大麦品种和制麦过程对麦芽含脂量的影响

脂类物质影响啤酒泡沫稳定性并对啤酒老化有重要作用.啤酒中脂类物质的浓度和性质取决于原料的组成和酿造过程.本文研究了大麦品种和制麦过程对麦芽含脂量的影响.采用意大利的四种春大麦和一种冬大麦作为样品,进行微型制麦和分析.本研究旨在确认大麦品种对麦芽含脂量及制麦过程中脂肪酸（FA）含量变化的影响.采用主成分分析（PCA）建立不同样品之间的关系,同样也对大麦的含脂量和制得麦芽品质的相关性进行了评估.数据显示制麦过程中大麦转化为麦芽时总脂含量显著下降;不同大麦品种的脂肪酸含量和脂肪酸图谱均不同.大麦含脂量和制得麦芽质量的相关性确认了脂类的负面影响.     

制麦过程大麦和麦芽中麦角甾醇和呕吐毒素含量的变化

本文测定了不同品种大麦和麦芽中的呕吐毒素和麦角甾醇含量,共分析了20个大麦和20个麦芽样品,用正己烷溶解谷物中的碱性水解提取物以获得麦角甾醇,用乙腈/水及固相萃取(SPE)法提取呕吐毒素,通过配有紫外检测器的高效液相色谱(麦角甾醇)和质谱(呕吐毒素)进行检测。分析了制麦过程对两种化合物的影响,其中大麦中麦角甾醇浓度为0.88～15.87mg/kg,麦芽中的浓度为2.63～34.96mg/kg,比制麦增加了95%。因此,制麦过程对麦角甾醇浓度的影响很大(P=0.07);同时发现大麦中呕吐毒素浓度最大为641μg/kg,麦芽中为499μg/kg,没有发现制麦过程对呕吐毒素生成有影响,而且麦角甾醇和呕吐毒素间的相关性非常低(大麦为0.02,麦芽为0.01),因此麦角甾醇含量不能作为呕吐毒素污染的一个指标。     

制麦过程中麦芽抗氧化性的研究

大麦和麦芽中存在的氧化还原酶类能催化氧化总多酚、不饱和脂类等物质,产生了一些风味老化前驱物和羰醛化合物等,从而降低啤酒的非生物稳定性和风味稳定性。研究了4个品种啤酒大麦在制麦过程中总多酚、老化前驱物及几种氧化还原酶酶活力的变化,分析了制麦过程中总多酚、老化物质含量的变化与氧化还原酶活力之间的关系,发现Prestige的抗氧化性最高,内蒙大麦的抗氧化性最低,且DPPH自由基清除率和总多酚、TBA和LOX相关系数分别0.930和0.784具有高度相关性。      

制麦工艺对麦芽氧化还原酶的影响

大麦和麦芽的氧化反应速率与其内源性氧化还原酶有直接联系.本文考察了各个制麦阶段对麦芽中氧化还原酶类的影响,实验结果显示,改变工艺条件能够有效降低氧化还原酶活力,从而为生产强抗氧化性麦芽提供方法及参考.     

Metabolite profiling of barley: Influence of the malting process

A metabolite profiling approach based on gas chromatography–mass spectrometry (GC/MS) was used to investigate time-dependent metabolic changes in the course of the malting process of barley. Barley grains were subjected to a micro-malting procedure involving steeping, germination and kiln-drying. Samples taken in the course of the malting process were subjected to an extraction and fractionation procedure covering a broad spectrum of lipophilic (e.g. fatty acid methyl esters, hydrocarbons, fatty alcohols, sterols) and hydrophilic (e.g. sugars, acids, amino acids, amines) low molecular weight barley constituents. Investigation of the obtained fractions by GC resulted in the detection of 587 distinct peaks of which 173 were identified by means of MS. Statistical assessment of the data via principal component analysis demonstrated that the metabolic changes during the malting progress are reflected by time-dependent shifts of the scores. Analysis of the corresponding loadings showed that polar metabolites were the major contributors to the malting time-driven changes in the metabolic profiles. Quantifications based on standardised peak heights revealed dynamic changes of the metabolites in the course of the different malting stages.     

