Regulation of acetic acid production by homo-and heterofermentative lactobacilli in whole-wheat sour-doughs

The efficiency of sour-dough as a possible preservative agent of microbial spoilage of bread depends on its acetic acid content. As a secondary metabolite of sugar fermentation by lactic acid bacteria, acetic acid may be promoted in the presence of O₂ or H⁺ acceptors. This paper studies the influence of O₂ and high fructose content products (pure sugar, invert sugar, fructose syrup) addition on acetic acid production by hetero- (Lactobacillus brevis 25a, B-21, L-62;L. sanfrancisco L-99) and homofermentative (L. plantarum B-39) lactobacilli in whole-wheat sour-doughs [280 and 250 dough yield (DY)]. The pH and total titratable acidity (TTA) of sour-doughs after 44 h fermentation varied with DY and strain. As expected, the addition of O₂ promoted greater increases in TTA with heterofermentative lactobacilli (15–42%) than withL. plantarum (15%). Fructose addition was only effective for heterofermentative strains, but the overall effects were smaller than those observed for oxygenation. The ability of lactobacilli to produce acetic acid in sour-doughs without treatment varied from 0.16 g/100 g flour at 44 h (B-39, 280, 350 DY) to 0.47–0.65% (L-62, 280, 350 DY). The production of acetic acid was positively promoted by all treatments. Oxygenation was again the most effective way of inducing acetic acid production; increases ranged from 54% (B-21) to 269% (L-99, 350 DY). The addition of H⁺ acceptors had variable effects. Pure fructose resulted, in general, in greater increases than invert sugar of fructose syrup. The main effects were detected forL. brevis 25a (280 DY) B-21 (350 DY) andL sanfrancisco L-99 (350 DY) with increases ranging from 92 to 123%. The highest levels of acetic acid (1.02–1.04%) corresponded to sour-doughs (44 h, 35° C shaking 150 rpm) started with L-62 (280, 350 DY) or L-99 (350 DY).

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Beeinflussung der Essigsäurebildung durch homo- und heterofermentative Laktobacillen in Weizenvollkornsauerteigen

Zusammenfassung Die Haltbarkeit von Sauerteig-Brot gegen mikrobiologische Verderbnis beruht auf seinem Säuregehalt. Als sekundäres Stoffwechselprodukt der Zuckergärung durch Milchsäurebakterien, kann die Essigsäure-Bildung von Sauerstoff- oder Wasserstoffacceptoren gefördert werden. Diese Veröffentlichung befaßt sich mit dem Einfluß von Sauerstoff und Produkten mit hohem Fructosegehalt (Rohrzucker, Invertzucker, Fructose-Sirup) auf die Essigsäure-Bildung durch hetero- (Lactobacillus brevis B-21, 25a, L-62;L. sanfrancisco L-99) und homofermentative (L. plantarum B-39) Laktobacillen in Weizenvollkornsauerteigen (TA 280 und 350). ph-Wert und Säuregrad von Sauerteigen nach 44-stündiger Gärung waren verschieden je nach TA und Stamm. Wie erwartet, verursachte die Zugabe von Sauerstoff eine größere Zunahme des Säuregrades mit heterofermentativen Laktobacillen (15–42%) als mitL. plantarum (15). Fructose-Zugabe war nur wirksam für die heterofermentativen Stämme, aber die allgemeinen Wirkungen waren kleiner als die bei der Behandlung mit Sauerstoff beobachteten. Die Fähigkeit von Laktobazillen, ohne Behandlung in Sauerteigen Essígsäure zu bilden, schwankte zwischen 0.16 g/100 g Mehl (B-39, 280, 350 TA) und 0.47–0.65% (L-62, 280, 350 TA). Die Bildung von Essigsäure wurde durch alle Behandlungen gefördert. Die Behandlung mit Sauerstoff war wieder die effizienteste zur Förderung der Essigsäurebildung; der Anstieg schwankte zwischen 54% (B-21) und 269% (L-99, 350 TA). Die Zugabe von Wasserstoffacceptoren hatte verschiedene Effekte. Reine Fructose ergab im allgemeinen größere Anstiege als Invertzucker oder Fructose Sirup. Die Haupteffekte wurden beiL. brevis 25a (280 TA), B-21 (350 TA) undL. sanfrancisco L-99 (350 TA) mit Anstiegen von 92% bis 123% nachgewiesen. Die mit L-62 (280, 350 TA) oder L-99 (350 TA) hergestellten Sauerteige (44 h, 35 °C, 150 rpm schütteln) ergaben die höchste Gehalte an Essigsäure (1.02–1.04%).

