Prevalence and impact of single-strain starter cultures of lactic acid bacteria on metabolite formation in sourdough

Flavour of type II sourdoughs is influenced by the ingredients, processing conditions, and starter culture composition. It is, however, not fully clear to what extent different sourdough lactic acid bacteria (LAB) contribute to flavour. Therefore, two types of flour (rye and wheat) and different LAB starter culture strains were used to prepare sourdoughs, thereby leaving the yeast microbiota uncontrolled. All LAB starter culture strains tested were shown to be prevalent and to acidify the flour/water mixture to pH values between 3.1 and 3.9 after 24 h of fermentation. Multiple aldehydes, alcohols, ketones, and carboxylic acids were produced by the sourdough-associated microbiota throughout the fermentation period. Based on the organoleptic evaluation of breads produced with these sourdoughs, five LAB strains were selected to perform prolonged wheat and rye fermentations as to their capacity to result in an acidic (Lactobacillus fermentum IMDO 130101, Lactobacillus plantarum IMDO 130201, and Lactobacillus crustorum LMG 23699), buttermilk-like (Lactobacillus amylovorus DCE 471), or fruity flavour (Lactobacillus sakei CG1). Upon prolonged fermentation, higher metabolite concentrations were produced. For instance, L. sakei CG1 produced the highest amounts of 3-methyl-1-butanol, which was further converted into 3-methylbutyl acetate. The latter compound resulted in a fruity banana flavour after 48 h of fermentation, probably due to yeast interference. Rye fermentations resulted in sourdoughs richer in volatiles than wheat, including 3-methyl-1-butanol, 2-phenylethanol, and ethyl acetate.     

Biodiversity of lactic acid bacteria and yeasts in spontaneously-fermented buckwheat and teff sourdoughs

In this study, four different laboratory scale gluten-free (GF) sourdoughs were developed from buckwheat or teff flours. The fermentations were initiated by the spontaneous biota of the flours and developed under two technological conditions (A and B). Sourdoughs were propagated by continuous back-slopping until the stability was reached. The composition of the stable biota occurring in each sourdough was assessed using both culture-dependent and -independent techniques. Overall, a broad spectrum of lactic acid bacteria (LAB) and yeasts species, belonging mainly to the genera Lactobacillus, Pediococcus, Leuconostoc, Kazachstania and Candida, were identified in the stable sourdoughs. Buckwheat and teff sourdoughs were dominated mainly by obligate or facultative heterofermentative LAB, which are commonly associated with traditional wheat or rye sourdoughs. However, the spontaneous fermentation of the GF flours resulted also in the selection of species which are not consider endemic to traditional sourdoughs, i.e. Pediococcus pentosaceus, Leuconostoc holzapfelii, Lactobacillus gallinarum, Lactobacillus vaginalis, Lactobacillus sakei, Lactobacillus graminis and Weissella cibaria. In general, the composition of the stable biota was strongly affected by the fermentation conditions, whilst Lactobacillus plantarum dominated in all buckwheat sourdoughs. Lactobacillus pontis is described for the first time as dominant species in teff sourdough. Among yeasts, Saccharomyces cerevisiae and Candida glabrata dominated teff sourdoughs, whereas the solely Kazachstania barnetti was isolated in buckwheat sourdough developed under condition A. This study allowed the identification and isolation of LAB and yeasts species which are highly competitive during fermentation of buckwheat or teff flours. Representatives of these species can be selected as starters for the production of sourdough destined to GF bread production.     

Effects of fermentation and rye flour on microstructure and volatile compounds of chestnut flour based sourdoughs

The study is aimed at developing a new cereal-based product, with increased nutritional quality, by using natural fermentation of blends of chestnut and rye flour. In spite of the remarkable similarity, the technological potential of combinations of both flours has never been explored before. Three spontaneous chestnut/rye sourdough fermentations were performed over a period of twelve days with daily back-slopping. Samples taken at all refreshment steps were used for culture-dependent and culture-independent evaluation of the microbiota present. Dominant species basically overlapped to those associated to sourdoughs strengthened with chestnut flour, such as Pediococcus pentosaceus or Weissella paramesenteroides. Microstructures, evaluated by means of Scanning Electron Microscopy, revealed the presence in chestnut sourdoughs of a distinguishable network surrounding starch granules, while rye flour-added sourdoughs showed a less structured matrix. By gas chromatography coupled to mass spectrometry, 51 volatile organic compounds were identified at 24 h and after prolonged fermentation. Within volatile organic compounds, alcohols, esters, acids, aldehydes and ketones, all well-known flavour compounds in sourdough fermentation, appeared as dominant. The PCA discriminated the sourdoughs into three distinct clusters and highlighted a clear influence of fermentation time on the volatile composition of sourdoughs.     

