Simple Methods for Determination of the Molecular Weight Distribution of Beer Proteins and Their Application to Foam and Haze Studies¹

Abstract

Degassed beer was directly applied to either a Bio-Gel P-100 or Sephacryl S-200 column, and beer proteins eluted from the column were assayed by the Bradford method either manually or automatically. Beer proteins were separated into two major fractions, I and II, with molecular weight values at the apex of about 4 × 10⁴ and 2 × 10⁴, respectively. Both fractions contributed to the foam and colloidal stabilities of beer; fraction I correlated more highly with the former and fraction Il more highly with the latter. The haze-stabilizing mechanism of silica gel was investigated with the aid of an automatic method. Beer was treated at a dosage of 400 mg (dry basis) per liter with seven kinds of silica gels, which removed polyphenols as well as proteins from beer. The amounts of proteins adsorbed were very small, so the foam stabilities were only slightly affected. The accelerated chill-haze test values of treated beers correlated well with the amounts of polyphenols removed. These results suggest that beer is haze-stabilized with silica gel by the combined reduction of polyphenols and proteins. These methods are also available for foam studies, and an example of their application is described.

• Foam
• Gel chromatography
• Haze
• Protein
• Silica gel
• Wet milling