电导率监测在啤酒发酵过程中的应用

采用电导率测量的方法对啤酒发酵过程进行了研究,通过计算机的辅助实现了发酵过程中电导率的在线监测.结果表明:在啤酒发酵过程中电导率的变化遵循一定的规律性,并且将电导率与还原糖、酵母数等过程参数进行数学建模,同时将麦汁浓度、酵母代数对电导率的影响进行了比较.     

发酵工艺参数对嫩啤酒抗氧化力的影响

为提高啤酒的抗氧化力及改善其风味稳定性,系统研究了麦汁发酵过程中抗氧化力的变化及发酵工艺参数包括麦汁浓度、酵母接种量、酵母代数与发酵温度对嫩啤酒抗氧化力的影响。结果表明:麦汁发酵过程中DPPH自由基清除活性、氧自由基吸收能力和还原力分别提高了6.27%、3.46%和31.38%。麦汁浓度从6°P增加到12°P,嫩啤酒的DPPH自由基清除活性、氧自由基吸收能力与还原力升高显著,浓度超过12°P后,抗氧化指标增速减缓或略有下降。酵母接种量在800～3200万个/mL之间的嫩啤酒抗氧化力随酵母接种量的增加而升高。1、2、4和5代酵母发酵嫩啤酒的抗氧化力随酵母代数的增加呈降低趋势。9、12和15℃发酵嫩啤酒的抗氧化力随发酵温度的升高而降低。因此,优化发酵工艺参数是提高啤酒抗氧化力的有效措施。      

啤酒酿造过程中控制二甲基硫含量的工艺研究

为了降低啤酒中DMS的含量,保持啤酒的整体风味一致性,通过对啤酒酿造过程进行降低DMS含量的工艺试验,用气相色谱法测定试验条件下DMS的生成量,找出啤酒中DMS含量的变化规律,为实际生产提供依据。初步研究了生产过程中糖化配料、麦汁煮沸、发酵温度、酵母代数对啤酒中DMS生产成量的影响,经优化啤酒生产工艺后能够使生产出的成品啤酒DMS含量控制在其口阚值以下,从而提高了啤酒的风味,并保持了啤酒风味的一致性。根据研究总结出了如下主要结论:1、成品麦汁中DMS的含量随着辅料比例的提高而降低,糖化配料时可适当加大辅料比例至48%;2、麦汁煮沸方式对成品麦汁中DMS的生成量有较大影响,麦汁强烈煮沸方式比阶段煮沸方式生产出的麦汁中DMS含量降低了30%;3、较高的酵母接种温度和发酵温度,使酵母能够较少的生成DMS,14°P麦汁发酵温度可采用12℃恒温发酵。4、不同代数的西德酵母发酵后DMS的生成量有很大差别,2代、3代酵母处在最佳时期,DMS生产成量较低,而且波动性较小。     

啤酒发酵过程中影响蛋白酶A分泌的因素

纯生啤酒中残存的蛋白酶A严重影响泡沫稳定性,制约了纯生啤酒的质量提升。为了探索啤酒发酵过程中影响蛋白酶A分泌的因素,作者分别考察了菌种、酵母生理状态、酵母代数、麦汁浓度、发酵时间等对蛋白酶A分泌的影响。结果发现,蛋白酶A分泌量高的菌株,处于稳定期之后的酵母、较高的酵母代数、较高的原麦汁浓度和在发酵阶段末期都会导致发酵液中蛋白酶A活性偏高。建议在实际生产中,采用蛋白酶A分泌量少的菌种、调整酵母生理状态、使用小于3代的酵母、采用18°P以下的麦汁发酵和尽早结束发酵都会对降低蛋白酶A的分泌量起到积极作用。     

