Recent developments in silica hydrogels for the treatment and processing of beers.

Hough, J.S. and Lovell, A.L.

Abstract
Silicas having a range of structures can be prepared in either hydrogel or xerogel form. For beer chillproofing, the optimum combination of high surface area coupled with appropriate pore size (30 to 120 Angstroms) is achieved most readily in a silica hydrogel. The particle size distribution of the stabilising material can significantly influence beer filtration and should not contain more than 5% below 5 micron. Under such conditions excellent filterability is achieved. Hydrogels of various particle sizes with equivalent filtration characteristics to commercially available kieselguhr filter aids, can also be made. Adsorption of haze precursors on silicas is not an instantaneous process, but is controlled by the diffusion of such precursors into the silica particles. A contact time of about 5 min is sufficient for most purposes (at a normal silica concentration of approx 1000 ppm) although it may be less than this where accumulation of silicas on a filter provides a compensating high ratio of chillproofing agent to beer. The materials removed from beer by treatment with silica hydrogel are polypeptides with isoelectric points in the pH range from 3.0 to 5.0. In addition these polypeptides contain conjugated carbohydrates and polyphenols and there is some evidence to suggest that a greater amount of polyphenolic material is associated with the adsorbed polypeptides than with those normally available in beer.
Keywords: beer chillproofing silica gel stabilisation