提高麦汁还原力对啤酒风味稳定性的影响

本文根据抗氧化假说理论,研究在糖化时添加掊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)。     

提高麦汁原力对啤酒风味稳定性的影响

本文根据抗氧化假说理论，研究在糖化时添加棓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)。     

提高麦汁还原力与啤酒风味稳定性

根据抗氧化假说理论，研究通过在糖化时添加过氯化氢酶与亚硫酸盐减少过氧化氢的积累，抑制活性氧的产生与自由基反应，增加麦汁的还原力(Chapon法)，从而提高麦汁的内源抗免化活性，延长啤酒的风味保鲜期(RSV)。     

聚乙烯聚吡咯烷酮吸附多酚物质性质研究及其在无甲醛酿造啤酒工艺中的应用

本文主要研究PVPP(聚乙烯聚吡咯烷酮)吸附多酚的性质,及其在无甲醛酿造工艺中的应用。结果表明,麦汁或啤酒中的敏感蛋白、酒精度、pH以及PVPP的添加量和添加方式等因素对PVPP吸附多酚都有一定影响。当pH在4.0左右,酒精度在3%(V/V)左右时PVPP的吸附效率最高。PVPP在添加量较低的情况下有一定的吸附专一性,主要吸附高分子的聚合多酚,但在添加量较高的情况下,不具备此性质,对单体酚的吸附迅速增加,会降低麦汁或啤酒的抗氧化能力。PVPP结合硅胶使用可以有效替代甲醛在啤酒酿造中的应用,在保证啤酒非生物稳定的条件下,改善啤酒风味稳定性和抗氧化能力。     

麦汁煮沸过程中源于酒花的抗氧化剂特性

使用ESR及DPPH自由基清除法评价麦汁制备各阶段的氧化稳定性及α-酸、β-酸、异-α-酸和酒花多酚浸膏的自由基清除特性。在未添加酒花的麦汁中自由基的产生与煮沸前的加热率正相关,但与溶解氧不相关。酒花α-酸及β-酸表现出相似的重要自由基清除能力。而异-α-酸与酒花多酚浸膏对自由基的清除能力较小。α-酸异构化后减小了麦汁的抗氧化活力,不同多酚含量的商用酒花制品由于酒花酸的作用表现出相似的自由基抑制特性。相对于不添加酒花的麦汁,添加酒花的麦汁制得的啤酒贮藏过程中Strecker醛的含量明显降低。     

超氧化物歧化酶改善啤酒风味稳定性的研究

超氧化物歧化酶（SOD）能够清除活性氧自由基,减少活性氧自由基氧化作用引起的危害。在啤酒酿造过程中,原料中的SOD是否对酿造过程、成品啤酒的风味稳定性产生影响以及产生什么样的影响,相关的研究较少。本文研究了制麦、糖化以及发酵过程中SOD活性的变化及其对酿造过程的影响。结果表明：麦芽SOD活性和协定麦汁的还原力之间存在显著的正相关性。向麦汁中单独添加SOD或过氧化氢酶（CAT）时,可以抑制羰基化合物的形成;SOD和CAT的协同作用可以有效提高麦汁的内源性抗氧化力。发酵前单独添加SOD、同时添加SOD与CAT后的啤酒中,反-2-壬烯醛含量比对照分别降低了12．2％和14．4％,不同程度地提高了啤酒的风味稳定性。     

酿造过程碳源和氮源的添加对酵母利用外观浸出物的影响

我们研究的是在以葡萄糖、麦芽糖和麦芽三糖为主要可同化糖的低氨基氮麦汁中，添加碳源和氮源对酵母的糖利用能力和生成乙醇速度的影响。外观浸出物浓度，也就是基于测量麦汁比重来衡量麦汁中全部干物质数量的浓度值，以此表示发酵程度(DF)的变化。当葡萄糖与麦芽糖的比例变化时。外观浸出物的减少速率无明显变化。高葡萄糖浓度会明显抑制麦芽糖和麦芽三糖的吸收。氮源的添加，特别是天门冬氨酸(Asp)的添加，最有效地增强浸出物的利用能力。通过间歇添加天门冬氨酸的方法，使外观浸出物浓度从14％(最初的外观浸出物浓度)降低至3．5％，即当DF达到75％时的发酵时间可缩短至对照试验的72％。Asp的添加也可增进细胞增殖和麦芽糖的吸收能力。     

