在啤酒生产中控制双乙酰含量的探讨

在啤酒生产中控制双乙酰含量的探讨张勍（哈尔滨亚洲啤酒有限公司）三酿造过程中的溶解氧１．麦汁中的溶解氧“有氧繁殖、厌氧发酵”，“有氧”能够增加单位麦汁中的酵母数即酵母浓度，增强酵母的发酵能力及还原双乙酰的能力。由于麦汁经强烈的煮沸后，麦汁中的溶解氧量很...     

麦汁组成对快速发酵中酶母代谢的重要性

在啤酒发酵过程中可以通过提高酵母接种量或者高浓酿造来提高产量,然而,这两种技术对酵母的新陈代谢都有显著的影响.在这项研究中,对高浓度酿造和高酵母数发酵相结合对酵母的生理和风味物质生成的影响进行了评价.此外,试验在快速发酵系统中通过优化麦汁中游离氨基氮含量来降低总双乙酰的产生.较高的麦汁浓度会导致酵母活力的下降,这与海藻糖含量的增加及与压力相关的基因表达水平的增加有关.不只是麦汁浓度,不同的可发酵性糖含量对酵母发酵性能及风味物质的生成都有强烈的影响.麦汁中高含量的蔗糖对氨基酸的吸收、酵母的生长、糖原的形成、海藻糖的重复利用、乙酯的合成和总双乙酰的还原速度都有促进作用.与其他的高浓度麦汁相比,酵母处于高浓度蔗糖环境中会经历更高的渗透压和压力相关的影响.尽管蔗糖相比于麦芽糖可以促进转录激活因子ATF1的活性,可以观察到乙酸酯类明显的降低.但是考虑到蔗糖对酵母性能的不利影响,采用蔗糖和麦芽糖组合来提高麦汁浓度还是可取的.     

麦汁组成对快速发酵中酵母代谢的重要性

在啤酒发酵过程中可以通过提高酵母接种量或者高浓酿造来提高产量,然而,这两种技术对酵母的新陈代谢都有显著的影响。在这项研究中,对高浓度酿造和高酵母数发酵相结合对酵母的生理和风味物质生成的影响进行了评价。此外．试验在快速发酵系统中通过优化麦汁中游离氨基氯含量来降低总双乙酰的产生,较高的麦汁浓度会导致酵母活力的下降,这与海藻糖含量的增加及与压力相关的基因表达水平的增加有关。不只是麦汁浓度。不同的可发酵性糖含量对酵母发酵性能及风味物质的生成都有强烈的影响。麦汁中高含量的蔗糖对氨基酸的吸收、酵母的生长、糖原的形成、海藻糖的重复利用、乙酯的合成和总双乙酰的还原速度都有促进作用．与其他的高浓度麦汁相比．酵母处于高浓度蔗糖环境中会经历更高的渗透压和压力相关的影响。尽管蔗糖相比于麦芽糖可以促进转录激活因子ATFI的活性,可以观察到乙酸酯类明显的降低。但是考虑到蔗糖对酵母性能的不利影响,采用蔗糖和麦芽糖组合来提高麦汁浓度还是可取的。     

离子与啤酒酵母生理代谢相关性的初步研究

从啤酒酵母厌氧发酵的营养环境角度来研究Na 、K 、Mg2 、Ca2 等在啤酒酵母生长代谢过程中的动态变化以及在其影响下酵母主要生长参数的变化趋势,并初步分析了离子与啤酒酵母生理代谢的相关性。结果表明:离子的动态变化表现出阶段性,而且这种阶段性变化因离子之间的协同作用而表现得更加明显;离子与啤酒酵母生理代谢存在着相关性,如pH、降糖和总酸等的变化趋势,这种相关性因酵母营养环境中离子种类和含量不同而存在差异。     

