Rye Sourdough Research Articles

Sucrose metabolism and exopolysaccharide production in wheat and rye sourdoughs by Lactobacillus sanfranciscensis.

The exopolysaccharide (EPS) produced from sucrose by Lactobacillus sanfranciscensis LTH2590 is predominantly composed of fructose. EPS production during sourdough fermentation has the potential to affect rheological properties of the dough as well as the volume, texture, and keepability of bread. Its in situ production by L. sanfranciscensis LTH2590 was demonstrated during sourdough fermentation after the hydrolysis of water soluble polysaccharides. In wheat and rye doughs with sucrose addition the concentration of fructose in the hydrolysate of polysaccharides was significantly higher than that in the hydrolysate of control doughs or doughs without sucrose addition. EPS production by L. sanfranciscensis in wheat doughs was confirmed by the determination of delta (13)C values of water soluble polysaccharides after the addition of naturally labeled sucrose, originating from C(3)- and C(4)-plants. In rye doughs, evidence for EPS production with the isotope technique could be demonstrated only by the determination of delta (13)C values of fructose from water soluble polysaccharides. In addition to EPS formation from sucrose, sucrose hydrolysis by L. sanfranciscensis in wheat and rye sourdoughs resulted in an increase of mannitol and acetate concentrations and in accumulation of glucose. It was furthermore observed that flour arabinoxylans were solublized during the fermentation.

Effects of Fermentation and Baking of Whole Wheat and Whole Rye Sourdough Breads on Cereal Alkylresorcinols

ABSTRACTAlkylresorcinol (AR) content was determined in multiple‐stage whole wheat and whole rye flour sours, as well as in whole wheat and whole rye flour doughs and breads. AR content decreased considerably during fermentation and baking. AR content was reduced by 20 and 46%, respectively, at the end of sourdough starter fermentation of whole wheat and whole rye flour sours. AR content, which was 512 and 210 μg/g in whole rye and whole wheat flour doughs, respectively, was 30 and 0 μg/g, respectively, after baking of breads. Synthetic AR added at different levels to doughs was also greatly reduced during fermentation and baking.

Production of sour maize bread using starter-cultures

Eight lactic acid bacteria were isolated from fermenting maize meal. They were identified as Lactobacillus brevis, L. casei, L. fermentum, Pediococcus acidilacti, P. pentosaceus, Lactobacillus spp. I and Pediococcus spp. I and II. L. brevis and Lactobacillus spp. I isolated from the spontaneously fermented maize meal together with L. brevis isolated from rye sour dough and L. plantarum from ogi, a fermented maize gruel, were selected as starter organisms. There was a decrease in the final pH from 4.9 to 3.8 and an increase in the acid equivalent and temperature of the spontaneously-generated sour maize meal at the end of 24h fermentation. There was a decrease in the pH and moisture content of the sour maize breads relative to the conventional wheat bread. An improvement in the shelf-life of the bread samples was also obtained. Crude protein values of the sour maize breads were between 4.36% and 8.87%, while crude fat contents ranged between 3.66% to 7.67%. The ash contents increased from 2.29% to 2.54% while total carbohydrate values were between 46.31% and 65.3%. Calcium, phosphorus and potassium contents ranged from 0.015, 0.26 and 0.018% to 0.036, 0.47 and 0.036% respectively. Physical examination of the bread samples showed that all were cracked and relatively hard. Weight, height and volume ranged from 316 to 380g; 4.2 to 5.2cm and 200 to 320cm3 respectively. Statistical analysis of the sensory attributes revealed a consumer acceptance of the sour maize breads, although ranking test showed preference for the baker's yeast leavened bread that served as a control.

Lactobacillus panis sp. nov., from sourdough with a long fermentation period.

