IMMUNOLOGICAL CHARACTERIZATION OF BARLEY POLYPEPTIDES IN LAGER FOAM

Eight monoclonal antibodies (mAb) recognising barley polypeptides have been identified from a library developed to wheat prolamins. The spec ificity of the mAb has been determined using enzyme-linked immunosorbe nt assay (ELISA) and immunoblotting. Six were of broad specificity, re cognising D, B, C and gamma-hordeins to varying degrees by both techni ques. IFRN 0610 preferentially recognised gamma-hordeins by ELISA but was highly specific for this hordein group by immunoblotting. Another mAb, IFRN 0624, bound to a M(r) similar or equal to 18 000 polypeptide belonging to the CM protein (trypsin/alpha-amylase inhibitor) family by immunoblotting. This, or a related protein, was detected by 0624 in all hordein fractions using ELISA. These mAb, together with two other s described previously and found to recognise the repeat motif of C ho rdein, were used in ELISA and immunoblot analysis of Octyl-Sepharose f ractions of lager foam. Hordein polypeptides were found in all foam fr actions, indicating that much foam protein originates from the malt. T he CM-like protein was found present in a virtually unmodified form. I n contrast, the repeat motif of C hordein was not detected, indicating that it had either been destroyed or masked by other beer constituent s. The foam stabilising agent, propylene glycol alginate (PGA), increa sed the apparent hydrophobicity of hordein fragments suggesting that a t least part of the activity of PGA is mediated by interactions with t he hordein components of foam.