     

Effects of flour from different barley varieties on barley sour dough bread

Twenty flours from 16 different barley varieties cultivated in 1990 and 1992, and a Swedish reference flour, were fermented by Lactobacillus plantarum A1 to sour doughs. Barley breads (40% barley/60% wheat flour) from each flour type were baked with and without an admixture of barley sour dough in order to investigate how the sour dough admixture would affect the baking properties. A trained panel carried out sensory evaluation by conventional profiling on breads made from three of the barley varieties and the Swedish reference flour, made with and without sour dough admixture.

The barley varieties influenced both the sour dough properties and the properties of the barley bread. The pH of bread with sour dough ranged from 4.6 to 4.8 as compared to 5.4 to 5.6 in bread without sour dough. The acidity of the breads with sour dough ranged from 4.1 to 5.0 ml NaOH/ 10 g bread crumb as compared to 2.4 to 3.6 in breads without sour dough. In 14 of the twenty bread types an addition of sour dough lowered the bread volume. Breads with a sour dough admixture scored higher for total taste and acidulous taste than breads without sour dough. The β-glucan content of the flours had no significant influence on the sour dough or the sensory characteristics of the bread, except for the breadcrumb colour.     

Influences of lactic acid bacteria on technological, nutritional, and sensory properties of barley sour dough bread

Barley bread was baked with and without admixture of barley sour doughs, individually fermented with seven starter cultures containing lactic acid bacteria (including two with β-glucanase activity).

The aim of the study was to investigate how starter cultures influenced the baking-technological, nutritional and sensory properties of barley bread. Could degradation of β-glucans caused by sour dough admixture result in bread that was more easy to chew?

The starter culture influenced the volume yield, the total titratable acidity (S °) and the sensory properties. The amounts of lactate and acetate ranged from 0.20 to 0.26 and 0.03 to 0.08 g/100 g sour dough bread, respectively. The total titratable acidity in the sour dough breads varied between 4.1 and 5.4 ml 0.1 N NaOH/10 g bread. There were negative correlations between barley taste and total titratable acidity (S °). The acidulous taste of the sour dough breads seemed to mask the barley taste. The phytate of the barley sour dough breads was reduced below 0.5 μ mol/g, which does not inhibit mineral absorption, irrespective of starter culture. There was no significant difference in the total content of β-glucans between bread made with and without admixture of sour dough, irrespective of starter culture, rejecting the hypothesis that barley bread made with sour dough would be more easy to chew.     

干酪乳杆菌发酵番茄酸汤的工艺优化

本试验探究应用干酪乳杆菌H1作为发酵剂接种西红柿优化制作酸汤发酵工艺。研究发酵温度、发酵时间、接种量和加盐量四个因素对番茄酸汤的品质的影响并对其发酵条件进行优化。在单因素实验的基础上,进行四因素三水平的响应面实验设计,基于模糊数学法得到的感官评定和总酸两个响应值,对人工接种干酪乳杆菌的番茄酸汤的发酵工艺进行优化,以确定其最佳发酵工艺。结果表明:在发酵温度25℃、发酵时间5 d,接种量2%,加盐量1.45%时,得到的番茄酸汤总酸达到1.23%,感官评分8.48±0.58,与理论值差异均不显著(p0.05),说明响应面的实验值和回归方程预测值基本吻合,响应面法建立的模型所确定的番茄酸汤的发酵条件稳定可靠,能为番茄酸汤工业化生产提供理论依据。     

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.     

