酿造水中的锌离子对啤酒酿造的影响

啤酒中的锌离子来源于麦芽、大米、酿造用水、酒花。实验表明在啤酒酿造过程中,锌离子可激活酶的活性、提高酶的催化作用,促进糖化、发酵;提高麦汁中糖、氨基酸的含量;促进双乙酰的还原,降低双乙酰的含量;激活乙醇脱氢酶,降低乙醛,提高酵母活力,降低酵母死亡率;提高发酵度,缩短发酵时间。     

一种新颖而实用的酵母活力检测方法——镁离子释放试验

将一种工业酿造用酵母接种至麦汁中，细胞会立刻释放出镁、钾及磷酸盐离子。而这可直接用来评价该酵母后来的发酵性能。通过试验表明，接种后立即释放明显数量离子的酵母生长快，发酵后会产生较高的酒精含量和较低的双乙酰水平。相反，吸收这些离子或释放浓度相当低的酵母则生长缓慢，发酵后酒精含量较低，双乙酰水平较高。通过实验确定和形成了一种快速、实用和高灵敏度的测定酵母镁离子释放或吸收的方法，用来评定酵母活力，预测其后来的发酵性能。下面就镁离子释放实验方法进行阐述。     

啤酒高浓酿造中氨基酸对酵母发酵性能和啤酒色值的影响

探讨在24?°P高浓啤酒发酵过程中8?种氨基酸（Met、Phe、Trp、Arg、His、Ile、Leu、Lys）的不同添加量（分别为原麦汁中相应氨基酸含量的0.5、1?倍和2?倍）对酵母生理特性、发酵性能和啤酒色值的影响。结果表明：8?种氨基酸的补充可显著提高麦汁发酵度、乙醇产量,促进酵母生长,提高酵母活细胞率,改善啤酒色值。其中,补充1?倍氨基酸的高浓麦汁发酵性能较好,与对照组相比,发酵度、乙醇产量、最大悬浮酵母细胞数和发酵结束时的酵母活细胞率分别提高了6%、17%、11%和10%。添加氨基酸的高浓酿造啤酒经稀释后,啤酒色泽依然鲜亮,且添加1?倍氨基酸酿造而成的啤酒经稀释后色差（ΔE）最小,色泽最接近青岛纯生啤酒。     

啤酒酿造过程中酵母胞内有机锌与风味代谢物质的相关性

为探究酵母不同传代次数和外源添加锌离子对酵母胞内有机锌的影响,并明确酵母胞内有机锌与发酵过程风味代谢物质的相关性,对不同发酵车间、不同代数以及外源添加锌离子发酵的酵母菌株YJ02进行胞内有机锌追踪检测,同时测定其发酵过程中风味代谢物质。结果表明:随着酵母菌株YJ02传代次数和发酵液外源锌离子含量的增加,酵母胞内有机锌均呈现先上升后趋于平稳的趋势,外加锌离子含量保持在0. 4～1. 4 mg/L范围内,对酵母菌株YJ02生长最有利;同时酵母胞内有机锌含量与发酵过程中酯类物质呈现显著正相关,与醛类和醇类物质呈现显著负相关。发酵过程中酵母菌株YJ02利用锌离子的能力是有限的,且胞内有机锌含量与发酵过程中风味代谢物质密切相关,可为后续啤酒酿造过程中风味物质的控制提供理论指导和参考。     

连续发酵过程中啤酒酵母对金属离子的积累和释放

镁、锌和钙等元素参与酵母代谢和其它过程,如酵母絮凝和酵母细胞分裂.在相同量酵母参与的连续发酵过程中,酵母对特殊离子的需求可能发生变化.本文的目的,就是分析酵母在麦芽培养基(9°P)中连续四次发酵过程中锌、镁和钙的浓度.通过对这些离子的分析,观察到在连续发酵过程中,酵母对离子吸收和释放的方式在本质上是相同的.在发酵的对数生长期,酵母细胞积累金属离子,以便在后面释放,至于释放量要取决于金属离子和发酵状况.在第一次发酵时,酵母细胞中每种离子的最大浓度都是后面几次发酵的2到3倍;钙、镁和锌的量分别没有超过1mg/g酵母干重、6mg/g酵母干重和0.6mg/g酵母干重.     

