Selection of phytate-degrading human bifidobacteria and application in whole wheat dough fermentation

Lately, whole wheat products are highly recommended from their healthy properties. However, the presence of phytic acid (InsP(6)) could partly limit their benefits because it decreases the mineral bioavailability due to its chelating properties. The objective of this work was to select strains with high phytate-degrading activity from human feces, and evaluate their suitability for the bread making process. Twenty-three different bifidobacterial strains (13 from infants and 10 from adults) were isolated, belonging to the species Bifidobacterium longum, Bifidobacterium breve and Bifidobacterium catenulatum. The phosphatase and phytase activities of these strains were evaluated as well as their ability to degrade InsP(6) during growth. Then, the fermentative ability of the strain showing the highest phytate-degrading activity (B. longum. BIF307) was determined in whole wheat breadmaking. The use of the selected bifidobacterial strain as starter during whole wheat fermentation resulted in bread with similar technological quality than the control (in absence of bifidobacteria) and crumb with lower levels of inositol phosphates. Therefore, the used of the selected Bifidobacterium strain in whole wheat breadmaking process could provide potential nutritional benefits by decreasing the antinutrient content of the product.     

Selection of lactic acid bacteria with high phytate degrading activity for application in whole wheat breadmaking

Whole wheat products although highly recommended from the nutritional point of view, contain high levels of phytic acid, an antinutrient that decrease the mineral bioavailability. The objective of this study was to select strains with high phytate-degrading activity from different parts of the gastrointestinal tract of chickens following a phytate-rich diet and to test their suitability for the breadmaking process of whole wheat bread. Different lactobacilli and bifidobacteria strains were isolated and individually assayed for phosphatase and phytase activities, since both enzymes could contribute to the degradation of phytate. The isolates showing the highest phytate degrading activity belonged to the species Bifidobacterium dentium, Lactobacillus reuteri (L-M15) and Lactobacillus salivarius (L-ID15). The two lactobacilli L-M15 and L-ID15 were selected and tested their fermentative ability in whole wheat breadmaking. Whole wheat breads in the presence of the selected lactobacilli had similar technological quality than the control (in absence of lactobacilli) and extended freshness; moreover, their presence resulted in bread crumbs with lower levels of inositol phosphates. Overall, the two intestinal lactobacilli strains showing high phytate degrading activity were proven to have good properties for being used as starters in whole wheat breadmaking process.     

Phytate degradation by human gut isolated Bifidobacterium pseudocatenulatum ATCC27919 and its probiotic potential

The growing awareness of the relationship between diet and health has led to an increasing demand for food products that support health above and beyond providing basic nutrition. Probiotics are live organisms present in foods, which yield health benefits related to their interactions with the gastrointestinal tract. Phytases are a subgroup of phosphatases that catalyse the desphosphorylation of phytate, which reduces its negative impact on mineral bioavailability, and generates lower inositol phosphates. The aims of this investigation were to (i) study the ability of the probiotic candidate Bifidobacterium pseudocatenulatum to degrade phytate in synthetic medium, to (ii) identify the lower inositol phosphates generated, to (iii) study its survival under conditions mimicking gastrointestinal passage and finally to (iv) assess adhesion of the bacteria to Caco-2 cells. The first steps of InsP₆ degradation by B. pseudocatenulatum phytate-degrading enzyme/s were preferentially initiated at the DL-6-position and 5-position of the myo-inositol ring. It suggests that the main InsP₆ degradation pathway by B. pseudocatenulatum by sequential removal of phosphate groups was D/L-Ins(1,2,3,4,5)P₅ or D/L-Ins(1,2,3,4,6)P₅; D/L-Ins(1,2,3,4)P₄; to finally Ins(1,2,3)P₃ and D/L-Ins(1,2,4)P₃/D/L-Ins(1,3,4)P₃. This human strain also showed a notable tolerance to bile as well as a selective adhesion capacity (adhesion to control surfaces was zero), to human intestinal Caco-2 cells comparable to the commercial probiotic B. lactis. The phytate-degrading activity constitutes a novel metabolic trait which could contribute to the improvement of mineral absorption in the intestine as a nutritional probiotic feature with potential trophic effect in human gut.     

