麦汁煮沸与蛋白质凝聚

[概述]麦汁煮沸是基本决定麦汁组成、浓度和色泽等的生产操作,最主要的变化是蛋白质的凝聚和分离。煮沸过程中的蛋白质凝聚有两种形式:一种是在加热以及 PH 条件影响下的蛋白质变性凝固,这种形式去除的多为溶于麦汁的可凝固性氮,另一种是蛋白质与其它成分,如单宁、卡拉胶、部分酒花树脂以及金属离子的络合与复合物。麦汁煮沸去除多余的蛋白质,对酒体的组成、口味及提高啤酒的非生物稳定性有其重要意义。     

麦汁煮沸时影响蛋白质凝聚的因素

麦汁煮沸的目的之一，是尽可能将麦汁中可凝固蛋白南凝聚并分离出来，以改善啤酒风味和非生物稳定性。文章从麦汁组成、煮沸强度、煮沸时间、煮沸方式，麦汁ｐＨ及酒花添加等方面分析了麦汁煮沸时影响蛋白质凝聚的因素。     

低压麦汁煮沸

节能是各个领域中的一个共同重要课题。啤酒工厂之40%的能量消耗在麦汁煮沸过程。探讨合理的麦汁煮沸,以节约啤酒厂的能耗,提高效益,具有重大的现实意义。目前,啤酒厂采用的麦汁煮沸有3大类型:(1)传统的常压煮沸;(2)麦汁釜外煮沸;(3)带能贮系统的低(表)压麦汁煮沸。本文对低(表)压麦汁煮沸做较详细的介绍,并与传统常压煮沸做比较。一麦汁常压煮沸系统常压麦汁煮沸系统由煮沸锅(带加热夹套或内加热器)、搅拌装置、排汽管等所组成。蒸发量每小时约10%。煮沸时间至少需90分钟。因为煮沸锅是敞口的,产生的二次     

麦汁煮沸过程中加热器表面结垢对麦汁质量的影响分析

麦汁加热和煮沸受加热器结垢程度的影响，加热器表面结垢可能会导致各批次的麦汁质量有差异。许多酿造厂已证明这种情况的发生。如果连续生产几锅麦汁而中间不对加热器进行洗涤。污垢层的存在导致热传递受阻，麦汁热负荷增加。实验分析了在不同结垢程度下生产麦汁的含氮物质组成，并指出了克服麦汁质量下降的方法。     

麦汁煮沸中相关问题的探讨

麦汁煮沸是啤酒酿造中糖化工段的一项重要的操作过程。该文通过对煮沸热传导原理及几种不同麦汁煮沸设备的介绍,提出了麦汁煮沸控制措施和结垢处理方法,以及使用麦汁煮沸装置时的注意事项。     

优化麦汁煮沸条件,提高麦汁质量

麦汁煮沸过程中TBA值有很大的改变,麦汁可凝固氮、酒花α-酸异构化率等也有所变化。本文拟从三个方面来论述麦汁煮沸对啤酒酿造质量的影响,在总结试验结果的基础上,提出优化麦汁的煮沸条件。     

现代麦汁煮沸中能源的节约途径

本文通过诸多设备及工艺途径分析,对降低麦汁煮沸过程中的能源消耗作了系统的论述,并说明了麦汁煮沸过程中节约能源的必要性与可行性。     

影响麦汁煮沸强度的主要因素

<正>煮沸强度是麦汁煮沸过程的重要技术参数,其含义为麦汁煮沸时,每小时蒸发出的水分相当于混合麦汁的百分数。麦汁煮沸强度直接影响麦汁组分、浓度、色度及可凝固氮的含量。合理控制煮沸强度对啤酒的非生物稳定性及口感具有重要意义。本文将结合煮沸强度公式煮沸强度=[混合麦汁量(L)-最终麦汁量(L)]/[混合麦汁量(L)×煮沸时间(h)]×100%,以及生产实际对影响煮沸强度的各种因素进行     

麦汁分段煮沸工艺的应用探讨

在确保产品保质期和风味稳定性的前提下,采用新的煮沸工艺,减少麦汁蒸发量,是麦汁分段煮沸工艺的要点。1麦汁分段煮沸的过程原理麦汁动态低压煮沸需要增加二次蒸汽回收设备和调节系统,分段煮沸工艺在一般啤酒厂中不需要增加设备即可执行。本公司在电器设备论证后得到了实际应用,取得了较好的成绩。麦汁煮沸只有麦汁不良气味需要挥发,其他     

