EPS-producing LAB exhibited distinctive dough fermentation characteristics, and the in situ EPS-producing W. cibaria L32 could improve steamed bread quality, which confirmed its potential application in steamed bread making.     

Functional properties of selected starter cultures for sour maize bread

This paper focuses on the functional properties of maize sour-dough microflora selected and tested for their use as starter cultures for sour maize bread. Lactic acid bacteria and yeasts isolated from spontaneously fermented maize dough were selected based on dominance during fermentation and presence at the end of fermentation. Functional properties examined included acidification, leavening and production of some antimicrobial compounds in the fermenting matrix. The organisms previously identified as Lactobacillus plantarum, Lb. brevis, Lb. fermentum, Lb. acidophilus, Pediococcus acidilactici, Leuconostoc mesenteroides and Leuconostoc dextranicum and Saccharomyces cerevisiae were used singly and as mixed cultures in the fermentation (fermentation time: 12h at 28+/-2 degrees C) of maize meal (particle size >0.2mm). The pH fell from an initial value of 5.62-3.05 in maize meals fermented with Lb. plantarum; 4.37 in L. dextranicum+S. cerevisiae compared with the value for the control (no starter) of 4.54. Significant differences (P 相似文献   

Biochemical properties of type I sourdough affected by wheat bran dietary fibre during fermentation

The supplementation of dietary fibre in sourdough is beneficial to increase the nutritional quality of fermented foods. The influence of different wheat bran dietary fibre (WBDF) levels (0%, 3%, 6%, 9%, and 12%) on the biochemical characteristics of sourdough during fermentation was investigated. This study showed that WBDF was slightly resistant to the reduced pH caused by the initial fermentation of sourdough dough. After 6 h of fermentation, whether or not it contained WBDF, the dough’s amylase activity was relatively stable (P > 0.05). However, in the samples containing WBDF, it took longer for the amylase activity to increase from 200 to 300 U g⁻¹. The content of free amino acids in the dough showed a tendency to first decrease and then increase with the metabolic activity of microorganisms, and WBDF could accelerate this rate. This study also provided evidence that insoluble dietary fibre may stimulate the growth and reproduction of lactic acid bacteria.     

发酵条件对酸樱桃发酵汁挥发性风味物质的影响探究

目的 考察发酵条件对酸樱桃发酵汁中风味物质的影响。方法 利用3株乳酸菌发酵酸樱桃汁, 以pH为指标明确最佳发酵菌种和稀释比例。随后利用气相色谱-离子迁移谱法(gas chromatography-ion mobility spectrometry, GC-IMS)探究糖添加量、pH、氮源、稀释比例对发酵挥发性风味物质的影响。结果 最佳发酵菌为鼠李糖乳杆菌(Lactobacillus GG, LGG), 最佳稀释比例为1:3, 氮源对挥发性风味物质几乎没有影响; 而不同添加量的碳源(葡萄糖)导致发酵液乙偶姻、双乙酰等含量差异; 随着pH增加, 乙偶姻、双乙酰、2-戊酮等含量显著升高; 稀释比例通过影响发酵原汁的浓度导致发酵后风味物质乙偶姻含量显著增加、2-戊酮含量显著降低。进一步差异比对3株乳酸菌酸樱桃发酵汁的风味, 发现LGG代谢脂肪酸可产生较多的2-庚酮及2-戊酮。结论 菌种、糖添加量、稀释比例、起始pH均可导致发酵液中乙偶姻、2-庚酮及2-戊酮等挥发性风味物质产生显著影响, 本研究为酸樱桃的加工利用提供理论指导。     

Acidification properties of lactic acid bacteria in rye sour doughs

The acidification properties of 33 different sour dough bacteria and starter cultures, one spontaneously generated sour dough and one commercial sour dough starter, a ‘Reinzuchtsauer’ from West Germany, were characterized. The bacteria were tested in three different sour dough processes, the Berliner short-sour-process, the Detmolder one-stage-process and the recently developed Lönner one-stage-process.The Lönner one-stage-process showed a number of advantages in comparison with the other processes. The organisms produced their lowest pH-values and their highest acid equivalents in this process. The rates of pH-decrease were also higher as well as the fermentation quotients. Some of the organisms previously isolated from sour doughs, showed very good properties of acidification. Among the homofermentative organisms, Lactobacillus acidophilus, L. alimentarius, L. plantarum and the unidentified organisms Lactobacillus spp. I and f showed the best properties. Among the heterofermentative organisms the best properties were displayed by L. brevis ssp. lindneri I and II and the unidentified Lactobacillus spp. e, g, h, k and n.     

