Experimental
Protein
Total high molecular protein was measured using Coomassie Plus reagent- and bovine serum albumin (BSA) standard. ELISA (enzyme linked immunosorbent assays) were carried out as previously described and antibody binding to extracts was monitored by absorbance at 414nm.

Stabilizer Treatments
A small ?C scale study was carried out where maturation beer (16P) was diluted with deaerated water (10P) and centrifuged at 10,000 rpm for 15 minutes. Stabilizer additions were made to samples (500ml) at the following rates; tannic acid (50ppm), silica hydrogel ( Lucilite PC9, 600ppm) and chillproofing enzyme (Profix, 6ppm). All samples were incubated on ice for one hour and then pasteurized to 15 PU.

For Pilot scale studies, maturation beer (10L, 10P) was treated with silica gel at a range of concentrations (0,100,300,600,1200 mg/l) and filtered through a plate and frame filter with filter sheets (Cuno) containing diatomaceous earth.

Results and Discussion
Impact of stabilizer treatments on beer protein content
A small ?C scale study was carried out in order to evaluate the impact of beer haze stabilizers on protein contents. Total beer protein (Bradford method) showed minor decreases (5% ?C 13%) following stabilizer treatments Table 1.

Table 1. Total Protein Contents of Beer (mg/l) after Stabilizer treatments

In a similar way, the profiles of beer proteins separated by electrophoresis were not significantly changed following stabilizer treatments. The two major molecular weight regions (detectable after Coomassie blue staining) at (1) Mr 40,000 and (2) Mr 5000 - 15,000 were at similar levels for each of the samples (data not shown). This result is in agreement with previous studies where it was seen that a small loss of total protein following stabilizer treatment is sufficient to ensure good colloidal stability of the resulting beer.

In order to carry out a more specific assessment of the impact of stabilizers on beer protein content immunological methods (ELISA) were employed using antibodies cross- reactive with barley B/C monomers, D/B aggregate subunits, protein Z (Mr 40,000) and LTP (Mr 10,000). For the three stabilisers investigated it was apparent that decreases in ELISA absorbances were significantly greater for hordein reactive fragments than for the other beer proteins measured (Protein Z, and Lipid Transfer Protein) Fig.1. In the case of beer polypeptides cross ?Creactive with hordein specific antibodies (monomeric B/C) the greatest decreases occurred with silica gel 67%, followed by tannic acid 58% and chillproofing enzyme 43%. Significant decreases were also seen for the polypeptide fraction reactive with the second hordein antibody type (D/B aggregate subunits), silica gel 42%, chillproofing enzyme 57% and tannic acid treated beer 37%. Decreases for other specific protein fractions were far lower in the range 3% to 6% for protein Z and 4% to 16% for Lipid transfer Protein.

Influence of Stabilizer Concentration on Beer Protein Content
The relationship between stabilizer dose rates (silica hydrogel, 0, 100, 300, 600, and 1200 mg/l) and protein contents of maturation beer was studied in a pilot- scale filtration trial. At low silica concentration hordein ELISA absorbances declined essentially in proportion to the amount of silica added and reached saturation at approximately 600mg/l silica. Decreases in total protein and other specific beer proteins (Protein Z and Lipid Transfer Protein) were far less even at higher silica concentrations (600- 1200 mg/l).

Further evidence for the high specificity of the stabilizer for hordein - derived beer polypeptides was seen from amino acid composition data of the silica adsorbed fraction (eluted with 2% ammonium hydroxide solution). This fraction contained a high proportion of proline (33.2 mole %) and glutamate/glutamine (32.7 mole %) consistent with the presence of hordein repeat sequences

(from:regional.org.au)