浅论啤酒的老化机制

啤酒的老化是由各种风味物质复杂氧化和分解、化合的结果,啤酒老化物质主要是以反二壬烯醛为代表的羰基化合物,其形成过程大都与氧有关。老化在原料、制麦、糖化、发酵、包装过程已经开始,而在成品酒贮存过程中,这些老化前驱物质进一步变化,从而使啤酒风味恶化。以下途径参与了老化味的形成,对啤酒的风味稳定性产生重大的影响。     

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.     

大麦、麦芽和啤酒酿造中的内源性氧化还原酶

由于大麦和麦芽中存在的内潭性氧化还原酶的作用，使内源性多酚、不饱和脂类等物质被氧化，导致成品啤酒风味稳定性和非生物稳定性的降低。酶促氧化反应可发生在不同的酿造阶段，包括发芽、焙爆和糖化等环节。五种主要的内源性氧化还原酶中，超氧化物歧化酶是最为重要的抗氧化酶，可防止超氧阴离子自由基的危害；而过氧化氢酶可催化具有活性的H2O2生成如，由此构成了清除活性氧的初级抗氧化酶体系。过氧化物酶和多酚氧化酶分别在H2O2和O2存在的情况下，可催化内源性酚类底物生成具有活性的醌类物质，所产生的次级氧化产物可改变啤酒的品质。脂肪酸氧化酶可氧化不饱和脂肪酸生成可挥发性的醛类物质，是导致啤酒风味老化的关键酶。酶促氧化的结果在成品啤酒上主要表现为老化异昧的出现、形成混浊、苦味和收敛性的改变，以及色泽的加深等。本文综述了这五种酶的基本性质，在制麦和糖化过程中的变化及其影响，并探讨了对啤酒酿造的影响。     

浸麦过程中添加金属离子对麦芽内源抗氧化活力的影响

以大麦为实验材料,通过在浸麦阶段添加不同量(0、20、40、60、80、100mg/kg)金属离子(K+、Mg2+、Zn2+、Ca2+和Cu2+),测定所制得成品麦芽的相关氧化还原酶(SOD、CAT、POD和PPO)活力、总酚含量、DPPH自由基清除率、还原力和TBARs值,以考察浸麦过程中添加的金属离子对麦芽内源性氧化还原酶与抗氧化活力的影响。结果表明:不同添加量的各金属离子对麦芽氧化还原酶类的影响不尽相同;适宜添加量的上述金属离子均有效增强了麦芽的总酚含量、DPPH自由基清除能力和还原力,降低了麦芽的TBARs值。     

老化的颗粒酒花对啤酒发酵抗氧化能力的影响

分析老化后酒花的主要成分,研究发现在酒花老化过程中α酸和β酸发生氧化降解,前期生成异α酸,随着老化的进行,继而产生葎草灵酮(humulinone)和希鲁酮(hulupones)等衍生氧化物。酒花中的总多酚含量逐渐减少,具有抗氧化性的酚酸也发生氧化聚合,使用液相色谱检测几乎无响应峰。并测定总多酚、DPPH清除率、TRAP值、TBA值等抗氧化指标来分析老化的酒花对麦汁和啤酒的抗氧化能力影响,实验发现老化的酒花对麦汁和啤酒的抗氧化能力影响较大,尤其是风味稳定性系数SI值,波动最为明显。     

多酚物质对啤酒风味稳定性的影响

研究多酚物质对啤酒风味稳定性的影响.结果表明,啤酒的风味稳定性与啤酒的抗氧化性显著相关,啤酒的抗氧化性与多酚含量显著相关;不同的单酚抗氧化能力差异较大;抗氧化性随单酚含量的增加而增加;酒体中的单酚抗氧化性随酒体保存的时间延长而减小;不同来源的多酚抗氧化性不同;不同辅料生产的啤酒抗氧化能力不同.多酚含量和组成影响啤酒的风味稳定性,多酚适量存在可提高啤酒风味稳定性.     

啤酒生产过程中氧化还原酶系的研究

啤酒生产过程中的氧化还原酶与啤酒风味陈化紧密相关。低水分下，其耐温活性远高于其它几种酶，在麦芽中酶活升高比例最大（与大麦中的酶活相比），其在糖化过程中氧化多酚的能力远大于多酚氧化酶。糖化过程中迅速失活，而脂肪酸氧化酶在糖化起始的低温阶段仍有部分酶活，影响不饱和脂肪酸的氧化。焙燥过程中适当延长50～70℃温度段时间，可有效降低麦芽中氧化还原酶的酶活。结合这些酶的性质，从部分抑制它们的活性角度出发，在糖化过程中，于50～60℃进行隔氧处理，可经济、有效的减少影响风味氧化的前驱物质的含量。同一质量等级不同品种的麦芽的氧化还原酶系差别相当大，相应制得的麦汁中与风味氧化有关的物质含量也有较大差别，这可能是造成不同批次原料酿造的成品啤酒风味保鲜期不稳定的原因之一。     

