Chill haze

Temperature can affect haze in several ways. Lowering temperature can result in reduced solubility of marginally soluble substances and may lead to a higher concentration of particles. This is responsible for the phenomenon known as "chill haze." Typically, warming a sample will dispel most of the turbidity provoked by chilling. On the other hand, elevated temperatures can speed interactions between substances that form insoluble particles, leading to more rapid haze development. 

Asano, K., Shinagawa, K., and Hashimoto, N. (1982). Characterization of haze-forming proteins of beer and their roles in chill haze formation. /. Am. Soc. Brew. Chem. 40,147-154. 

Lopez, M. and Edens, L. (2005). Effective prevention of chill-haze in beer using an acid proline-specific endoprotease from Aspergillus niger.. Agric. Food Chem. 53, 7944 7949. McCarthy, S. L., Melm, G. D., and Pringle, A. T. (2005). Comparison of rapid physical stability tests. ]. Am. Soc. Brew. Chem. 63, 69-72. 

Permits fermentation by converting starch to fermentable sugar Prevents chill haze in beer (a complex which includes protein, carbohydrates and tannins)... 

At least initially, the protein-polyphenol complexes are held together by weak associations and haze can be dispersed by warming, which in brewing is commonly referred to as reversible haze or chill haze. The practical consequence of this phenomenon is that beer should be bltered at the lowest possible temperature. The mechanism of haze formation appears to be... 

Other enzymes are required to obtain good quality beer with good shelf-life. The major use of non-malt enzymes is an enzyme that is added to fermented beer to chillproof the beer. Beer is fermented and aged under chilled conditions. Almost all packed beer is filtered while cold to achieve clarity. In spite of the filtration steps beer becomes cloudy after it is packed, distributed and chilled again for serving. The cloudiness that develops is caused by formation of haze particles called chill haze which are the result of the interaction between peptides and polyphenol compounds. 

Clarifying agents or flocculants are used to eliminate turbidity or suspend particles from liquids, e.g., chill haze in beer, precipitates in fruit juices and wines, and haze in oils. Often, they provide a nucleation site for suspended fines. Examples of clarifying agents are lime in sugar juice clarification, pectic enzymes to break down pectins in fruit juices, and gelatin for clarification of fruit juices. 

Prevention of chill haze in beer resulting from protein—phenolic interactions... 

Over the past thirty years, powder filters have become increasingly popular, either as a complete filtration system or as the first step of a two-stage filtration in which sheet filtration follows. The most popular powder for this purpose is kieselguhr or diatomaceous earth which is mined from Miocene deposits in a number of areas in Europe and the Americas. An alternative is the volcanic material called Perlite obtained from certain Greek islands. Very recently it has been shown that silica hydrogel can substitute for kieselguhr and at the same time stabilize the beer against chill haze [13]. 

Beers infected with bacteria or wild yeast will rapidly go turbid and develop a biological haze but with the widespread use of pasteurization and sterile filtration such infections are fairly rare. However, uninfected beers when stored for any length of time, usually in bottle, also become cloudy and deposit a haze. Such beers are usually unacceptable and the rate of development of this non-biological haze determines the shelf-life of bottled beer. Before a beer shows any permanent haze at room temperature it may form a chill haze if suddenly cooled to 0°C. Such hazes redissolve when the beer is warmed up again to room temperature (20 C). Chill hazes are obviously a more serious problem with lager beers which are served at a lower temperature than ales. 

Such bonding may be sufficient to account for chill haze formation but it is generally believed that the formation of permanent hazes involves oxidation and the production of covalent bonds. 

During brewing, trimeric and polymeric proanthocyanidin (polyphenols) easily form insoluble complexes with proteins in the wort as a result of their high affinity for proteins consequently they precipitate out and are removed with the spent grains. However, procyanidin B3 and catechin remain and, when stored, undergo oxidative polymerisation. This increases their affinity for haze-forming protein and they can induce extensive chill haze (Asano et al., 1986). 

Chill haze (or reversible haze), defined by non-covalent bonds between polyphenols and active proteins, can eventually turn into permanent haze that no longer dissolves as the beer warms. 

Asano K, Ohtsu K, Shinagawa K, Hashimoto N (1984) Turbidity formed in beer at low temperatures. Affinity of proanthocyanidins and their oxidation products for hazeforming proteins of beer and the formation of chill haze. Agric Biol Chem 48 1139-1146... 

The addition of 20-30 mg/1 ascorbic acid prevents the formation of colloidal turbidity (called chill haze) in beer, and also prevents adverse changes in flavour due to the oxidation that occurs during pasteurisation and storage. The use of ascorbic acid in winemaking can reduce the amount of sulfur dioxide used for fumigation. 

The earliest practical uses of papain were medicinal, e.g., in the treatment of dyspepsia and intestinal worms (86). Today most of the papain is consumed by various industries. Thus, it is used commercially for tenderizing meat, in the textile industry to prevent wool shrinkage, in the brewing industry to prevent oxidation and chill hazes in beer, in the tanning industry to bate skins and hides, and..in the manufacture of chewing gum. It is difficult to estimate the world consumption however, the United States alone imports about 500,000 pounds of crude papain annually (161). 

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