Two Lactobacillus strains isolated from rye sourdough most closely resemble Lactobacillus oris on the basis of their physiological, morphological, and chemotaxonomic characteristics. A 16S ribosomal DNA sequence analysis showed that these two strains clustered with, but were separate from, L. oris, Lactobacillus vaginalis, and Lactobacillus pontis. The results of DNA-DNA hybridization experiments indicated that the new two isolates represent a new Lactobacillus species, for which we propose the name Lactobacillus panis; strain DSM 6035T is the type strain of this species.

Degradation of phytate by using varied sources of phytases in an oat-based nutrient solution fermented by Lactobacillus plantarum strain 299 V

A formula has previously been developed for an oat-based nutrient solution, fermented by Lactobacillus plantarum strain 299 V, to be used as a probiotica for people with a damaged intestinal microflora. Oats are nutritious and rich in minerals, but also contain large amounts of phytate (myoinositol hexaphosphate), which is one of the main inhibitors of absorption of iron and zinc in humans. The effects of phytases of varied sources (malted barley flour, malted oat flour, rye sour dough and of wheat phytase and phytase from Asperigillus niger), on the phytate degradation, acidity, bacterial counts and aroma of the oat-based nutrient solution were studied. The degradation of phytate varied between 100% and 72% of the initial value, depending on the source of phytase added. Malted barley flour and malted oat flour had the same capacity for degrading phytate in oats. The rate of pH decrease, final pH values, acidity, and viable counts of lactic acid bacteria varied in the solutions depending on the source of phytase. The most efficient phytate degradation was achieved by adding phytase from A. niger to the oat-based nutrient solution. However, by using the enzyme, the nutrient solution became bitter tasting and had low counts of lactic acid bacteria.

Degradation of phytate by using varied sources of phytases in an oat-based nutrient solution fermented by Lactobacillus plantarum strain 299 V

A formula has previously been developed for an oat-based nutrient solution, fermented by Lactobacillus plantarum strain 299 V, to be used as a probiotica for people with a damaged intestinal microflora. Oats are nutritious and rich in minerals, but also contain large amounts of phytate (myoinositol hexaphosphate), which is one of the main inhibitors of absorption of iron and zinc in humans. The effects of phytases of varied sources (malted barley flour, malted oat flour, rye sour dough and of wheat phytase and phytase from Asperigillus niger), on the phytate degradation, acidity, bacterial counts and aroma of the oat-based nutrient solution were studied. The degradation of phytate varied between 100% and 72% of the initial value, depending on the source of phytase added. Malted barley flour and malted oat flour had the same capacity for degrading phytate in oats. The rate of pH decrease, final pH values, acidity, and viable counts of lactic acid bacteria varied in the solutions depending on the source of phytase. The most efficient phytate degradation was achieved by adding phytase from A. niger to the oat-based nutrient solution. However, by using the enzyme, the nutrient solution became bitter tasting and had low counts of lactic acid bacteria.

Utilization of electron acceptors by lactobacilli isolated from sourdough

Lactobacillus sanfrancisco is frequently a prevalent organism in wheat and rye sourdoughs. Its growth and metabolism are strongly affected by agitation and the availability of maltose and electron acceptors such as oxygen and fructose. Upon agitation of a culture the length of the lag phase was reduced. The growth rate and final cell yield increased in the presence of oxygen and electron acceptors. Growing cells formed lactate and ethanol from maltose under anaerobic conditions. Intermediately excreted glucose did not repress maltose utilization. Upon aeration or addition of fructose to cultures growing on maltose, acetate was formed instead of ethanol. Fructose was reduced to mannitol. Added fumarate and malate were converted to lactate and did not serve as electron acceptors. The following observations are suggested to contribute to the competitiveness ofL. sanfrancisco in sourdough. Glucose is excreted in abundance of maltose and represses the maltose metabolism of competitors, maltose is split by maltose phosphorylase without the expenditure of adenosine 5′-triphosphate (ATP), and additional metabolic energy is generated by the activity of acetate kinase in the presence of fructose which is abundant in the polyfructosanes of flour. The metabolic features ofL. pontis, L. reuteri, L. amylovorus andL. fermentum are to be described in a following communication.

