Study of the behaviour of Lactobacillus plantarum and Leuconostoc starters during a complete wheat sourdough breadmaking process

The acidification properties, metabolic activity and technological performance of four individual Lactobacillus plantarum or Leuconostoc freeze-dried starters were investigated during a complete wheat sourdough breadmaking process including 0.2 g/100 g baker's yeast. Microbiological contents (lactic acid bacteria and yeasts), acidification characteristics (pH and total titratable acidity), soluble carbohydrates (maltose, glucose and fructose) and fermentative end-products (lactic and acetic acids, ethanol) contents were evaluated during both sourdough and corresponding bread dough fermentation. Biochemical and technological analysis of the resulting bread products are also presented. Some differences among strains in acidification properties and soluble carbohydrates availability were outlined both in sourdough and bread dough. Each individual Leuconostoc or Lb. plantarum starter was able to produce a characteristic fermentation and was found to ensure the production of breads with overall satisfactory acceptance.     

Propionic acid production by cofermentation of Lactobacillus buchneri and Lactobacillus diolivorans in sourdough

Cooperative metabolism of lactobacilli in silage fermentation converts lactate to propionate. This study aimed to determine whether propionate production by Lactobacillus buchneri and Lactobacillus diolivorans can be applied for bread preservation. Propionate formation was observed in cofermentation with L. buchneri and L. diolivorans in modified MRS broth as well as sourdough with low, medium and high ash contents. 48 mM of propionate was formed in sourdough with medium ash content, but only 9 and 28 mM propionate were formed in sourdoughs prepared from white wheat flour or whole wheat flour, respectively. Acetate levels were comparable in all three sourdoughs and ranged from 160 to 175 mM. Sourdough fermented with L. buchneri and L. diolivorans was used in breadmaking and its effect on fungal spoilage was compared to traditional sourdough or propionate addition to straight doughs. Bread slices were inoculated with Aspergillus clavatus, Cladosporium spp., Mortierella spp. or Penicillium roquefortii. The use of 20% experimental sourdough inhibited growth of three of the four moulds for more than 12 days. The use of 10% experimental sourdough deferred growth of two moulds by one day. Bread from traditional sourdough with added acetate had less effect in inhibiting mould growth.     

Evolution of aroma volatiles during storage of sourdough breads made by mixed cultures of Kluyveromyces marxianus and Lactobacillus delbrueckii ssp. bulgaricus or Lactobacillus helveticus

Two mixed starter cultures were used for sourdough bread making to evaluate their ability to improve quality and increase bread shelf-life: Lactobacillus delbrueckii ssp. bulgaricus or Lactobacillus helveticus mixed with the lactose fermenting yeast Kluyveromyces marxianus as alternative baker’s yeast. Control sourdough breads (K. marxianus) without the addition of bacteria, were also prepared. The changes on the headspace aroma volatiles during storage were assessed using solid-phase microextraction (SPME) GC–MS analysis. The effect of these changes on bread flavour was evaluated by consumer preference evaluations and the results were co-evaluated with those from the GC–MS analysis. The obtained results showed differences in the volatile composition of the different types of breads examined, as well as dramatic decreases of the number and the amount of volatiles after five days of storage. The sourdough breads made with K. marxianus and L. bulgaricus, had a more complex aroma profile, longer shelf-life and achieved the highest scores in the sensory tests.     

Immobilization of kefir and Lactobacillus casei on brewery spent grains for use in sourdough wheat bread making

New types of bread were produced employing baker’s yeast, kefir or Lactobacillus casei immobilized on brewer’s spent grains. Bread was produced either by the straight-dough or the sourdough method. All the studied biocatalysts and their corresponding sourdoughs were found efficient for breadmaking. Good rising was achieved and the produced breads had good overall quality and remained fresher for longer, compared to commercial type baker’s yeast bread. The best results were obtained for sourdough breads, with higher moisture retention during baking, lower rates of water evaporation and staling, and maintenance of freshness for longer (4–5 days). Consumer evaluation showed bigger preference for the sourdough breads as far as aroma, taste and overall quality were concerned, justified by the GC-MS analysis of volatiles that revealed a different aroma profile, with more compounds identified than in breads produced by the straight-dough method, obviously due to variations in microbial populations.     

