Beer Haze Research Articles

Beer Hazes. II. Further Analyses of Basic Components by High Performance Liquid Chromatography

Hazes 1–4 and phenolic concentrates 5–8 were prepared from ale and lager. Lager Hazes 2 and 4 were then treated with acid and alkali buffers to prepare Samples 9–12. Hydrolysates of lager Hazes 1–4...

Beer Hazes. II. Further Analyses of Basic Components by High Performance Liquid Chromatography

Beer Hazes. II. Further Analyses of Basic Components by High Performance Liquid Chromatography

Beer Hazes. I. Isolation and Preliminary Analysis of Phenolic and Carbohydrate Components

Beer Hazes. I. Isolation and Preliminary Analysis of Phenolic and Carbohydrate Components

Beer Hazes. I. Isolation and Preliminary Analysis of Phenolic and Carbohydrate Components

Beer Hazes. I. Isolation and Preliminary Analysis of Phenolic and Carbohydrate Components

The interaction of oxidation products of pyrogallol with poly-L-lysine. A model oxidative beer haze

Iodate oxidation of pyrogallol at pH 4 produces an agent capable of precipitation poly-l-lysine and lysozyme. This substance is neither purpurogallin nor one of its oxidation products. The solubility of the poly-l-lysine precipitate in 6m-guanidine hydrochloride and in 1m-NaOH indicates that hydrogen bonding is responsible for precipitation. While the oxidized pyrogallol solutions do not contain tannins detectable by the method ofChapon, polyvinylpyrollidone (PVP) does prevent precipitation. Once formed, the precipitate does not redissolve in PVP. The pyrogallol oxidation products have no effect on the lysine-free polypeptide (poly-N(5) hydroxyethyl-l-glutamine.

THE USE OF14C-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.

KINETICS AND MECHANISM OF QUERCETIN OXIDATION

The kinetics of quercetin oxidation in air were determined spectrophotometrically in the pH region 4 to 7 in 50% alcohol solution at 50° C. The rate at constant pH, found to be first order with respect to quercetin, exhibited pH dependence, with the rate rising with decreasing hydrogen ion concentration. Decrease in oxygen concentration was found to decelerate the reaction. Experiments using diphenyl picrylhydrazyl indicated the presence of free radicals. The mechanism of quercetin oxidation could be fitted into the model consistent with initial ionization of quercetin to its anion and its subsequent reaction with oxygen in a fast step, followed by a unimolecular decomposition to the oxidized quercetin and hydroxyl ion via a one electron transfer mechanism. The primary step in the formation of chill haze in beer appears to be the oxidation of the phenolic entity.

Observations on Beer Haze

(1969). Observations on Beer Haze. Proceedings. Annual meeting - American Society of Brewing Chemists: Vol. 27, Proceedings of the Annual Meeting 1969, pp. 142-148.

MEETING OF THE HAZE GROUP HELD IN LONDON ON 29th APRIL, 1964: THE POLYPHENOL COMPOSITION OF NON-BIOLOGICAL HAZES OF BEERS

Collaborative studies have shown that the polyphenolic fractions of haze preparations from different beers contain major quantities of anthocyanogens. Methylated phenolic acids, derived presumably from lignin, and catechins are also important constituents. Beer haze material is derived from both malt and hops, the contribution from malt being the more important, and the tannins in haze are ultimately derived, by polymerization, largely from comparatively simple polyphenols. Nylon 66 and PVP 700 (polyvinyl pyrrolidone) adsorb or precipitate anthocyanogen-protein associations, thus enhancing potential stability. Future work on beer hazes is likely to involve detailed study of the dynamic oxidation-reduction balance of proteins and tannins in relation to metallic ions and materials such as sulphydryl-containing compounds.

A Novel and Practical Instrument for Measuring Haze in Beer

A Novel and Practical Instrument for Measuring Haze in Beer

PARTICLE SIZE OF BEER TURBIDIGENS AND ITS INFLUENCE ON NEPHELOMETRY

Since it can be deduced from the theory of light scattering that nephelometric estimates of turbidity must be strongly affected by the particle size of the material responsible for the turbidity, it is of interest to ascertain experimentally the quantitative importance of this factor in the nephelometry of beer hazes. A simple and reproducible method has been applied for providing a measure of the particle diameter of beer turbidigens; it has been shown that while these particles are of the same order of magnitude as the wavelength of visible light, their size varies considerably from one beer to another. Concurrent estimates of absolute turbidity, nephelometric turbidity and particle diameter on the permanent haze in a variety of beers have proved that nephelometric estimates of turbidity are in fact very sensitive, in the expected inverse sense, to variations in particle size. For the materials examined, and using instruments calibrated against formazin standards, nephelometric estimates may vary, in relation to true turbidity, from 25% too high with the smaller particles to 70% too low with the larger.

