Microbial Sour Doughs Influence Acidification Properties and Breadmaking Potential of Wheat Dough

Breads from sour doughs were started with Lactobacillis plantarum (L-73, or B-39) or Lactobacillus brevis (L-62)-, and incorporated at 10, 17.5, or 25%. Lactic and acetic acid production depended on bacterial starter and yeast. Started doughs had longer mixing time, stability, more softening with time; lower resistance to extension; shorter fermentation, less stability, and greater oven rise. Breads had greater volume, lower density, softer crumb and higher slice height. Interactive effects between inoculum and microbial composition of starter were reflected in sensory scores. Adequate sour dough inoculum was lower for heterofermentative strains (10%, L-62) than for homofermentative strains (17.5%, B-39; 25%, L-73), due to deleterious effects on rheological properties.     

洛阳传统绿豆酸浆工艺优化及发酵特性分析

用绿豆酸浆制成的浆面条是洛阳的传统特色小吃,采用单因素和正交试验研究绿豆酸浆的最佳加工工艺,并对其发酵过程中氨基酸、有机酸等物质的变化进行检测分析。结果表明,在料液比1:15,微生物接种量3.2×105 CFU/mL,25℃发酵24 h的条件下,得到可溶性蛋白质和可溶性固形物含量分别为36.7 g/L和1.21%,感官评分为83.9的绿豆酸浆产品。在发酵过程中,淀粉含量在发酵9 h后逐渐下降,还原糖含量在发酵过程中先上升后下降,蛋白质含量降低幅度较小。发酵24 h时,绿豆酸浆pH下降到4.3,总酸含量为13.62 g/L,乳酸是绿豆酸浆中主要有机酸。游离氨基酸含量上升至1 718.56 mg/100 mL,甘氨酸、谷氨酸、亮氨酸含量较高。结合相关性分析和主成分分析结果得出,富马酸、琥珀酸和酒石酸3种有机酸,谷氨酸、赖氨酸和苯丙氨酸等氨基酸对绿豆酸浆品质影响较大,发酵24 h时游离氨基酸综合评分最高。     

D-Erythroascorbic Acid in Bakers'Yeast and Effects on Wheat Dough

Extraction of hydrated and freeze-dried bakers’yeast yielded ～ 50 μg erythroascorbic acid (EAA) and 5 μg ascorbic acid (AA)/g dry yeast as determined by HPLC with electrochemical detection. D-EAA (82 ppm based on flour) slightly increased the flow of dough as rest time increased. Gluten isolated from a flour-water dough containing 82 ppm D-EAA or 100 ppm Lcysteine stretched at a faster rate than control gluten. EAA like AA did not change dough development time. Unlike AA, EAA showed neither oxidizing effect on dough and gluten nor improving effects on bread.     

Water Content, Water Soluble Fraction, and Mixing Affect Fundamental Rheological Properties of Wheat Flour Doughs

Fundamental rheological behavior of wheat flour doughs were compared with empirical results from a farinograph. Water contents of 42-47% and mixing times of 8, 16, and 24 min were examined. The storage modulus, G′, decreased when water content was increased from 42 to 45%. Dough produced from water extracted flours had high G′ and low δ. Increasing water content or mixing time decreased G′. There was a linear relationship (slope = 0.30) between G′ and the farinogram peak height for the reconstituted (water-soluble fraction added back), flour-water, and freeze-dried flour-water doughs. The extracted flour doughs also showed a linear relationship between G′ and farinogram peak height with slope = 1.07.     

Effect of Amino Acids and Peptides on Mixing and Frozen Dough Properties of Wheat Flour

Free amino acids, peptides, and vital wheat gluten were investigated to determine their effect on the mixing and frozen dough baking properties of wheat flour. Addition of 1% cysteine and aspartic acid decreased and glutamic acid, histidine, arginine, and lysine increased the mixing tolerance of flour. Cystine, methionine, tryptophan, and phenylalanine increased but isoleucine, histidine, glycine, arginine, glutamic acid, aspartic acid, and lysine decreased loaf volume of nonfrozen dough breads. However cystine, methionine, tryptophan, and phenylalanine did not increase loaf volume of bread prepared from frozen dough. Vital wheat gluten increased mixing tolerance and bread loaf volume only for the nonfrozen dough. However, wheat gluten hydrolysate, corn, and bonito peptides decreased mixing tolerance after optimum mixing time and were effective in increasing loaf volume for both frozen and nonfrozen dough. As the amount of corn and bonito peptide increased, specific loaf volumes also increased. Addition of 2.5% corn peptide was most effective in increasing loaf volume of frozen dough bread. Crust browning and crumb stickiness increased, whereas crumb softness decreased with addition of peptides. Addition of less than 1% peptide did not adversely affect the aftertaste and off‐flavor of bread. These results suggest that addition of peptides are effective for improving the baking quality of frozen dough, whereas amino acids and gluten have no effect.     

