Beer haze

Chemical analysis of haze materials isolated from a beverage must be interpreted with caution because composition is often not well-related to cause. For example, beer hazes typically contain a high proportion of carbohydrate, with a modest amount of protein, and little polyphenol (Belleau and Dadic, 1981 Siebert et al., 1981). In order to prevent or delay haze formation, however, it is not necessary or helpful to remove carbohydrate. Reducing the amount of either protein or polyphenol typically has that effect. As a result, it appears that the large amount of carbohydrate found in the haze was coagulated with or adhered in some way to the protein-polyphenol haze backbone. 

Only proteins that contain proline bind polyphenols. Asano et al. (1982) demonstrated that the haze-forming activity of a protein is roughly proportional to the mole percentage of proline it contains (see Fig. 2.3). DNA has codes for exactly 20 amino acids. If each of these were equally present in a protein, there would be 5 mol% of each one. In fact, most proteins have much less proline than this. There are a few exceptions. Casein has about 8 mol% proline and the grain prolamins (proline-rich, alcohol-soluble proteins) are even higher. Hordein, the barley prolamin, contains about 20 mol% proline. As a result, it readily forms haze with polyphenols and is the main beer haze-active (HA) protein. Hordein contains even more glutamine (Q) than proline (P), and often these amino acids are adjacent in the protein (see Fig. 2.4). In fact, the sequence P-Q-Q-P occurs... 

Belleau, G. and Dadic, M. (1981). Beer hazes. II. Further analyses of basic components by high performance liquid chromatography. /. Am. Soc. Brew. Chem. 39,142-146. 

Armstrong, D.E., Chesters, G. (1964). Properties of protein-bentonite complexes as influenced by equilibration conditions. Soil Sci., 98, 39-52 Bamforth, C.W. (1999). Beer haze. J. Am. Soc. Brew. Chem., 57, 81-90... 

Ahrenst-Larsen B and Erdal K. Anthocyanogen-free barley—a key to natural prevention of beer haze. Proceedings of the 17th Congress of the European Brewery Convention, Berhn, 1979 631-644. ISSN 0367-018X. 

Two major developments have occurred in sheet manufacture. The first relates to concern about the carcinogenic properties of certain types of asbestos. In Britain, although most wines and spirits are now filtered through sheets free of asbestos, such replacement has been slower in the case of beers. Alternatives to charged asbestos fibres include aluminium oxide fibres and zirconium oxide fibres. A second development has been the incorporation of insoluble polyvinyl pyrrolidone (PVPP) into the sheet material which adsorbs phenolic materials from the beer, especially the tannin materials associated with beer haze. The PVPP can be regenerated by washing the sheet in a 0-5 % solution of sodium hydroxide at ambient temperatures. 

Phenolic acids do not participate in beer haze formation [27, 104], but vinylphenol and cinnamic acid have been described as potential pigments [105-108],... 

Delcour J, Schoeters M M, Meysman E W, Dondeyne P, Moerman E 1984 The intrinsic influence of catechins and procyanidins on beer haze formation. J Inst Brew 90 381-384... 

Tannins Astringent condensed polyphenolic compounds present in some cereals such as bird-resistant sorghums that are antinutritional because they bind digestive enzymes and dietary proteins lowering feed efficiency. Tannins are also antimicrobial and prevent grain from sprouting in the field. Today, tannins are viewed as potent antioxidants and nutraceuticals. The tannins associated with hops bind proteins, decreasing beer haze and, upon oxidation, form colored compounds necessary in beer. 

---