全麦发酵面团菌群结构分析及对风味物质的影响

采用宏基因组学的方法解析全麦传统发酵面团细菌菌群结构组成,确定其核心菌属为乳酸菌科乳杆菌属短乳杆菌种。对全麦传统发酵面团和商业发酵面团的风味物质进行了测定,发现传统发酵面团风味物质种类比商业发酵多9种,在含量上也存在差异,但均以烃的含量最多。说明传统发酵剂更有利于全麦面团风味物质的形成,更易让消费者接受,为传统发酵剂在全麦制品中的应用提供理论支持。     

Effects of soaking, germination and fermentation on phytic acid, total and in vitro soluble zinc in brown rice

Rice is an important staple food in Asian countries. In rural areas it is also a major source of micronutrients. Unfortunately, the bioavailability of minerals, e.g. zinc from rice, is low because it is present as an insoluble complex with food components such as phytic acid. We investigated the effects of soaking, germination and fermentation with an aim to reduce the content of phytic acid, while maintaining sufficient levels of zinc, in the expectation of increasing its bioavailability. Fermentation treatments were most effective in decreasing phytic acid (56–96% removal), followed by soaking at 10 °C after preheating (42–59%). Steeping of intact kernels for 24 h at 25 °C had the least effect on phytic acid removal (<20%). With increased germination periods at 30 °C, phytic acid removal progressed from 4% to 60%. Most wet processing procedures, except soaking after wet preheating, caused a loss of dry mass and zinc (1–20%). In vitro solubility, as a percentage of total zinc in soaked rice, was significantly higher than in untreated brown rice while, in steeped brown rice, it was lower (p < 0.05). Fermentation and germination did not have significant effects on the solubility of zinc. The expected improvement due to lower phytic acid levels was not confirmed by increasing levels of in vitro soluble zinc. This may result from zinc complexation to other food components.     

Fermentation of rice using amylolytic Bifidobacterium

Twenty-two amylolytic bifidobacteria grown in BHI-starch media were compared for the amylase activity of the intra- and extra-cellular enzymes. The activity of the cells grown in the liquid medium differed considerably. Among the strains tested B. adolescentis Int57 and B. adolescentis ZS8 exhibited higher activities than others. In rice medium containing 0.05% -cysteine·HCl and 0.2% yeast extract, the amylolytic Bifidobacterium strains grew considerably better than non-amylolytic Bifidobacterium strains. B. adolescentis Int57, which showed highest growth and amylase activity in the rice medium, was chosen and rice fermentation was investigated. The titratable acidity (TA) reached 2.43 and pH decreased to 4.4 after 24 h fermentation. The relative ratio of acetic acid to lactic acid gradually decreased during fermentation. The concentration of reducing sugar and amylase activity gradually increased and reached 14 mg maltose equivalent/ml and 35 mU/ml min, respectively, in 24 h. The accumulated reducing sugar was mostly maltotriose. The layer-separation of fermented product was stabilized by the addition of 1% gelatin. It was suggested that amylolytic bifidobacteria may be used for the production of fermented rice products.     

麸皮预处理对全麦面团及面包的影响

本实验分别采用微波、烘烤、常压蒸汽、高压蒸汽对小麦麸皮进行预处理,研究比较了不同预处理方法对全麦面团和面包品质的影响。结果表明：和未处理全麦粉相比,烘烤、常压蒸汽和高压蒸汽处理均使全麦粉的稳定时间提高,其中常压蒸汽效果最显著,提高了4.2 min;同时,这三种处理方式分别使全麦面包的比容增加了6.92%、9.34%、5.19%,硬度分别降低11.81%、21.79%、19.57%,弹性分别提高2.59%、3.06%、1.65%。推测原因是这三种处理方式均显著降低了麸皮中的还原型谷胱甘肽含量,使全麦面团的游离巯基显著减少,二硫键显著增加,其中常压蒸汽和高压蒸汽效果最显著,分别使还原型谷胱甘肽减少了66.77%、69.30%,使游离巯基减少了40.43%、42.77%,使二硫键增加了51.35%、38.63%。综上,采用烘烤、常压蒸汽、高压蒸汽对麸皮预处理,可以通过降低还原型谷胱甘肽含量、提高二硫键含量来提高面团的稳定性,进而改善面包品质,且常压蒸汽处理的改善效果最好。     