固定化酵母发酵啤酒实验研究

通过测定发酵过程中还原糖和双乙酰的含量变化研究了海藻酸钠固定化啤酒酵母细胞生产啤酒的性能。实验结果表明,固定化酵母发酵啤酒比游离酵母发酵啤酒能更快地利用还原糖,还原双乙酰。固定化酵母发酵啤酒第一批发酵由于需要酵母的大量增殖,主发酵约需要72h;在随后的批次发酵中,固定化细胞发酵啤酒主发酵48h,还原糖降至1.0%以下,双乙酰降至0.15mg/L以下,pH、酸度等均达到啤酒产品质量标准。该工艺菌种可反复利用,发酵时间短,提高了啤酒生产效率。     

钙离子对酵母凝聚性的影响

1.前言啤酒酿造过程中钙离子含量的高低对酵母细胞的生长和凝聚有很大影响。通过在麦汁中添加不同浓度的钙离子(以添加CaSO_4计算钙离子浓度),比较出发酵过程中钙离子对酵母细胞凝聚性以及对发酵过程的影响。     

固定化酵母发酵啤酒的研究

分别研究游离态酵母和固定化酵母发酵啤酒过程中总糖、还原糖、酒精度、双乙酰含量的变化,结果表明固定化酵母发酵啤酒具有发酵短、对麦汁中糖转化效率高的优势。用不同浓度海藻酸钠和氯化钙固定酵母发酵啤酒实验表明,2%海藻酸钠与4%氯化钙在本研究中固定酵母效果最好。     

连续发酵过程中啤酒酵母对金属离子的积累和翻译

镁、锌和钙等元素参与酵母代谢和其它过程,如酵母絮凝和酵母细胞分裂。在相同量酵母参与的连续发酵过程中,酵母对特殊离子的需求可能发生变化。本文的目的,就是分析酵母在麦芽培养基（9°P）中连续四次发酵过程中锌、镁和钙的浓度。通过对这些离子的分析,观察到在连续发酵过程中,酵母对离子吸收和释放的方式在本质上是相同的。在发酵的对数生长期,酵母细胞积累金属离子,以便在后面释放,至于释放量要取决于金属离子和发酵状况。在第一次发酵时,酵母细胞中每种离子的最大浓度都是后面几次发酵的2到3倍;钙、镁和锌的量分别没有超过1mg／g酵母干重、6mg／g酵母干重和0．6mg／g酵母干重。     

酿造工艺对啤酒中有机酸的影响

有机酸是啤酒中重要的风味物质,其组成与含量同酿造工艺有着密切的关系.采用离子色谱法探索了不同酵母菌种、酵母接种景、发酵温度、麦汁pH值以及原麦汁浓度5个因素对啤酒中有机酸的影响.结果表明,酵母菌种、酵母接种量以及原麦汁浓度是有机酸组成和含量的主要影响因素;啤酒最终的pH值和总酸受原麦汁浓度的影响显著,且呈正相关性.     

高浓高温对啤酒酵母发酵性能的影响

以啤酒酵母S-6为实验菌株,研究了主发酵温度和原麦汁浓度对啤酒发酵的残糖、酒精度、风味物质和絮凝性等性能指标的影响。结果表明,原麦汁浓度一定时,主发酵温度对高级醇和乙酸酯的含量影响较大,主发酵温度由10 ℃提高至16 ℃时,高级醇含量提高了10%～20%,乙酸酯含量提高了8%～16%,但CO2累积质量损失、残糖、酒精度和絮凝性基本不受温度的影响;主发酵温度一定时,原麦汁浓度对酵母絮凝性影响较大,原麦汁浓度越高,酵母絮凝性越低,将高浓（18 °Bx）发酵液稀释50%至常浓（12 °Bx）,残糖、酒精度和高级醇的含量与常浓发酵液基本相同。该研究为选育高温高浓发酵低产高级醇同时强絮凝性酵母菌株提供了重要依据。     

