荞麦蛋白的研究进展

荞麦蛋白是天然抗消化蛋白,由球蛋白、清蛋白、谷蛋白和少量醇溶蛋白构成,具有多种优良的功能特性和生理功能。本文探讨了养麦蛋白的结构、制备工艺、加工功能特性以及作为抗消化蛋白的机理,并指出荞麦蛋白作为一种“药食兼用“的天然活性成分具有广泛的应用前景。     

Part III: the influence of serial repitching of Saccharomyces pastorianus on the production dynamics of some important aroma compounds during the fermentation of barley and gluten‐free buckwheat and quinoa wort

The present paper is the last report of a comprehensive study regarding the influence of the serial repitching of Saccharomyces pastorianus TUM 34/70 on the composition of a barley, buckwheat or quinoa fermentation medium. In particular, it focuses on the production dynamics of important volatile compounds typically associated with the aroma of beer. Samples were taken every 24 h after 11 serial repitchings of a single starter culture, analysed for the particular aroma compound content by distillation followed by gas chromatography with flame ionization detection. The term ‘serial repitching factor’ is used for the first time to support the visual evaluation of the influence of serial repitching. Results showed that the levels of methanol in the quinoa wort fermentation were only slightly higher than in barley and in practical terms independent of successive fermentation. The behaviour of acetaldehyde in quinoa was similar to that in barley. However, there was a final 2‐fold lower production of some important aroma compounds compared with barley and buckwheat and for this reason quinoa cannot be recommended as a gluten‐free substitute to produce a bottom‐fermented beer. Regarding the buckwheat wort fermentation, a 2‐ to 3‐times lower final acetaldehyde content than in barley is desirable, whereas a relatively high methanol content is not desirable. Barley and buckwheat showed comparable sum concentrations and similar overall profiles of some important aroma compounds. From this perspective, buckwheat appears to be a promising substitute for barley as a brewing raw material. The overall conclusions of our comprehensive study (Parts I–III) are that buckwheat shows adequate brewing properties to substitute for barley in the commercial preparation of a bottom‐fermented gluten‐free beer‐like beverage, and yeast can be repitched at least 11 times. In contrast, quinoa in practical terms shows no substitutional potential for barley in beer; however, it has many nutritious advantages, thus the commercial preparation of a unique, bottom‐fermented gluten‐free ‘non‐beer‐like’ beverage – where the yeast could be repitched six times at most – appears feasible. Copyright © 2015 The Institute of Brewing & Distilling     

Part II: the influence of the serial repitching of Saccharomyces pastorianus on the uptake dynamics of amino acids during the fermentation of barley and gluten‐free buckwheat and quinoa wort

The present paper is part of a comprehensive study regarding the influence of the serial repitching of Saccharomyces pastorianus TUM 34/70 on the composition of the barley, buckwheat and quinoa fermentation medium. In particular, it focuses on the uptake dynamics of amino acids during 11 successive fermentations. Samples were taken every 20 h after pitching, analysed for the particular amino acid content and statistically evaluated. The term ‘completion time’ (t₉₅), here defined as the percentage attenuation time necessary for ~95% of the total assimilation, has been introduced. In addition, ‘the serial repitching factor’ is used for the first time to support the visual evaluation of the influence of serial repitching. Amino acids that were essentially affected by serial repitching were glutamine, arginine, alanine and tryptophan in barley, aspartate, glutamate and tryptophan in buckwheat, and all in the quinoa wort fermentation. As opposed to buckwheat and quinoa, in barley the amino acids behaved more or less independently from each other, which for buckwheat and quinoa indicates a more general systemic change in the yeast. From the amino acids point of view, buckwheat can be fully regarded as a suitable gluten‐free substitute for barley beer since the amino acid assimilation was very consistent and hardly influenced by the serial repitching, especially regarding the final amino acid assimilation. In the case of quinoa, the assimilation of all amino acids became significantly affected after the sixth fermentation and quinoa is probably unsuitable for the production of beer‐like beverages. Results suggest no substitutional potential of quinoa for barley beer, but if a nutrient‐rich beverage of choice from quinoa malt is intended to be prepared, it seems that the serial repitching is limited to six fermentations at most. Copyright © 2015 The Institute of Brewing & Distilling     

半固态发酵法酿造苦荞小曲酒糖化工艺优化

为提高半固态发酵法酿造苦荞小曲酒中苦荞的淀粉转化率和出酒率,考察糖化工艺中小曲添加量、糖化时间、糖化温度对其还原糖含量和淀粉含量的影响。在单因素试验基础上,利用正交试验优化糖化工艺,对苦荞小曲酒进行感官品评及理化指标检测,并采用气相色谱-质谱联用法（GC-MS）分析其挥发性风味成分。结果表明,最佳糖化工艺为：小曲添加量0.6%,糖化时间25 h,糖化温度30 ℃。在此优化条件下,苦荞小曲酒清亮透明,香气自然,清香纯正,酒体醇和,香味协调,余味较长;其酒精度为51.3%vol、平均出酒率为57.25%、总酸含量为0.656 g/L、总酯含量为1.95 g/L,感官评分为83分;并共检测出31种挥发性物质,其中酯类14种、酸类3种、醇类9种、其他类5种。     