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.     

Application of Kluyveromyces marxianus, Lactobacillus delbrueckii ssp. bulgaricus and L. helveticus for sourdough bread making

The application of Kluyveromyces marxianus (IFO 288), Lactobacillus delbrueckii ssp. bulgaricus (ATCC 11842) and Lactobacillus helveticus (ATCC 15009) as starter cultures for sourdough bread making was examined. Production of lactic and acetic acids, bread rising, volatile composition, shelf-life and organoleptic quality of the sourdough breads were evaluated. The amount of starter culture added to the flour, the dough fermentation temperature and the amount of sourdough used were examined in order to optimise the bread making process. The use of mixed cultures led to higher total titratable acidities and lactic acid concentrations compared to traditionally made breads. Highest acidity (3.41 g lactic acid/kg of bread) and highest resistance to mould spoilage were observed when bread was made using 50% sourdough containing 1% K. marxianus and 4% L. delbrueckii ssp. bulgaricus. The use of these cultures also improved the aroma of sourdough breads, as shown by sensory evaluations and as revealed by GC–MS analysis.     

Survival of human derived Lactobacillus plantarum in fermented cereal extracts during refrigerated storage

The aim of this study was to investigate the survival of a potentially probiotic Lactobacillus plantarum strain in barley, wheat and barley malt extracts. The extracts were produced from three flour/water suspensions, i.e., 5%, 20%, 30% w/w. After inoculation, the cultures were incubated for 24 h at 37 °C, and were subsequently stored at 4 °C for up to seventy days. The lactic acid and reducing sugar concentrations at the beginning of storage were significantly different between the fermented media, ranging from 0.5 g/L to 17 g/L and from 0.8 g/L to 6.5 g/L respectively, while the pH ranged between 2.9 and 3.4. It was observed that the cells survived much better in the malt extracts compared to barley and wheat extracts during refrigerated storage. Based on the results from a study using model media and supplemented cereal extracts it was derived that this was most likely due to their higher sugar concentration and the presence of protective unidentified compounds, albeit the fact that the malt extracts contained higher amounts of lactic acid.     

Selection of Lactobacillus plantarum strains to use as starters in fermented table olives: Oleuropeinase activity and phage sensitivity

Fermented table olives (Olea europaea L.) are largely diffused in the Mediterranean area. Olives are picked at different stages of maturity and after harvesting, processed to eliminate the characteristic bitterness caused by the presence of the oleuropein glucoside and to become suitable for human consumption. The spontaneous fermentation of table olives mainly depends on lactic acid bacteria (LAB), and in particular on Lactobacillus plantarum which plays an important role in the degradation of oleuropein. The hydrolysis of oleuropein is attributed to the β-glucosidase and esterase activities of the indigenous LAB microflora. This study investigated the potential of L. plantarum strains isolated from dairy products and olives to be used as starters for fermented table olives. Forty-nine strains were typed by RAPD-PCR and investigated for the presence of the β-glucosidase (bglH) gene. The full sequence of the bglH gene was carried out. All the 49 L. plantarum strains were also tested for phage resistance. A total of six strains were selected on the basis of genotypic polymorphism, bglH gene sequence analysis, and phage resistance profile. These strains were further characterized to assess the acidifying capability, the growth at different temperatures, the tolerance to different NaCl concentrations, and the oleuropeinolytic activity. Although further characterizations are required, especially concerning the influence on sensory properties, L. plantarum proved to have the potential to be used as a debittering and fermentative agent in starter culture for fermented table olives.     