The microflora of fermented nixtamalized corn

Nixtamalization is a traditional process that improves the nutritional quality of corn. To provide a means of utilizing the nutritional benefits of nixtamalized corn and improve product acceptability, lactic acid fermentation was applied. The objective of the study was to study the microbial profile and establish the important lactobacilli of fermenting nixtamalized corn dough. Two batches of cleaned whole corn were subjected to the process of nixtamalization, using two concentrations of lime (0.5 or 1.0%), milled, made into a dough (50% moisture) and fermented spontaneously for 72 h. A control sample was prepared without alkaline treatment. pH and titratable acidity of the dough were measured. Aerobic mesophiles, lactic acid bacteria, yeasts and molds were enumerated on Plate Count Agar (PCA), deMan, Rogossa and Sharpe (MRS) Agar and Malt Extract Agar (MEA), respectively. The identity of lactobacilli present was established at the species level using API 50 CHL. The pH of all the fermenting systems decreased with fermentation time with concomitant increase in titratable acidity. Lactic acid bacteria in numbers of 1.6 x 10(9), 2.3 x 10(9) and 1.8 x 10(9) cfu/g, respectively yeasts and molds, and numbers of 8.0 x 10(7), 5.0 x 10(5) and 1.7 x 10(5) cfu/g, respectively were observed in the control and the two nixtamalized (0.5% and 1.0% lime) samples after 48 h of fermentation. Lactobacilli identified in the fermenting nixtamalized corn dough were Lactobacillus plantarum, Lactobacillus fermentum and Lactobacillus cellobiosus as well as Pediococcus spp. The study demonstrates that nixtamalized corn though alkaline in nature can be subjected to spontaneous fermentation to produce a sour product.     

On the nonexistence of propionic acid in various kinds of breeds (author's transl)]

Analyses of 45 samples of sour dough and various kinds of bread have shown that no appreciable amounts of propionic acid are formed during sour dough fermentation. Bread has no natural propionic acid content.     

Souring and breakdown of cyanogenic glucosides during the processing of cassava into akyeke

The population and composition of the lactic acid bacteria microbiota as well as the content of cyanogenic glucosides occurring at various stages of fermentation and subsequent processing of cassava roots into akyeke, a steamed sour cassava meal, were investigated. The number of lactic acid bacteria and percentage titratable acidity increased during 5 days of fermentation, but decreases were observed in the subsequent operations of 'washing' the dough with water followed by partial drying and steaming. In field and laboratory samples, Lactobacillus plantarum accounted for 59.3% and 52.3%, Lactobacillus brevis 23.3% and 22.8% and Leuconostoc mesenteroides subsp. cremoris 14.5% and 15.8%, respectively, of all lactic acid bacteria isolated at various stages of fermentation and processing. A reduction of about 98% occurred in the total cyanogens (CN) content of cassava roots during processing, from 69.3 to 1.4 and 110.3 to 2.8 mg CN equivalent/kg dry weight for laboratory and field samples of akyeke, respectively.     

酸肉发酵中蛋白质降解及影响因素的研究

目的：了解蛋白质降解与酸肉品质间的关系以指导合理消费。方法：分析酸肉在发酵过程中主要环境因素、乳酸菌数及蛋白质降解产物的变化。结果：总蛋白质、肌原纤维蛋白和肌浆蛋白随发酵时间延长逐渐下降,非蛋白氮逐渐增加;蛋白质降解中间产物多肽氮及氨态氮呈先升后降趋势,发酵60d时挥发性盐基氮为19.56g/100g;氨基酸组成分析显示,发酵可提高蛋白质氨基酸分;相关性分析显示总蛋白质、肌原纤维蛋白和肌浆蛋白含量变化与乳酸菌数和氯化钠含量变化呈显著负相关,而与水分活度和pH值呈显著正相关;非蛋白氮与乳酸菌数和氯化钠含量显著正相关,而与水分活度和pH值显著负相关。结论：发酵可提高酸肉蛋白质营养价值,综合安全及风味因素,建议酸肉发酵时间在20～40d为宜。     