The selection and modification of brewer's yeast strains

In order to achieve a beer of high quality, the yeast culture must be effective in removing the desired nutrients from the growth medium (i.e. the wort), it must impart the required flavour to the beer and finally, the micro-organisms themselves must be effectively removed from the fermented wort after they have fulfilled their metabolic role. Brewer's wort contains the sugars sucrose, fructose, glucose, maltose and maltotriose, together with dextrin material. In the normal situation, brewer's yeast strains are incapable of fermenting the dextrin material; however, yeast strains capable of fermenting at least a part of this dextrin material and producing a palatable beer are now available.One of the important factors known to affect the fermentation rate is the intracellular yeast glycogen concentration which has been found to be influenced by storage conditions. The glycogen level at pitching significantly affects the fermentation rate of the yeast culture.     

THE CONTROL OF VOLATILE ESTER SYNTHESIS DURING THE FERMENTATION OF WORT OF HIGH SPECIFIC GRAVITY

Some effects have been studied of fermenting wort of unusually high specific gravity, followed by dilution with water to give beer of normal original gravity. This procedure permits increased overall rates of beer production, but matching of flavours requires control of the level of flavour determinants. If not controlled, the concentration of volatile esters may be disproportionately increased so that, after dilution, beer flavour is markedly different. Higher alcohol production is not affected in this way. The concentration of esters can be adjusted to appropriate levels by increasing the production of yeast mass during fermentation. Unsaturated fatty acids, which increase yeast dry matter production without altering the rate of fermentation, are particularly effective in reducing the extent of ester synthesis.     

SOME FACTORS AFFECTING THE CONCENTRATION OF DIACETYL IN BEER

Investigations of factors affecting the production of diacetyl during fermentation have shown large differences in the abilities of different strains of brewer's yeast to produce diacetyl. Studies on pilot scale and on small laboratory fermentations have established a connection between the concentration of amino acids in the wort and that of diacetyl in the fully fermented beer. Control of the ratio of amino acids to sugars in wort is thus an important factor in maintaining concentrations of diacetyl in beer at an acceptable level. The effects of increased pitching rate and of high-temperature fermentation in enhancing the production of diacetyl are demonstrated.     

Comparing the Impact of Environmental Factors During Very High Gravity Brewing Fermentations

The impact of the initial dissolved oxygen, fermentation temperature, wort concentration and yeast pitching rate on the major fermentation process responses were evaluated by full factorial design and statistical analysis by JMP 5.01 (SAS software) software. Fermentation trials were carried out in 2L‐EBC tall tubes using an industrial lager brewing yeast strain. The yeast viability, ethanol production, apparent extract and real degree of fermentation were monitored. The results obtained demonstrate that very high gravity worts at 22°P can be fermented in the same period of time as a 15°P wort, by raising the temperature to 18°C, the oxygen level to about 22 ppm, and increasing the pitching rate to 22 × 10⁶ cell/mL. When diluting to obtain an 11.5°P beer extract, the volumetric brewing capacity increased 91% for the 22°P wort fermentation and 30% using the 15°P wort. After dilution, the fermentation of the 22°P wort resulted in a beer with higher esters levels, primarily the compound ethyl acetate.     

