Introduction
The presence of cloudiness or haze in beer is one of the more obvious quality defects discernable to the consumer. In addition, ever increasing demands are being placed on product quality with pressure to maximize output, expanding market areas and requirements for “use by date” labeling.

The most frequent cause of haze in packaged beer is due to complex formation between proteins and condensed polyphenols (tannins). It is common practice for brewers to employ beer stabilizer treatments to remove one or both of these principal haze constituents. In order to eliminate proteinaceous material that impacts on haze, beers are treated in one of the following ways: protein may be degraded (chillproofing enzyme), precipitated by addition of polyphenols (tannic acid) or adsorbed by silica gels. The effectiveness of these reagents is dependent on their capacity to specifically target the “haze sensitive” protein fraction of beer with minimal negative effects on the protein fraction involved in beer foam quality.

The precise protein fraction removed by these treatments is not clearly defined due to the analytical difficulties involved in characterization of beer proteins. This is because the original barley proteins are chemically modified and subject to proteolysis during processing resulting in a complex mixture of polypeptide fragments in beer.

When malt beers are fractionated by electrophoresis (SDS polyacrylamide gel electrophoresis) and stained with Coomassie blue reagent, polypeptides contained within high molecular weight, (Mr 40,000) and low molecular weight (Mr 5,000- 15,000) regions are seen. Two major beer polypeptides that are present within these molecular weight fractions have been characterized. These are barley ?C derived protein Z (Mr 40,000) (Kaersgaard and Hejgaard, 1979) and Lipid Transfer Protein (LTP, Mr 10,000) (Sorensen et al. 1993). Recently, quantitative ELISAs developed against protein Z and LTP were described (Evans and Hejgaard, 1999) and used to evaluate the impact of these proteins on beer foam quality (Evans et al. 1999).

Previously we characterized beer samples using two groups of hordein reactive antibodies (Sheehan and Skerritt, 1997) group 1 cross ?C reactive with subunits from B/D aggregates and group 2 cross ?C reactive with B/C monomers. By this approach it was seen that malt beers contained a number of hordein ?C derived fragments. The beer samples contained polypeptides of molecular weight >50,000 which primarily reacted with group 1 antibodies while the second group of antibodies recognized beer polypeptides of 30,000 or lower molecular weight.

The aim of the present study was to investigate the impact of haze stabilizer treatments on beer protein content by employing the specific protein measurements described above.

(from:regional.org.au)