啤酒酿造过程中脂转移蛋白糖基化形式的检出

利用MALDI TOF生物质谱检测出了啤酒中LTP的糖基化形式,肯定了啤酒中糖蛋白的存在。LTP糖基化形式存在于从麦芽到啤酒泡沫的整个啤酒酿造过程。酿造过程中蛋白质糖基化的发生增加了蛋白的亲水性,从侧面解释了LTP等强疏水性蛋白稳定存在于啤酒中的原因。     

酿造过程对贮藏啤酒中含氮化合物的影响

本文分析了工业生产全麦芽麦汁和玉米辅料麦汁的含氮化合物,以及不同分离技术[麦汁过滤机(Meura 2001)和过滤槽(Steinecker FVAS 26)]的影响.数据表明,(1)与全麦芽麦汁相比,玉米辅料麦汁含较低的总氮化合物;(2)全麦芽麦汁和辅料麦汁的可同化氮均占总氮的20%～24%;(3)与辅料麦汁相比,全麦芽麦汁游离氨基氮几乎是其两倍;(4)脯氨酸和天冬酰胺是两麦汁中最丰富的氨基酸;(5)麦汁发酵过程中铵消失,含氮量降低.此外,对于全麦芽麦汁而言,利用过滤槽,总氮减少80%,利用过滤机,总氮减少25%;对于辅料麦汁而言,利用过滤槽,总氮减少87%,而利用过滤机,总氮减少29%.麦汁过滤后,可同化氮含量足够用于有效发酵,但经过过滤槽分离之后,可同化氮到达到一个值,该值可能影响全麦芽麦汁和辅料麦汁的正常发酵过程.因此,在使用过滤槽时,我们必须控制减少其对含氮化合物的影响,或利用麦汁氮补充来克服发酵中止和缓慢发酵.     

酿造水中影响麦汁质量的因素及处理方法

酿造水中的余氯、硬度、pH等因素均能对麦汁质量产生影响，通过活性炭吸附技术，可以减少这些因素的影响。     

酿造过程的离子平衡

很多酿造科技的书籍主要讨论多糖、蛋白质和脂肪对酿造过程及产品质量的影响,近年来逐渐增加了对核酸的关注,这主要是由于分子生物技术的发展及其在遗传转录和菌株特征上的应用。另外也有许多文章是关于低分子物质的研究,特别是啤酒中的风味组成物质。     

啤酒酿造过程对麦芽蛋白结构的影响研究

研究了啤酒酿造过程对麦芽蛋白组分结构和理化性质的影响.结果表明,在酿造过程中蛋白含量逐渐降低,二级结构逐步打开,并使其理化性质发生改变,影响着啤酒的最终品质.从麦汁到发酵液,α-螺旋含量明显降低而无规则卷曲含量却显著增加,导致表面疏水性值和巯基含量降低,形成高分子量蛋白亚基;而从发酵液到啤酒,二级结构变化较小,但表面疏水性值和巯基含量明显增加,蛋白亚基强度降低且有部分蛋白亚基消失.     

工业规模酿造过程对Lage啤酒含氮化合物的影响

本文主要分析了工业规模下,全麦芽或者添加玉米辅料所制麦汁的含氮化合物,然后分析了其在酿造过程中的变化,以及麦汁压滤机和过滤槽过滤麦汁对含氮化合物的影响。数据显示：（11与全麦芽麦汁相比,添加玉米辅料的麦汁总氮含量较低;（2）全麦芽麦汁和玉米辅料麦汁中可同化氮含量占总氮的20％～24％;（3）全麦芽麦汁中游离氨基氮的含量几乎是玉米辅料麦汁的两倍;（4）两种麦汁中脯氨酸和天冬酰胺的含量是最高的;（5）含氮量最低的麦汁（即添加玉米辅料的麦汁）在酿造过程中铵消失。同时,在使用FVAS26过滤槽和使用Meura2001压滤机两种技术条件下,全麦芽麦汁酿造过程中总氮含量分别下降80％和25％;辅料麦汁分别下降87％和29％。醪液采用压滤机过滤,全麦芽麦汁和辅料麦汁中所含可同化氮的量均已足够于高效发酵,但是采用过滤槽过滤,可同化氮的含量均只能达到常规发酵。因此,当使用过滤槽过滤时,必须采取措施以降低含氮化合物对发酵的影响,或者是补充氮源以克服缓慢发酵和不发酵。     

