5-羟甲基糖醛作为啤酒老化评价指标的研究

将5-羟甲基糠醛（5-HMF）与其他啤酒老化评价方法相比较，考察自然老化啤酒以及外加5-羟甲基糠醛标样啤酒的老化情况，对以5-羟甲基糠醛作为啤酒老化评价指标进行研究。5-羟甲基糠醛在一定程度上能够准确评价啤酒老化情况，但是有一定的局限性。     

5-羟甲基糠醛作为啤酒老化评价指标的研究

将5-羟甲基糠醛(5-HMF)与其他啤酒老化评价方法相比较,考察自然老化啤酒以及外加5-羟甲基糠醛标样啤酒的老化情况,对以5-羟甲基糠醛作为啤酒老化评价指标进行研究.5-羟甲基糠醛在一定程度上能够准确评价啤酒老化情况,但是有一定的局限性.     

测定啤酒中5—羟甲基糠醛——评价啤酒老化程度

由于5-羟甲基糠醛对啤酒老化具有指示作用,通过研究啤酒中5-羟甲基糠醛水平的高低与啤酒存储期间老化程度存在的相关性,利用高效液相色谱法,测定啤酒中5-羟甲基糠醛含量,来评价啤酒风味老化的程度。     

通过测定啤酒中5-羟甲基糠醛评价啤酒老化程度

由于5-羟甲基糠醛对啤酒老化所具有的指示作用。通过研究啤酒中5-羟甲基糠醛水平的高低与啤酒存储期间老化程度之间存在的相关性，利用高效液相色谱法，测定啤酒中5-羟甲基糠醛含量，来评价啤酒风味老化的程度。     

测定啤酒中5－羟甲基糠醛评价啤酒老化程度

由于5-羟甲基糠醛对啤酒老化具有指示作用，通过研究啤酒中5—羟甲基糠醛水平的高低与啤酒存储期间老化程度存在的相关性，利用高效液相色谱法，测定啤酒中5—羟甲基糠醛含量，来评价啤酒风味老化的程度。     

啤酒和麦汁中的4-羟基呋喃酮及其前驱物

本文通过分析啤酒酿制不同阶段的风味活性物质(4-羟基呋喃酮、5-甲基-4-羟基呋喃酮(MHF)、2，5-二甲基呋喃酮(DMHF)、5-乙基-2-甲基-4-羟基呋喃酮(EMHF))的含量，研究了糖化加热时间和强度、煮沸时间、麦汁冷却速率、及原辅料、发酵温度、稳定剂(PVPP、PC5)对麦汁及啤酒中4-羟基呋喃酮的影响。结果表明，影响啤酒中呋喃酮含量的主要因素是原辅料的组成、麦汁冷却速率和发酵温度。酵母代谢也能产生MHF和EMHF，因此，发酵工艺对啤酒最终呋喃酮含量至关重要。同时，麦芽中的呋喃酮前驱物可通过关拉德反应或酵母代谢转化成4-羟基呋喃酮，且其数量要远远高于麦芽中呋喃酮本身。因此，了解其前驱物的特性对控制啤酒中呋喃酮的含量尤为重要。     

β-葡聚糖和工艺条件对啤酒膜过滤效能的影响

本试验采用0．45μm膜进行过滤试验，研究了β-葡聚糖、剪切力、pH、酒精含量和储藏时间对过滤性能的影响。结果表明，β-葡聚糖的存在会降低啤酒过滤性。通过膜过滤器的最大啤酒过滤能量Vmax和初始过滤速度Qinit随着大分子量β-葡聚糖浓度的增加而降低。剪切啤酒(0—10℃)的Vmax和Qinit较低。pH值较高时可以改善啤酒的过滤能力。和无醇啤酒相比，酒精含量在5％和10％(v/v)的啤酒呈现出较低的Qinit和较高的Vmax值。然而，和不含β-葡聚糖的啤酒样品相比，在含有β-葡聚糖的啤酒中添加5％和10％的酒精会降低相对Vmax。结果还表明在4℃冷储藏两周不会影响β-葡聚糖处理过的啤酒的过滤性。     