Selenium enriched green tea increase stability of Lactobacillus casei and Lactobacillus plantarum in chitosan coated alginate microcapsules during exposure to simulated gastrointestinal and refrigerated conditions

The effects of selenium enriched green tea (SGT; 85.8–96 mg/kg) in different concentrations of 1 g and 2 g/100 mL, on the in vitro exposure to simulated gastrointestinal juice and refrigerated storage of encapsulated Lactobacillus casei and Lactobacillus plantarum were investigated in chitosan coated alginate beads. The encapsulation yield of viable cells in chitosan coated alginate beads with and without SGT was not significantly different (P < 0.05). These results together with the study about the survival of probiotic bacteria in microspheres with SGT during storage at 4 °C, demonstrated significantly higher number (P < 0.05) of survival bacteria in microcapsules with SGT 2 g/100 mL. Microencapsulated L. casei and L. plantarum with SGT 1 g and 2 g/100 mL were resistant to simulated gastric conditions (pH 2.0, 2 h) and bile solution (3 g/100 mL, 2 h) resulting in significantly (P < 0.05) improved survival when compared with microencapsulation without SGT addition.     

Functional properties of Lactobacillus plantarum strains: A multivariate screening study

Thirty-two Lactobacillus plantarum strains isolated from different sources were genetically characterized at subspecies level with recA gene based multiplex PCR and pulsed-field electrophoresis.     

Metabolism of food phenolic acids by Lactobacillus plantarum CECT 748

Phenolic acids account for almost one third of the dietary phenols and are associated with organoleptic, nutritional and antioxidant properties of foods. This study was undertaken to assess the ability of Lactobacillus plantarum CECT 748^T to metabolize 19 food phenolic acids. Among the hydroxycinnamic acids studied, only p-coumaric, caffeic, ferulic and m-coumaric acids were metabolized by L. plantarum. Cultures of L. plantarum produced ethyl and vinyl derivatives from p-coumaric and caffeic acids, 4-vinyl guaiacol from ferulic acid, and 3-(3-hydroxyphenyl) propionic acid from m-coumaric acid. Among the hydroxybenzoic acids analysed, gallic acid and protocatechuic acid were decarboxylated to pyrogallol and catechol, respectively. Inducible enzymes seem to be involved, at least in m-coumaric and ferulic acid metabolism, since cell-free extracts from cultures grown in the absence of these phenolic acids were unable to metabolize them. Further work is needed for the identification of the enzymes involved, since the knowledge of the metabolism of phenolic compounds is an important issue for the food industry.     

Growth,survival, and peptidolytic activity of Lactobacillus plantarum I91 in a hard-cheese model

In this work, we studied the growth, survival, and peptidolytic activity of Lactobacillus plantarum I91 in a hard-cheese model consisting of a sterile extract of Reggianito cheese. To assess the influence of the primary starter and initial proteolysis level on these parameters, we prepared the extracts with cheeses that were produced using 2 different starter strains of Lactobacillus helveticus 138 or 209 (Lh138 or Lh209) at 3 ripening times: 3, 90, and 180 d. The experimental extracts were inoculated with Lb. plantarum I91; the control extracts were not inoculated and the blank extracts were heat-treated to inactivate enzymes and were not inoculated. All extracts were incubated at 34°C for 21 d, and then the pH, microbiological counts, and proteolysis profiles were determined. The basal proteolysis profiles in the extracts of young cheeses made with either strain tested were similar, but many differences between the proteolysis profiles of the extracts of the Lh138 and Lh209 cheeses were found when riper cheeses were used. The pH values in the blank and control extracts did not change, and no microbial growth was detected. In contrast, the pH value in experimental extracts decreased, and this decrease was more pronounced in extracts obtained from either of the young cheeses and from the Lh209 cheese at any stage of ripening. Lactobacillus plantarum I91 grew up to 8 log during the first days of incubation in all of the extracts, but then the number of viable cells decreased, the extent of which depended on the starter strain and the age of the cheese used for the extract. The decrease in the counts of Lb. plantarum I91 was observed mainly in the extracts in which the pH had diminished the most. In addition, the extracts that best supported the viability of Lb. plantarum I91 during incubation had the highest free amino acids content. The effect of Lb. plantarum I91 on the proteolysis profile of the extracts was marginal. Significant changes in the content of free amino acids suggested that the catabolism of free amino acids by Lb. plantarum I91 prevailed in a weakly proteolyzed medium, whereas the release of amino acids due to peptidolysis overcame their catabolism in a medium with high levels of free amino acids. Lactobacillus plantarum I91 was able to use energy sources other than lactose to support its growth because equivalent numbers of cells were observed in extracts containing residual amounts of lactose and in lactose-depleted extracts. The contribution of Lb. plantarum I91 to hard-cooked cheese peptidolysis was negligible compared with that of the starter strain; however, its ability to transform amino acids is a promising feature of this strain.     