Identification of Lactobacilli from Sourdough and Description of Lactobacillus pontis sp. nov.

The microflora of sourdough preparations was investigated by examining the physiological characteristics, whole-cell protein patterns, and 16S rRNA sequences of Lactobacillus isolates. Strains isolated from sourdough were placed in the species Lactobacillus brevis, Lactobacillus sanfrancisco, and Lactobacillus reuteri. 16S rRNA sequences were determined for L. brevis, Lactobacillus fructivorans, Lactobacillus fermentum, L. sanfrancisco, and L. reuteri, and oligonucleotide probes for fast specific identification of these sourdough lactobacilli were deduced. The physiological characteristics, protein patterns, and 16S rRNA sequences of these organisms were compared with data for other sourdough lactobacilli and additional reference strains. Strains of a Lactobacillus species were isolated from rye sourdough; these strains may account for most of the flora in sourdough made from wheat or rye. These organisms were differentiated from other sourdough lactobacilli by their protein pattern, 16S rRNA sequence, G + C content, and physiological properties. The 16S rRNA sequence of this species was determined, and we constructed a phylogenetic tree which reflected the relationships of this species to other lactobacilli. This organism is closely related to L. reuteri. A new Lactobacillus species, Lactobacillus pontis, is proposed. The type strain is L. pontis LTH 2587 (= DSM 8475 = LMG 14187). We describe a general strategy in which a polyphasic approach was used to characterize a new species.

Factors Affecting Rye Sour Dough Fermentation with Mixed-culture Pre-ferment of Lactic and Propionic Acid Bacteria

The effect of factors such as dough yield, temperature and pre-ferment quantity on rye dough fermentation using mixed-culture pre-ferments of Lactobacillus brevis together with Propionibacterium acidi-propionici or P. jensenii was examined according to a statistical experimental design and empirical modelling. The dough yield and temperature were the most dominating factors affecting the second-degree polynomial models to described pH, titratable acidity, lactic acid concentration, acetic acid concentration, molar ratio of lactic to acetic acid and propionic acid concentration during rye dough acidification. Further, under the experimental rye sour dough fermentation conditions, a pH less than 4 and a typical titratable acidity of about 16 (ml 0·1 M NaOH/5 g flour) of fermented sour were obtained usually in 17 to 24 h with both bacteria combinations used in the pre-ferment. A dough yield of 320%, temperature of 35°C and amount of pre-ferment of 32% (rye flour weight basis) gave the highest propionic acid concentration of 0·55 g/100 g sour dough with the pre-ferment of L. brevis together with P. acidi-propionici. Titratable acidity values of about 27 to 35 ml 0·1 M NaOH/5 g flour, indicative of medium to strong sour rye dough, were obtained, and the lactic to acetic acid molar ratio of 1·9 to 4·0 were within the optimal range. Consequently, the mixed-culture pre-ferment of lactic and propionic acid bacteria appeared to be a potential alternative along with conventional starters in rye sour dough fermentation, providing for an improved mould-free shelf-life of bread.

Identification and Characteristics of Lactic Acid Bacteria Isolated from Sour Dough Sponges.

Lactic acid bacteria in four samples of sour dough sponges were studied quantitatively and qualitatively. In each sponge, there were one or two species of the genus Lactobacillus: L. reuteri and L. curvatus in San Francisco sour dough sponge, L. brevis and L. hilgardii in panettone sour dough sponge produced in Italy, L. sanfrancisco from a rye sour dough sponge produced in Germany, and L. casei and L. curvatus from a rye sour dough sponge produced in Switzerland. For all isolates except the L. reuteri strains oleic acid, a component of the Tween 80 added to the medium, was essential for growth. It was of interest that lactobacilli requiring oleic acid were the predominant flora of lactic acid bacteria in the microbial environment of sour dough sponges.

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.