Monoclonal antibody probe for assessing beer foam stabilizing proteins.

Abstract

A monoclonal antibody (Mab; IFRN 1625) has been produced, which is specific for the most hydrophobic polypeptides responsible for foam stabilization. The binding characteristics of the Mab suggest that it is the conformation of certain hydrophobic polypeptides which is important for foam stabilization. An enzyme-linked immunosorbent assay (ELISA) for assessing the foam-positive form of the foam-stabilizing polypeptides in beer was developed using IFRN 1625. A good correlation was obtained between ELISA determination of foam-stabilizing polypeptides and an empirical means of determining foaming, that is, the Rudin head retention values, for a collection of beers of various foam qualities. Application of the ELISA to different stages of the brewing process showed that the amounts of foam-positive polypeptides increased during barley germination. During the brewing process the proportion of foam-positive polypeptides present after fermentation increased slightly, although a large amount was lost along with other beer proteins during subsequent steps, such as filtering. The present study demonstrates that the amounts of beer polypeptide present in a foam-positive form have a direct relationship with the foaming potential of beer, that their levels are altered by processing, and that there is potential for greater quality control.