苦荞菜中总黄酮的测定

目的测定苦荞菜中总黄酮的含量。方法可见分光光度法。结果在420 nm波长处测得即食型苦荞菜中的总黄酮含量为6．87%;苦荞芽苗在生长1,3,5,7 d的总黄酮含量分别为3．31%,4．19%,4．20%,4．15%。结论苦荞菜中富含黄酮,具有广阔的开发前景。测定方法操作简单、快速,适合中、小型食品加工企业应用。     

苦荞黄酮的纯化及抗氧化活性的研究

利用AB-8大孔吸附树脂对苦荞黄酮提取物样品进行纯化,利用薄层色谱分析了纯化前后苦荞黄酮的成分变化,并以维生素C为参照,比较了纯化前后苦荞黄酮对O2-·和DPPH·体外清除能力。试验结果表明:经过AB-8纯化后,苦荞黄酮提取物2中黄酮的含量由78.42%提高到98.73%,纯化后主要成分为芦丁;其清除O2-·的半数清除浓度IC50由0.099 mg/mL升高到0.123 mg/mL,纯化后清除能力反而降低;清除DPPH·的IC50由0.273 mg/mL降低到0.185 mg/mL,清除能力有所提高。     

Fractionation and characterization of tartary buckwheat flour proteins

Protein fractions (albumin, globulin, prolamin and glutelin) were extracted from defatted tartary buckwheat flour. Albumin was the predominant protein fraction (43.8%) followed by glutelin (14.6%), prolamin (10.5%), and globulin (7.82%). Albumin was relatively rich in histidine, threonine, valine, phenylalanine, isoleucine, leucine and lysine. Globulin had high levels of methionine and lysine. Prolamin was high in histidine, threonine, valine, isoleucine, and leucine. Glutelin was rich in histidine, threonine, valine, isoleucine, and leucine. SDS–PAGE analysis, under non-reductive and reductive conditions, showed that disulfide bonds existed in the four fractions. Non-reduced albumin showed major bands at 64, 57, 41, and 38 kDa, and globulin at 57, 28, 23, 19 and 15 kDa. Reduced albumin and globulin shared two common bands at 41 and 38 kDa. Reduced prolamin showed major bands at 29, 26, 17 and 15 kDa. In vitro pepsin digestibility of the four fractions (from high to low) was: albumin > globulin > prolamin and glutelin.     

超声波辅助乙醇提取苦荞酒酒糟及底锅水总黄酮工艺优化

采用超声波辅助乙醇提取法探讨了未经蒸煮的苦荞、蒸煮过的苦荞、苦荞酒酒糟和"苦荞酒酒糟+底锅水"中总黄酮含量,得出苦荞酒酒糟及底锅水中总黄酮含量最高,并以此为研究对象,探究了苦荞黄酮提取的最佳工艺。在单因素试验的基础上结合正交试验,分别考察了乙醇体积分数、萃取温度、萃取时间和固液比对总黄酮含量的影响。得出较优的提取方案为:乙醇体积分数为85%、萃取温度为40℃、萃取时间55 min、固液比1∶45(g∶mL)。在最优的条件下,得出苦荞酒酒糟及底锅水中总黄酮含量为55.49 mg/g。结果表明,超声波辅助乙醇提取能明显提高苦荞酒酒糟及底锅水中黄酮的提取率,并为以后苦荞黄酮的提取提供了参考。     

大孔吸附树脂对苦荞黄酮吸附分离特性研究

筛选出一种适合于精制苦荞总黄酮的吸附剂。选择在黄酮类化舍物精制过程中效果较好的15种树脂，通过静态吸附、解吸试验，比较了各种树脂对苦荞总黄酮的吸附量、吸附率、解吸率以及吸附动力学曲线。DM-2型树脂的静态吸附量达到了109mg／g以上，吸附率超过了83％。用70％乙醇解吸，其解吸率达到了52％。该树脂对苦荞总黄酮具有良好的静态吸附动力学特性，是可供苦荞黄酮精致工业化生产选择的理想材料。     

基于图像处理的苦荞品种判别

为了建立不同品种苦荞种子的正确分类方法,以11个不同品种的苦荞种子为研究材料,使用扫描仪获取种子彩色图像,通过图像处理软件提取每个种子的特征变量28个,建立了一个包含11个品种440个苦荞种子,12 320个数据的矩阵。通过逐步法筛选有效特征变量,并利用有效变量构建判别模型。结果表明,筛选出的18个变量中,颜色变量为苦荞品种判别的主要变量。颜色变量和形态变量相结合,构建的贝叶斯判别模型,回判正确率达到了96.8%,交互验证正确率达到了94.7%。利用计算机图像处理技术和现代统计方法,能有效地对苦荞种子的颜色与形态特征进行精确量化和快速分析,可作为不同品种苦荞种子分类鉴别的一种客观,准确、有效的方法。