HAZE- AND FOAM-FORMING SUBSTANCES IN BEER

A study of recent literature on haze- and foam-forming substances in beer suggests the following picture: Traces of true protein, apparently above 150,000 in molecular weight (MW), exist in beer. Apart from these, the main complex nitrogenous substances are present in compounds in the 5,000–70,000 MW region. Nevertheless, these are not proteins, but amino-acid complexes (proteoses) coupled with non-nitrogenous substances. As is well known, haze and haze precursors are proteoses coupled with polyphenols. These two species can be joined by hydrogen bonds to give compounds which are readily dissociated. However, a much firmer, covalent, linkage can be formed. This type of linkage arises from oxidation of polyphenols to quinones, which in turn can oxidize and couple with several groupings on proteoses. One of the most probable points of attack is the sulphydryl group of cystine, and the relatively high percentage of cystine in haze indicates that this occurs. It seems likely that this reaction, to form acidic complexes, occurs mainly in the initial stages of mashing and boiling. In beer, further coupling between pairs or triplets of polyphenolic or quinolic groupings can take the products into the very high molecular weight region of hazes. Correspondingly, the foam-enhancing proteoses tend to be lower in cystine content and to show less combination with polyphenols. However, they too are largely in the form of complexes and the evidence suggests that here the proteoses are mainly combined with glucose polymers, a reaction which takes place during kilning and possibly during boiling. These complexes are less acidic than the polyphenolic ones and tend to be rather lower in molecular weight. Suggestions arising from these concepts may be helpful in controlling the haze and foam potentialities of beers.     

ELECTROFOCUSING STUDIES ON THE FORMATION OF BEER HAZE

The composition of protein fractions obtained from beers stored under differing conditions has been studied using a modified system for isoelectric focusing in thin layers of polyacrylamide gel which permitted the numerical evaluation of the focused bands by a scanning densitometer. The incorporation of concentrated urea in the gel enabled beer hazes to be assessed in this manner. The ageing of an unstabilized all-malt beer resulted in an increase in the proportion of acidic material (pl <5.0) although no new protein bands were formed. The derived hazes were enriched with acidic components but contained all except the most basic fractions present in the beer.     

THE APPLICATION OF MASS SPECTROMETRY IN BEER FLAVOUR STUDIES

Beer is a complex mixture of over 600 substances. Many of those which are responsible for the aroma and taste of beer are present only in trace amounts. Mass spectrometry, particularly when used in combination with gas chromatography, currently provides the only realistic means of identifying and quantifying many beer flavour constituents by virtue of its high sensitivity and specificity. Various techniques which are available for use in conjunction with modern mass spectrometry are discussed, with particular emphasis on high resolution chromatography, different ionisation methods and the role of computers.     

FURTHER STUDIES ON THE OXIDATION OF HOP RESINS

The autoxidation of humulone, isohumulone, colupulone and cohulupone has been studied using chromatography on an ion-exchange resin. Humulone gave a mixture of products which were largely insoluble in light petroleum whereas most of the products obtained by autoxidation of colupulone were soluble in that solvent. Cohulupone was isolated for the first time from the autoxidation of colupulone. The brewing value of a water-soluble fraction of hops was also examined. The degree of resolution obtained from the ion-exchange chromatographic system enabled a detailed examination of the constituents of hop concentrates and extracts to be made.     

IMMUNOCHEMICAL STUDIES ON THE NITROGENOUS CONSTITUENTS OF BEER FOAM*

Samples of foam prepared by two different procedures were analysed using immunoelectrophoretic methods with anti-barley and anti-chill haze immune sera and their constituents were compared to those of beer (total and defoamed) and of chill-haze. Two, and probably three, constituents reacting with the immune sera have been detected in both foam preparations and it was shown that at least two of the constituents are identical with the main nitrogenous components of chill-haze. Defoamed beer contains the same substances but at a low concentration when compared on the basis of weights of dry matter. These observations may have some practical applications.     

ON THE DETERMINATION OF VOLATILE THIOLS IN BEER

The method of Ikeya for the determination of volatile thiols in beer by aspiration of these compounds into mercuric acetate has been examined. Cadmium acetate has been found to be unsuitable as an absorbant for removing hydrogen sulphide since it also combines with thiols. This reagent has been replaced by aqueous zinc acetate in a separate absorption trap. The proposed modification has the advantage of enabling estimations of hydrogen sulphide and of volatile thiols to be carried out on the same sample.     