传统酸面团中植物乳杆菌发酵馒头抗氧化特性及挥发性风味物质特征

为了探究具有不同菌种关系的乳酸菌和酵母菌在泡菜发酵过程中的发酵性能,本实验选取不同食品来源的8株乳酸菌和5株酵母菌,通过代谢产物交叉培养及菌株共培养方法,筛选到一对具有互促关系的乳酸菌和酵母菌,即植物乳杆菌（Lactiplantibacillus plantarum）J05和酿酒酵母（Sacchromyces cerevisiae）Y21。分别从培养方式、接种顺序、接种比例等方面分析该组菌共培养关系,并测定了泡菜发酵过程中pH、总酸、还原糖含量、亚硝酸盐的含量。结果显示,添加酿酒酵母Y21静置培养无菌代谢产物对处于生长期的植物乳杆菌J05具有明显促生长作用,先接种酿酒酵母Y21后接种植物乳杆菌J05可促进两种菌的生长,筛选到两株菌共培养的最佳比例为30:1和40:1。在30:1的接种比例下,泡菜发酵进入稳定期后,与自然发酵组、单菌组、互抑组相比较,互促组pH维持在3.4~3.5之间,显著低于其他各组（P<0.05）;总酸含量最高值为1.25 mg/kg,显著高于其他各组（P<0.01）;还原糖含量较低,维持在0.10 g/100 g左右,亚硝酸盐峰值含量为5.38 mg/kg,显著低于除酿酒酵母Y21组外的其他三组（P<0.01）。本实验筛选所得互促菌组发酵性能较强,可缩短泡菜发酵周期,降低泡菜中亚硝酸盐含量。     

pH and dose-dependent effects of quercetin on the fermentation capacity of Lactobacillus plantarum

This article reports a study of how quercetin affects the capacity of Lactobacillus plantarum RM71 to ferment different media, including a chemically defined medium (CDM) and media relevant for practical fermentation processes. It is shown for the first time that quercetin exerts pH- and dose-dependent effects on the fermentation performance of L. plantarum. At an initial pH of 5.5, quercetin promoted quicker growth upon inoculation at increased quercetin concentrations, while a detrimental dose-dependent lengthening of the lag phase was observed at an initial pH of 6.5. The time course of sugar consumption and lactic acid production data tracking in pH 5.5 CDM showed that quercetin promoted quicker sugar consumption as a result of earlier sugar uptake and lactic acid production than in the control. A model wine and a similar medium with modified sugar composition were fermented with L. plantarum RM71 on quercetin. Quercetin improved several key fermentation traits for the performance of L. plantarum in food production, including accelerated fermentation of various sugars, and accelerated malolactic fermentation and lactic acid production. Quercetin was not catabolized by L. plantarum in the fermentations, so the antioxidant properties of the flavonol were protected against degradation while the bacterium improved its growth performance.     