啤酒麦汁外煮沸技术在高原地区的应用

<正> 麦汁煮沸是啤酒糖化过程生产麦汁的一项重要工序,它直接影响啤酒的非生物稳定性及其风味。在煮沸过程中,若煮沸条件(如煮沸温度、沸腾的状况)达到理想状态,将加速蛋白质凝聚,从而降低麦汁中的可凝固性氮的含量。若将麦汁煮拂温度提高4℃,可以达到同样的蛋白质凝固效果而煮     

PROTEIN PRECIPITATION DURING WORT BOILING: QUALITY ASPECTS OF DIMINISHED WORT BOILING TIMES OF BREWS PREPARED FROM PROANTHOCYANIDIN-FREE OR REGULAR RAW MATERIALS

When using proanthocyanidin-free materials for the production of beer, a reduction of the wort boiling time can be considered. In worts prepared with regular malt and tannin-free hop extract there is a continuous precipitation of the malt flavanoids while in brews prepared from proanthocyanidin-free malt and regular hops there is a simultaneous extraction and removal of the hop flavanoids leading to constant levels of these hop flavanoids. The results also show that the level of Kjeldahl nitrogen in worts boiled with hops will be the same as that in worts boiled with n-hexane tannin-free hop extracts. These results and the fact that more protein precipitates in brews containing no malt or hop proanthocyanidins suggest that, unlike what is the case during the development of beer haze, polyphenols are not necessary for an effective protein precipitation during wort boiling.     

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.     

CONTENTS OF SIMPLE,POLYMERIC AND COMPLEXED FLAVANOLS IN WORTS AND BEERS AND THEIR RELATIONSHIP TO HAZE FORMATION

The highest concentrations of complexed and polymeric flavanols were found in the early runnings from a small-scale mash tun. Formation of break during and after boiling was accompanied by the removal of flavanols from solution, especially the complexed and polymeric fractions. Variations in boiling procedure affected the amount of break formed, the amount of residual soluble flavanols and the colloidal stability of the resultant worts. Colloidal stability in beer was influenced by the contents of simple flavanols and the availability of air during storage. Dimeric and trimeric flavanols seemed especially susceptible to oxidation which implied an important role in haze formation. Flavanols found in commercial beers were mainly monomeric and complexed forms.     

EVOLUTION OF VOLATILE COMPOUNDS DURING WORT-BOILING

Pilot scale trials have been carried out to determine the nature and patterns of evolution of compounds present in condensates obtained from boiling worts at atmospheric pressure. Analytical procedures involving gas chromatography and gas chromatography-mass spectrometry have been used to identify 70 compounds in condensates from unhopped ale worts. Over 30 of these volatile compounds have been classified according to one of three patterns of evolution. The rate of evolution for one class remained constant throughout the boiling period, for the second class decreased gradually towards the end of boiling, and for the third was sufficiently rapid to lead to the removal of most of a component during the early stages of boiling. Many of the compounds identified in the condensates are highly flavour-active.     

WORT-BOILING IN RELATION TO BEER QUALITY

Comparisons of beers from worts mashed with pale ale malts (nitrogen 1·3%) at 150°F. (65·5°C.) and boiled for 1/2, 1 and 2 hr. show that increase in boiling time leads to slightly increased hop-utilization, decreased head-retention, improved non-biological stability and slight differences in flavour. Findings were very similar when the mashing temperature was either 145°F. (63°C.) or 155°F. (68°C.) except that, in the latter case, no difference in flavour was detectable between beers from long and short boiled worts. Stirring can replace vigorous boiling to secure normal hop-utilization and shelf-life but simmered worts give beers of characteristic flavour probably as a result of enhanced contents of hop oil. Use of a lightly kilned malt of high nitrogen content (1·8%) produced a characteristically different flavour from that obtained with pale-ale malt and reduced the utilization of hop substances by provoking a greater loss of this material during fermentation.     

Use of High Hydrostatic Pressure to Increase the Content of Xanthohumol in Beer Wort

During beer production, xanthohumol (XN) extracted from hop through wort boiling is largely converted into its isomeric flavanone, isoxanthohumol (IXN), due to the thermal treatment. XN has a great biological interest as a functional compound (being anti-carciogenic, antioxidant, anti-inflammatory, and anti-infective) and its loss leads to beers with very small amounts of XN and reduced functional properties. In this work, we studied the use of high-pressure treatments (HP; 100, 200, 250, 300, 400 and 500 MPa for 5 min and 250 and 400 MPa for 15 min), applied to previously boiled worts with a second hop dosage, as an extractive procedure, to produce XN-enriched beer worts. The results indicated that beer worts processed by HP showed higher levels of XN. The best results were obtained for 250 MPa, 5 min, resulting in an increase of 4-fold in XN, compared with beer worts produced only by boiling, and 2-fold compared with a method mimicking a recently proposed methodology also intended to improve XN in wort (called XAN method). Combinations of lower pressures with short pressurisation periods proved to be more efficient to increase the amount of XN in the wort. Moreover, HP-processed worts showed lower levels of IXN compared with samples produced by the mimicked XAN method. Physical–chemical characteristics of worts (pH, colour, bitterness and original extract) produced by HP, were similar to those produced only by boiling. These results clearly indicate the potential of using HP treatments to increase the XN content in beer wort, together with less isomerisation to IXN, and open promising possibilities to produce beers with higher amounts of XN, with potentially enhanced functional properties and health promoting properties.     

