固定化后期添加啤酒酵母菌降低啤酒中双乙酰含量的探讨

为探索用后期添加固定化酵母菌降低啤酒中双乙酰的工艺,通过单因素和正交试验,发现后期接入固定化啤酒酵母菌降低双乙酰含量的最佳工艺为:发酵温度为12℃,接入时间为发酵第16d,发酵再次接入固定化酵母菌的接种量为1.0%,此时双乙酰的量为0.083mg/L,啤酒口感达到9.2分。固定化的酵母菌可以重复利用3次,啤酒的双乙酰值和口感维持稳定。该研究表明利用固定化细胞的后期添加可以降低啤酒中的双乙酰含量。     

High gravity primary continuous beer fermentation using flocculent yeast biomass

The current work assessed a new immobilized cell reactor system throughout a long‐term (54 days) continuous primary fermentation of lager‐type wort of high specific gravity. The experiment was performed in a 4 L airlift bioreactor and immobilization of biomass was attained solely by flocculation. Despite the constant liquid agitation and washout of biomass, up to 53 g dry wt/L of yeast remained immobilized in the system. Two types of beer were produced without interrupting the reactor, based on two types of wort: a Pilsener type with high specific gravity of 15.6 ± 0.3°P; and a dark lager wort with specific gravity of 14.4 ± 0.03°P. Even during the inlet of high gravity wort, the desired attenuation was achieved without the need for either recirculation or an auxiliary second stage bioreactor. The specific saccharide consumption rate was kept around 7.9 ± 0.4 g/L/h and ethanol productivity oscillated at 3.36 ± 0.2 g/L/h for nearly a month. During this period the volumetric productivity of the current bioreactor reached 1.6 L beer/L/day. The green beers produced from the Pilsener and dark lager worts met the standards of regular finished primary beer fermentation. The productivity of diacetyl through the entire experiment could be correlated to the free amino nitrogen consumption rate. Copyright © 2014 The Institute of Brewing & Distilling     

三种啤酒酵母菌种发酵性能的比较

采用三种不同酵母菌种,对其进行了发酵性能比较。测定了热死灭温度、凝聚性、死亡率、双乙酰还原能力、发酵速度、高级醇与酯及发酵终了理化性质等方面的综合指标。结果显示菌种JB的综合性能最佳,具有应用于啤酒生产的潜能。     

操作条件对双乙酰测定的影响

研究各种操作条件对ＥＢＣ分析法测定啤酒中双乙酰的影响,得到了较有价值的结果。     

啤酒生产中双乙酰的代谢调控研究

双乙酰是啤酒生产过程中由酵母在合成氨基酸的途径中产生的重要风味物质,其含量是衡量啤酒成熟的重要标志。本文简要综述了啤酒生产中双乙酰的形成机制和代谢调控研究进展。     

Carrier‐free,continuous primary beer fermentation

Developing a sustainable continuous fermentation reactor is one of the most ambitious tasks in brewing science, but it could bring great benefits regarding volumetric productivity to modern breweries. Immobilized cell technology is often applied to reach the large densities of yeast needed in a continuous fermentation process. However, the financial cost associated with the use of carriers for yeast immobilization is one of the major drawbacks in the technology. This work suggests that yeast flocculation could address biomass immobilization in a gas‐lift reactor for the continuous primary fermentation of beer. Nearly 25 g dry wt L^?1 of yeast was flocculated in the reactor before interruption of the fermentation. Stable sugar consumption and ethanol production (4.5% alcohol by volume) from an 11°P wort was evidenced. The key esters and higher alcohols measured in the young beer met the standards of a finished primary beer fermentation. Copyright © 2014 The Institute of Brewing & Distilling     

连续发酵啤酒风味的研究

研究了工艺因素，连续时间，发酵方式等对连续发酵啤酒风味的影响，结果发现，在本连续发酵系统中，稀释率D选择0．5d^-1，温度T选择13℃，对形成良好的风味物质更为粗利，当连续时间由15d延长至90d后，只有3－甲基丁醇超过了风味阈值20％，乙酸乙酯的差异是造成连续发酵啤酒和分批发酵啤酒风味不同的主要原因。     