馒头加工过程中发酵及蒸制对小麦淀粉结构特性的影响

以甘肃省白银市银春10号小麦粉为原料制作馒头。通过碱法提取面团发酵和馒头蒸制阶段的淀粉,对其结构特性进行研究。结果表明面团发酵不改变淀粉形态,馒头蒸制过程淀粉结构严重破坏,颗粒之间相互粘连形成片状结构。面团发酵过程中淀粉结晶度随面团发酵时间的增加先增加后降低,面团发酵20 min时达到最大(49.35%),馒头蒸制过程中淀粉结晶度显著低于小麦淀粉。面团发酵淀粉的1 047/1 022 cm^-1和1 022/995 cm^-1值高于小麦淀粉,而馒头蒸制淀粉的1 047/1 022 cm^-1值随着蒸制时间的延迟而降低至0.606,1 022/995 cm^-1则呈先增加后降低。面团发酵10 min和20 min时,淀粉粒径显著降低了3.0%和1.7%。面团发酵30 min淀粉T_o、T_p和T_c显著高于小麦淀粉,馒头蒸制时间从10 min延长至20 min过程中,淀粉ΔH显著升高了70.60%。     

Effect of fortification on physico-chemical and microbiological stability of whole wheat flour

Stability of fortified whole wheat flour (WWF) was evaluated using NaFeEDTA, elemental iron, ZnSO₄ and ZnO as fortificants. Fortified WWF was stored in tin boxes and polypropylene bags for 60 days under ambient storage condition (ASC) and controlled storage condition (CSC). Fortification significantly (p ? 0.05) decreased moisture and protein content and increased ash content to 5.44%, 6% and 23%, as compared to control. Fortified WWF, assayed periodically for mould contamination manifested a significant inhibition (∼1 log reduction) in flours containing elemental iron. Low storage temperature and relative humidity (RH) indicated lower level of mould count during extended storage time. Tin boxes, as storage material, exhibited a better protection against mould attack, acting as an effective barrier for moisture. Fortificants exerted a slight deteriorative effect on texture characteristics of the chapattis made of these flours but chapattis were still accepted by the judges. Zinc fortificants seemed like having little or no effect on the quality of the flours and chapattis, made of such flours. Shelf life of fortified flour may be extended by using elemental iron as fortificant and storing the product in tin boxes under relatively low temperature and RH.     

Effects of milk products fermented by Bifidobacterium longum on blood lipids in rats and healthy adult male volunteers

The effects of milk products fermented by Bifidobacterium longum strain BL1, a probiotic strain, on blood lipids in rats and humans were studied. Rats were fed a cholesterol-enriched experimental diet, supplemented with lyophilized powders of 1) acid milk (control), 2) milk fermented with a mixed culture of ordinary yogurt starters composed of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus (SL), and 3) bifidobacterium milk fermented with the probiotic B. longum strain BL1, respectively. The bifidobacterium milk feeding brought about significant lowering of the serum concentrations of total cholesterol, low-density lipoprotein cholesterol, and triglycerides, in comparison with the control, while no change in high-density lipoprotein cholesterol concentration was observed. On the other hand, supplementation with SL milk resulted in only slight, nonsignificant decreases in serum lipid concentrations in comparison with the control. In the human study, 32 subjects with serum total cholesterol ranging from 220 to 280 mg/dl were randomly assigned to two treatments: 1) intake of a low-fat drinking yogurt prepared with ordinary yogurt starters composed of S. thermophilus and L. delbrueckii subsp. bulgaricus (P-group) and 2) intake of a low-fat drinking yogurt prepared with the two ordinary yogurt starters plus B. longum strain BL1 (B-group). After intake for 4 wk at 3 x 100 ml/day, reduction of serum total cholesterol was observed in approximately half of the B-group subjects; a particularly significant decrease in serum total cholesterol was found among subjects with moderate hypercholesterolemia (serum total cholesterol > 240 mg/dl). However, the serum lipid concentrations in the P-group subjects were almost stable during the experimental periods. The present results indicate the potential of the probiotic B. longum strain BL1 in serum lipid improvement.     