Solid state fermentation process for producing chickpea (Cicer arietinum L) tempeh flour. Physicochemical and nutritional characteristics of the product

Solid state fermentation (SSF) represents a technological alternative for processing a great variety of legumes and/or cereals to improve their nutritional quality and to obtain edible products with palatable sensorial characteristics. The objectives of this work were (1) to determine the best combination of SSF process variables (fermentation temperature FT/fermentation time Ft) for producing chickpea tempeh flour and (2) to characterise the physicochemical and nutritional properties of the product. Response surface methodology was applied as optimisation technique over three response variables: in vitro protein digestibility (PD), true protein (TP) and water absorption index (WAI). A central composite experimental design with two factors and five levels was used. The process variables FT and Ft had variation levels of 31–36 °C and 48–72 h respectively. Rhizopus oligosporus (1 × 10⁹ spores l^?1 in distilled water) was used as starter. Prediction models for response variables were developed as a function of process variables. A conventional graphical method was applied to obtain maximum PD, TP and WAI. Contour plots of each of the response variables were superimposed to obtain a contour plot for observation and selection of the best combination of FT (34.9 °C) and Ft (51.3 h) for producing of chickpea tempeh, which was dried (52 °C, 24 h) and milled to pass through an 80‐US mesh (0.180 mm) screen to obtain optimised chickpea tempeh flour. This flour had higher (p ≤ 0.05) TP (25.7 vs 19.7% dry matter (DM)), total colour difference (30.3 vs 16.7), WAI (4.18 vs 2.15 kg gel kg^?1 DM), available lysine (42.7 vs 30.4 g kg^?1 protein) and PD (83.2 vs 72.2%) and lower lipid content (2.6 vs 6.1% DM), phytic acid (1.1 vs 10.85 g kg^?1 DM), tannins (2.65 vs 21.95 g catechin kg^?1 DM) and pH (5.9 vs 6.3) than raw chickpea flour. Copyright © 2004 Society of Chemical Industry     

Utilization of various starter cultures in the production of Amasi, a Zimbabwean naturally fermented raw milk product

Fermented milk was prepared from unpasteurised milk using natural fermentation (R), back-slopping (B) and by addition of two different starter cultures (C1 and DL). The numbers of Escherichia coli, coliforms, lactic acid bacteria (LAB) and the changes in pH, carbohydrates, organic acids and volatile compounds were recorded during 48-h fermentation. After 48-h fermentation, the highest numbers of E. coli were found in R and B fermentations and the lowest in the DL fermentation. The DL culture reduced the pH faster than the other starter cultures. The DL and C1 had higher levels of LAB in the beginning of the fermentation than the other two. Galactose and lactic acid increased fastest in the DL and C1 fermentation, and R was slowest. The highest levels of succinate, ethanol and malty compounds were found in the R and B fermentations. Lower levels of LAB in the first part of the fermentations, but higher number of E. coli could explain the increased levels of succinate, ethanol and malty compounds.     

Adaptability of lactic acid bacteria and yeasts to sourdoughs prepared from cereals, pseudocereals and cassava and use of competitive strains as starters

The adaptability of lactic acid bacteria (LAB) and yeasts to sourdoughs prepared from cereals, pseudocereals and cassava was investigated using PCR-DGGE and bacteriological culture combined with rRNA gene sequence analysis. Sourdoughs were prepared either from flours of the cereals wheat, rye, oat, barley, rice, maize, and millet, or from the pseudocereals amaranth, quinoa, and buckwheat, or from cassava, using a starter consisting of various species of LAB and yeasts. Doughs were propagated until a stable microbiota was established. The dominant LAB and yeast species were Lactobacillus fermentum, Lactobacillus helveticus, Lactobacillus paralimentarius, Lactobacillus plantarum, Lactobacillus pontis, Lactobacillus spicheri, Issatchenkia orientalis and Saccharomyces cerevisiae. The proportion of the species within the microbiota varied. L. paralimentarius dominated in the pseudocereal sourdoughs, L. fermentum, L. plantarum and L. spicheri in the cassava sourdough, and L. fermentum, L. helveticus and L. pontis in the cereal sourdoughs. S. cerevisiae constituted the dominating yeast, except for quinoa sourdough, where I. orientalis also reached similar counts, and buckwheat and oat sourdoughs, where no yeasts could be detected. To assess the usefulness of competitive LAB and yeasts as starters, the fermentations were repeated using flours from rice, maize, millet and the pseudocereals, and by starting the dough fermentation with selected dominant strains. At the end of fermentation, most of starter strains belonged to the dominating microbiota. For the rice, millet and quinoa sourdoughs the species composition was similar to that of the prior fermentation, whereas in the other sourdoughs, the composition differed.     