不同酒花品种的还原力

脂类物质在麦汁煮沸过程中发生的自氧化反应对于啤酒老化风味的出现具有决定作用，对煮沸锅中添加的酒花还原力进行了考察。一种基于引发剂AAPH存在的情况下，对亚油酸氧化作用抑制的分析使我们能够辨别酒花的种类及老化情况。低α－酸酒花相对于苦味型酒花和酒花CO2浸膏而言，其抗氧化活性较高，这是因为它们所含的酒花类黄酮含量差别较大。当减少α－酸的还原力时，抑制时间和酒花颗粒中类黄酮的含量具有很好的相关性。对酒花多酚含量的分析发现类黄酮占酚类化合物的80％以上。正如所期望的一样，在煮沸锅中添加酒花颗粒能够有效提高麦汁的还原性。由于超临界酒花CO2浸膏所含的多酚非常低，所以对麦汁的还原力没有什么影响。由于酒花显示出产好的还原力，所以加酒花的煮沸麦汁中所含啤酒老化标志物反－2－壬烯醛的浓度低。     

非淀粉多糖酶改善麦汁品质的研究

在常规的麦汁制备过程中加入非淀粉多糖(NSP)酶,研究该酶对麦汁品质的影响。方差分析结果表明,酶的添加量、添加温度和作用时间对麦汁的过滤速度、糖化时间、还原糖、总氮、α-氨基氮和麦汁收率均有显著影响(p<0.05)。试验确定NSP酶添加的最佳工艺条件为:添加量1.00%,添加温度45℃,作用时间为20min。     

大豆蛋白美拉德反应产物在肉糜保鲜中的应用

研究美拉德反应产物(MRPs)对熟肉糜理化性质的影响,测定硫代巴比妥酸反应物值(TBARS值)、红度值、p H,并进行感官评定。结果表明:MRPs具有抗氧化作用,能够抑制脂肪氧化,更好的保持肉的新鲜颜色,感官上具有良好的总体可接受性,并且随着MRPs添加量的增加,效果越明显。其中添加2.0%MRPs的处理组与添加0.02%丁基羟基茴香醚的处理组在护色和抗氧化方面无显著性差异(P0.05),与其他处理组和对照组存在显著性差异(P0.05)。因此,大豆分离蛋白美拉德反应产物能够作为一种安全的抗氧化剂添加到熟肉糜中,提高抗氧化能力,保持感官特性,延长货架期。     

新型添加剂Brewbrite在麦汁制造中的应用

对Brewbrite在麦汁中的应用进行了初步研究．通过麦汁外观和其他指标的分析。结果表明，在麦汁煮沸结束前10min添加Brewbrite 30mg／L，可以有效地澄清麦汁，降低麦汁中的可凝固性氮含量。与卡拉胶、单宁、HD-003，DHG，PVPP等添加剂相比，Brewbrite可降低麦汁和啤酒中的总多酚含量、可凝固性氮含量、麦汁色度、麦汁浊度等，减少高分子氮的比例，有助于提高啤酒的非生物稳定性。（孙悟）     

低浓度淡爽型啤酒的酿造

以改善低浓度淡爽型啤酒品质为目的 ,提出了一种新颖的低浓度淡爽型啤酒的酿造方法 .采用二次煮出二段式糖化法 ,用 70 %麦芽和 3 0 %大米的原料配比 ,提高麦芽汁中糖与非糖的比值 ,并在糖化过程中添加啤酒酵母提取物作啤酒发酵的补充氮源 .所酿造的啤酒口味纯正 ,泡沫洁白细腻 ,持久挂杯 .     