二次发酵降低葡萄酒中双乙酰的含量

该文通过在葡萄酒发酵后期添加蔗糖,促使酵母进行二次发酵降低双乙酰的含量。结果表明,二次发酵的最适加糖量为28 g/L,与常规发酵相比,二次发酵后双乙酰含量降低了29.87%;在此基础上,对酵母菌株WY1、WY1-1、WY1-2和WY1-12进行加糖二次发酵试验,测定出4株菌均可降低发酵液中双乙酰的含量,其中菌种WYI-12的发酵液中双乙酰的含量最低,为4.05 mg/L,比常规发酵降低了37.21%,改善了葡萄酒的感官质量。     

Investigation of foam‐active polypeptides during beer fermentation

During ale fermentation there was an accumulation of total and hydrophobic polypeptides in the foam relative to the wort. Comparisons were made not only of the total and hydrophobic polypeptide contents but also of the molecular weights of these polypeptides present in wort, partially fermented wort and its concomitant foam. Wort, fermented wort and foam fractions had very similar polypeptide compositions with a major group having molecular weights of 40–43 kDa. Material of molecular weight in the range of 5–17 kDa and at 66 kDa was also detected. The polypeptides accumulated in foam displayed both hydrophobic and non‐hydrophobic character. The presence of yeast polypeptides in foam was confirmed. Comparison was also made between the fermentations of 10°Plato and 15°Plato wort. The results of the work may contribute to a better understanding of the mechanism of foam formation during beer fermentation, leading to reduced foaming and enabling an increase in the working capacities of fermenters. Copyright © 2004 Society of Chemical Industry     

灵芝啤酒的发酵生产初探

灵芝真菌与啤酒酵母菌混合发酵可生产营养价值极高的灵芝啤酒，因生产工艺简单，成本低，口感佳，其前景看好。该文探索了灵芝与酵母的接种量、装液量、酒花添加量以及麦芽的糖化时间和温度等技术参数。     

混菌发酵生产啤酒醋工艺的研究

通过实验确定了以醋酸菌AS1．41和产香酵母XJB45为实验菌种发酵生产啤酒醋的最佳工艺。实验结果表明,啤酒醋的最佳生产工艺为：菌种混合比例4：2,接种量15％,酒精含量5．5％,发酵温度30℃,转速180r／min。     

A RAPID PROCEDURE FOR REDUCING THE DIACETYL CONTENT OF BEER*

Beer produced by rapid fermentation procedures can contain a substantial quantity of precursor substances which give rise to diacetyl and 2,3-pentanedione when the beer is stored. A conditioning unit has been developed which rapidly converts these precursors to the free diketones, which are then removed by yeast. Maturation of the beer is thus achieved at a rate similar to that of the initial fermentation.     

CAN总线在啤酒发酵控制系统中的应用

研究了基于CAN总线技术的啤酒发酵控制系统,给出了系统整体结构,并且重点阐述了CAN总线智能节点的硬件电路实现及软件设计的方法。结果证明,该系统具有结构简单、易于扩充、可靠性高、性价比高等特点。     

Fed‐batch fermentation with glucose syrup as an adjunct for high‐ethanol beer brewing

To produce a beer with a high ethanol content, preliminary research on fed‐batch fermentation profiles with glucose syrup as an adjunct during the primary fermentation period was conducted. The ethanol concentration of the beer was elevated by feeding a glucose syrup into the fermentors at a later stage of primary fermentation. Fermentation trials were carried out using a typical lager strain, SC‐9, with a pitching rate at 7.0 × 10⁶ cells/mL. An all‐malt wort (12.5°P) was employed and the primary fermentation temperature was 14 °C. Glucose syrup was supplemented when the concentration of residual reducing sugars was decreased to ~10 g/L. Results showed that the supplemented glucose was consumed rapidly and that the ethanol concentration in the final beer was raised to 67.9 g/L. Additional growth of yeast was observed after feeding accompanied by a low yield of ethanol (~0.46 g/g). Formation of diacetyl was enhanced by yeast growth and two additional peaks were obtained after feeding. The peak value of the diacetyl concentration was 1.90 mg/L. The fed‐batch fermentation resulted in a beer with an overproduction of higher alcohols and esters, indicating that brewing under these experimental conditions led to an unbalanced flavour profile. Results of optimization demonstrated that the optimal conditions were found to be 15°P for initial wort extract, 10 °C for fermentation temperature and 20 × 10⁶ cells/mL for yeast pitching rate, leading to total higher alcohols of 173.8 mg/L, total esters of 22.8 mg/L and an acetaldehyde concentration of 40.5 mg/L. A 12 day maturation and fermentation temperature of 8 °C was needed to reduce the acetaldehyde to 14.3 mg/L. Copyright © 2014 The Institute of Brewing & Distilling     