Influence of barley variety, timing of nitrogen fertilisation and sunn pest infestation on malting and brewing

BACKGROUND: This paper presents a multivariate approach to investigate the influence of barley variety, timing of nitrogen fertilisation and sunn pest infestation on malting and brewing. Four spring and two winter barley varieties were grown in one location in southern Europe. Moreover, one of the spring varieties was infested with sunn pest, in order to study the effects of this pest on malting quality, and subjected to different nitrogen fertilisation timing regimes. The samples were micromalted, mashed, brewed and analysed. RESULTS: The data showed that even though the two winter barleys seemed to be the best regarding their physical appearance (sieving fraction I + II > 82%), this superiority was not confirmed in the malt samples, which showed low values of Hartong extract (27.1%) and high values of pH (6.07–6.11) and β‐glucan content (12.5–13.2 g kg^?1), resulting in low‐quality beers. The barley sample subjected to postponed fertilisation had a total nitrogen content (19.5 g kg^?1 dry matter) exceeding the specification for malting barley and gave a beer with a low content of free amino nitrogen (47 mg L^?1) and high values of viscosity (1.99 cP) and β‐glucan content (533 mg L^?1). The beer obtained from the barley sample subjected to pest attack had good quality parameters. CONCLUSION: All spring barleys gave well‐modified malts and consequently beers of higher quality than the winter barleys. Moreover, postponed fertilisation was negatively related to the quality of the final beer, and sunn pest infestation did not induce important economic losses in the beer production chain. Copyright © 2010 Society of Chemical Industry     

制麦条件对麦芽氨基酸组成的影响

在制麦过程中,大麦中的蛋白质在蛋白酶的作用下逐渐分解为低分子肽类和氨基酸,这些营养物质为酵母的生长和代谢提供了保障。实验采用反相高效液相色谱法(RP-HPLC)测定麦芽中氨基酸的含量和组成,并研究了不同麦芽品种和工艺条件下,麦芽氨基酸组成的变化规律。结果表明,不同大麦品种在相同的工艺下,其氨基酸组成差异并不显著;同种大麦采用不同的制麦工艺其氨基酸含量和组成差别明显。     

小麦麦芽制麦过程中酸感物质的变化

为了能够更好地了解小麦麦芽在不同制麦阶段酸感物质的变化,为小麦麦芽制麦工艺的优化提供技术参考,本研究选取琥珀酸、乙酸、柠檬酸、苹果酸和乳酸作为酸感物质的代表,按照微型制麦工艺对样品进行制麦操作,采用高效液相色谱~（HPLC）对不同制麦时间的酸感物质进行检测分析,结果发现：小麦在发芽期间,总酸感物质含量逐渐升高;苹果酸在整个制麦过程一直处于动态平衡过程中;乙酸、乳酸、柠檬酸和琥珀酸都随时间逐渐升高,较小麦分别增加了11．2倍、6．1倍、7．0倍、4．7倍,且都在发芽阶段时大量增加。     

大麦发芽过程中蛋白质组的变化研究

通过双向电泳技术监测大麦发芽过程中水溶蛋白质组的变化,明确大麦发芽过程中蛋白质组的变化规律,为麦芽制造提供一定理论依据。以澳麦\     

制麦工艺对SN1391小麦麦芽质量的影响

以小麦SN1391为试材,采用三因素三水平正交实验设计,研究浸麦度（40%～48%）、发芽温度（12～20℃）及焙焦温度（78～83℃）对麦芽质量的影响。通过对成品麦芽指标的分析,发现浸出物含量受制麦工艺参数影响不大;糖化力、糖化时间、α-AN含量、库尔巴哈值、麦芽β-葡聚糖含量、麦汁粘度受工艺参数影响较大;提高浸麦度与发芽温度,降低焙焦温度可以降低成品麦芽中β-葡聚糖的含量和麦汁粘度。以糖化力为主要指标时,对糖化力影响的主次因素顺序为:发芽温度>浸麦度>焙焦温度;得到最佳制麦工艺参数为:浸麦度47%～48%、发芽温度为18～20℃、焙焦温度为80～81℃。      

