Production of hop bitter acids and related compounds (LFA3092)
Project nummer:
lfa3092
Omschrijving van het onderzoek
For studies of the quality of beer and for the quality control the
availability of hop bitter acids and other related compounds is required.
Presently none of these compounds is (commercially) available. The present
project deals with different approaches to produce these compounds on
small (laboratory) scale. One approach is to develop a centrifugal
countercurrent chromatography method to isolate the alpha- and
bèta-acids from hop extracts and iso-alpha-acids (cis and trans
isomers) from converted alpha-acids. Another approach will be to use a
combination of synthesis and in-vivo (plant cell cultures) and/or in-vitro
(isolated enzymes) bioconversions to obtain the naturally occurring
alpha- and bèta-acids as well as a series of closely related
compounds useful in determining the structure-activity relationship of
these compounds for taste and foaming of beer.
These studies are
based on the results of an Eureka-feasibility project executed in the
past year, and will be performed in close collaboration with the brewing
industry.
Resultaten van het onderzoek
Hops of hop extracts are used for the preparation of beer. Hop acids consist
of alpha-acids and beta-acids; beta-acids are less water
soluble than alpha-acids, precipitate during brewing and therefore
less important for beer taste. During brewing, alpha-acids are
converted into iso-alpha-acids which are the bittering compounds in beer.
Analysis of hop quality is hampered by the fact that standards for hop
acids are not available. Objectives of this project is to obtain pure
hop acids on a preparative scale (0.1-1 g) by using two different approaches.
First, centrifugal partitioning chromatography (CPC), agentle method to
isolate natural products, is tested for its suitability to purify the
labile hop acids. Secondly, a combination of synthesis and biosynthesis
is studied as a way to generate hop acids in vitro.
By means of CPC, the isolation of hop acids on a preparative scale has
now become feasible. This study also shows that methanolic solutions of
hop acids are stable when stored at los temperatures (<4°C). Using
NMR it is possible to quantify the absolute amount of the isolated hop
alpha-acid humolone.
The studies in the second approach show that three groups of enzymes are
involved in the biosynthesis of hop acids. A new enzyme catalysing the
formation of acylphloroglucinol intermediates has been purified.
Arylprenyltransferases, a group of enzymes catalysing the second
type of reactions in the biosynthesis, have been detected in hop protein
extracts. Thirdly, it was shown that an oxidation, catalysed by an unknown
enzyme, led to the formation of alpha-acids.
As a result of this project, the division of Pharmacognosy in Leiden is now able to
provide hop acid solutions upon request. Please contact prof. dr. R. Verpoorte
for more information: tel. +31 71 5274528, fax: +31 71 5274511,
e-mail: VERPOORT@LACDR.LeidenUniv.NL
Gebruikers
Twee bedrijven en twee non-profit organisaties.
Projectleider
Prof.dr. R. Verpoorte
Universiteit Leiden
Centrum for Bio-Farmaceutische Wetenschappen
Gorlaeus Laboratoria
Postbus 9502
2300 RA LEIDEN.
Status van het project
| Gestart | : 15/05/1994
|
| Einddatum | : 22/11/1997
|
Trefwoorden
biosynthese, biotechnologie, chemie, levensmiddelentechnologie, bier,
hopbitterzuur.
.
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