贵州少数民族酸肉、酸鱼中乳酸菌的分离鉴定

采用传统微生物分离方法进行乳酸菌纯种分离,利用16S rRNA序列分析方法进行乳酸菌鉴定,从7个酸肉、酸鱼样品中共分离出14株乳酸菌,有乳杆菌属、环丝菌属、乳球菌属3个属,9个种.从其中鉴定出7株乳酸菌,分别是:植物乳杆菌(Lactobacillus plantarum)、消化乳杆菌(Lactobacillus alimentarius)、清酒乳杆菌(Lactobacillus sakei)、泡菜乳杆菌(Lactobacillus kinchi)、清酒乳杆菌亚种(肉)(Lactobacillus sakei subsp.carnosus)、草乳杆菌(Lactobacillus graminis)、弯曲乳杆菌(Lactobacillus curvatus).     

Antistaling Additives, Flour Type and Sourdough Process Effects on Functionality of Wheat Doughs

Antistaling additives—distilled monoglycerides (MGL), diacetyl tartaric ester of monodiglycerides (DATEM), sodium stearoyl lactylate (SSL), carboxymethylcellulose (CMC), hydroxypropylmethylcellulose (HPMC) and fungal α-amylase—were studied for effects on rheological and fer- mentative properties of white/whole wheat bread doughs, made following straight/sour dough processes. A fractionated factorial design (L³²) was used to evaluate single additive effects and interactions. Single addition of DATEM, followed by SSL, α-amylase and hydrocolloids improved oven rise and final volume. In presence of DATEM, synergistic (MGL) and antagonistic (SSL) effects of additional emulsifiers were found on gassing power. SSL was the only effective conditioner for enhancement of mixing properties. Dough plasticity was negatively affected by MGL addition and by CMC/HPMC in white/whole flours respectively. Some combinations resulted in detrimental dough handling properties.     

以小麦粉为基质的地衣芽孢杆菌与酵母混酵氨基酸代谢特征

为阐明白酒酿造微生物液态纯种混合发酵的代谢特征,本研究以传统固态发酵中的常见细菌(地衣芽孢杆菌)和酵母(汉逊酵母、弗比恩毕赤酵母、酿酒酵母和鲁氏酵母)为研究对象,以小麦粉为发酵唯一基质,分析了在芽孢杆菌和不同单一酵母共酵条件下氨基酸代谢特征。结果显示,汉逊酵母是混酵下主要乙醇生成酵母,最高乙醇浓度达(93.33±4.71) mg/L,相应的还原糖水平最低,不超过1 g/L。气相色谱分析结果表明有11种氨基酸(甘氨酸、缬氨酸、亮氨酸、异亮氨酸、苏氨酸、脯氨酸、谷氨酸&谷氨酰胺、苯丙氨酸、组氨酸和酪氨酸)在四种混合发酵条件下都会被合成。对只在特定微生物组合下才出现的氨基酸,汉逊酵母比毕赤酵母更容易积累丝氨酸、蛋氨酸、半胱氨酸和赖氨酸。丙氨酸是地衣芽孢杆菌与毕赤酵母混合发酵所特有。本研究结果揭示白酒酿造微生物混酵下氨基酸代谢特征,为深入研究氨基酸与风味之间的关系提供了理论基础。     

酸水解麦麸蛋白质及氨基酸分析

探讨小麦麸蛋白的酸水解工艺。研究了盐酸浓度、料液质量体积比、水解时间对小麦麸蛋白水解度的影响,并对麦麸蛋白水解液的氨基酸组成进行了分析。在100℃,盐酸浓度4mol/L,料液质量体积比1∶6,水解时间18h的条件下麦麸蛋白的水解度为59.22%。氨基酸分析结果表明,呈甜味和鲜味的氨基酸总和达到53.77%。通过酸水解麦麸蛋白,可获得呈鲜味和甜味氨基酸含量较高的蛋白水解液,为麦麸蛋白水解液的生产提供理论参数。     