多酚物质对啤酒非生物稳定性及风味稳定性的影响

本文简要综述了多酚物质对啤酒非生物稳定性和风味稳定性的影响。多酚物质既是啤酒潜在的浑浊物质，同时也是风味物质。多酚是影响啤酒风味的重要因素，多酚—蛋白质生成的络合物作为非生物浑浊的前驱也属于啤酒风味老化的过程范围。因此，有必要控制啤酒酿造过程中的多酚物质含量和组成。     

麦汁煮沸对啤酒风味老化物质形成影响

麦汁煮沸是啤酒煮沸一个重要环节，对啤酒风味老化物质前驱体形成有重大影响。啤酒风味老化物质主要在成品酒贮存期间形成并积累。但啤酒风味老化前驱物质形成却贯穿于啤酒生产的全过程。羰基化合物特别是挥发性长链不饱和醛，是啤酒风味老化物质主要代表物。     

巴西啤酒在自然老化和强制老化过程中多酚及抗氧化特性的变化研究

生产啤酒的主要原料为大麦,但在酿造过程中往往加入如玉米、大米和小麦等其它谷物。啤酒中含有具抗氧化特性的酚类物质,主要来自麦芽及酒花。啤酒又是一种不稳定的产品,在其储藏过程中会发生一系列物理、化学及风味物质的转化反应。本研究对两种巴西啤酒在自然老化（室温,4个月）及强制老化（42℃,6天）过程中的氧化特性进行了研究。主要检测了以下指标：总多酚含量、DPPH值（自由基清除能力）、还原力及铜离子还原活力等。结果表明,在啤酒的强制老化过程中总多酚含量以及抗氧化活力并没有明显改变,自然老化过程中多酚含量和抗氧化活力有所降低。     

不同品种啤酒大麦间游离酚类化合物及其相关酶类的研究

大麦中的酚类化合物及相关酶(如酚类合成酶苯丙氨酸解氨酶,酚类氧化酶过氧化物酶和多酚氧化酶)对大麦的生长发育、抗病特性及啤酒质量有重要影响。本文研究了16种不同品种、22种不同样本啤酒大麦中酚类物质的含量及相关酶活性的差异性和相关性,并测定了不同品种大麦的抗氧化活力。研究结果表明:不同品种和同一品种不同产地啤酒大麦的酚类化合物含量和酚类酶活性因品种特性和生长、种植条件而存在显著差异(P<0.05);游离总多酚含量和抗氧化力之间存在显著的正相关性(r=0.794);苯丙氨酸解氨酶活性并不与游离总多酚含量呈正相关性,过氧化物酶和多酚氧化酶的活性也不与总多酚含量呈相关性,这可能和大麦中同时存在酶类氧化酶和酚类合成酶有关。研究认为,通过测定大麦游离总多酚含量和DPPH自由基清除率可初步判断啤酒大麦的内源性抗氧化力,以此作为评价酿造原料品质的检测手段。     

挤压膨化对青稞中不同形态多酚组成及抗氧化活性的影响

以独立花青稞为材料,探究挤压膨化对青稞中不同形态多酚组分及抗氧化活性的影响。采用福林酚法测定膨化前后青稞样品的多酚含量;采用高效液相色谱法测定醇提物中的7种多酚单体含量;采用1,1-二苯基-2-三硝基苯肼自由基清除法测定抗氧化能力的变化。结果表明,经挤压膨化处理后,总多酚、游离型多酚和结合型多酚分别降低了52.7%,89.3%,23.7%,酯化型多酚含量较低,略微增加了2.49 mg/100 g;游离型多酚中检测出的多酚种类增加了3种,7种多酚单体在结合型多酚中均有测出;其中阿魏酸含量最高且主要以结合态存在,其含量处理后显著增加;此外,两种条件下青稞提取物抗氧化活性分别为1.76,0.93 mg/g,多酚含量与抗氧活性呈极显著正相关。表明挤压膨化技术运用于青稞加工之中,在改变青稞质构和口感的同时会降低多酚含量及抗氧化活性。     

Influence of barley variety and malting process on lipid content of malt

The lipid content of a beer affects its ability to form a stable head of foam and plays an important role in beer staling. The concentration and the quality of lipids in beer depend on their composition in the raw materials and on the brewing process and they may exert considerable influence on beer quality. This paper presents an investigation of the influence of barley variety and malting process on the lipid content of finished malt. Five barley samples, grown in Italy, representing 4 spring barley and 1 winter barley were used. The samples were micro-malted and analysed. The aim of this research was to verify the influence of different barley varieties on the lipid content of malt and also on the changes in fatty acid (FA) profile during the malting process. Lipid content and FA profile were evaluated. Principal component analysis (PCA) was used to establish relationships between the different samples. An evaluation of the correlation between lipid content of barleys and the quality of the resulting malts was also conducted. The data showed that the total lipid content during the malting process decreased significantly as barley was converted into malt. Different barley varieties present different FA contents and different FA patterns. The correlation between the lipid content of barley and the quality of the resulting malt confirmed the negative influence of lipids.     