乳杆菌代谢产生抑菌物质的特性研究

从内蒙古传统发酵食品中筛选出具有抑酵母作用的乳杆菌,对其特性进行研究。结果表明,ALAC-3和ALAC-4菌株经排酸后,对酵母仍有抑菌效果。活性物质对热有很好的稳定性,并且对紫外线辐射不敏感。Ca2+、Mn2+对ALAC-3代谢产物的抑菌作用起促进作用,而K+、Na+、Mg2+对其代谢产物的抑菌作用起抑制作用。K+,Ca2+,Na+,Mg2+,Mn2+对ALAC-4代谢产物的抑菌作用均起抑制作用。经过氧化氢酶处理后,仍有抑菌效果。经木瓜蛋白酶、蛋白酶K、胰蛋白酶、胃蛋白酶处理后,抑菌活性均有不同程度降低,说明抑菌物质对蛋白酶敏感,故判定抑菌物质中有蛋白类物质。     

酵母食物在啤酒生产中的应用研究

由于淡爽型啤酒酿造的需要,辅料的添加比例不断增加。高辅料比生产工艺的采用无疑可降低酿造成本,但会使发酵麦汁组成发生较大变化,它降低了酵母增殖所必需的氨基酸、生物素以及保持发酵酶活性所必需的无机离子,结果导致发酵过程中酵母细胞密度降低,双乙酰峰值升高,酵母双乙酰还原能力减弱,甚至影响发酵速度。为解决上述发酵过程中的问题,改善麦汁的组成及啤酒发酵中酵母的营养状况,在发酵过程中添加一定量的酵母营养盐是一个非常有效且简便的方法。结果证实酵母营养盐的添加在高辅料比和添加各种糖浆的啤酒生产工艺中对酵母增殖、双乙酰峰值降低、双乙酰还原以及高级醇的形成等方面效果均良好。另外,还可使其酵母使用代数得以增加,对成品啤酒的质量不会产生不良影响。     

啤酒中双乙酰成分的形成与控制

介绍了啤酒酿造过程中双乙酰的形成机理及影响因素和控制方法,从酵母菌种、麦汁组分、通氧量等工艺进行调节,可以有效控制啤酒中双乙酰的含量,改善啤酒的成熟度.     

啤酒风味物质的影响和控制

啤酒发酵期间,酵母利用麦汁中的营养物质,产生乙醇和二氧化碳,另外还会有一些代谢产物,如双乙酰、乙醛、高级醇等,通常将这些发酵副产物称为风味物质.啤酒中风味物质的组成和含量主要取决于所采用的原料、酿造工艺、酵母品种等.……     

麦汁中α-氨基氮的最适含量研究

麦汁中α—氨基氮是影响啤酒中高级醇、双乙酰含量和啤酒质量的关键因素。通过不同的α—AN含量的麦汁对酵母生长、pH变化、外观糖度变化、α—氨基氮含量变化、双乙酰含量变化、高级醇含量变化的影响分析，结果表明，将麦汁中的α—AN含量控制在167mg／L时比较适当，发酵产生的高级醇和双乙酰比较适中，啤酒的pH比较适当；可添加糖化辅料，降低生产成本。扩大生产时控制麦汁中α—AN含量在160—180mg／L，可酿造出口味比较协调的优质啤酒。(孙悟)     

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。     

DIACETYL—A REVIEW: PART I—ANALYTICAL AND BIOCHEMICAL CONSIDERATIONS: PART II—BREWING EXPERIENCE

Diacetyl and 2,3-pentanedione are normal products of yeast metabolism and are formed in every brewery fermentation. The desired level in the final beer depends on the particular flavour aimed for but, in all types of beer, flavour defects are caused by excessive concentrations of diacetyl and many brewers might be happy to have no diacetyl in the beer. Recent improvements in analytical techniques show that many of the problems associated with diacetyl are due to the occurrence of compounds which can give rise to diacetyl in the finished beer. These compounds include the so-called “precursor,” acetolactic acid, but possibly other compounds such as the bisulphite addition compound of diacetyl are also involved. Study of the factors affecting diacetyl formation and removal by yeast shows how the concentration of diacetyl in beer can be controlled, and the processes at present used to regulate the diacetyl concentration in beer are described. The yeast strain used, the condition of the pitching yeast, the wort composition, the detailed management of the fermentation and the treatment of the beer during packaging and storage can all affect the diacetyl content of the beer.     