Impact of Dark Specialty Malts on Extract Composition and Wort Fermentation

Dark specialty malts are important ingredients for the production of several beer styles. These malts not only impart colour, flavour and antioxidative activity to wort and beer, they also affect the course of wort fermentations and the production of flavour‐active yeast metabolites. The application of considerable levels of dark malt was found to lower the attenuation, mainly as a result of lower levels of fermentable sugars and amino acids in dark wort samples. In fact, from the darkest caramel malts and from roasted malts, practically no fermentable material can be hydrolysed by pilsner malt enzymes during mashing. Compared to wort brewed with 50% pilsner malt and 50% dark caramel malt or roasted malt, wort brewed with 100% pilsner malt contained nearly twice as much fermentable sugars and amino acids. Reduced levels of yeast nutrients also lowered the fermentation rate, ranging from 1.7°P/day for the reference pilsner wort of 9 EBC to 1.1°P/day for the darkest wort (890 EBC units), brewed with 50% roasted malt. This additionally indicates that lower attenuation values for dark wort are partially due to the inhibitory effects of Maillard compounds on yeast metabolism. The application of dark caramel or roasted malts further led to elevated levels of the vicinal diketones diacetyl and 2,3‐pentanedione. Only large levels of roasted malt gave rise to two significant diacetyl peaks during fermentation. The level of ethyl acetate in beer was inversely related to colour, whereas the level of isoamyl acetate appeared to be affected by the use of roasted malt. With large levels of this malt type, negligible isoamyl acetate was generated during fermentation.     

应用糖浆高浓酿造啤酒的工艺浅析

高浓酿造啤酒起源于20世纪70年代美国和加拿大，现已遍及欧美啤酒行业。其优点有：(1)提高糖化和发酵设备利用率，节省投资；(2)降低能耗和成本；(3)提高糖分的转化率；(4)提高啤酒非生物稳定性和质量；(5)可添加稀释水、麦芽提取物、酒花萃取物及糖浆生产多类型产品，灵活性较大。缺点有：(1)酒花利用率低；(2)起泡性和稳定性下降；(3)对啤酒酵母有不利影响；(4)发酵时间延长；(5)对水质要求严格；(6)需调整原料、糖化工艺和发酵工艺；(7)长期生产需专门的糖浆贮存设备和糖浆添加泵；(8)不宜酿造浓醇型啤酒。     

酵母自溶的成因及其对啤酒质量的影响

酵母自溶由酵母胞内蛋白分解酶外泄引起，影响酵母自溶的因素有：(1)酵母菌种；(2)麦汁营养成分组成不合理；(3)酵母使用代数过高；(4)酵母添加量过多；(5)温度、压力、pH值等发酵工艺条件控制不当；(6)酵母回收时间、方法、压力、酵母贮存条件；(7)微生物污染。酵母自溶会影响啤酒风味稳定性，使啤酒苦味、涩味加重；啤酒双乙酰含量增加；啤酒的泡持性下降；啤酒总酸偏高；啤酒pH值升高；增加啤酒过滤成本。防止酵母自溶的方法有：(1)选择优良强壮的出发菌株；(2)控制酵母添加量和使用代数；(3)制备营养丰富、组成合理的麦汁；(4)严格发酵工艺奈件；(5)加强酵母质量管理；(6)加强卫生管理，保证纯种发酵。     

The effect of wort aeration on fermentation,maturation and volatile components of beer produced on an industrial scale

The aim of the study was to determine the effect of the initial beer wort aeration on the process of fermentation, maturation, content of the volatile components of beer and abundance and vitality of yeast biomass. The experiments were performed on an industrial scale, with fermentation and maturation performed in fermentation tanks with a capacity of 3800 hL. The wort was aerated with sterile air in quantities as follows: 7, 10 and 12 mg/L. During fermentation and maturation, the changes in the content of the extract, yeast growth and vitality and more importantly volatile components were investigated. The experiments showed that differentiated aeration has a significant impact on the course of fermentation and metabolic changes. With the increase in wort aeration, the content of acetaldehyde decreased and the concentration of higher alcohols increased. On the other hand, the contents of esters and vicinal diketones did not change. The level of aeration did not affect the final quality of beer. Copyright © 2017 The Institute of Brewing & Distilling     

发酵环境变化对酵母生长和成品啤酒的影响

啤酒发酵是一个复杂的生物和物质转化过程,在整个酿造过程中,从原料粉碎到开始发酵直至发酵结束降温冷贮,环境变量因素很多,会影响啤酒酵母生长,从而影响成品啤酒中的挥发性风味物质和啤酒品质。该文重点总结介绍麦汁浓度、接种率、发酵温度、压力变量对发酵过程的影响,旨在为解决啤酒酿造过程可能出现的问题提供一些思路,从而提高啤酒质量。