四氢嘧啶对澳麦Gairdner和国麦甘啤3号制麦过程的影响

四氢嘧啶作为一种酶保护剂,首次被应用于澳麦Gairdner和甘啤3号制麦过程中。通过在2种大麦制麦工艺中添加四氢嘧啶,与未添加四氢嘧啶的工艺进行比较,研究结果表明两种大麦发芽后绿麦芽中淀粉酶、β-葡聚糖酶、纤维素酶经过高温干燥过程酶活性均有不同程度的损失,而四氢嘧啶对这3种酶的热稳定性起到保护作用,同时对制麦过程其他物质变化未产生不良影响。对2种工艺制备的麦芽进行理化指标分析,结果对比表明:采用添加四氢嘧啶工艺制备的麦芽具有更好的酿造性能。     

Protein content of grains of different size fractions in malting barley

The negative relationship between grain size (percentage >2.5 mm) and protein content usually observed in barley grain samples is attributed to the presence of thin grains. The objective of this study was to determine whether, in grain samples from a given environment, thin grains had a different protein content than plump grains. Grain samples from field experiments were analysed for grain yield, size and protein content of the whole sample and of four size fractions within each sample. Grain yield ranged from 1.5 to 6.5 mg ha^?1 and grain protein (whole sample) ranged from 6.8 to 13.4 %. Most of the variation observed in protein content was explained by the ratio of nitrogen availability to grain yield. Within a grain sample, thin grains had more protein than plump grains (>2.5 mm) only when the protein content of the whole sample was high, that is, when the grain sample came from an environment with a high relative abundance of nitrogen. The fact that grain samples with low grain size tend to have high protein content is not due to the presence of a high proportion of thin grains, because thin grains do not always have more protein than plump grains. Copyright © 2014 The Institute of Brewing & Distilling     

小麦芽脂肪酶酶学性质以及制麦过程的酶活变化

以对硝基苯酚丁酸酯为底物,确定了小麦芽脂肪酶的酶学性质:最适温度为37℃;最适pH为8.0;4～35℃脂肪酶的热稳定性较好,35℃下保温60 min后其活力仍可保持在88.37%,45℃保温60 min后其活力保持在46.81%,55℃保温60 min酶失活;pH5.5～6.0范围内对脂肪酶的破坏力相对较小,保温60 min其活力仍可分别保持在95.11%和91.11%;Fe3+对脂肪酶有较强的抑制作用;Cu2+、Mn2+、Al3+对脂肪酶的抑制作用较小;Ca2+、EDTA对脂肪酶有较强的激活作用。小麦制麦过程中发芽第4天酶活达到最大值,为8.52 u/g,随后酶活下降;干燥会破坏部分脂肪酶的酶活,损失率为27.06%。小麦芽籽粒、胚芽、胚根中的脂肪酶酶活依次降低,分别为8.01 u/g、7.55 u/g、6.83 u/g;协定法麦汁糖化过程中,无胚芽麦芽脂肪酶的酶活比有胚芽的低,且酶的失活速度也比较大,在55 min(70℃)时,脂肪酶完全失活。     

Effect of malting on antioxidant capacity and vitamin E content in different barley genotypes

Unprocessed barley is known to contain relatively high levels of antioxidants, which play a critical role in human health and the preservation of food and drink products. However, there are limited data on how the antioxidant levels in barley are affected by malting, and whether the level of antioxidants in the processed malt differs between barley varieties. This study aimed to determine the levels of individual vitamin E isomers, total vitamin E content and total antioxidant capacity before, during and after malting in 12 covered and two hulless barley genotypes. Vitamin E content and antioxidant capacity were determined by high‐performance liquid chromatography (HPLC) and ability to scavenge DPPH radicals, respectively. The vitamin E content of most genotypes was reduced after steeping, germination and kilning compared with the unprocessed samples. However, the antioxidant capacity in the malt was higher than in the unprocessed samples for the majority of the genotypes. While there was variation in the percentage change in antioxidant capacity between varieties, the antioxidant capacity of samples after malting was directly correlated with their antioxidant capacity before processing (r = 0.9, n = 14, p < 0.05). These results indicate that barley varieties that have higher antioxidant capacity at harvest retain their antioxidants after malting. Thus, these varieties are likely to be the most suitable for producing malts with the added health benefits and anti‐spoiling properties associated with greater antioxidant content. Copyright © 2015 The Institute of Brewing & Distilling     

Influence of barley malting operating parameters on T-2 and HT-2 toxinogenesis of Fusarium langsethiae,a worrying contaminant of malting barley in Europe