侗族传统发酵酸肉中乳酸菌的筛选、发酵特性及安全性分析

为得到适合肉制品发酵的菌株,本研究采用传统微生物分离方法对侗族传统发酵酸肉中的乳酸菌进行分离鉴定,并对其发酵特性和安全性进行分析。结果表明,从发酵酸肉中分离得到54株乳酸菌,按照肉用发酵剂的基本原则进行筛选后得到S26、S42、S53三株性能优良菌株,结合形态学、生理生化特征和16S rRNA序列分析后确定:S26为香肠乳杆菌(Lactobacillus farciminis),S42为植物乳杆菌(Lactobacillus plantarum),S53为乳酸片球菌(Pediococcus acidilactici);三株菌生长良好且产酸速度快,24 h内可以将pH降到3.5左右;菌株对于氨基糖苷类、青霉素类、头孢类等大多数抗生素无耐药性,且无质粒和溶血现象;并且三株菌之间无拮抗作用,可将三株菌复配后用于肉类的发酵。     

氨基酸态氮含量测定条件探讨

探讨所用水质、不同纯度的缓冲溶液、复合电极的使用、NaOH溶液的浓度等条件对兰陵美酒中氨基酸态氮含量测定的影响,从而得出最佳测定条件,达到较为准确地测定氨基酸态氮的含量。     

新收获小麦后熟过程中蛋白质和氨基酸含量的变化

分析了储存在4℃和室温条件下新收获的软麦和硬麦在后熟过程中的生理生化变化。新收获小麦在20℃的发芽率超过80%,在收获后3~4个月中呼吸有2次高峰,尤其第1个呼吸峰非常明显,室温条件较4℃提高第1个呼吸峰值。当呼吸速率趋于不变时,软麦硬度增大在第4个月,硬麦在第5个月。水溶蛋白、盐溶蛋白及谷蛋白各有2次合成高峰。硬麦醇溶蛋白在第60天有一个积累高峰,软麦至少有2个积累高峰,分别在第30天和60天。谷蛋白合成最高峰在第90天,与水溶蛋白类似,而醇溶蛋白合成最高峰在第60天,与盐溶蛋白类似。随着醇溶蛋白和游离巯基含量减少,谷蛋白迅速积累。常温条件下谷蛋白的氧化聚合较低温条件下迅速,积累量大。软麦谷蛋白氧化聚合过程较硬麦早。谷蛋白积累之前,绝大部分氨基酸急剧积累,在室温条件较4℃下积累明显。半胱氨酸含量在90~120天时增加到最大,之后迅速减少。     

面团发酵过程中小麦淀粉理化性质的变化

以小麦粉为原料,结合水洗和离心提取小麦淀粉,研究面团发酵过程中一次发酵、二次发酵和醒发工序对直链淀粉含量、溶解度、溶胀度、糊化特性和凝胶特性等理化性质的影响。试验结果表明:发酵后直链淀粉质量分数提高3.7%～8.18%;采用黏度速测仪(RVA,Rapid visco analyzer)分析醒发后小麦淀粉的峰值黏度、谷值黏度和最终黏度分别上升52 RVU、58.67 RVU和73.33 RVU;采用质构仪(TPA,Texture profile anal-ysis)对发酵过程小麦淀粉凝胶特性进行研究,发现醒发后凝胶特性有所改善,硬度提高48.60 g,弹性提高0.03,内聚性、回复性分别提高0.05、0.15。     

冻干酸面团发酵剂对发酵面团及面包香气的影响

采用HPLC和SPME/GC-MS,研究冷冻干燥(冻干)旧金山乳杆菌酸面团发酵剂对普通和全麦发酵面团及其面包香气的影响。结果显示,冻干旧金山乳杆菌(Lactobacillus sanfranscensis,L.s.)酸面团发酵剂对发酵面团和面包香气的影响显著。酸面团面包面团中有机酸和游离氨基酸含量均高于相应的非酸面团面包面团;乳酸菌酸面团发酵显著提高了面包中挥发性物质的含量,L.s.高筋粉酸面团面包(SSAB)和L.s.全麦酸面团面包(SSWB)较非酸面团高筋粉面包(NSHB)和非酸面团全麦面包(NSWB)分别提高了11.31%和14.98%。全麦体系含有更多的游离氨基酸,其面包具有更浓郁的风味,全麦酸面团面包所含挥发物质总量大幅高于普通面包,NSWB和SSWB较NSHB和SSAB分别提高了22.54%和26.58%。3-甲基-1-丁醇、乙酸、糠醛、苯乙醇、3-羟基-2-丁酮、3-甲基丁酸、2-甲基丙酸、3-甲基丁醛和E-2-壬烯醛是面包中重要的香气物质。L.s.酸面团发酵剂在不同面粉面团体系中产生的作用不同,SSAB含有较多的内酯类化合物;SSWB含有更多的3-甲基-1-丁醇和3-羟基-2-丁酮。     