Lactobacillus reuteri CRL 1100 as starter culture for wheat dough fermentation

The effect of sucrose on the fermentation balance of Lactobacillus reuteri CRL 1100 and the invertase activity of this strain in wheat dough and culture medium (MRSs) was evaluated. The enzyme activity was dependent on the environmental pH releasing glucose and fructose from sucrose hydrolysis. Glucose was used as carbon source, while fructose was mainly used as electron acceptor to produce mannitol up to 10h of fermentation. Thereafter, fructose seemed to be metabolized by the heterofermentative pathway, which determined an increase in the concentration of acetate (6 mmol l(-1)), lactate (2 mmol l(-1)) and ethanol (1 mmol l(-1)) and the lack of mannitol formation after glucose depletion. The fermentation balance of Lb. reuteri CRL 1100 during the dough fermentation resulted in lower (63%) ethanol, higher (75%) acetate production and soluble carbohydrates concentrations, like MRSs cultures. This fermentation profile would be important to obtain an optimal growth of yeast and the optimal bread flavor and taste.     

母乳胞外囊泡促进乳双歧杆菌BB-12生长的转录组学分析

胞外囊泡是母乳中的重要功能成分之一,作者所在实验室前期研究发现,母乳胞外囊泡能够显著促进乳双歧杆菌BB-12的生长,但具体机制不清楚。作者采用超速离心法与超滤法相结合从母乳中提取胞外囊泡,通过纳米颗粒追踪技术、透射电镜以及蛋白质免疫印迹法对母乳胞外囊泡进行了鉴定表征。利用转录组学技术分析母乳胞外囊泡促进乳双歧杆菌BB-12生长的关键基因。研究发现,添加母乳胞外囊泡后,乳双歧杆菌BB-12菌体中ABC寡肽转运系统相关基因pstC、pstA、metI,淀粉和蔗糖代谢相关基因BIF＿02090,磷酸戊糖途径相关基因prsA、BIF＿01321,D-氨基酸代谢相关基因murD、BIF＿02122,乙醛酸和二羧酸代谢相关基因pccA的表达显著上升。结果表明,母乳胞外囊泡可能作为一种新型益生元促进婴幼儿肠道中双歧杆菌的生长,为母乳胞外囊泡在新一代母乳化奶粉中的开发应用提供了理论依据。     

Effect of sourdough fermentation on stabilisation,and chemical and nutritional characteristics of wheat germ

Lactic acid bacteria strains were identified from wheat germ by 16S rRNA partial sequencing, subjected to RAPD-PCR typing and screened. Lactobacillus plantarum LB1 and Lactobacillus rossiae LB5 were used as starters to produce sourdough fermented wheat germ (SFWG). The chemical and nutritional characteristics of SFWG were compared to those of the raw wheat germ (RWG). Lipase activity in SFWG was ca. 2.6-fold lower than that found in RWG. As shown by SPME/GC/MS analysis, most of the volatile compounds derived from lipid oxidation during storage (40 days) were at markedly lower levels in SFWG compared to RWG. Fermentation of wheat germ increased of ca. 50% the concentration of free amino acids. Glu markedly decreased in SFWG, due to its conversion in GABA. The concentration of the anti-nutritional factor raffinose also decreased in SFWG. The in vitro protein digestibility, the concentration of total phenols, phytase and antioxidant activities were increased by fermentation.     