大麦蛋白组分对糖化麦汁的影响

根据不同蛋白组分溶解特性,以不同溶剂依次提取了大麦中蛋白组分,将各组分蛋白重组到麦芽粉中进行糖化。结果表明,醇溶蛋白是对糖化过程和糖化麦汁质量有较大负面影响的组分,其中非凝胶醇溶蛋白中的一些组分或被一定程度降解得到的多肽是导致麦汁混浊的主要成分;而凝胶醇溶蛋白是导致麦汁分离困难的主要因素。      

中性蛋白酶对啤酒酿造中麦汁质量的影响

随着啤酒工业的发展,酶制剂在啤酒酿造中的应用越来越广泛.文中主要对中性蛋白酶在糖化过程的应用及对麦汁的影响进行了研究.研究表明,中性蛋白酶添加量在250mg/(kg麦芽)以下,可以使麦汁中α-氨基酸态氮含量提高25%以上,高于250mg/(kg麦芽)反而不利于酶的作用.添加中性蛋白酶只能在一定程度上降低麦汁浊度和敏感蛋白含量,若要进一步提高麦汁稳定性,需要同时采取相应措施,控制麦汁中多酚物质的含量.     

High Gravity Brewing by Continuous Process Using Immobilised Yeast: Effect of Wort Original Gravity on Fermentation Performance

The present work evaluated the influence of all‐malt wort original gravity on fermentative parameters and flavour‐active compound formation during primary fermentation of high gravity brewing by a continuous process using a lager yeast immobilised on a natural carrier obtained from brewer's spent grain (the main brewery by‐product). The all‐malt worts with original gravity (OG) ranging from 13.4 to 18.5°Plato were prepared by diluting a very‐high‐gravity wort (20°Plato) with sterile brewery water. The continuous assay was carried out in a bubble column bioreactor with a total working volume of 5.2 litres, at 15°C, using a constant gas flow rate of 250 mL/min (200 mL/min of CO₂ and 50 mL/min of air) and a dilution rate of 0.04 h^?1 (residence time of 25 h). The results indicated that as the wort OG was increased, the ethanol concentration of the outflowing beer increased. On the other hand, the continuous fermentation of the most concentrated worts (16.6 and 18.5°Plato) resulted in beers with unbalanced flavour profiles due to excessive ethyl acetate formation. The immobilised cell concentration appeared to be nearly independent from increasing wort OG.     

Degradation of a Foam‐Promoting Barley Protein by a Proteinase from Brewing Yeast

The degradation of a major protein component in beer, the lipid transfer protein (LTP1), by the yeast proteinase A was determined. Another major protein fraction in beer, the protein Z‐fraction, was not degraded by this enzyme. Protein preparations from beer and barley containing LTP1 were examined for degradation by proteinase A using SDS‐PAGE, immunoblotting and RP‐HPLC. LTP1 from barley was completely resistant to proteinase A, whereas LTP1 concentrated from beer was cleaved. We conclude that LTP1 was modified during the brewing process, thus rendering it more susceptible to proteinase A degradation.     

Effects of Lipid‐Transfer Protein from Malting Barley Grain on Brewers Yeast Fermentation

A lipid‐transfer protein (LTP), which belongs to a family of pathogenesis‐related (PR) proteins, was isolated from malting barley grain. This LTP significantly decreased fermentation and respiration of brewers yeast (Saccharomyces cerevisiae) and caused the leakage of cell constituents. These effects were dose dependent tending to saturation at higher concentrations (～ 200 μg/mg yeast dry weight cells). It was found that LTP survives the thermal treatment during the mashing process. Despite yeast fermentation inhibition in vitro, this LTP did not appear to cause impairment of yeast fermentation capability in the brewing process.     