啤酒发酵过程中甲醛代谢影响因素初步研究

甲醛是啤酒酵母的一种代谢产物,在啤酒发酵过程中,甲醛经历了积累和随后的还原两个阶段,通过引入甲醛峰值和谷值两个概念研究了啤酒生产过程中的一些影响甲醛积累和还原的控制,结果表明:(1)过低或过高的麦汁溶氧量均会增加甲醛的积累,在12～13mg/L的麦汁溶氧条件下甲醛积累最小。(2)低代酵母甲醛积累要少于高代酵母,并且低代酵母在后期甲醛的还原能力要高于高代酵母,酵母接种量在2×107个/ml时甲醛峰值最低。(3)相对较高的还原温度有利于甲醛还原。(4)麦汁浓度对甲醛的积累影响较大,高麦汁浓度条件下的甲醛峰值要比低麦汁浓度高出许多。(5)啤酒酿造后期延长还原时间并不能显著增加甲醛的还原量。     

啤酒生产过程中影响乙醛含量的因素

影响成品啤酒风味物质-乙醛含量的因素较多,本研究主要针对以下几个影响因素分析其对乙醛含量的影响,包括:不同代数酵母接种发酵中乙醛含量的变化情况;发酵工艺条件-麦汁浓度差异的影响;接种酵母质量的影响;灭菌前清酒溶解氧含量与灭菌后啤酒中乙醛含量的关系;添加剂-酵母营养盐对发酵末乙醛含量的影响;污染微生物-发酵单胞菌对乙醛含量的影响。     

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。     

酵母营养盐在啤酒生产中的应用

在啤酒酿造过程中,麦汁α-氨基氮低,酵母代数高等因素都会使酵母的活力下降,从而引起啤酒发酵度低、发酵期长、酵母凝聚性差等问题。为了解决这个问题,我厂试用了国产酵母营养盐。一、实验步骤1、实验室小型对比试验:固体斜面原菌用11°P麦汁经试管扩大培养至300毫升麦汁的三角瓶,于A、B、C 三个三角瓶中,各装:     

啤酒生产过程中影响乙醛含量的因素

影响成品啤酒风味物质-乙醛含量的因素较多，主要针对以下几个影响因素分析其对乙醛含量的影响，包括；发酵周期中不同代数酵母接种发酵周期乙醛含量的变化情况；发酵工艺条件-麦汁浓度差异对乙醛含量的影响；接种酵母质量对发酵末乙醛含量的影响；灭菌前清酒溶解氧含量与灭菌后啤酒中乙醛含量的关系；添加剂-酵母营养盐末乙醛含量的影响；污染微生物-发酵单胞菌的对乙醛含量的影响。     

高效液相色谱法测定麦汁、发酵液和啤酒中的嘌呤含量

通过高效液相色谱法测定了不同浓度的麦汁、发酵液及成品啤酒中的嘌呤含量,分析了嘌呤在发酵过程中的变化情况。此外,还分析了不同辅料比的麦汁中嘌呤含量的差异,发酵液中含有酵母与不含有酵母时检测的差异性,以及活性碳吸附对啤酒中嘌呤含量的影响。该研究为开发低嘌呤啤酒提供了可靠的检测方法和研究思路。     

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.     

酵母形态指标百分数离散度与啤酒质量的关联性

通过跟踪不同发酵罐相同发酵时间的啤酒发酵液中的酵母形态指标百分数离散度,检测发酵结束后各发酵罐的啤酒的质量指标,得出啤酒酵母指标百分数离散度与啤酒质量的关联性,即酵母形态指标百分数离散度与酒精度、发酵度、总酸这三个啤酒质量指标成负相关,与原麦芽汁浓度、外观糖度、乙醛浓度、pH值、双乙酰这五个啤酒质量指标成正相关.     