Relationship between thermomechanical properties and baking expansion of sour cassava starch (Polvilho azedo)

The factors involved in the baking expansion of native and sour cassava starch doughs were compared with those of native corn starch. Unlike corn starch dough, native and sour cassava starch doughs showed expansion properties during baking. The storage modulus E ′ decreased for cassava starch doughs before baking expansion, but remained unchanged for corn starch dough. Expansion during the baking of sour cassava starch was attributed to water vaporisation and the fluidity of starch paste. The fact that temperature and weight loss variations at adequate water contents were significantly greater for cassava than corn starch dough is indicative of the important role played by starch melting in expansion. Expansion ability could be correlated with changes in dough–crumb thermomechanical properties when close to the starch melting temperature. © 2001 Society of Chemical Industry     

Staphylococcus aureus growth and survival during curding of Manchego type cheese produced with normal and subnormal starter activity

Manchego type cheese was manufactured from milk from cows, goats and ewes artificially contaminated with 2 X 10(4) S. aureus cells ml. Lactic starter culture was added to the milk at the rate of 1.0 or 0.1% (v/v). the industrial process of Manchego type cheese manufacture was imitated. Cheeses were analyzed for both staphylococcal and non-staphylococcal total aerobic counts, as well as for the pH and enterotoxin production. Growth differences in staphylococcal counts in cheeses prepared with both starter concentrations were seen only after the brine treatment, the counts were 10 times greater with the 0.1% starter. Nevertheless, with the 1% starter culture the staphylococcal counts did not decrease from the moment of inoculation remaining high after brine treatment. For a similar inoculum, the strains used responded in a different manner, the highest values corresponding to strains FRI-100, S6 and FRI-472, and the lowest to FRI-137 and FRI-361. No differences in pH were seen between batches prepared with both starter concentrations.     

Sourdough-isolated<Emphasis Type="Italic"> Lactobacillus fermentum</Emphasis> as a potent anti-mould preservative of a traditional Iranian bread

Sourdough bread is an ancient method for making long microbial shelf life and strongly flavoured breads. Traditional sourdough bread-making has been practised for centuries in Iran. Although rural bread-making is still highly reliant on sourdough, urban bakeries usually use bakers yeast and also sodium bicarbonate instead. In this study the anti-mould preservative effects of three lactic acid bacteria isolates were investigated on one of the popular traditional Iranian bread (Lavash). Starter cultures were prepared using 20 h cultures of three sourdough-isolated strains, Lactobacillus casei, Lactobacillus plantarum and Lactobacillus fermentum. Different concentrations (0.5%, 1%, 2%, 4% and 8%) of lactobacillus starter cultures were used to prepare a variety of sourdoughs. Lavash doughs were inoculated with 20% of each lactobacilli-fermented sourdough. After a 20 h incubation at 30 °C, a decrease in pH was observed in the different lactobacilli sourdoughs. However an 8% inoculum of L. fermentum resulted in a significant decrease in pH (3.87 to 2.70). Concentrations of 2% and higher of the three lactobacilli used in Lavash sourdough delayed mould growth during storage. However this preservative effect was more significant when an 8% inoculum of L. fermentum was used. These results tend to suggest that selected strains of lactobacilli have a beneficial role in prevention of bread waste by mould spoilage, and hence could extend bread shelf life.     

响应面法优化金银花枸杞风味酸奶的发酵工艺

以金银花、枸杞、全脂奶粉为原料,采用单因素试验研究了金银花汁添加量、枸杞汁添加量、白砂糖添加量、发酵温度、发酵时间、发酵剂接种量对金银花枸杞风味酸奶发酵的影响。以感官评分为响应值,采用响应面法对金银花枸杞风味酸奶的发酵工艺条件进行优化。结果表明,金银花枸杞风味酸奶的最佳发酵工艺条件为金银花汁添加量5%、枸杞汁添加量6%、白砂糖添加量8%,发酵剂接种量10%,发酵温度43 ℃,发酵时间5.1 h。在此优化工艺条件下,发酵的金银花枸杞风味酸奶组织细腻,酸甜可口,具有独特的中药香,感官评分为91分。     

Characterization and Technological Properties of Lactic Acid Bacteria Isolated from Traditional Argentinean Goat’s Milk Products

A total of 286 lactic acid bacteria isolated from goat’s dairy products in northwest of Argentina were characterized. Lactobacilli (38%) and cocci (62%) were identified according to morphological, physiological, and relevant technological properties. L. plantarum (14%) and Enterococcus (34%) were the predominant species. S. thermophilus, Pediococcus and L. plantarum were the highest acid producers. Eight strains of L. fermentum produced bacteriocins or metabolites similar to bacteriocins. The API-ZYM test was applied to 39 isolates. Eight strains were selected from their both technological properties and enzymatic activities for use as starter or adjunct culture in the manufacture of artisanal goat cheeses.     