The Impact of Low Heat Load and Activated Carbon Treatment of Second Wort on Beer Taste and Flavour Stability

There is a vast repository of knowledge regarding improving beer taste stability via wort boiling. However, as far as we are aware, there are few reports dealing with taste stability improvement in terms of quality characteristics by boiling, under proper conditions, the first wort and second worts separately. In this study, more than 50 brews in a pilot scale brewing facility were conducted to investigate suitable boiling conditions for first and second worts. When the second wort (i.e., the last 10% of the total filtered wort) was kept under a low heat load atmosphere (78°C), casted to the boiling first wort, and then re‐boiled for 10 min, the produced beer exhibited no significant differences compared to that of the general beer in terms of taste stability. However, when an adsorbent (bentonite, silica gel, activated carbon or PVPP) was individually added to the second wort and the same boiling procedure was performed, the oxidized flavour of the forced aged beer, treated with activated carbon, significantly decreased, compared to that of the general brew (level of significance α = 0.01). The data from the chemical analysis and fermentation behavior are presented.     

啤酒酿造过程中影响乙醛变化因素的研究

有针对性地提出了酿造过程中影响乙醛形成的生理内因和环境外因 ,并从主要的几个方面进行了研究。结果表明 ,酿造过程染菌、麦汁充氧控制不合理、二次发酵酒添加是造成成品啤酒中乙醛含量偏高的主要环境外因。在实际生产中 ,应加强CIP清洗 ,特别是种酵母罐的清洗及无菌空气过滤的控制工作 ,并合理控制麦汁的溶解氧含量 ,尽可能减少二次发酵酒的添加。     

The Effect of Proteinase A on Foam‐Active Polypeptides During High and Low Gravity Fermentation

The ability of beer to produce good foam is influenced by the level of foam‐active polypeptides. Specific polypeptides with hydrophobic domains, such as Lipid Transfer Protein (LTP1), are important components of beer foam. Although, high gravity brewing is a commercially viable technique, it has the disadvantage of producing beer with less foam stability compared to lower gravity brewed counterparts. It is thought that proteinase A plays a key role in the degradation of these hydrophobic polypeptides responsible the beer foam stability. The object of this study was to compare and quantify the loss of hydrophobic polypeptides and specifically foam‐LTP1 during high gravity (20°Plato) and low gravity (12°Plato) wort fermentations and to evaluate the effect of proteinase A on these polypeptides. The losses of hydrophobic polypeptides and foam‐LTP1 were generally greater in high gravity brews. Furthermore, the results obtained suggest that proteinase A alters the hydrophobicity of these polypeptides rather than their molecular size. Approximately 20% of hydrophobic polypeptides and approximately 57% of foam‐LTP1 appeared to be proteinase A resistant. These differential losses of hydrophobic polypeptide and foam‐LTP1 could have implications for the foam stability of the finished product.     

纯生啤酒存放过程中泡沫稳定性与酵母蛋白酶A以及蛋白含量与组成变化的研究

酵母蛋白酶A已经被证实对啤酒泡沫稳定性有负面作用。通过测定纯生啤酒存放过程中酵母蛋白酶A活性变化、泡持性衰减及蛋白含量的变化,进一步说明酵母蛋白酶A以及蛋白种类与含量对纯生啤酒泡沫稳定性的影响及其相互关系。对不同存放时期纯生啤酒样品中蛋白质进行电泳鉴定的结果显示,存放3月后的纯生啤酒中脂肪转运蛋白1(LTP1)完全消失,这一结果表明LTP1是影响啤酒泡沫稳定性的主要蛋白,该蛋白降解可能是酵母蛋白酶A作用的结果。     

高浓发酵和酸洗对酿造酵母的影响

用磷酸类杀菌物质来洗涤接种酵母，以避免细菌污染是许多啤酒厂通用的方法，使用不正确的方法洗涤酵母将使其发酵特性下降并产生不良影响。酵母酸洗后接种于１２Ｐ麦汁，发酵特性没有明显下降；而接种于２０Ｐ麦汁，在发酵的第一个２４小时，酵母的活力就有所下降，但酵母的发酵特性没有变化。