Identification of lactic acid bacteria isolated from oat sourdoughs and investigation into their potential for the improvement of oat bread quality

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.     

Isolation of lactic acid bacteria starters from <Emphasis Type="Italic">Jeung</Emphasis>-<Emphasis Type="Italic">pyun</Emphasis> for sourdough fermentation

Lactic acid bacteria (LAB) are key for the fermentation of sourdoughs to improve the quality and nutritive value of bread. The aim of this study was to isolate the LAB starter for sourdough fermentation from Jeung-pyun, a Korean traditional rice cake. Among the twenty two LAB screened, five isolates were selected based on exo-polysaccharide production. Among them, three isolates showed cell growth greater than 8.5 Log CFU/g, maximum increase in the volume of dough, and dextran concentration up to 0.16%. During the sourdough fermentation, pH and total titratable acidity (TTA) were changed, as the three isolates synthesized lactic acid and acetic acid with fermentation quotients less than 2.0. They were identified as Leuconostoc lactis EFEL005, Lactobacillus brevis EFEL004, and Le. citreum EFEL006. They displayed good fermentation properties (growth, dextran production, pH, and TTA) in dough and they are regarded as potential starters to be used in sourdough fermentation.     

功能性乳酸菌发酵黑豆麦麸酸面团面包的营养及烘焙特性

将黑豆及麦麸作为发酵基质,分别以高产植酸酶的乳酸片球菌(Pediococcus acidilactici)L-19及产β-葡萄糖苷酶的戊糖片球菌(Pediococcus pentosaceus)J-28作为发酵剂制作酸面团面包。探究菌株的生长、酸化及产酶特性,分析体系中植酸与膳食纤维的变化,采用低场核磁共振及磁共振成像技术表征面筋的水合情况,并比较面包面团的物性与微观结构差异,同时对黑豆麦麸酸面团面包的营养及感官品质进行评价。结果表明:在黑豆麦麸基质中,两株乳酸菌生长良好,酸化能力强,两者表现出不同的产酶特性。经发酵后,两种酸面团的植酸降解率分别达到81.08%、59.79%,可溶性膳食纤维含量在总膳食纤维中的占比由发酵前的22.49%分别提高至31.47%、44.15%。黑豆及麦麸干扰面筋水合,不利于形成连续的网络结构,而乳酸菌发酵能够降低黑豆及麦麸对面筋网络的破坏作用。在营养方面,两种酸面团面包的总膳食纤维含量均高于6%,蛋白质含量分别达到13.82%、13.91%,并且具有更优的氨基酸组成模式及更高的体外蛋白消化率。因此,实验中的两株乳酸菌能够有效改善黑豆麦麸酸面团面包的营养及感...     

The use of a starter culture in the fermentation of cassava for the production of "kivunde", a traditional Tanzanian food product