Effect of bacteriocin‐producing Pediococcus acidilactici K10 on beer fermentation

Beer is generally considered to be a beverage that has high microbiological stability. However, some undesirable lactic acid bacteria (LAB) can grow in beer and consequently spoil this beverage. In this study, bacteriocin‐producing Pediococcus acidilactici K10 was used as a means of bio‐acidifying the mash and reducing the spoilage LAB content of the beer. The K10 strain had antimicrobial activity against two beer spoilage LAB strains in wort and did not grow in a beer environment. The K10 strain was inoculated before the mashing step. The effect of K10 as a starter culture was investigated and compared with a control. As a result, filtration time was shortened by 17 min, alcohol content was increased by 137%, foam stability was increased by 156%, bitterness was increased by two bitterness units and there was a significant difference (p < 0.05) in aromatic and sour odour. The feasibility of using bacteriocin‐producing LAB strain in beer brewing is envisaged. Copyright © 2016 The Institute of Brewing & Distilling     

Pre-inoculation enrichment procedure enhances the performance of bacteriocinogenic Lactococcus lactis meat starter culture

Sodium nitrite and sodium chloride may inhibit growth and bacteriocinogenesis of protective starter cultures. To reduce sensitivity of a lacticin 3147-producing starter culture to nitrite, prior to production of salami, Lactococcus lactis DPC 4275 was placed in a number of pre-inoculation treatments, containing (a) 1% glucose, (b) 2.5 ppm manganese (Mn), (c) 250 ppm magnesium (Mg), (d) 2.5 ppm manganese + 250 ppm magnesium (Mn + Mg), and held at ambient temperature for 30 min and 4 degrees C for 2 h. The growth, pH reduction, and bacteriocin production was monitored in beaker sausage over a period of 10 days at 28 degrees C, corresponding to typical salami production time, and compared to untreated starter culture. The effect of 1% tryptone and inoculum level on growth and bacteriocin production was also determined. Challenge tests were performed using Listeria innocua DPC 1770 and Staphylococcus aureus MMPR3 as target strains. All treatments gave a significantly higher (P < 0.05) initial starter level than the untreated starter. Beaker sausage inoculated with either low (10(7)) or high (10(9)) levels of starter culture, treated with Mn + Mg reached significantly (P < 0.05) higher levels by day 10 than other treatments. Trends indicate that Mn + Mg also gave best pH reduction in sausage containing the low-level starter culture, sausage and significantly lower (P < 0.05) values for sausage produced with higher inoculum. Bacteriocin production was also higher in starter culture treated with Mn, or glucose. Pre-treatment with Mg gave a 2-fold increase in bacteriocin, the addition of Mn augmenting this increase further. The incorporation of tryptone gave no additional effect. In beaker sausage, both L. innocua and S. aureus populations showed significant reductions (P < 0.05) in the presence of the bacteriocinogenic strain compared to a non-bacteriocinogenic control strain.     

Isotrichid protozoa influence conversion of glucose to glycogen and other microbial products

