Natural Foam Stabilizing and Bittering Compounds Derived from Hops (1). Robert J. Smith (2) and Darwin Davidson, S. S. Steiner, Inc., P.O. Box 9009, Yakima, WA 98909; and Richard J. H. Wilson, Steiner Hops Limited, 319A High Street, Epping, Essex CM16 4DA, England. (1) Presented at the 63rd Annual ASBC Meeting, Palm Springs, CA, June 1997. (2) Corresponding author. Phone: (509) 574-0220; Fax: (509) 457-4638. J. Am. Soc. Brew. Chem. 56(2):52-57, 1998. Accepted January 20, 1998.

Various naturally occurring hop resin acids have been isolated by preparative HPLC from hops and hop products. Two resin acids have been tentatively identified by nuclear magnetic resonance techniques to be the minor constituent alpha-acids, adprehumulone and prehumulone. The isomerized derivative of the former considerably improved the foam stability and lacing of a commercial brand of beer. Dihydro-alpha-acids have previously been shown to occur and form in hops and hop products. Two of the dihydroiso-alpha-acids have been isolated by preparative HPLC, and dihydroisohumulone has also been shown to substantially improve foam stability and lacing of various brands of commercial beer as compared with the iso-alpha-acids. Keywords: Foam lacing, Foam stability, Hop acids, Reduced alpha-acids.