The fungus Fusarium langsethiae, exclusively described in Europe at present, seems to have taken the place of other Fusarium species in barley fields over the last 5 years. It has proved to be a highly toxic type-A trichothecene producer (T-2 and HT-2 toxins). The aim of this work was to study the ecotoxinogenesis of this fungus the better to identify and manage the health risk it may pose during the beer manufacturing process. The influence of temperature and water activity on its growth rate and production of toxins are particularly assessed from a macroscopic point of view. Different cultures were grown on sterilized rehydrated barley with a water activity between 0.630 and 0.997 and a temperature ranging from 5 to 35°C. Biomass specific to F. langsethiae and T-2 and HT-2 toxins were quantified by real-time polymerase chain reaction and liquid chromatography-mass spectrometry, respectively. It appears that the optimal temperature and water activity for F. langsethiae toxinogenesis are 28°C and 0.997. This fungus was able to produce 2.22 g kg^?1 of these toxins in 16 days on barley in optimal production conditions. The malting process seems to be a critical step because, in its temperature range, specific production was six times higher than under optimal temperatures for fungus growth. In the short-term, this work will help redefine the process conditions for malting. In the medium-term, the results will contribute to the development of a molecular tool to diagnose the presence of this contaminant and the detection of the toxins in barley, from fields to the end product.     

不同添加物对大麦发芽过程中热稳定蛋白含量的影响

为了解发芽过程中热稳定蛋白动态变化趋势,以澳麦为原料,模拟工业制麦条件,系统分析了麦芽制备过程中热稳定蛋白分布变化。通过在浸麦最后一天添加Mg2+、K+、赤霉素(GA3)调节蛋白酶酶活及分解。采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)电泳和考马斯亮蓝法(Bradford法),研究添加金属离子及赤霉素后热稳定蛋白分布及含量。结果表明,麦芽中热稳定蛋白分子质量主要分布在约40 ku和10 ku两个区域。经制麦后,40 ku分子质量蛋白质含量增加,10 ku附近蛋白质含量变化不明显。Mg2+和赤霉素添加降低了热稳定蛋白含量,K+有利于热稳定蛋白含量增加。     

影响麦芽溶解度的关键制麦参数及参数优化

麦芽溶解度是衡量麦芽酿造性能的重要指标,针对影响该指标的关键制麦参数即浸麦度、发芽温度、凋萎温度、干燥温度,以进口大麦为原料,进行了单因素试验,并分别采用荧光染色法和冷场发射扫描电子显微镜观察麦芽胚乳溶解情况来确定麦芽溶解度。并在此基础上采用响应面设计优化制麦工艺。结果表明,各因素对麦芽溶解度影响程度的大小顺序为B(发芽温度)D(干燥温度)C(凋萎温度)A(浸麦度)。优化制麦工艺条件为:浸麦度为46%,发芽温度为16℃,凋萎温度为48℃,干燥温度为78℃。优化制麦工艺后,麦芽溶解度从81%提高到87%。     

Monitoring of malting process by characterization of glycation of barley protein Z

Glycation is a common form of non-enzymatic modification that influences the properties of proteins. Although occurrence of protein glycation in food is known for several years, qualitative and quantitative analysis of its reaction products is still a challenging task. Our attention was focused on monitoring of changes in the glycation degree of protein Z, one of the most important protein components of barley malt that influences the properties of beer. The modification during the malting period was studied by a combination of gel electrophoresis, liquid chromatography and mass spectrometry. Water soluble proteins were extracted from barley grains at different times of malting and separated by gel electrophoresis. Protein Z was clearly identified in the band at a position of about 43 kDa and further studied by MS with matrix-assisted laser desorption/ionization technique in detail. From the analysis, we found that protein Z glycation is detectable from the second day of malting. The glycated peptide was observed as a weak signal of m/z 2,619 in the MS spectrum. To confirm the presence of glycation, the MS/MS experiments of both unmodified (m/z 2,457) and modified peptides (m/z 2,619) were carried out. We successfully established a procedure based on the monitoring of glycated peptides in positive reflectron mode to monitor the progress of malting using protein Z as a model protein that might be a potential marker reflecting this technological process. We also demonstrated the high suitability of MS/MS analyses to provide more structural information on peptide modifications.