STUDIES ON BEER HAZE FORMATION. II. DIMERIC FLAVANOIDS OBSERVED IN PROFILES OF BEER: NYLON 66 ADSORBATES

A peak in the gas chromatographic profile of beer: Nylon adsorbates has been found to comprise three unresolved biflavan components. One of these, molecular formula C₃₀H₂₆O₁₂, consists of two C—C linked catechin units and has the same structure as a biflavan obtained by the acid catalysed interaction between cyanidiol and catechin. It appears to be the same as the procyanidin previously isolated from beer. The other components, both with molecular formula C₃₀H₂₆O₁₃, have the same skeletal structure as the first, but are linked catechin-gallocatechin pairs, one being a prodelphinidin, the other a procyanidin. Dicatechin, a tannin obtained by treatment of catechin with dilute mineral acid, also seems likely to be a component of the adsorbate profiles.     

QUANTITATIVE DETERMINATION OF BITTER SUBSTANCES IN BEER,BY THIN LAYER CHROMATOGRAPHY

A method is described which allows the separation of hop bitter components and derivatives present in beer by combined thin-layer chromatography on a mixture of silica gel and cellulose. This method can be used to evaluate the purity of beer bitterness and to recognize the beer hopping.     

金川保健啤酒对小白鼠耐缺氧能力影响的实验研究

通过灌胃和自由饮用两种方式给予小鼠以不同浓度的金川保健啤酒,通过测定室温常压下小鼠耐缺氧的存活时间来反映金川保健啤酒对小鼠耐缺氧能力的影响。结果:50%浓度啤酒组小鼠耐缺氧存活时间高于对照组和100%浓度啤酒组(0.010.05)。结论:饮用适量的金川保健啤酒能够提高小鼠的耐缺氧能力。     

ON THE SUNSTRUCK FLAVOUR OF BEER

It has been confirmed that sunstruck flavour is due to the formation of 3-methyl-2-butene-1-thiol formed by photolysis of iso-α-acids in the presence of sulphur-containing amino acids.     

THE ESTIMATION OF p-HYDROXYBENZYLAMINE IN BEER

A simple method has been developed to allow the estimation of p-hydroxy-benzylamine in beer in the presence of other amines including tyramine. Analysis of commercial beers has shown a low and variable content. At the levels found, p-hydroxybenzylamine seems unlikely to be of physiological significance even when monoamine oxidase inhibitor drugs are being taken. The biosynthetic route for p-hydroxybenzylamine has not been identified but synthesis of the compound appears to be associated with the barley husk.     

THE DETERMINATION OF PAPAIN IN BEER

The quantitative determination of papain in beer has been achieved by means of turbidity measurements on a casein substrate. The method, which is quick and simple, will measure activities of the order of 1–20 p.p.m. of crude papain. This will cover any amount likely to be found in beer     

啤酒用玉米米工艺检测指标的研究

通过对啤酒用辅料玉米米的工艺检测指标的研究，从水分、粒度、浸出物、脂肪等几方面制定啤酒用玉米米产品标准。以其为根据，采购原料玉米，验证、修订、完善玉米联产加工工艺(中试)及其参数，选择最佳加工工艺，确定更为合理的工艺参数。     

QUANTITATIVE ANALYSES OF BEER BITTERING SUBSTANCES BY THIN-LAYER CHROMATOGRAPHY

Bittering substances in beer have been isolated by thin-layer chromatography and some have been identified. The method can be used for the quantitative assessment of isohumulones A, isohumulones B, hulupones and a further directly-derived α-acid material. In beers hopped with hops of a normal age in our breweries, 80% of the total material extractable with petroleum ether consists of these substances.     

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.     

灵芝主要活性物质及液体深层发酵技术研究进展

灵芝是我国著名的药用真菌和新资源食品.在分析研究灵芝主要活性物质的基础上,对灵芝液体深层发酵技术作了较全面的综述,指出了影响灵芝液体深层发酵主要因素,最后对灵芝液体深层发酵技术在医药及食品中的应用前景作了展望.     

THE DETECTION OF ISINGLASS FININGS IN BEER

A method for the detection of isinglass finings in beer is described. Protein is precipitated from the beer with a large excess of sodium alginate and hydrolysed; the hydrolysate is examined colorimetrically for the presence of hydroxyproline. The presence of this imino acid, which is found in substantial proportions only in collagen and gelatin, indicates that the beer has been fined.