啤酒酵母在红薯淀粉麦芽汁中的发酵特性研究

本实验研究了酵母在红薯淀粉做辅料的麦汁中的发酵特性,并与其在大米做辅料的麦汁中的发酵特性作了对比,结果表明其完成主发酵所用的时间、可发酵浸出物的变化、还原糖含量的变化、α-氨基氮的利用情况、双乙酰的生成量等均无明显的区别,而且酵母的生长繁殖正常。红薯淀粉作辅料的啤酒色度较大。     

Vitamins in brewing: presence and influence of thiamine and riboflavin on wort fermentation

Thiamine and riboflavin vitamers are present in a wide range of foods including beer. These vitamers play critical roles in a variety of enzymatic complexes and can promote and maintain metabolism. Currently, the presence and role of these vitamers in the malting and brewing industry have not been widely explored. This research investigated the effects of various fermentation conditions that may lead to the variations in the vitamin content in beer observed by previous researchers. The present research found that during fermentation, the thiamine content of wort is quickly utilized within the first 6 h of a standard fermentation and the uptake of this vitamin is not affected by increases in wort gravity. While no significant changes were observed in extracellular phosphorylated vitamers of thiamine, both free thiamine and thiamine diphosphate accumulated intracellularly during the wort fermentation. Meanwhile extracellular riboflavin vitamers were only poorly utilized during beer fermentations, however flavin mononucleotide rapidly accumulated intracellularly and more so under aerobic conditions. When yeast was exposed to an all‐malt high‐gravity wort, the thiamine or riboflavin utilization was not affected. However, thiamine utilization was reduced in adjunct‐driven high‐gravity worts. Notwithstanding the lowered thiamine uptake under high‐gravity conditions; there were some minor improvements in fermentation performance and yeast viability. The addition of thiamine to an all‐malt wort did appear to enhance yeast viability, both under normal and high‐gravity conditions. Copyright © 2016 The Institute of Brewing & Distilling     

SIMPLE PEPTIDES OF WORT AND BEER

The nitrogenous constituents of wort and beer have been fractionated and peptides have been separated from amino acids by chromatography on DEAE cellulose. Examination of corresponding fractions by electrophoresis and chromatography reveals that whereas there is a selective uptake of wort peptides by yeast, other peptides in beer are not present in the wort and have been formed during fermentation. Approximately 40% of wort peptides are used during fermentation.     

发泡酒酿造用贫氮酵母性质的研究

研究了贫氮酵母在发酵过程中麦汁各组成成分的利用情况及其生理特性，研究发现，贫氮酵母在贫氮麦汁中能利用少部分的脯氨酸和相当部分的麦芽三糖，发酵后的啤酒中总含氮量符合淡爽啤酒的要求；它是一株中等凝聚性的酵母，具有一定的实际应用价值。     

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。     

Yeast Proteolytic Activity During High and Low Gravity Wort Fermentations and its Effect on Head Retention

The aim was to discover the effect of high gravity brewing on yeast protease activity during fermentation, on the loss of hydrophobic polypeptides from wort during fermentation, and on the foam stability of stored beer. The hydrophobic polypeptide content of low (10° Plato) gravity worts showed a steady decline throughout fermentation, but for the 20° Plato wort there was a rapid decline over the first 8 days of fermentation, followed by little change over the remaining period. The decrease in hydrophobic polypeptides was greater in the high gravity fermentation. Proteinase A increased during fermentations with the highest levels being present at the end of fermentations. High gravity fermentations exhibited levels of yeast protease that from the 3rd to 11th day of fermentation were at least twice the values of the low gravity fermentations. The high gravity brewed beer contained significantly higher levels of proteinase A activity than the low gravity brewed beer. The inclusion of FERMCAP™, an antifoam, in high gravity wort did not affect either the hydrophobic polypeptide levels or foam stability of the resultant beer. This suggests that proteinase A, rather than fermenter foaming, must be the major contributor to the lack of foam stability of high gravity brewed beer. Head retention measurements conducted on the high and low gravity brewed bottled beers, over a five month period, demonstrated a steady decline in foam stability for both beers. The declines in head retention did not occur in high and low gravity beers that had been pasteurised.