The goal of this in vitro study was to determine the influence of isotrichid protozoa (IP) on the conversion of glucose (Glc) to glycogen (Glyc) and transformation of Glc into fermentation products. Treatments were ruminal inoculum mechanically processed (blended) to destroy IP (B+, verified microscopically) or not mechanically processed (B-). Accumulated microbial Glyc was measured at 3 h of fermentation with (L+; protozoa + bacteria) or without (L- predominantly protozoa) lysis of bacterial cells in the fermentation solids with 0.2 N NaOH. Two 3-h in vitro fermentations were performed using Goering-Van Soest medium in batch culture vessels supplemented with 78.75 mg of Glc/vessel in a 26.5-mL liquid volume. Rumen inoculum from 2 cannulated cows was filtered through cheesecloth, combined, and maintained under CO₂ for all procedures. At 3 h, 0.63 and 0.38 mg of Glc remained in B- and B+. Net microbial Glyc accumulation (and Glc in Glyc as % of added Glc) detected at 3 h of fermentation were 3.32 (4.69%), −1.42 (−2.01%), 6.45 (9.10%), and 3.65 (5.15%) mg for B-L-, B+L-, B-L+ and B+L+, respectively. Treatments B+ and L+ gave lower Glyc values than B- and L-, respectively. Treatment B+L- demonstrated net utilization of α-glucan contributed by inoculum with no net Glyc production. With destruction of IP, total Glyc accumulation declined by 44%, but estimated bacterial Glyc increased. Microbial accumulation of N increased 17.7% and calculated CH₄ production decreased 24.7% in B+ compared with B-, but accumulation of C in microbes, production of organic acids or C in organic acids, calculated CO₂, and carbohydrates in cell-free medium did not differ between B+ and B-. Given the short 3-h timeframe, increased N accumulation in B+ was attributed to decreased Glyc sequestration by IP rather than decreased predation on bacteria. After correction for estimates of C from AA and peptides utilized by microbes, 15% of substrate Glc C could not be accounted for in measured products in B+ or B-. Approximately 30% of substrate Glc was consumed by energetic costs associated with Glc transport and Glyc synthesis. The substantial accumulation of Glyc and changes in microbial N and Glyc accumulation related to presence of IP suggest that these factors should be considered in predicting profiles and amounts of microbial products and yield of nutrients to the cow as related to utilization of glucose. Determination of applicability of these findings to other soluble carbohydrates could be useful.     

Influence of sequential inoculum of Starmerella bacillaris and Saccharomyces cerevisiae on flavonoid composition of monovarietal Sangiovese wines

The selection of Starmerella bacillaris strains to be used with Saccharomyces cerevisiae as mixed cultures has been recently suggested in order to produce wines containing lower ethanol and higher glycerol concentrations and to promote fructose degradation due to their fructophilic character. However, studies about effects of such mixed starter cultures on phenolic compounds, which are responsible for the colour and health-enhancing properties in red wines, are currently lacking. Therefore, in this work, the influence of sequential inoculated fermentation (SIF) with Starm. bacillaris and S. cerevisiae on phenolic content of monovarietal Sangiovese wine was evaluated by fermentations at laboratory scale. Axenic fermentations (AXFs) with S. cerevisiae were performed as control. S. cerevisiae attained higher cell densities in AXF compared with SIF. The experimental wines obtained by SIF showed significant lower ethanol and higher glycerol concentrations, whereas no significant difference was detected in colour intensity. The total phenol index reached significantly lower values in SIF. Furthermore, the wines produced by SIF contained higher concentrations of vitisin A that has a greater colour stability than the anthocyanin monomer. Finally, a lower content of both free anthocyanins and flavan-3-ols, key compounds for wine quality possessing also health-enhancing properties, was found in wines obtained by SIF. On the contrary, no significant difference was detected on flavonol concentration between SIF and AXF. This study highlighted that the use of sequential inoculum of Starm. bacillaris and S. cerevisiae can contribute to increasing the colour stability of red wines, even if at the expense of compounds with health properties.     

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.     

苗族白酸汤中优势乳酸菌及酵母菌的筛选与应用

目的:为了得到适合白酸汤发酵的发酵剂,实现传统白酸汤的规范性生产。方法:采用溶钙圈法结合总酸产量和耐酸耐胆盐实验筛选乳酸菌优良菌株;采用糖苷酶活性实验筛选酵母菌优良菌株;通过生理生化实验、16S rDNA序列和ITS序列进行菌株鉴定。将两株优良发酵菌株复配应用于白酸汤中,对其pH、总酸、总糖、还原糖和感官品质进行分析。结果:从128株乳酸菌中筛选出1株产酸能力较强的菌株G1-3,该菌株在pH3.0与0.3%牛胆盐环境中均生长良好,从20株酵母菌中筛选出1株糖苷酶活性较强的菌株G2-2。经鉴定菌株G1-3为副干酪乳酸杆菌(Lactobacillus paracasei),G2-2为印迪卡有孢圆酵母(Torulaspora indica)。两株菌复配发酵后的籼米白酸汤的总酸含量较自然发酵提高了5倍,总糖与还原糖含量分别降低了61.53%与81.02%;糯米白酸汤中的总酸含量较自然发酵提高了18倍,总糖与还原糖含量分别降低了68.86%与86.99%。两株菌复配发酵后的白酸汤的感官品质也优于自然发酵。结论:G1-3与G2-2的复合发酵剂发酵得到的白酸汤具有较好的品质,有望应用于白酸汤的发酵生...     