压力对啤酒酵母生长及某些发酵性能的影响

以气体为加压介质,研究了不同压力下酵母细胞生长及压力对酵母发酵性能的影响.高压对酵母细胞的生长代谢有明显的影响:压力使酵母细胞的比生长速率和生物量降低,细胞的倍增时间延长;电子显微镜显示,压力使酵母菌细胞的形态发生明显的改变;压力也导致酵母的发酵速度、耗糖率、乙醇生成量、双乙酰的生成和还原速率下降.     

125th Anniversary Review: Diacetyl and its control during brewery fermentation

Diacetyl is a butter‐tasting vicinal diketone produced as a by‐product of yeast valine metabolism during fermentation. Concentration is dependent on a number of factors including rate of formation of the precursor α‐acetolactate by yeast, spontaneous decarboxylation of this acetohydroxy acid to diacetyl and removal of diacetyl by yeast via the action of various reductase enzymes. Lowering concentrations of diacetyl in green beer represents an expensive and time‐consuming part of the brewing process and strategies to minimize diacetyl formation or hasten its reduction have potential for improving overall efficiency of the lager brewing system. Here we review the processes that determine diacetyl levels in green beer as well as the various ways in which diacetyl levels can be controlled. The amount of diacetyl produced during fermentation can be affected by modifying process conditions, wort composition or fermentation technique, or by yeast strain development through genetic engineering or adaptive evolution. The process of diacetyl reduction by yeast is not as well understood as the process of formation, but is dependent on factors such as physiological condition, cell membrane composition, temperature and pH. The process of diacetyl removal is typically rate‐limited by the reaction rate for the spontaneous decarboxylation of α‐acetolactate to diacetyl. Copyright © 2013 The Institute of Brewing & Distilling     

啤酒中双乙酰的产生还原及反弹问题分析

啤酒中双乙酰是啤酒发酵过程中酵母代谢的中间产物，虽然双乙酰含量较低，但对啤酒质量却有着举足轻重的影响，双乙酰是啤酒风味物质和啤酒成熟的重要标志。成功地控制双乙酰是酿造优质啤酒的关键。本文从双乙酰的形成和被还原的生化过程入手，结合生产实际，阐述了双乙酰产生的途径，分析了发酵过程中双乙酰变化情况及啤酒在灌装前后双乙酰的变化趋势，剖析了啤酒在贮藏过程中双乙酰反弹的原因，提出了避免和预防双乙酰反弹的措施。     

三种不同酵母对啤酒发酵及风味的影响

本实验采用Y1110、安琪、模式三种不同的啤酒酵母,在同种工艺条件下测定发酵过程中α-氨基氮(α-AN)、pH、双乙酰、高级醇等指标,并比较三种不同啤酒的风味物质含量。结果表明:Y1110增殖最快,α-AN和pH值下降最快,双乙酰还原较快,后酵结束双乙酰含量最低,啤酒样品含醇量较高,适于醇厚型啤酒酿造;安琪酵母增殖最慢,α-AN和pH值下降最慢,啤酒样品含酯量较高,适于淡爽型啤酒酿造;模式酵母酯类与醇类含量都很高,不适于实际生产。     

关于抗老化低双乙酰啤酒酵母的研究进展

老化和双乙酰含量是影响啤酒风味的重要因素,其制约了啤酒生产技术的发展,影响企业提高产品质量和经济效益.笔者从啤酒中双乙酰的合成、降低啤酒中双乙酰含量、提高啤酒抗老化能力几个方面对抗老化、低双乙酰啤酒酵母的研究进展进行了综述.(孙悟)     

