Hard resins: New insights into a long-known hop fraction. Martin Biendl

Transcription

1 Hard resins: New insights into a long-known hop fraction Martin Biendl

2 Woellmer hop fractionation (invented 1916) soluble in methanol: total resins soluble in hexane: soft resins approx. 90 % (w/w) alpha-acids beta-acids? insoluble in hexane: hard resins approx. 10 % (w/w) xanthohumol????

3 Recent publication on hard resin components hard resin have a positive impact on taste and bitterness J. Am. Soc. Brew. Chem. 2015, 73,

4 Recent publication on hard resin components J. Agric. Food Chem. 2015, 63,

5 Investigations of Dresel et al.* sensory evaluation of the total hard resin fraction isolation of all the flavour active components (> 40!) identification of their chemical structures characterization of their sensory profiles (receptor tests) determination of their human threshold concentrations recombination experiments to verify their taste contributions quantification in different hop varieties, products and beers * J. Agric. Food Chem. 2015, 63,

6 Components of the hard resin fraction (Dresel, 2015) component (bitter) taste threshold (mg/l) concentration in a beer / example (mg/l) xanthohumol 3.5 < 0.1 isoxanthohumol 5.6 X desmethylxanthohumol 5.4 < prenylnaringenin prenylnaringenin xanthohumol B 9.2 < 0.1 xanthohumol C 2.1 < 0.1 dihydro-xanthohumol C dihydro-isoxanthohumol C 2.1 < additional taste active prenylflavonoids were identified

7 Xanthohumol and other prenylflavonoids xanthohumol B xanthohumol C xanthohumol (A) discovered: 1913 correct structure: 1961 xanthohumol D xanthohumol E

8 Wort boiling: Isomerisation xanthohumol isoxanthohumol O H O H O O H O O O C H 3 O O C H 3 O dihydro-xanthohumol C dihydro-isoxanthohumol C

9 Other hard resin single components (Dresel, 2015) component (bitter) taste threshold (mg/l) concentration in a beer / example (mg/l) coumaric-acid 3.6 < 0.1 coumaric-acid ester 35 < 0.1 n-trans-feruloyltyramine glycosidically bound polyphenols: quercetin-glucoside kaempferol-glucoside kaempferol-malonyl-glucoside co-multifidol-glucoside 1.8 X ad-multifidol-glucoside especially co-multifidol-glucoside seems to be relevant for bitter taste

10 Multifidol-glucosides HO OH HO HO OH O OH O O R R= CH 2 CH(CH 3 ) 2 n- CH(CH 3 ) 2 co- CH(CH 3 )CH 2 CH 3 ad- discovery in hops and structure identification: Bohr et al., 2005 O O R OH OH alpha-acids OH multifidol-glucosides are intermediate products of the alpha-acids biosynthesis

11 Conclusions from the paper of Dresel et al. abstract: Trial brews with hard and soft resins demonstrated that the bitter taste, in particular the bitter quality of a finished beer is positively influenced by hard resin. additive contribution of iso-alpha-acids and the identified hard resin components to be truly necessary and sufficient for constructing the authentic bitter percept of beer therefore, hop products containing hard resins are preferable (i.e. pellets, ethanol-extract)

12 Hard resin components in hop products (Dresel, 2015) component pellet ethanolextract carbon dioxide extract xanthohumol other prenylflavonoids multifidol-glucosides other glycoside bound polyphenols some components are only partially transferred to ethanol-extract

13 Questions for consideration is ethanol-extract an equivalent replacement for pellets? direct comparison of both hop products in brewing trials are there any (potential) negative aspects of hard resins? brewing trial with a hop extract strongly enriched in hard resins

14 Our investigations: trial design production of beers with different hop products 6 hl scale (at Chair Prof. Becker, TU Munich-Weihenstephan) one single hop addition at start of boil (60min) goal: 20 ppm iso-alpha-acids (lager beer) each hop product was tested in duplicate special analysis using LC-MS/MS sensory: two trained panels (TU and Hopsteiner)

15 Production of a hard resin enriched extract ethanol-extract secondary extraction with supercritical CO 2 CO 2 -extract: total soft resins alpha- and beta-acids further (unspecified) components essential oil extraction residue: total hard resins prenylflavonoids glycosides residual (iso-)alpha

16 Composition of the hop products* all products from the variety Hall. Taurus, crop 2013 % pellet type 90 P90 ethanol-extract EX hard resin extract EXH iso-alpha-acids alpha-acids cohumulone (% rel.) beta-acids xanthohumol total resins X hard resins (% rel.) total oil (ml/100 g) * according to (modified) methods of Analytica-EBC

17 Dosage of the hop products per hl, at begin of wort boiling trial nr. product g g alpha g hard resins g xanthohumol 1 P P EX EX X 9 5 EXH EXH exceptionally high hard resin dosage with hard resin extract!

18 Results of beer analysis* -1- bitter compounds (HPLC-UV) trial / product bitter units iso-alpha (mg/l) alpha (mg/l) 1 P P EX EX EXH EXH very consistent iso-alpha concentrations: solid basis for sensory analysis * according to methods of Analytica-EBC

19 Analysis methods for primary compounds of the hop hard resin fraction xanthohumol / isoxanthohumol analysis by HPLC-UV (Hopsteiner in-house method) co-multifidol-glucoside, quercetin- and kaempferol-glucoside analysis by LC-MS/MS (Hopsteiner in-house method)

20 Results of beer analysis -2- single components from hard resin fraction (mg/l) trial / product xanthohumol isoxanthohumol co-multifidol-glucoside 1 P90 < P90 < EX < EX < X 7 5 EXH X 7 6 EXH verification: successful transfer of single components from hard resins

21 Results of beer analysis -3- single components from hard resin fraction (mg/l) trial / product co-multifidolglucoside quercetinglucoside kaempferolglucoside 1 P P X 2 X > 3 3 EX 0.3 < 0.1 < EX 0.3 < 0.1 < EXH EXH verification: low concentrations of quercetin/kaempferol-glucosides via EX

22 Tasting results

23 Duo-Trio Test Mebak Methods of Sensory Analysis, 2014

24 Duo-Trio Test This method can be employed to reveal slight differences between two samples One (uncoded) sample is first placed, afterwards two coded samples are given to the tasting panel, one of which is identical to the uncoded sample The tasting panel (preferable 20 or more members) is then asked which of the two samples is different from the first one

25 Duo-Trio-Test* with fresh beers beer A (P90) distinguishable from beer B (EX)? fresh beers Hopsteiner / Technical University: 22 panelists correct assignment 15 panelists significant difference* no preference: A / B / none 6 / 9 / 0 * MEBAK Methods of Sensory Analysis, 2014

26 Duo-Trio-Test* with fresh beers beer A (EX) distinguishable from beer B (EXH)? fresh beers Hopsteiner / Technical University: 22 panelists correct assignment 15 panelists significant difference* no preference: A / B / none 8 / 4 / 3 * MEBAK Methods of Sensory Analysis, 2014

27 Ranking DLG* Tasting Panel at Technical University ,2 4,3 4,4 4,1 4,2 4, pellet type 90 ethanol-extract hard resin extract fresh 6 months 5 C * DLG = Deutsche Landwirtschaftsgesellschaft

28 Conclusions of our investigations is ethanol-extract an equivalent replacement for pellets? yes are there any negative aspects of hard resins? no ethanol pure resin extract = total resin extract to emphasize that all components of the soft and hard resin fraction are transferred into the brewing process which can make a contribution to the total bitterness of beer

29 Last but not least components from hard resin fraction improve the positive image of beer