Dry and Wet Milling of Malt. A Preliminary Study Comparing Fermentable Sugar,Total Protein,Total Phenolics and the Ferulic Acid Content in Non‐Hopped Worts

In this work, fermentable sugar, total protein, phenolics and ferulic acid content were estimated in sweet worts at different points of lautering. Transfer of these selected malt compounds into worts was analyzed in relation to the method of malt milling (wet milling of malt — the “test worts” or dry milling of malt — the “reference worts”). Glucose, maltose and maltotriose were more rapidly transferred into sweet worts at the early stages of lautering (40 hL and/or 80 hL of wort) after wet milling in comparison to dry milling. Total protein content in the test worts was significantly higher than in the corresponding reference worts at each stage of lautering. Transfer of phenolic compounds and ferulic acid (in the free as well as in the ester form) from the mash into sweet worts was significantly improved by dry milling, but not by wet milling. No difference in the total antioxidant activity was observed between the two types of worts. In conclusion, it can be stated that wet conditioning of malt before milling enhances the fast transfer of fermentable sugars and proteins from the mash into the sweet wort during lautering. Lautering is a time‐consuming process, and time reduction without the loss of wort quality should be a priority. Therefore, wet milling can be of interest to professionals in the field as an interesting alternative method to improve the mashing process.     

PREDICTION OF WORT COLD BREAK PERFORMANCE OF MALT AND ITS APPLICATIONS

A new test for wort cold break performance of malt was developed, based on laboratory mashing and boiling, followed by adding a range of concentrations of copper finings at different wort pH values. The test predicted successfully brewery wort cold break performance, with malts being ranked on the basis of production of wort cold break which required a low concentration of copper finings for precipitation and flocculation. A relationship between wort pH and the concentration of copper finings required to give an acceptable cold break was established with both brewery and laboratory worts. A strong correlation (r = 0.922, p << 0.01) was found between copper finings concentration and the two variables wort pH and the amount of cold break protein. Differences in brewery cold break performance were explained largely by a difference in wort pH, although other as yet unidentified factors appeared to be involved. Cold break performance of malts was affected by both crop year and protein modification, but not total nitrogen or total soluble nitrogen. A brewing trial is described in which wort pH is increased at the end of boiling, leading to significant improvements in both cold break and isinglass finings performance.     

Electrophoretic and HPLC methods for comparative study of the protein fractions of malts,worts and beers produced from Scarlett and Prestige barley (Hordeum vulgare L.) varieties

Sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and reversed-phase high performance liquid chromatography (RP-HPLC) methods were used for studying the protein fractions (hordeins; albumins and other soluble proteins) of Scarlett and Prestige barley malts and to follow changes of the protein profile of worts and beers from these two malt varieties. Similar industrial brewing conditions were applied for both varieties.     

The effects of three mash separation systems on the isomerisation of hop alpha-acids

This study investigates the effects of wort composition from three lautering systems on hop utilisation at different hop boiling and dosing times. A response surface methodology was applied with 60 single tests at a 5 litre scale. The parameters, which were varied, were lautering system, boiling time without hops, boiling time with hops and α-acid dosage. It was shown that the wort composition from the different lautering systems requires different boiling times or enables the reduction in boiling time with hops. Although the pH and original gravity of the lauter tun and mash filter worts were similar, different boiling times were necessary to achieve the same concentration of iso-α-acids. Further, there were variations in fatty acid composition of the worts. In order to be able to assess the effects on a larger scale, six brews were performed in a 10 hL pilot brewery. The utilisation of hop bitter substances differed despite the same boiling time and the same α-acid dosage in relation to the total quantity of wort. In addition, no significant losses of hop bitter substances were observed in the wort from a continuous mash filtration system due to the process related higher dosage of α-acid. Both sets of experiments showed that the boiling times depend on the wort composition and increased as follows: novel continuous mash filtration system < mash filter < lauter tun. The results lay the foundation for calculating the optimal parameter settings for each brewery to optimise the hop isomerisation rate. © 2020 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling