啤酒中的混浊活性蛋白质

1前言啤酒的成分复杂,稳定性不强,易产生混浊沉淀。最常见的啤酒非生物混浊是蛋白质混浊。形成蛋白质混浊的原因在于啤酒中有两种主要成分,即蛋白质和多酚物质。在啤酒中,某些多酚物质("混浊活性多酚")可以与蛋白质("混浊活性蛋白")结合形成复杂的复合物,且二者存在一定     

饮料中蛋白质——多酚的作用机制

蛋白质－多酚的相互作用是引起饮料混浊的重要原因之一。蛋白质具有混浊形成活性主要取决于它的脯氨酸含量，多酚形成混浊的能力与其分子结构有关，蛋白质与多酚的比例强烈影响到饮料中混浊的形成量。文中叙述了饮料中蛋白质－多酚的作用机制和最新进展。     

活性炭对苹果汁中多酚和混浊物的吸附研究

利用苹果汁工业化生产线上取样 ,采用香草醛 盐酸法、正丁醇 盐酸法以及液相色谱测定多酚 ,用浊度仪测定混浊程度 ,研究了活性炭吸附对苹果汁中的多酚和混浊的影响。结果表明 :活性炭吸附可减轻混浊 ,减少后混浊的前体物质及缩合单宁含量 ,减少活性蛋白的含量     

苹果汁中与混浊有关的活性蛋白质的分离纯化

采用疏水作用色谱PhenylSepharoseCL-4B和固相萃取C18柱分离纯化了浓缩苹果汁和鲜榨苹果汁中与混浊有关的活性蛋白质。经过SDS-PAGE,结果表明浓缩苹果汁和鲜榨苹果汁中的活性蛋白质为同一类蛋白,均为疏水性蛋白质,其分子量为36kDa。     

饮料中的多酚-蛋白质反应及其稳定化处理

多酚-蛋白质反应是啤酒、葡萄酒和果汁等饮料中产生混浊沉淀的原因,限制了饮料的货架期。本文阐述了混浊反应的机理、影响因素及其稳定化处理。     

影响浊苹果汁混浊稳定性的因素

对影响混浊苹果汁混浊稳定性的因素进行了综述。总体看来,混浊苹果中可溶性果胶的含量,多酚-蛋白质复合物的形成、酚类的氧化聚合和原花青素的聚合都对悬浮颗粒的尺寸有影响。同时,对今后的研究重点进行了讨论。     

与浓缩苹果汁后混浊有关的蛋白质组成分析

从新鲜苹果和浓缩苹果汁中分离纯化蛋白质，用肽质量指纹谱对其进行鉴定，测定氨基酸组成和多酚及多糖的含量，结果表明，新鲜苹果蛋白的丰要组分为Thaumatin-1ike protein1，是一糖蛋白，其疏水性氨基酸含量高，易引起苹果汁的后混浊。浓缩苹果汁中蛋白组分比较复杂，在贮存过程中与多酚及多糖发生结合，使分子量增大，其分子量均大于新鲜苹果蛋白。     

浓缩苹果汁多糖对浊度的影响

采用醇沉法从浓缩苹果汁中提取多糖,HPLC测得苹果汁多糖由葡萄糖、果糖、阿拉伯糖组成,阿拉伯糖和葡萄糖聚合参与混浊的形成。建立多糖-蛋白质模拟体系(pH3.7的磷酸钠缓冲溶液)发现,浊度随着多糖和蛋白质浓度的增加呈上升趋势,多糖能降低蛋白质-单宁酸聚合产生的浊度。     

由多酚、蛋白质引起啤酒非生物混浊的研究

啤酒是一种成分复杂，稳定性不强的胶体溶液，有很多因素会导致啤酒混浊，但啤酒混浊物的主要成分是多酚、蛋白质所引起的。本文主要探讨了多酚、蛋白质由于分子间的亲和性不同而形成啤酒混浊复合物的原理以及由活性蛋白、活性多酚之间相互作用的结合机制；最后还讨论了由多酚和蛋白质形成混浊物的动态无差异曲线图，从而从分子的角度对啤酒混浊物形成机制得到进一步的阐述，并且就如何提高啤酒非生物稳定性提供了解决思路。     

酶解对苹果汁混浊的影响

本论文利用测定果汁的浊度、酸度、糖度、活性蛋白、活性多酚，研究了酶解对苹果汁混浊的影响。结果表明：酶解可减轻混浊；酶解过程中，酚类发生缓慢化学氧化，呈降低趋势；和混浊有关的蛋白变化不大；果胶、淀粉定性检验呈阴性，不能准确表征果胶、淀粉完全水解。     

EFFECT OF VARIOUS POLYPHENOLS ON THE RATE OF HAZE FORMATION IN BEER

The effect of the addition of a range of monomeric, dimeric and polymeric polyphenols to beer on the rate of haze formation has been examined. Monomeric polyphenols had no significant effect on haze formation. The addition to beer of dimeric or polymeric polyphenols caused a large increase in the rate of haze formation.     

THE REACTIONS BETWEEN POLYPHENOLS AND ALDEHYDES AND THE INFLUENCE OF ACETALDEHYDE ON HAZE FORMATION IN BEER

The reactions and interactions between proteins and polyphenols are, among other phenomena, responsible for haze formation in beer. The participation of aldehydes in the polymerisation of polyphenols is considered. The formation of phenolic Baeyer-type condensation products containing phenolic residues linked by CH₃CH-bridges through reaction with acetaldehyde is possible at the pH of beer (4.0). These and other reactions with acetaldehyde in beer participate in beer haze formation.     

THE USE OF 14C-LABELLED POLYPHENOLS TO STUDY HAZE FORMATION IN BEER

Haze formation in beer is claimed to involve the gradual polymerization of polyphenols and their subsequent reaction with proteins to form insoluble complexes. The mechanism of haze formation has now been studied using ¹⁴C-labelled epicatechin and dimeric catechin. Epicatechin does not polymerize to form dimeric or trimeric polyphenols when beer is stored and is only incorporated into beer haze to a small extent. Some of the epicatechin combines with nitrogen-containing compounds during storage to form soluble complexes. However, dimeric catechin does not form soluble complexes with nitrogen-containing compounds and instead there is a substantial incorporation of this dimer into beer haze. Dimeric polyphenols are important haze precursors which form insoluble complexes with one or more of the polypeptides of beer, probably by an oxidative coupling mechanism.     

Turbidity and Haze Formation in Beer — Insights and Overview

Beer is a complex mixture of over 450 constituents. In addition, it contains macromolecules such as proteins, nucleic acids, polysaccharides and lipids. Proteins influence the entire brewing process with regard to enzymes, which degrade starch, β‐glucans and proteins; with protein‐protein linkages that stabilize foam and are responsible for mouthfeel and flavour stability; and in combination with polyphenols, thought to form haze. With this complexity, problems in processability are as various as the constituents. Several substances in beer are responsible for haze formation. Organic components such as proteins, polyphenols and carbohydrates (α‐glucans, β‐glucans) are known to form haze. In addition, inorganic particles such as filter aids and label remains can cause increased turbidity. In this article only non‐microbiological induced hazes are described. Many studies have been conducted on the identification of haze and foam active components in beer. Hence the aim of this work was to survey the different possibilities of haze formation and for haze identification. A summary is provided on methods for haze identification including dyeing methods, microscopic analyses and size exclusion chromatography.     

EUROPEAN BREWERY CONVENTION: HAZE AND FOAM GROUP. TOWARDS THE CHEMICAL PREDICTION OF SHELF LIFE

Rapid chemical methods are described for assesssing in beer the levels of “oxidizable polyphenols” and “sensitive proteins,” both of which influence non-biological shelf life. The method for oxidizable polyphenols depends on the formation of an insoluble complex with cinchonine sulphate. Freshly processed beers form only a slight haze on the addition of cinchonine sulphate, but the haze produced is greatly increased if the beers are previously oxidized. For beers stabilized by a process involving reduction of the polyphenol content, it is found that the rate of haze formation is then directly related to shelf life and is inversely proportional to it.     

Evaluating haze formation in flavoured lager beers using a range of forcing methods

Haze formation is a quality problem that can affect a wide range of drinks for a number of different reasons. Although well‐characterized in traditional beers, the emergence of novel beer‐based beverages has led to the potential for chemical interactions that can result in the precipitation of haze material. In this study, the haze formation in 19 commercially available flavoured lager beers was investigated. The chemical parameters of each of the drinks were measured and haze formation was induced through three forcing tests, developed for use in both the beer and wine industries, as well as using a novel forcing test, designed for this study. Several of the products were particularly susceptible to a number of haze forcing tests and the EBC temperature cycling and the Wine Forcing (70°C) tests were found to generate the most forced haze (measured at 90 and 13° scatter angles, respectively) in these products. There was no overall correlation between the drinks' chemical parameters and their susceptibility to haze formation. However, a weak, but statistically significant, correlation (p  = 0.044) was observed between the concentration of polyphenols in the products and the presence of haze measured by 90° scatter angle. Copyright © 2017 The Institute of Brewing & Distilling     

The chemical components in malt associated with haze formation in beer

In bright beer, haze formation is a serious quality problem, which reduces beer storage and shelf life. In this study, haze‐active proteins, alcohol chill haze formation ability, α‐amylase activity, the contents of total polyphenol, protein and its fractions and amino acids were analysed using 23 barley accessions to investigate the relationship between the quality components in the malt and the haze character in beer. The results showed that there were largely genotypic variations for all examined traits among the 23 barley accessions. However, there was no significant correlation between the haze character and α‐amylase activity. All haze characteristics were significantly and positively correlated with total protein content, albumin, globulin and the hordein content, as well as the glutamic acid (glutamine), proline and phenylalanine content, and were not correlated with total polyphenols. A model describing the relationship between the chill haze in the beer and the protein content in the malt was developed. Copyright © 2016 The Institute of Brewing & Distilling     

苹果多酚提取浓缩过程中混浊的形成及控制

对苹果多酚提取浓缩过程中的混浊现象进行研究。通过分析苹果多酚提取浓缩液中引起混浊的主要成分,采用离心法脱除混浊中的蛋白质,观测脱除蛋白质前后大孔树脂对苹果多酚吸附解析的影响。结果表明引起混浊的主要成分是蛋白质、多糖、果胶、多酚,低速离心脱除蛋白质后大孔树脂对苹果多酚的比吸附量提高了25%,比解吸量提高了23%。     

用浊度法预测香蕉汁中混浊活性蛋白质和多酚

本研究采用浊度仪测香蕉汁混浊活性(HA)蛋白和多酚含量。为减少内源性蛋白和多酚的影响,分别用聚乙烯吡咯烷酮(polyvinyl polypyrrolidone, PVPP)和膨润土吸附多酚和蛋白质。将单宁酸加入PVPP处理与未处理香蕉汁中,果汁浊度变化与蛋白质含量呈线性相关,在蛋白质含量相同情况下,PVPP处理果汁的浊度较未处理样品小。热处理添加适量明胶的香蕉汁可反映果汁中HA多酚的含量,膨润土处理与未处理系列样品的浊度与其HA多酚含量呈线性相关。浊度法可用于测定香蕉汁中HA蛋白和HA多酚。     

Phenolic compounds present in natural haze protein of Sauvignon white wine

Protein haze in white wines remains a problem for wineries. In addition to protein composition, many other factors have been identified that can participate in and even trigger the appearance of hazes. Phenolic compounds may be one of the non-protein factors involved in protein haze formation. The aim of this study was to identify and quantify the polyphenols present in the natural precipitate of a Sauvignon wine. The identification and quantification of polyphenols present in wine before and after natural precipitation and also in a natural precipitate were carried out by GC/MS and HPLC/ESI-TOF. The natural precipitate was also hydrolyzed in an acidic medium (Bate-Smith reaction). The results indicate that several phenolic compounds were present in the protein haze (tyrosol, trans-p-coumaric, trans-caffeic, vanillic, protocatechuic, syringic, gallic, ferulic, shikimic acids, (+)-catechin, ethyl coumaric acid ester and quercetin). Moreover, the detection of cyanidin after acid hydrolysis indicates the presence of procyanidins.