Behavior of mono-, di-, and trihydroxyoctadecenoic acids during mashing and methods of controlling their production

The behavior of mono-, di-, and trihydroxyoctadecenoic acids was investigated during laboratory-scale mashing under various conditions with a view to controlling their production. Using a malt in which the lipoxygenase activity was at only a trace level (less than 0.01 U/g) or starting the mashing at a higher temperature than that conventionally used (65 degrees C instead of 48 degrees C) significantly decreased the production of these hydroxy fatty acids. Lowering the pH of the mash to inhibit lipoxygenase activity and preventing O2 uptake by the mash using carbon dioxide were also effective in reducing the amounts of these acids produced during mashing. From the viewpoint of industrial-scale beer production, the prevention of O2 uptake by the mash was selected as an appropriate method for reducing oxidation during wort production without affecting the subsequent brewing process or the taste of the finished beer. After introducing oxidation prevention procedures, the content of trihydroxyoctadecenoic acids decreased by about 30% and the foam stability and taste were improved in commercial products brewed using less than 25% malts.     

Increased protein–thiol solubilization in sweet wort by addition of proteases during mashing

The flavour stability of beer is of major concern for breweries and is closely linked to oxidative processes in the beer. In this study, a new approach to boost the antioxidative capacity of beer was investigated. Protease treatment during mashing was performed in order to solubilize or extract more thiol‐containing protein‐derived compounds into the wort. Five different proteases were tested, and they were all capable of solubilizing increased amounts of thiols in wort during mashing but with different efficiencies. The wort was characterized by measuring total nitrogen by Kjeldahl, protein concentration by the Bradford method and protein composition by SDS–PAGE, in combination with matrix‐assisted laser desorption ionization–mass spectrometry. The results indicated that the proteases increased thiol concentrations by solubilizing thiol‐containing peptide fractions and not full‐length proteins. Copyright © 2014 The Institute of Brewing & Distilling     

Release of phenolic flavour precursors during wort production: Influence of process parameters and grist composition on ferulic acid release during brewing

In this study, the effects of mashing variables such as mashing-in temperature, time and pH, mash thickness, grist coarseness and composition, and stirring regime on the release of ferulic acid were examined. Ferulic acid is a precursor for the formation of flavour-active volatile phenols and a potent natural antioxidant in beer. Given one barley malt variety, the multitude of choice in setting various process parameters and adding brewery adjuncts during brewhouse operations can give rise to worts with widely varying ferulic acid levels. A clear difference in temperature- and pH-dependence between the release of the water-extracted and the enzymatically hydrolyzed fraction was found. The T,t-dependencies of arabinoxylan-degrading enzyme activities were correlated with ferulic acid release during mashing. Results from laboratory-scale mashing experiments were validated with those from a pilot-scale (5 h) wort production process. Enhancing the enzymatic release of phenolic flavour precursors from bound forms during mashing can greatly enhance the phenolic aroma potential of wort. Optimising this precursor release during mashing may be a means for controlling final volatile phenol levels in beer.     

TECHNOLOGICAL FACTORS OF FLAVOUR STABILITY

The flavour stability of a beer primarily depends on the oxygen content of the bottled beer, but the individual steps of wort production are of similar importance viz:-

• (a) preservation of reducing substances by avoidance of oxygen pick-up during mashing, lautering and wort boiling.
• (b) elimination of substances which are prone to react to flavour active compounds like carbonyls by good mash and wort separation procedures,
• (c) avoidance of an excessive exposure of the wort to heat, to limit the formation of Maillard reaction products and related substances.

Existing brewhouses offer some possibilities to improve the process and thus flavour stability. For analytical control Gas Chromatography and High Performance Liquid Chromatography are excellent tools, even simple analyses help to avoid unwelcome changes in the day to day practice.     

50t上面发酵小麦啤酒中试生产工艺技术研究

小麦啤酒是以小麦麦芽为主要原料(占原料总量的40％以上)，采用上面酵母发酵酿制而成。该实验对50t上面发酵小麦啤酒进行了研究，低蛋白白皮软质小麦麦芽、优质大麦麦芽、大米、酒花的选取及合理配比是小麦啤酒风味及质量的可靠保证；双醪浸出糖化工艺操作简便，是可行的；合理调整发酵接种量、接种温度、主发酵温度及发酵罐压力等工艺参数：对改善小麦啤酒风味，提高小麦啤酒质量起到了至关重要的作用；小麦啤酒成品稳定性测试取得了满意的结果。