Three cassava fermentation methods (spontaneous fermentation, back-slopping and the use of starter culture) for the production of kivunde, executed in three trials at 30 degrees C, were compared in terms of cyanide level reduction, microbiology and product quality improvement. Among the isolates from spontaneously fermented cassava batches, four strains were selected on the basis of their enzymatic activities and acid production. All were identified as Lactobacillus plantarum and were used as starters in this study. Lowest residual cyanide levels were detected after 120 h fermentation time in samples fermented with the starter culture and were below the maximum value of 10 mg/kg recommended by the Codex/FAO for cassava flour. This finding seems to be related to the alpha-glucosidase activity of the inoculated strains of which API-zyme (Bio-Merieux) tests showed activities of between 20 and > or = 40 nmol/4 h. The total residual cyanide levels of the spontaneous and back-slopping fermentations at 96 h were respectively 43.5 and 47.7 mg/kg dry weight of cassava. Extension of the fermentation period to 5 days, lead to further substantial reduction in the residual cyanide level in both these processes, but not below the recommended maximum value as in the case of starter culture fermented products. The spontaneous and back-slopping fermented cassava showed signs of deterioration after 3 days of fermentation. There was a sharp drop of pH and an increase of titratable acidity for all three batches during the first 48 h followed by a slow rise of pH and drop in titratable acidity towards the end of fermentation. The samples fermented with the starter culture had a smooth texture and pleasant fruity aroma, as opposed to the course and dull appearance and more complex flavour of the samples of spontaneous and back-slopping batches. During fermentation with starter culture, Enterobacteriaceae and yeasts and moulds could not be isolated throughout the period of fermentation (detection limit: 10 colony forming units/g). The present findings indicate the suitability of these Lb. plantarum strains as starter cultures for cassava fermentation in the kivunde process. The paper highlights the potential for the improvement of a traditional African fermented food (kivunde) through the use of a starter culture.     

Lactic Acid Bacteria Isolated from Indigenous Fermented Bamboo Products of Arunachal Pradesh in India and Their Functionality

Ekung, eup and hirring are some common indigenous fermented bamboo products of Northeast India. We have isolated, characterized, and identified the predominant lactic acid bacteria (LAB) from 44 samples of ekung, eup, and hirring and studied their technological properties. The phenotypic characterizations of LAB isolates were based on physiological, biochemical tests and API kits, and were identified as Lactobacillus plantarum, L. brevis, L. casei, L. fermentum, Lactococcus lactis, and Tetragenococcus halophilus. Technological properties of LAB such as acidifying capacity, antimicrobial activities, degradation of phytic acid and oligosaccharides, bile-salt tolerance, enzymatic activities, biogenic amines production, and degree of hydrophobicity also were studied. This study showed that strains of LAB played important roles by their functional properties related to acidifying capacity, degradation of antinutritive factors, tolerance to bile-salt, wide enzymatic activities, and nonproducers of biogenic amines. Understanding the biological and biochemical basis of indigenous knowledge of the ethnic people of Northeast India for production of nonperishable bamboo shoots by lactic acid fermentation has merit. It helps to develop both low-cost functional foods, and understand the functionality of microbial diversity. Some of the LAB strains possess functional properties, which render them interesting candidates for use as LAB starter cultures.     

Potential of LAB starter culture isolated from Chinese traditional fermented foods for yoghurt production

A total of 32 indigenous lactic acid bacteria (LAB) isolates were previously obtained from 7 samples of traditional dairy products in specific ecological niches throughout the northwestern area of China. Among the 32 isolates, 9 strains of LAB were selected for their potential in fermented dairy products and identified by 16S rDNA sequence analysis. In this study, these 9 isolates were combined each other and 8 combinations were selected according to their fermentation characteristics in yoghurt production. The effects of these 8 combinations on acidification, post acidification, texture and sensory quality of yoghurt were analysed. Results indicated that Streptococcus thermophilus SP1.1 combined with Lactobacillus delbrueckii ssp. bulgaricus 3 4.5 was the best combination and better than the commercial starter culture in terms of yoghurt fermentation time and sensory quality, suggesting that the combination has potential as a commercial starter to improve the quality of yoghurt.     

Molecular characterization of lactic acid bacteria and in situ amylase expression during traditional fermentation of cereal foods

Lactic acid bacteria play an important role in traditional fermented foods consumed in different countries. Study of their taxonomic structure and diversity is necessary for starter culture selection, improved safety and nutritional enhancement. To achieve these objectives, microbial genomic typing methods were used to study genetic differences of autochthonous bacteria and their distribution in two traditional African fermented cereal foods. A total of 85 predominant bacterial species were isolated from ogi and kunu-zaki obtained from Northern and Southern geographical region of Nigeria. They were identified using combination of 16S rRNA gene sequencing, multilocus sequence analysis (MLSA) based on rpoA, pheS and atpA genes as well as M13-PCR gel fingerprints. The results showed that Lactobacillus fermentum was the most frequently isolated species in ogi (71.4%) and kunu-zaki (84.5%). Other species of lactic acid bacteria (LAB) identified were Lactobacillus plantarum, Streptococcus gallolyticus subsp. macedonicus and Pediococcus pentosaceus. Non lactic acid bacteria isolated from these foods were species belonging to the Bacillus and Staphylococcus. Non-metric multidimensional scaling (nMDS) analysis of the M13-PCR fingerprints for LAB strains showed clonal diversity among strains of the same species. In vitro and in situ expression of amylase gene during fermentation by amylolytic L. plantarum ULAG11 was detected, indicating the potential usefulness of such species for development of starter cultures and for controlled fermentation processes.     

高产植酸酶乳酸菌及其黑豆酸面团发酵低植酸营养面包研究

从自然发酵的黑豆中筛选出一株具有高植酸酶活性的乳酸菌L-19并将其作为发酵剂制作黑豆酸面团。通过响应面分析法对黑豆酸面团的发酵工艺进行优化,探究最佳发酵条件下目标菌株的生长及产酸特性,并分析体系中多肽的分子量分布及抗营养因子含量变化,同时以感官品评的方式对黑豆酸面团面包的烘焙特性进行评价。结果表明:乳酸菌L-19经鉴定为乳酸片球菌(Pediococcus acidilactici),其胞外酶与胞内酶活性分别为1.36,0.30 U/mL。通过响应面设计确定的最优发酵条件为面团得率(DY)300、发酵温度37℃、接种量8%,黑豆基质中,目标菌株生长良好、酸化能力适中。黑豆酸面团经发酵后,体系中的多种抗营养因子得到有效降解,其中植酸降解率高达62.70%。此外,黑豆蛋白水解后释放出多种肽,其中小分子肽占比达51.47%。与对照组相比,L-19黑豆酸面团面包表现出更高的整体可接受度。因此,乳酸片球菌L-19能够有效改善黑豆酸面团面包的营养及感官品质,具有较佳的应用潜力。     

Silage review: Recent advances and future uses of silage additives

Additives have been available for enhancing silage preservation for decades. This review covers research studies published since 2000 that have investigated the efficacy of silage additives. The review has been divided into 6 categories of additives: homofermentative lactic acid bacteria (LAB), obligate heterofermentative LAB, combination inoculants containing obligate heterofermentative LAB plus homofermentative LAB, other inoculants, chemicals, and enzymes. The homofermentative LAB rapidly decrease pH and increase lactic acid relative to other fermentation products, although a meta-analysis indicated no reduction in pH in corn, sorghum, and sugarcane silages relative to untreated silages. These additives resulted in higher milk production according to the meta-analysis by mechanisms that are still unclear. Lactobacillus buchneri is the dominant species used in obligate heterofermentative LAB silage additives. It slowly converts lactic acid to acetic acid and 1,2-propanediol during silo storage, improving aerobic stability while having no effect on animal productivity. Current research is focused on finding other species in the Lb. buchneri group capable of producing more rapid improvements in aerobic stability. Combination inoculants aim to provide the aerobic stability benefits of Lb. buchneri with the silage fermentation efficiency and animal productivity benefits of homofermentative LAB. Research indicates that these products are improving aerobic stability, but feeding studies are not yet sufficient to make conclusions about effects on animal performance. Novel non-LAB species have been studied as potential silage inoculants. Streptococcus bovis is a potential starter species within a homofermentative LAB inoculant. Propionibacterium and Bacillus species offer improved aerobic stability in some cases. Some yeast research has focused on inhibiting molds and other detrimental silage microorganisms, whereas other yeast research suggests that it may be possible to apply a direct-fed microbial strain at ensiling, have it survive ensiling, and multiply during feed out. Chemical additives traditionally have fallen in 2 groups. Formic acid causes direct acidification, suppressing clostridia and other undesired bacteria and improving protein preservation during ensiling. On the other hand, sorbic, benzoic, propionic, and acetic acids improve silage aerobic stability at feed out through direct inhibition of yeasts and molds. Current research has focused on various combinations of these chemicals to improve both aerobic stability and animal productivity. Enzyme additives have been added to forage primarily to breakdown plant cell walls at ensiling to improve silage fermentation by providing sugars for the LAB and to enhance the nutritive value of silage by increasing the digestibility of cell walls. Cellulase or hemicellulase mixtures have been more successful at the former than the latter. A new approach focused on Lb. buchneri producing ferulic acid esterase has also had mixed success in improving the efficiency of silage digestion. Another new enzyme approach is the application of proteases to corn silage to improve starch digestibility, but more research is needed to determine the feasibility. Future silage additives are expected to directly inhibit clostridia and other detrimental microorganisms, mitigate high mycotoxin levels on harvested forages during ensiling, enhance aerobic stability, improve cell wall digestibility, increase the efficiency of utilization of silage nitrogen by cattle, and increase the availability of starch to cattle.     

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.     

Studies on the low-salt Chinese potherb mustard (Brassica juncea, Coss.) pickle. I—The effect of a homofermentative l(+)-lactic acid producer Bacillus coagulans on starter culture in the low-salt Chinese potherb mustard pickle fermentation

A homofermentative l(+)-lactic acid producer Bacillus coagulans B179 has been evaluated as starter cultures for low-salt potherb mustard pickle process. This study examined the impact of inoculation by B. coagulans B179 as starter culture on the spontaneous lab-scale fermentation process of potherb mustard pickle. Three different salt concentrations trials, i.e., 5 g/100 g, 8 g/100 g and 10 g/100 g, respectively, were carried out. As a result, the addition of starter culture of B. coagulans B179 to 5 g/100 g salinity fermentation showed an inhibiting effect upon the population of non-lactic acid bacteria (LAB) and marked increase in population of LAB and production of titratable acidity but did not significantly influence the pickle end products quantity of acid produced by fermentation as compared with a treatment without inoculation. However, in the higher salt concentrations, i.e., 8 g/100 g and 10 g/100 g NaCl trials, inoculation had no impact on the fermentation of the pickle. From the standpoint of fermentation, as a functional starter culture, inoculated B. coagulans B179 can effectively improve desired native LAB growth and inhibit the growth of undesired fungi, which will thereby allow it to shorten fermentation period and enhance the pickle quality in the low-salt potherb mustard pickle production.     

Influence of lactic acid bacteria on the oxidation–reduction potential of buckwheat (Fagopyrum esculentum Moench) sourdoughs

The influence of lactic acid bacteria (LAB) growth on oxidation–reduction potential (ORP) of buckwheat sourdoughs was investigated. Sourdough fermentations are widely used for the production of bread and other bakery products. Until now the pH value is the most used control parameter taken into account during sourdough technology and no information is available about the influence of sourdough microbiota on the ORP or the use of redox potential (E _h7) measurements as a fermentation control parameter. The influence of growth and metabolism of lactobacilli on the oxidation–reduction potential of buckwheat (Fagopyrum esculentum Moench) sourdoughs was investigated. Upon inoculation with LAB, ORP changes were observed. Each strain exhibits a different ORP time course curve. The E _h7 after 8?h using Lactobacillus plantarum, Lactobacillus sakei, Weissella cibaria and Pediococcus pentosaceus reached 89.2?±?4, 104.5?±?15.3, 30.2?±?4 and 181.5?±?2.6?mV, respectively. W. cibaria showed the highest reducing activity and P. pentosaceus the lowest one. The maximal reduction rate was neither correlated with the highest acidification rate nor with the maximal growth rate. Nevertheless, the reduction rate shows a similar trend like the acidification rate during the time course of fermentation. The ORP changes occurred concomitantly with the acidification, and the acid production decreased after 2?h from the reducing step. These results showed the possibility to carry out ORP measurements in dough system. As strains exhibit very characteristic ORP curves, this parameter can be used as real-time control tool to monitor the time course of fermentation and metabolic activity. This enables an evidence-based determination of fermentation end and/or (intermediate) harvesting point, which is especially helpful in the development of new cereal fermentation types as in gluten-free sourdoughs.     

酵母与乳酸菌的相互作用模式及其在发酵食品中的应用研究进展

酵母与乳酸菌作为被广泛应用的微生物在发酵食品的生产过程中起着举足轻重的作用,二者在发酵体系中的作用方式直接决定了产品的品质。研究发酵体系中酵母-乳酸菌间的相互作用模式有助于揭示微生物与食品功能的关系,对发酵进程的正向调控具有重要意义。本文综述了酵母与乳酸菌在发酵过程中发生的协同/拮抗作用、营养代谢产物交换、群体感应及生物膜包被等相互作用模式,探讨了酵母-乳酸菌相互作用对改善发酵食品风味质构、缩短发酵周期、提升产品益生特性等的积极作用。最后,对酵母-乳酸菌作为组合发酵剂进行强化发酵的应用前景进行了总结与展望。