Safety and intestinal microbiota modulation by the exopolysaccharide-producing strains Bifidobacterium animalis IPLA R1 and Bifidobacterium longum IPLA E44 orally administered to Wistar rats

Bifidobacterium animalis subsp. lactis IPLA R1 and Bifidobacterium longum IPLA E44 strains were tested for their safety and ability to modulate the intestinal microbiota in vivo. Chemically simulated gastrointestinal digestion showed considerably lower survival of E44 than R1 strain, the first microorganism also being more sensitive to refrigerated storage in 10% skimmed milk at 4 °C. Harmful glycosidic activities were absent, or at low levels, in the strains R1 and E44. Both strains were sensitive to most antibiotics and resistant to aminoglycosides, a common feature in bifidobacteria. Similar to several other bifidobacteria strains, B. animalis subsp. lactis IPLA R1 displayed a moderate resistance against tetracycline which correlated with the presence of tet(W) gene in its genome. The general parameters indicating well-being status, as well as translocation to different organs and histological examination of the gut tissues, revealed no changes induced by the administration of bifidobacteria to rats. Twelve-week-old male Wistar rats were distributed into three groups, eight rats in each. Two groups were administered daily over 10⁸ cfu of the corresponding strain suspended in 10% skimmed milk for 24 days, whereas rats in the placebo group received skimmed milk without microorganisms added. The microbiota and short chain fatty acids (SCFA) were monitored in faeces at different time points during treatment and in caecum content at the end of the assay. Quantitative PCR (qPCR) showed that faecal and caecal Bifidobacterium levels were higher in bifidobacteria-fed rats than in the placebo rats at the end of the intervention, whereas total anaerobic plate counts did not show significant differences. Quantification of B. animalis and B. longum by qPCR showed that, independent of the microorganism administered, treatment with bifidobacteria resulted in higher levels of B. animalis in the caecum. PCR-DGGE analysis of microbial populations revealed a higher diversity of bands in caecum content of rats fed B. animalis IPLA R1 than in the placebo group and rats fed B. longum IPLA E44. Remarkably, although no variations in the proportion of acetate, propionate and butyrate were found, at the end of the assay the total SCFA concentration in the faeces of rats fed bifidobacteria was significantly higher and those in caecum content significantly lower, than that of the placebo group. This suggests a displacement of the SCFA production to parts of the colon beyond the caecum in rats receiving bifidobacteria. Therefore, the oral administration of B. animalis IPLA R1 and B. longum E44 can be considered safe, these microorganisms having the ability to modulate the intestinal microbiota of rats by influencing SCFA and the bifidobacterial population levels.     

Behaviour ofYersinia enterocolitica andAeromonas hydrophila in skim milk during fermentation by various lactobacilli

In this study, behaviour ofYersinia enterocolitica andAeromonas hydrophila in skim milk during fermentation by various_{lactobacillus} sp. were determined. pH values of the skim milk samples were also examined during fermentation. The amount of produced lactic acid and diacetyl/acetoin productions of theLactobacillus sp. were estimated. Antimicrobial effects of the lactobacilli onY. enterocolitica andA. hydrophila were also determined by an agar diffusion method. WhileY. enterocolitica was not inhibited and grew during fermentation,A. hydrophila was inhibited, in part, and the growth was retarded. Results were supported by the agar diffusion method forY. enterocolitica, whereas inhibition activity was not found forA. hydrophila. The highest lactic acid productions were estimated inL. bulgaricus (7.50 mg/ml) andL. acidophilus (5.63 mg/ml) and four out of sixLactobacillus sp. were found to be diacetyl/acetoin producers.     

