Isolation and Characterization of Foaming Proteins of Beer¹

1 Presented at the 46th Annual Meeting, Minneapolis, MN, May 1980.

Abstract

“Foaming proteins” that retained the full foaming capacity of the original beer were isolated by ultrafiltration followed by ammonium sulfate precipitation and ion-exchange chromatography on diethylaminoethylcellulose. Because the content of foaming proteins correlated well with head formation of many samples of beer, these foaming proteins seem to be responsible for beer foaming. Foaming proteins consisted of three fractions with molecular weights of 90,000–1,000,000, 40,000, and 15,000. These three fractions were all surface-active but differed in the mechanism of their contribution to foaming. The higher and medium molecular weight fractions combined with isohumulones through ε-amino groups to form more surface-active complexes and thereby enhanced foaming. The lower molecular weight fraction did not form these complexes appreciably, probably because of its low content of ε-amino groups. Immunological studies showed that foaming proteins were formed primarily during germination of barley. The level of foaming proteins decreased considerably during brewing, particularly during kettle boiling; 160–620 mg/L of foaming proteins survived in finished beer.

• Beer
• Brewing process
• Foam
• Isolation
• Malting
• Protein