牛肉酶解物的氨基酸组成分析

采用日立835-50型氨基酸自动分析仪测定了牛肉酶解物的氨基酸含量.结果表明:除色氨酸被水解破坏外,其他17种氨基酸含量丰富,配比良好,其氨基酸的总含量最高为12.78%,低的为0.7%,并含有其他7种人体必需氨基酸.     

人工冬虫夏草不同部位氨基酸含量测定

目的：检测人工冬虫夏草不同部位中氨基酸的含量。方法：使用氨基酸分析仪,以茚三酮为衍生试剂,采用柱后衍生法测定人工虫草不同部位中氨基酸含量。结果：在蛹虫草的固体培养残基、子实体、菌丝体中都至少含有17种常见氨基酸和8种必需氨基酸,总氨基酸含量分别为8.32%、21.68%和23.19%,必需氨基酸的含量分别为3.74%、8.11%和8.88%。结论：人工虫草中不但子实体含有腺嘌呤、腺苷和虫草素,菌丝体及固体培养残基也含有这3种主要核苷类物质,具有进一步开发利用价值。     

Sour beer production: impact of pitching sequence of yeast and lactic acid bacteria

Lactic acid bacteria have long been used in brewing to acidify mash or wort and in the production of traditional sour beer styles (Lambic, Gueuze) using spontaneous fermentation. This approach is time consuming (some sour beers are matured for three years to obtain the appropriate flavour), so many brewers choose a faster approach using mixed cultures (yeast and bacteria). In this study, the influence of the pitching sequence of bacteria and yeast on the fermentation process was evaluated (by rate of fermentation and acidification, attenuation degree and ethanol concentration). The trials were performed using three procedures: (i) the addition of bacteria followed by the yeast; (ii) the addition of the yeast followed by the bacteria and (iii) the simultaneous addition of yeast and bacteria. In each trial the following time intervals were applied: 24, 48 and 72 h. Weight loss of samples and drop in pH were measured daily, and ethanol content, real extract and lactic acid concentration measured at the end of the process. It was shown that the order of addition of yeast and bacteria determines the success of the lactic acid fermentation. The appropriate yield of lactic acid (ca. 6 g/L) and the drop in pH (<3.6) can be achieved by inoculating the bacteria prior to the inoculation of yeast. When yeast was pitched before the bacteria, the lactic acid content was ca. 2 g/L and pH was 3.9–4.2. © 2019 The Institute of Brewing & Distilling     

荔枝酒酿造过程中氨基酸的变化

利用高效液相色谱法(HPLC)对不同发酵温度的荔枝酒酿造过程中氨基酸含量的动态变化进行了分析研究。结果表明,荔枝汁和荔枝酒中均含有丙氨酸、苏氨酸、缬氨酸、谷氨酸、丝氨酸等14种氨基酸,其中,丙氨酸是荔枝汁和荔枝酒中的主体氨基酸,含量分别达1 139.682 mg/L、341.049～412.161 mg/L。不同发酵温度的荔枝酒酿造动态过程中,其游离氨基酸的种类和含量变化较大,且变化趋势各异。不同贮藏方式对荔枝酒中氨基酸含量和种类影响也不同。通过比较,发酵温度12℃优于15℃,发酵温度为15℃的荔枝酒中氨基酸含量在贮藏过程中变化幅度较大,不稳定,且影响风味的氨基酸较多。     

酵母菌发酵柑橘皮渣生产柠檬酸

以柑橘皮渣为原料,用酵母菌发酵生产柠檬酸,发酵液成分采用纸层层析进行鉴定,发酵液经过钙盐法处理获得柠檬酸固体。通过改变发酵温度、发酵时间、发酵液中甲醇添加量和发酵液中菌种添加量研究发酵最佳条件,根据L9（34）正交试验,最终确定酵母菌发酵柑橘皮渣生产柠檬酸的最佳条件为：发酵温度29℃,发酵时间108h,发酵液中添加8％的酵母活化液和2％的甲醇。