酒花中的黄腐酚及其他含异戊二烯基类黄酮

黄腐酚是啤酒雌花中主要的含异戊二烯基的类黄酮。人们主要通过饮用啤酒来摄入黄腐酚和其他含异戊二烯基类黄酮（8-异戊二烯基4，5，7-三羟黄烷酮和异黄腐酚）。研究发现，黄腐酚是一种用途广泛的癌症化学预防剂，而8-异戊二烯基4，5，7-三羟黄烷酮则被认为是目前最有效的植物雌激素。可以通过改变种植方法或利用生物工艺学方法，增加啤酒中的黄腐酚以及制药产品中8-异戊二烯基-4，5，7-三羟黄烷酮的含量。     

用气相色谱-质谱联用的方法检测啤酒中的日光臭

将啤酒暴露于350～500nm 的日光中会产生一种不愉快的、腐败的、类似臭鼬的气味一日光臭味。形成这种气味的主要物质为3-甲基-2-丁烯-1-硫醇(MBT),据报道它在啤酒中的感官阀值为4.4-35ng/L,与啤酒中大多数的挥发物质相比,它的阀值是相当低的。目前已经找到一种方法检测浓度低于感官阀值水平的 MBT,就是用气相色谱-质谱检测器并用吹扫-捕集的方法来检测。应用这一方法可以对塑料箱中瓶装啤酒 MBT 的形成进行检测实验。     

HPLC方法测定5-HMF含量及对啤酒老化评价的研究

5-羟甲基糠醛（5-HMF）是啤酒风味老化的指示性组分之一。啤酒老化程度的感官评价与啤酒储存过程中5-HMF的含量变化存在着对应的关系。本文研究开发了检测5-HMF的HPLC方法,应用简单的流动相对啤酒中5-HMF含量进行测定,重复性以及回收率结果良好。本文还对啤酒生产过程及成品酒储藏过程中的5-HMF含量变化进行了跟踪,结合感官品评,形成了对啤酒老化程度的综合评价。     

Predicting the organoleptic stability of beer from chemical data using multivariate analysis

Delaying flavour staling, to prolong the shelf life of beer, is one of the greatest challenges facing the brewing industry today. In this study, a series of lager beers were brewed using five European barley varieties and four chemical indicators of the degree of beer ageing were correlated with the sensory evaluation: E-2-nonenal, β-damascenone, 2-furaldehyde and 5-hydroxymethyl-2-furaldehyde (5-HMF). A statistical strategy using principal component analysis and multiple linear regression was applied to draw relationships between the sensory and chemical data sets. Additionally, the relative significance of each of the chemical data on the organoleptic stability of beer was evaluated within the method. 5-HMF was the only studied carbonyl compound whose concentration cannot be used for predicting the total taste score of beers. E-2-nonenal, in contrast, was found to be the most discriminant carbonyl compound under consideration for predicting the flavour stability of beer.     

温度和氧对啤酒老化的影响

研究了4℃、20℃和38℃三种温度条件下,不同溶解氧含量的啤酒其老化物质和香气成分的变化。贮存6个月后有关风味稳定性指标结果如下:贮存温度升高时5-羟甲基糠醛(5HMF)含量显著增加,从20℃到38℃增加了244%,氧含量对5HMF影响很小。TBN变化与5HMF相似,但不如5HMF敏感,从20℃到38℃只增加了5.3%。色度随着氧和贮存温度的增加而增加,38℃贮存的溶氧高的啤酒比4℃对照啤酒色度增加了3.18EBC。DPPH还原力随着贮存温度的升高而下降。贮存期间,对主要挥发性香气的跟踪分析表明,双乙酰在贮存过程持续增加,溶氧高的啤酒其含量更高,贮存2个月后,含量达到其风味阈值,导致啤酒产生“双乙酰”味。乙酸乙酯和乙酸异戊酯在贮存过程含量下降,38℃贮存6个月后,2种酯含量比4℃对照分别降低了18%和21%,溶氧高的啤酒降低程度更大,将会影响啤酒的香气。因此,减少成品啤酒的溶解氧含量,降低贮存温度,可以提高啤酒的抗老化能力。     

Influence of Pasteurising Intensity on Beer Flavour Stability

While it is preferred that flavour improves during the beer maturation process, formation of undesirable flavours inevitably occurs during beer storage. Beer ageing problems occur during beer storage and can damage the beer style, especially for lager beer of a more delicate style. In this research, the impact of pasteurising intensity on beer ageing and flavour stability was studied. Through process adjustments, three types of bottled beer were obtained from one fermenter and classified by their PU values as 2 PU, 8 PU and 14 PU. The dynamic changes of related indices (taken every month) characterizing the ageing and flavour of the beer under different pasteurising intensities were investigated during a 6‐month room temperature storage period. The key factors of colour, the thiobarbituric acid (TBA) index, 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging activity, bitterness and total polyphenol composition, the concentration of beer volatile compounds (BVCs), and 5‐hydroxymethyl furfural (5‐HMF) were examined. Statistically, the 14 PU sample showed the highest degree of damage, with the greatest flavour change compared to the other samples.     

The Influence of Hopping on Formation of Carbonyl Compounds During Storage of Beer

Improving beer flavour stability is an important brewing goal. Pilot scale brewing trials (50 L) were performed that focused on the determination of the influence of hop pellet dosage and dosage timing on carbonyl compounds in stored beer. The reducing activity of experimental worts, beers and stored beers appeared to depend on the hop pellet dose. Brews with lower amounts of hop antioxidants showed an enhanced formation of carbonyl compounds over the course of beer storage. A correlation between DPPH reducing activity and the content of some carbonyls, including the important markers 2‐furfural and (E)‐2‐nonenal, was found. Fresh and aged beers hopped by different amounts of hop pellet doses were clearly distinguishable according to their carbonyl content using Cluster analysis. Results of the sensorial analysis corresponded to the analytical criteria values. Results of this study bring further evidence of the indispensable impact of hop antioxidants on the suppression of undesirable carbonyl compound formation in the course of beer staling, which can be significant in beers hopped by aroma hops. However, hop antioxidants are only one of many factors affecting beer staling.     

麦汁煮沸对啤酒老化前驱物质形成的影响

麦汁煮沸是啤酒生产的一个重要环节,煮沸过程影响着啤酒内味老化前驱物质的形成。避免过高的热负荷、隔氧煮沸、有效去除麦汁固形物等方法,可以减少麦汁中的羰基化合物的含量,从而提高啤酒的风味稳定性。     

INFLUENCE OF pH ON FLAVOUR STALING DURING BEER STORAGE

A decreasing pH accelerated an increase in the chemiluminescence production and degradation of isohumulones and procyanidins during the storage of beer and using a model system. The sensory test showed that the addition of HCI to fresh beer accelerated the flavour staling during beer storage but that the addition of HCI to stored beer did not significantly accelerate the flavour staling. Therefore, it was thought that the acceleration of beer flavour staling is not dependent on a decrease in pH such that the decreasing pH isolates stale flavour aldehydes by a dissociation from staling-flavour aldehyde adducts but based on the fact that the decreasing pH accelerates the flavour staling reactions, free radical reactions, during beer storage.     

提高麦汁还原力对啤酒风味稳定性的影响

根据抗氧化假说理论 ,研究了在糖化时添加木丹宁螯合去除金属离子 ,以抑制Fenton反应 ,减少过氧化氢的积累 ,抑制活性氧的产生与自由基反应 ;煮沸时添加亚硫酸盐可增加麦汁的还原力 (Chapon法 ) ,从而提高麦汁的内源抗氧化活性 ,延长啤酒的风味保鲜期(RSV)。