Program Book - Master Brewers Association of the Americas

P-151
Citra—A new special aroma hop variety
GENE PROBASCO (1), Jason Perrault (1), Scott Varnum (1)
(1) Hop Breeding Company, Yakima, WA
Citra was selected to become a new hop variety because of a special
flavor and aroma that it imparts to beer that is hopped using the
variety. Depending on the brewing process and the hopping rate,
the flavors and aromas of beer hopped with Citra can range from
grapefruit to lime, melon, gooseberry, and lychee fruit. The variety
Citra originated from a cross between the female European noble
aroma variety Hallertauer mittelfrueh and a male that was derived
from the variety known as U.S. Tettnanger. Citra is 50% Hallertauer
mittelfrueh, 25% U.S. Tettnanger and the remaining 25% is East
Kent Golding, Bavarian, Brewers Gold and unknown. The α-acids
content of Citra ranges between 10% and 12%, the β-acids content
is between 3.0% and 4.0% and the cohumulone content is between
22% and 24%. The oil content ranges between 2.0% and 3.0%. Citra
produces solid yellow-green hop cones that mature during the first
week of September. Production acreage for Citra is expanding.
Gene Probasco received an undergraduate degree in biology and a
M.S. degree in plant pathology from Washington State University.
After graduation he spent six years in hop research at Washington
State University, where he conducted research on hop breeding and
diseases of hops. After joining John I. Haas, Inc., he started the
first private hop-breeding program in the United States and has
released numerous new hop varieties to the hop industry, several of
which constitute major varieties. In addition to hop breeding he has
conducted agronomic research for the U.S. hop industry. For the past
15 years he has been a vice president for John I. Haas, Inc. and had
additional responsibility for hop production on company hop farms.
For many years he has represented his company as a member of the
Hop Research Council and has in the past served the council as chair
of the Budget Committee, vice president, and president.
140
P-152
Thermal isomerization of cohumulone
PATRICK TING (1), Susan Kay (1), David Ryder (1)
(1) Miller Brewing Company, Milwaukee, WI
Thermal isomerization is a key step in converting α-acids into isoα-acids
during the kettle boiling process. In an effort to understand
the nature of this reaction and to produce the products more
efficiently, we studied this thermal isomerization of α-acids under
more closely controlled conditions in the absence of acid, base,
metal ion catalyst, oxygen, and light. Cohumulone was synthesized
and thermally isomerized in a non-aqueous solution under dark and
nitrogen environments. It was found that mainly cis-isocohumulone
was produced by a non-concerted reaction, but very inefficiently.
The stereochemical assignment of cis- and tran-isocohumulone was
re-investigated using C-13 NMR.
Patrick Ting, principal hop scientist, received his M.S. degree in
bioanalytical chemistry and Ph.D. degree in organic chemistry. From
1976 to 1977 he worked as a post-doctoral fellow at Southwestern
Medical School, University of Texas, on the oxidation reaction
in the biological system employing spin-trap ESR and HPLC. In
1978 he joined Miller Brewing Company, since then he has been
working on hops, hop flavor, and hop chemistry research and has
published several papers and patents. Patrick is an active member
of the ASBC and American Chemical Society and participates on the
International Subcommittee for Isomerized Hop α-Acids.