The chemical components in malt associated with haze formation in beer

In bright beer, haze formation is a serious quality problem, which reduces beer storage and shelf life. In this study, haze‐active proteins, alcohol chill haze formation ability, α‐amylase activity, the contents of total polyphenol, protein and its fractions and amino acids were analysed using 23 barley accessions to investigate the relationship between the quality components in the malt and the haze character in beer. The results showed that there were largely genotypic variations for all examined traits among the 23 barley accessions. However, there was no significant correlation between the haze character and α‐amylase activity. All haze characteristics were significantly and positively correlated with total protein content, albumin, globulin and the hordein content, as well as the glutamic acid (glutamine), proline and phenylalanine content, and were not correlated with total polyphenols. A model describing the relationship between the chill haze in the beer and the protein content in the malt was developed. Copyright © 2016 The Institute of Brewing & Distilling     

啤酒大生产中抗氧化能力影响因素的研究

研究了在啤酒大生产过程中的不同阶段抗氧化指标的变化,发现在麦汁制备过程中,糖化和麦汁煮沸是啤酒老化物质大量生成的阶段,同时这两个阶段的还原力有较大幅度的增加。在发酵过程中,酵母可大量还原发酵液中的老化物质,同时提高最终发酵液的还原力。不同的酵母对最终发酵液抗氧化能力的影响是极其显著的。     

青稞啤酒的研究进展及发展探讨

青稞是生活在青藏高原地区人民的主要粮食,同时也是该地区研发功能食品创收的最佳原料。青稞具有“三高两低”营养特点,所含多酚类化合物有助于预防心脑血管类疾病,还有良好的抗氧化作用。在加工领域有着广泛的应用,制成的青稞啤酒,口感纯净、杀口力强、醇香浓郁、风味独特、具有特殊的迷人酯香,深受消费者喜爱。本文汇总了近些年青稞啤酒取得的研究进展,从啤酒酿造工艺、存在不足等方面进行归纳,旨在为青稞的精深加工提供新的研发思路。     

4种典型谷物中酚类化合物的抗氧化和抗癌细胞增殖活性

将荞麦、大麦、小麦、水稻4种全谷物用70%(v/v)乙醇水浸提后,经AB-8大孔吸附树脂富集/分离,分别得到4种全谷物酚类提取物,测定其总酚和总黄酮含量,并运用高效液相质谱联用(HPLC-MS)法鉴定酚类化合物组成。在此基础上,通过体外法测定4种谷物的抗氧化能力和抗Caco-2细胞增殖能力,并探讨多酚含量与活性之间的相关性。结果表明:4种谷物酚类提取物中总酚和总黄酮含量从高到低的顺序均依次为:荞麦>大麦>水稻>小麦。从4种全谷物中成功确定了21种酚类化合物。4种谷物酚类化合物均具有一定的抗氧化能力和抗Caco-2细胞增殖能力,其强弱顺序均为:荞麦>大麦>水稻>小麦,而且其总酚含量与抗氧化和抗Caco-2细胞增殖活性之间以及抗氧化活性与抗Caco-2细胞增殖活性之间均具有良好的相关性。     

Assessment of endogenous antioxidative compounds and antioxidant activities of lager beers

BACKGROUND: Flavour stability is increasingly becoming the limiting factor in the shelf life of beer. Increasing the antioxidant activity of beer itself could suppress the rate of oxidative reaction and improve the flavour stability of beer. This report describes the levels of phenolic compounds, melanoidins and sulfur dioxide, and antioxidant activities of 40 lager beers. The relationships between antioxidative compounds and antioxidant activity were elucidated by multivariate analysis techniques. RESULTS: The results showed that the total phenolic content and the melanoidins content correlated well (P < 0.05) with antioxidant activity, while there was no significant correlation (P > 0.05) between total sulfur dioxide content and antioxidant activity. Satisfactory discrimination among beer samples with significantly different antioxidant activity was achieved by principal component analysis. Results from stepwise linear regression further demonstrated that different antioxidative components responsible for antioxidant activity were dependent on the assay used. The phenolic compound group is by far the most antioxidative compounds in beer and total phenolic content, melanoidins and sulfur dioxide together made a 22–68% contribution to the antioxidant activities of beers. CONCLUSION: Therefore, it might be an efficient means for brewers to increase total phenolic content during brewing for improvement in flavour stability of the final beer. © 2012 Society of Chemical Industry     

Brewing with 100% Oat Malt

Oats are a cereal with beneficial nutritional properties and also unrealized brewing potential. Furthermore, oats can be tolerated by the majority of people who suffer from celiac disease. Malting of oats produced a malt, which was found suitable for brewing a 100% oat malt beer. The mashing regime, designed by using mathematical modelling, was successfully transferred to a pilot scale plant. The improved lautering performance of oat malt was due to its higher husk content, which also led to a lower extract content in oat wort when compared to barley wort. The protein profile of oat wort, as measured by using Lab‐on‐a‐Chip analysis, revealed that there was no significant difference in the protein profile between oat and barley wort. The fermentation of oat and barley worts followed the same trend; differences could only be seen in the higher pH and lower alcohol content of the oat beer. The flavour analysis of oat beer revealed some special characteristics such as a strong berry flavour and a lower amount of staling compounds when forced aged. This study revealed that it was possible to brew a 100% oat malt beer and that the produced beer was comparable to a barley malt beer.