Effects of trypsin‐hydrolyzed wheat gluten peptide on wheat flour dough

BACKGROUND: Gluten peptide was prepared by trypsin hydrolysis and characterized by high‐performance liquid chromatographic analysis. The effects on non‐frozen and frozen doughs of trypsin‐hydrolyzed gluten peptide (THGP) and its combination with ascorbic acid or KBrO₃ were investigated. RESULTS: Molecular analysis of THGP showed a decrease in the high‐molecular‐weight and an increase in the low‐molecular‐weight sodium dodecyl sulfate‐soluble fractions, compared with those of control wheat gluten. The addition of 8% THGP decreased the mixing time and tolerance of the dough, both with and without ascorbic acid or KBrO₃. However, the maximum resistance and extensibility of the rested dough containing 8% THGP, with and without ascorbic acid or KBrO₃, were not significantly different from those of the control dough. The addition of 8% THGP significantly increased the loaf volume of bread baked from non‐frozen dough when combined with 60 ppm ascorbic acid or 30 ppm KBrO₃, but it had a significant effect both with and without ascorbic acid or KBrO₃ on frozen‐dough bread. A large difference in volume was observed between breads made with and without THGP at the oven‐spring, rather than at proofing. CONCLUSION: The addition of 8% THGP increased the loaf volume of bread made from freeze‐damaged dough and this effect increased when THGP was combined with 60 ppm ascorbic acid. Copyright © 2008 Society of Chemical Industry     

Effect of wheat bran dietary fibre on the rheological properties of dough during fermentation and Chinese steamed bread quality

The effects of wheat bran dietary fibre (WBDF) on the rheological properties of dough during fermentation and quality of Chinese steamed bun (CSB) were investigated. The study revealed that with the increase of the content of WBDF, the dough extensibility and time at which gas starts to escape from the dough significantly decreased but the dough firmness significantly increased (P < 0.05). The elastic modulus and viscous modulus showed an upward trend, probably due to the increased molecular weight of the viscoelastic body resulting from the presence of WBDF. Additionally, by changing the quality of the gluten network, the specific volume and L^* value significantly decreased from 2.52 to 1.31 mL g⁻¹, and from 87 to 51, respectively, these adverse effects on CSBs could be moderated by the fermentation process.     

麸皮红枣乳酸发酵饮料工艺研究

研究麸皮红枣汁乳酸发酵饮料的主要加工工艺和参数。以麸皮和红枣为材料,制汁复合后,经过乳酸发酵、调配和澄清等工序,制成麸皮红枣汁乳酸发酵饮料。结果表明,采用保加利亚乳杆菌和嗜热链球菌以1∶1(体积比)混合,发酵30h时产酸量最高;当麸皮汁∶红枣汁=1∶2、乳酸菌种添加量8%、初始糖度11%、发酵温度40℃时,发酵效果最好;调配最优工艺参数为:发酵液∶水=1∶10、蔗糖添加量5.0%、NaCl添加量0.3%、甘油添加量0.1%,此时饮料酸甜适宜、口感良好;离心条件为3000r/min,10min时,饮料的澄清和成分保留效果佳。本试验结论对麸皮红枣乳酸发酵饮料的生产提供了一定的理论依据。      

真空碱溶液润麦处理对全麦粉稳定性和品质特性的影响

为了得到低脂肪酶活性、高稳定性的全麦粉,将小麦在不同真空度(-0.04,-0.07 MPa)下用不同浓度Na_2CO_3溶液(0.10%,0.25%,0.50%)润麦处理,利用低场核磁共振技术(LF-NMR)探究真空润麦过程中水分迁移情况,测定不同浓度Na_2CO_3溶液润麦下小麦中脂肪酶的相对活性。将润麦后的小麦制成全麦粉后,测定重组全麦粉的储藏稳定性和品质特性。结果表明:润麦过程中小麦籽粒的A_(21)值持续上升,结合水含量增加;真空碱溶液润麦可以降低小麦籽粒中脂肪酶活性,增加全麦粉贮藏稳定性,当Na_2CO_3溶液浓度为0.5%时脂肪酶活性最低;对全麦粉的粉质特性、RVA和面团流变学分析表明,真空碱溶液润麦能显著延长全麦粉的稳定时间,增强面团中面筋筋力,提高全麦粉的糊化特性,增加全麦面团的黏弹性,Na_2CO_3溶液润麦可有效改善全麦粉的品质特性。