Measurement of Chill Haze in Beer

Measurement of Chill Haze in Beer

Measurement of Chill Haze in Beer

Measurement of Chill Haze in Beer

THE E.B.C. SCALE OF FORMAZIN HAZE UNITS

Directions are given for the preparation of E.B.C. standard units of formazin haze. Preparations of this haze are more stable than alternatives which have been proposed, they are more reproducible, and their light-scattering behaviour is more closely analogous to that of beer haze. It is recommended that the standardized hazes should be used directly for eye comparison in simple types of haze meter and should be used periodically to check the calibration of the various types of photo-electric haze meter. Because of the peculiarities of light scattering by beer and by formazin hazes, this system of standardizing overcomes most of the difficulties of comparison introduced by the use of different types of haze meter.

NON-BIOLOGICAL HAZE IN BOTTLED BEERS: A SURVEY OF THE LITERATURE

The published information concerning non-biological beer haze has been surveyed, and what are considered the outstanding facts from papers which have appeared since 1911 are presented under the following headings: (a) measurement of haze; (b) chemical composition and physical properties of the haze material; (c) a comparison of chill haze and permanent haze; (d) beer composition in relation to haze constituents; (e) analytical investigations of beer constituents which may contribute to haze; (f) prediction of shelf life; and (g) control of stability in production brewing.

STUDIES ON NON-BIOLOGICAL HAZES OF BEERS VI. COMPOSITION OF CHILL HAZES IN BEER WITH PARTICULAR REFERENCE TO POLYPHENOLS*

Four representative chill hazes isolated from beers contained, apart from 45–67% of protein, considerable amounts of at least three separate broad groups of polyphenols, including anthocyanogens, methoxylated compounds believed to be related to lignin, and esters containing simple phenolic acids. These findings are discussed in relation to studies on other beer hazes and to the polyphenols of both malt and hops.

STUDIES ON NON-BIOLOGICAL HAZES OF BEERS V. ROLE OF HOP AND MALT TANNINS

An earlier suggestion that both hop tannins and malt tannins participate in the formation of beer hazes is confirmed by the results of experimental brewings, using malt from which the husks had been removed as the basic raw material, together with additions to the wort of fractions of malt-husk tannin together with hops or isohumulone. With regard to haze development, it was shown that under certain conditions the most active tannin fraction is one derived from malt husk and containing leucoanthocyanins (anthocyanogens) related to the anthocyanidins, cyanidin and delphinidin. Under other conditions, e.g. using higher hopping rates, the corresponding compounds of hops played a greater part. Anthocyanogens were found in various hazes isolated from British beers, especially in chill hazes. Further observations, based on the results of fractionating proteintannin compounds in beer, bear out earlier indications that the effective anthocyanogens are possibly present in beer in bound form.

STUDIES ON NON-BIOLOGICAL HAZES OF BEERS VII. THE USE OF POLYAMIDE RESINS FOR REMOVING THE HAZE-FORMING POLYPHENOLS FROM BEER*

Insoluble polyamide resins in powder form are selective adsorbents for the anthocyanogens which occur among the poiyphenolic derivatives in beer. In extension of earlier work which indicated that such poiyphenolic derivatives are in large measure responsible for the formation of beer hazes, it has been shown that removal of the anthocyanogens from beer by means of polyamide resins enhances the shelf-life.

Measurement of Chill Haze in Beer

Measurement of Chill Haze in Beer

STUDIES ON THE NON-BIOLOGICAL HAZES OF BEER

The properties of “testinic acid” extracted from barley, from malt and from various fractions derived therefrom, depend to some extent on the physical state of the sample. Probably, however, it is an artefact derived from protein and part or all of the husk polyphenols. That recovered from whole barley contained 35–56% protein, 21–38% lignin (based on methoxyl content), 2.0–6.5% ash, and a small amount of carbohydrate; it therefore resembled in composition typical beer hazes. It is perhaps significant, therefore, that malt prepared from barley after steeping in alkali contained no leucoanthocyanidins and yielded beers which deposited haze more slowly on storage than did a control.