Construction of recombinant industrial brewer’s yeast with lower diacetyl production and proteinase A activity

The characteristic buttery taste of diacetyl has long been a major problem in the brewing industry, and the foam stability of unpasteurized beer is often influenced by proteinase A (PrA), which is encoded by PEP4 and released from yeast cells into beer during brewing. A recombinant industrial brewer’s yeast strain that reduces the diacetyl content of beer and improves foam stability was constructed. We constructed a PGK1p-ILV5-PGK1t expression cassette, which was introduced into one of the PEP4 alleles via PCR-mediated homologous recombination. Then, the second PEP4 allele was disrupted using the Cre-loxP recombination system, and the recombinant strain was designated as S-CSIK12. The results show that the diacetyl production of S-CSIK12 is always lower than that of the host strain at all stages of beer fermentation. In addition, brewing with S-CSIK12 reduced the PrA activity of the final beer by 44 % compared with that using the wild-type strain. The head retention of the beer brewed with S-CSIK12 (260 ± 2 s) was better than that of the host strain S-6 (212 ± 3 s). Considering that more PrA is released from yeast cells during the final stage of main fermentation and that the timing of yeast cropping is determined by diacetyl reduction, brewing with strains that have low diacetyl production also reduced the PrA activity of the beer and improved its head retention. The present study provides reference for the brewing industry as well as research on the diacetyl reduction and foam stability of beer.     

啤酒成熟度——连二酮之研究

本文对啤酒中连二酮的气相色谱检测法与蒸馏法（分光光度法）进行了比较,结果表明蒸馏法虽然灵敏度低,但由于操作方便,可以用来指导生产;而气相色谱法可以同时定量测定双乙酰、戊二酮、α-乙酰乳酸和乙偶姻,能分别反应发酵液中的连二酮情况。气相色谱法的检测结果表明,国内市售啤酒中游离双乙酰含量高于戊二酮,双乙酰与戊二酮比例在1—12：1之间。使用试验酵母菌株,本公司在正常发酵（14．4°P）情况下,游离双乙酰低于50ppb,双乙酰与戊二酮比例在1～3：1,乙偶姻低于5ppm。     

富锌豌豆啤酒的研制

于30℃将豌豆放入锌离子浓度分别为600×10-6、700×10-6和800×10-6,pH值5.5的ZnSO4·7H2O溶液中浸泡,经发芽、干燥、糖化制汁、杀菌、冷却后,添加富锌啤酒酵母发酵研制了富锌豌豆啤酒,并设置空白对照。实验中主要研究了ZnSO4·7H2O添加量不同时,富锌豌豆芽汁发酵过程中酵母细胞数、pH、外观糖度、双乙酰含量、高级醇含量的变化,以及后酵结束双乙酰、高级醇、酒精度、真正浓度、原豌豆汁浓度和真正发酵度等各项指标的测定。实验结果表明,豌豆发芽的浸泡液中,ZnSO4·7H2O添加量为700×10-6时,糖化所得豌豆芽汁经富锌酵母发酵后,控制了适当的酵母增殖倍数,并且使双乙酰和高级醇的含量适中,制得的啤酒很符合现代淡爽型啤酒的风味要求,并且可以大大缩短发酵时间,提高生产率。     

THE INFLUENCE OF OXYGEN ON THE PRODUCTION OF DIACETYL DURING FERMENTATION AND CONDITIONING

Although varying concentrations of oxygen in wort at pitching do not affect the production of diacetyl, its availability during fermentation has a significant effect. The enhanced production of diacetyl resulting from access of oxygen during fermentation is caused by its effect in increasing yeast growth and in altering the balance of amino acids relative to sugars and not by a direct oxidation of acetoin. Oxygen has no effect upon the concentration of diacetyl during storage and conditioning, provided that the beer is free from contamination.