Effect of proteolytic starter cultures as leavening agents of pizza dough

Lactic acid bacteria (LAB) and yeasts were selected on the basis of in vitro proteolytic activity against wheat gluten protein and then assayed as leavening agents for pizza dough. Trials were carried out to compare a proteolytic starter (Prt(+)), consisting of Lactobacillus sakei T56, Weissella paramesenteroides A51 and Candida krusei G271, and a non-proteolytic starter (Prt(-)), consisting of Lb. sakei T58, W. paramesenteroides A58 and Saccharomyces cerevisiae T22. The proteolytic activity of the starter cultures was monitored immediately after mixing of the dough and throughout the fermentation process. The proteolytic activity was assessed by analysing the salt-soluble protein (SSP) and the dioxane-soluble protein (DSP) fractions of the pizza dough by discontinuous SDS-PAGE. Only the Prt(+) starter exhibited considerable qualitative and quantitative changes in the electrophoretic patterns of the protein fractions extracted. After the fermentation, the Prt(+) and Prt(-) doughs were tested to evaluate the influence of the proteolytic activity on the mechanical properties of the dough before and after baking. Indications emerged suggesting an influence of the proteolytic activity on the viscoelasticity of pizza dough. The pizza dough with Prt(+) strains showed an increase in viscous properties during the fermentation as compared with the Prt(-) dough. Moreover, an increase in the firmness of the crumb was observed in Prt(+) baked pizza dough.     

The bacteriocin producer Lactobacillus amylovorus DCE 471 is a competitive starter culture for type II sourdough fermentations

Type II sourdoughs were prepared using Lactobacillus amylovorus DCE 471, a producer of the bacteriocin amylovorin L. The strain was used as a starter culture for rye and wheat sourdoughs on laboratory scale (10 L), and in rye sourdough on pilot scale (100 L). The sourdoughs were acidified to a pH of around 3.5 within 15 h (laboratory dough) to 25 h (pilot‐scale dough). Final amylovorin L titres of 0.3–0.4 (laboratory scale) and 0.2 (pilot scale) MAU kg^?1 of sourdough were detected. After baking of wheat dough that was supplemented with the pilot‐scale sourdough, no amylovorin L activity was recovered from the breadcrumbs. On laboratory scale, aeration or the addition of complex carbohydrates hardly affected growth or amylovorin L production. Rye and wheat sourdough fermentation were rather similar despite differences in sugar concentrations. The persistence of L. amylovorus DCE 471 during rye sourdough fermentation, both on laboratory and pilot scale, was confirmed by repetitive sequence‐based polymerase chain reaction (rep‐PCR) and by testing isolates towards an amylovorin L‐sensitive organism. Further, rep‐PCR indicated that the background microbiota of the flour—probably responsible for the production of low amounts of acetic acid—grew poorly and were overgrown by L. amylovorus DCE 471 during the pilot‐scale fermentation. Copyright © 2007 Society of Chemical Industry     

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.     

Phytase activity in sourdough lactic acid bacteria: purification and characterization of a phytase from Lactobacillus sanfranciscensis CB1

The phytase activity of 12 species of sourdough lactic acid bacteria was screened. It was intracellular only, largely distributed among the species and strains of Lactobacillus sanfranciscensis possessed the highest levels of activity. A monomeric ca. 50-kDa phytase was purified to homogeneity from L. sanfranciscensis CB1 by three chromatographic steps. L. sanfranciscensis CB1 exhibited the highest hydrolysing activity on Na-phytate after reaching the stationary phase of growth (ca. 12 h). Cells cultivated in the presence of maltose and fructose showed an increase of the phytase activity of ca. 35% with respect to the other carbon sources used. The phytase was optimally active at pH 4.0 and 45 degrees C. The enzyme was strongly inhibited by 2 mM of phenylmethylsulfonyl fluoride (PMSF), and 2 mM Hg(2+) and Fe(2+). It had a pI of ca. 5.0. The substrate specificity was dependent on the type of phosphate ester; a very low activity was detected on alpha-D-glucose-1-phosphate and D-fructose-6- and 1,6-phosphate, while the highest hydrolysis was found towards adenosine-5'-tri-, di- and mono-phosphate. Compared to these substrates, the activity on Na-phytate was also relevant. The enzyme was thermo-stable after exposure to 70 degrees C for 30 min; the D value calculated at 80 degrees C was ca. 10 min. As shown by the Central Composite Design (CCD) applied to study the individual and interactive effects of pH, temperature and NaCl, acidic conditions and elevated temperatures were indispensable for the enzyme adaptation to high NaCl concentrations. L. sanfranciscensis CB1 cells or the correspondent cytoplasmic extract were used to ferment a sourdough for 8 h at 37 degrees C; a marked decreased (64-74%) of the Na-phytate concentration was found compared with the unstarted dough. The sourdough started with L. sanfranciscensis CB1 cells was re-used for several times and the phytase activity was maintained to a considerable level.     