Rotary jet head – a device for accelerating the fermentation process in brewing

The world beer market is dominated by lagers, with production estimated at hundreds of millions of hectolitres per year. The vast majority of the beer is produced using CCT (cylindro‐conical tank) technology. Fermentation and maturation are time‐consuming processes and the bottlenecks of beer production. A rotary jet head (RJH) – a device originally used as a cleaning device – is proposed for use as a tool to provide homogeneity in the tank and to increase the activity of the yeast cells by keeping them in suspension during the fermentation process. The main objective of the study was to analyse the impact of mixing the content of the fermentation tank (by the means of an RJH) on the time of fermentation, maturation and cooling. The experiments were carried out under full industrial operational conditions. It was concluded that mechanical mixing, in a CCT of 3800 hL, shortened the time of lager beer production process by ca. 15%, the time of fermentation by ca. 24 h and the cooling time by ca. 35 h. Copyright © 2016 The Institute of Brewing & Distilling     

A novel approach for the production of a non‐alcohol beer (≤0.5% abv) by a combination of limited fermentation and vacuum distillation

Despite the increasing demand, the production of non‐alcohol beers is still limited by unsatisfactory or artificial flavour and taste. In this study, a novel approach to producing non‐alcohol beer is presented, in which the alcohol‐reducing techniques, limited fermentation and vacuum distillation were combined. Starting from barley and wheat malts, wort with a low level of fermentable sugars was prepared by infusion mashing and lautering. Limited fermentation was carried out by Saccharomycodes ludwigii at 18°C. When the level of fermentable sugar was reduced by 25%, the fermented wort was quickly cooled from 18 to 0°C and held at that temperature for two days. The young beer was obtained after degassing and removal of yeast and was then subjected to vacuum distillation at 0.06 MPa to remove the alcohol. The concentrated extract is suitable for storage and transportation. The final product of non‐alcohol beer was obtained by dilution with deoxygenated water and carbonation with 6.0 g/L CO₂, followed by addition of 8–12% of regular beer and equilibration for 2–3 days to develop normal beer aroma. The results showed that the non‐alcohol beer had several favourable properties, including the alcohol level of <0.5% (v /v), colour 7.0 (EBC), thiobarbituric acid value of 1.05 and ratio of alcohols to esters of 1.08. Compared with other methods for the production of non‐alcohol beer, this novel approach produced a favourable alternative to regular beers with similar flavour characteristics and satisfactory stability. Copyright © 2017 The Institute of Brewing & Distilling     

OCCURRENCE OF DIKETONES AND α-ACETOHYDROXYACIDS IN FERMENTATIONS

Diketone and α-acetohydroxyacid levels have been monitored during ale fermentations both in stirred fermentors and in a pilot brewery. It was found necessary to bring samples to neutral pH and protect them from air until assayed. Little diketone was formed during normal fermentations. Addition of sodium metabisulphite trapped α-acetohydroxyacids and high concentrations persisted in the beer. Lowering the wort pH decreased the peak concentrations of α-acetohydroxyacids without a corresponding increase in diketone concentrations. Alterations in the oxygen supply during preculture of the yeast or at pitching had little effect on diketone formation. α-Acetohydroxyacids have been detected in beer in keg from a continuous fermentation.     

基于Smith预估补偿的啤酒发酵温度控制策略

在啤酒发酵过程中,发酵液的温度控制具有大时滞、非线性和分阶段性等特点,这些特点造成发酵罐内发酵液的温度波动频繁,偏差较大。为了更好地对啤酒发酵温度进行控制,在常规PID控制的基础上,提出了基于Smith预估补偿的非线性PID控制策略。在对啤酒发酵温度控制系统的辨识模型进行Matlab仿真分析的基础之上,将该控制策略用于实际生产。结果表明:该控制策略可以有效改善控制系统的稳定性和抗干扰能力。     

啤酒发酵过程中有害菌对双乙酰含量影响的分析

双乙酰是影响啤酒风味的重要因素.啤酒发酵过程中双乙酰含量先升高后下降.该文通过对啤酒发酵过程中有害菌对啤酒中双乙酰的影响,深入了解双乙酰含量的变化趋势.从生产的各个环节入手进行微生物的管理和控制,以保证啤酒的微生物安全,进而稳定啤酒的质量和风味.