A study on the properties of silica gel as a filter aid for beer.

Matsuzawa, K., Takahashi, S., Nagashima, Y., Itoh, M. and Yamauchi, K.

Abstract
The properties of "VH" hydrosilica gel, developed as a stabilizing additive for use in beer filtration, were studied in connection with its potential use as a filter aid in its own right. Observation of VH gel particles by scanning electron microscopy revealed a fairly uniform rounded polygonal shape, differing considerably from kieselguhr with its wide variety of honeycombs, rods, needles and other particle shapes. This suggests that it would be difficult to form a stable filter cake from VH gel alone, but blending it with kieselguhr should remedy that defect. Its particle size range and distribution, as well as its filterability, are similar to those of fine kieselguhr, but when mixed with kieselguhr the blend's filtration speed was lower than the average of those of the two products used separately. VH gel was found to form a much denser filter cake than other filter aids. Although it precipitates very slowly when dispersed in water, the actual dispersal is quite rapid. It dissolves readily in hot caustic solutions (2 to 5% sodium hydroxide), ensuring the complete removal of gel residues from filtration equipment during CIP. VH gel is structurally stable and does not support microorganisms, allowing it to be stored for long periods without special precautions (unlike other forms of silica gel), while its high degree of purity (99.8% silicon dioxide) practically rules out the possibility of chemical contamination of the beer (e.g. with metallic ions or salts).
Keywords : filter aid properties silica gel