糖化发酵剂对黄酒中高级醇含量的影响

文中分别对麦曲添加量、酵母菌种、接种量等3个工艺条件对黄酒发酵过程中高级醇积累的影响进行了研究。以麦曲为糖化剂,28℃主发酵5d,15℃后发酵15d,发酵结束后气相色谱外标法测定酒样中的高级醇。实验结果表明,当麦曲添加量在原料米重的4%～8%这一范围内,酒样中高级醇的含量随着麦曲添加量的增加而增加;在接种量0.8×107个/mL～1.2×107个/mL这一范围内,酒样中的高级醇含量随着接种量的增加而增加;菌种对于酒样中高级醇含量的影响较大,在所考察的4种菌种中以AS2.1392黄酒酵母作为发酵剂的酒样中的高级醇含量最少。     

东北酸菜汁分离乳酸菌发酵鹿肉干加工工艺优化

为研制营养风味俱佳的发酵鹿肉干新产品,从东北自然发酵的酸菜汁中分离、纯化、鉴定乳酸菌菌株,分析该菌株与汉逊德巴利酵母菌的发酵特性,将二者以一定配比组成混合发酵剂用于块状鹿肉发酵并研究其发酵特性。单因素试验、Plackett-Burman优选试验和响应面优化块状鹿肉发酵工艺研究表明,发酵时间、发酵温度、接种量对鹿肉发酵特性影响显著;酸菜汁分离乳酸菌和汉逊德巴利酵母菌发酵鹿肉产酸快,利于风味物质形成,适宜作发酵鹿肉干发酵剂;得到发酵鹿肉的p H值、发酵鹿肉干感官评分与发酵时间、发酵温度、接种量间关系的二次回归方程;鹿肉最佳发酵工艺条件:发酵时间20.86 h、发酵温度27.51℃、接种量2.16 m L/100 g;发酵鹿肉的平均p H值为5.07时,发酵鹿肉干感官评分最高。     

Structure and Dynamics of Wheat Starch in Breads Fortified with Polyphenols and Pectin: an ESEM and Solid-State CP/MAS 13C NMR Spectroscopic Study

Two sets of breads formulated with a 20% difference in water quantity in the absence (control bread), or presence (fortified bread) of high methoxyl pectin (HM) and an apple, kiwifruit, or blackcurrant polyphenol (PP) extract (APE, KPE or BPE) were examined by Environmental Scanning Electron Microscopy (ESEM) and Cross Polarization/Magic Angle Spinning ¹³C NMR Spectroscopy. ESEM revealed that all the bread doughs had similar microstructures, comprising starch granules and yeast cells embedded in a continuous gluten matrix. However, the microstructure of the finished breads differed. NMR studies revealed differences in amylopectin-related crystalline domains and the amylose-related amorphous domains among the breads. All the breads showed V-type or amorphous starch structures by NMR, and the control bread may also contain some A-type starch. Breads formulated with 20% extra water showed a greater degree of starch gelatinization, a smoother crumb microstructure, and a lower amorphous starch content. It is feasible to incorporate PPs and pectin in breads at reasonably high concentrations.     

Effect of Lactobacillus plantarum on the survival of acid‐tolerant non‐O157 Shiga toxin‐producing E. coli (STEC) strains in fermented goat's milk

The ability of goat's milk fermented with a Lactobacillus plantarum strain B411, and in combination with commercial starter culture, to inhibit acid‐adapted (AA) and non‐acid‐adapted (NAA) environmental non‐O157 STEC strains was investigated. Acid‐adapted and NAA non‐O157 STEC strains were not inhibited in the L. plantarum‐fermented goat's milk, while the goat's milk fermented with the combination of L. plantarum and starter culture inhibited AA more than NAA non‐O157 STEC strains. Environmental acid‐tolerant non‐O157 STEC strains were not inhibited by L. plantarum, starter culture or combination of starter culture with L. plantarum unless they were subjected to prior acid adaptation such as backslopping.