High-salt brines compromise autoinducer-mediated bacteriocinogenic Lactobacillus plantarum survival in Spanish-style green olive fermentations

The effect of NaCl on plantaricin production by five Lactobacillus plantarum strains was investigated. Plantaricin production in these strains was found to be regulated by three-component regulatory systems ruled by two different autoinducer peptides (AIPs), either PLNC8IF or Plantaricin A. Bacteriocin activity exhibited by these strains came to a halt in liquid medium containing NaCl concentrations of or above 2%. In contrast, bacteriocin activity was still observed when the producing strains were growing on solid medium containing up to 4% NaCl. Bacteriocin activity in liquid medium containing up to 2% NaCl could be restored by coculturing the producing strains with a selected plantaricin-production inducing strain of Lactococcus lactis. Growth of these bacteriocinogenic L. plantarum strains was monitored in traditional Spanish-style green olive fermentations. Survival of these strains could not be enhanced when provided with a range of plantaricin-production inducing mechanisms previously described, such as constitutive AIP production or coinoculation with a specific bacteriocin-production inducing strain of L. lactis. Our results suggest that it is advisable the use of constitutive bacteriocin producers, or at least non-AIP-dependant ones, as starters for olive fermentations due to the intrinsic physical characteristics of this food fermentation, especially the high salt concentration of the brines currently used.     

Effect of Lactobacillus plantarum and chitosan in the reduction of browning of pericarp Rambutan (Nephelium lappaceum)

The effects of Lactobacillus plantarum alone or in combination with chitosan were evaluated on quality and color retention in rambutan fruits (Nephelium lappaceum) stored at 25 °C and 10 °C with 75 ± 2.5% of relative humidity for 10 and 15 days, respectively. The development of the microorganisms was evidenced by viability analyses and lactic acid production. The application of L. plantarum significantly improved color retention (a* and L*), and reduced weight losses. The lactobacilli, alone or in combination with chitosan, preserved fruit quality characteristics such as firmness, total soluble solids and titratable acidity. The lactobacilli application on rambutan pericarp produced acidification of pericarp and avoided the browning; thereby desiccation was prevented due to biofilm formation.     

冻干保护剂对植物乳杆菌的代谢特性的影响

通过分析植物乳杆菌Lactobacillus plantarum CGMCC 6016(L. P. dy-1)冻干菌粉发酵后胞内游离氨基酸、有机酸、菌体蛋白的谱图变化,对比研究了不同冻干保护剂对L. P. dy-1冻干菌粉代谢特征的影响。结果显示,直接活化组L. P. dy-1的胞内氨基酸总量为625.23 μg/100 μL,10%菊粉保护剂组有所增加,为753.72 μg/100 μL;22.4%菊粉保护剂组、菊粉复合保护剂组和脱脂乳复合保护剂组则相对减少;直接活化组L. P. dy-1的胞内有机酸总量为62.84 mg/L,冻干保护剂组均显著降低,其中菊粉复合保护剂组与直接活化组最为接近,为52.99 mg/L;不同菊粉保护剂组冻干菌粉发酵后,菌体蛋白的谱图较为相近,且与直接活化组差异不大,脱脂乳复合保护剂组较未冻干菌体蛋白谱差异明显,表现为有较多条带的缺失,且谱带较浅。结果表明,与常用的脱脂乳复合保护剂相比,菊粉保护剂,尤其是菊粉复合保护剂的添加,能够使植物乳杆菌冻干菌粉的代谢特性更接近正常组。     

植物乳杆菌微胶囊化研究

为保护植物乳杆菌的活性以增强乳杆菌在动物肠道内的益生功能,以天然发酵玉米青贮饲料中优良植物乳杆菌作为芯材,乳清蛋白和明胶为壁材,利用喷雾干燥法制成微胶囊,并以植物乳杆菌包埋率为响应值,研究壁材配比、壁材添加量、进风温度、进料量4个因素,进行中心组合实验(Box-Behnken),通过响应面分析对喷雾干燥法制备植物乳杆菌微胶囊条件进行优化。结果表明:最优条件为壁材配比(乳清蛋白与明胶质量比)1:2、壁材添加量22%、进风温度127℃、进料量35%,在此条件下,植物乳杆菌包埋率为62.15%。结论:本研究为应用喷雾干燥法制备植物乳杆菌微胶囊奠定了基础。