The effect of fermentation temperature, flour type, and starter on the properties of sour wheat bread

The effects of the type of wheat flour (white or dark), fermentation temperature (25°C or 30°C) and origin of starter (bakery A compared with bakery B) on acid production and bread properties were examined in a factorial design. The type of flour was the most important factor; with dark flour (ash content 1.64%) the acetic acid concentration in the bread was almost double that from white flour (ash content 0.86%); lactic acid was 30 to 50% higher. Acid production increased as fermentation temperature increased to 30°C, but was not influenced by the origin of the starter.
Loaf specific volume decreased with acid concentrations, but souring lengthened the mould-free time from 4 days to 5 to 8 days or more as acidity increased. Sour wheat bread had a characteristic taste. Those with higher acidity values were more bitter and pungent.
Rye sour and rye sour bread production technology could also be utilized in white bread making.     

HS-SPME-GC-MS法分析发酵过程中荞麦和小麦面团香气成分变化

采用顶空固相微萃取技术和气相色谱-质谱联用技术对比分析荞麦和小麦在不同发酵剂作用下发酵过程中产生香气成分的差异。并基于保留指数和质谱鉴定对挥发性化合物进行鉴定。研究发现未发酵荞麦面团检出38?种香气成分,在酵母和乳酸菌发酵过程中共分别检测出80?种和63?种香气成分;未发酵小麦面团检出11?种香气成分,在酵母和乳酸菌发酵过程中共分别产生42?种和17?种。发酵过程中,荞麦和小麦面团香气种类增加,其中荞麦面团呈现更多香气成分。烃类和酯类是荞麦面团酵母发酵前后主要香气成分,烃类主要为单萜烯和倍半萜烯类,酯类是荞麦面团经乳酸菌发酵前后主要香气成分。小麦经过酵母发酵产生香气成分包括烃类、酯类、醇类、酸类、醛类及醚类,经过乳酸菌发酵产生香气成分种类相对较少,有烃类、酯类、酮类及醛类。荞麦发酵后产生更多活性香气成分。酵母和乳酸菌发酵荞麦和小麦后,香气成分有明显差异。在发酵过程中,香气成分随着发酵时间延长而发生转化。     

Tarhana as a traditional Turkish fermented cereal food. Its recipe, production and composition

As a fermented product tarhana is the dry form of yogurt-cereal mixture and represents an important part of the diets of many people in Turkey. It is prepared by mixing wheat flour, yogurt, yeast and a variety of cooked vegetables (tomatoes, onions, green pepper etc.), salt, and spices (mint, paprika) followed by fermentation for one to seven days. Generally one part yogurt is mixed with two parts of wheat flour (w/w). In commercial production there are two methods for tarhana making. First method is called straight method and ingredients in the recipe is mixed and kneaded, fermented, dried and finally sieved. Second method is called sour dough method that contains three steps, each one has a different recipe. Throughout fermentation lactic acid bacteria and yeast give the characteristic taste and flavour of tarhana by producing lactic acid, ethanol, carbondioxide and some other organic compounds. Organic acids composed in fermentation period lower the pH (3.4-4.2), and low moisture content (6-10%) is a poor medium for pathogens and spoilage organisms. The nutrient content of tarhana depends upon yogurt and flour ratios as well as some other ingredients, and it is also considered to be a useful high-protein dietary supplement with average 15% protein content. Addition of set yogurt due to high dry matter content and baker's yeast increase protein content and enhances it's amino acid composition.     

乳酸菌发酵剂对杂粮面团及馒头品质的影响

为研究混合乳酸菌发酵对杂粮面团及馒头品质的影响,将黄豌豆粉、莜麦粉、谷朊粉及燕麦β-葡聚糖（oatmeal β-glucan,OBG）复配成杂粮粉基质,利用直投式混合乳酸菌发酵剂发酵面团制作馒头。探究乳酸菌在面团中的酸化能力,分析杂粮面团中OBG、抗性淀粉（resistant starch,RS）和游离氨基酸含量的变化以及面团的微观结构变化,并对发酵前后的杂粮馒头和小麦粉馒头进行品质及营养特性比较。结果表明,在发酵杂粮面团中乳酸菌酸化能力强,发酵24 h后乳酸和乙酸质量浓度分别达到24.85、8.98 mg/mL。与未发酵的杂粮面团相比,乳酸菌发酵杂粮面团中OBG含量下降32.56%,RS含量上升32.88%,游离氨基酸总量提升至1.46倍,氨基酸组成模式更优,部分蛋白质和纤维素发生降解,面筋网络结构更加紧密且连续。在营养方面,乳酸菌发酵前后的杂粮馒头膳食纤维质量分数均高于6%,蛋白质质量分数分别为40.35%和38.38%,属于高纤维高蛋白食品,显著优于小麦粉馒头。乳酸菌发酵杂粮馒头具有更高的体外蛋白消化率和比容,且乳酸菌发酵杂粮馒头感官评价总评分显著高于未发酵杂粮馒头,整体可接受度...