TALK 1: Influence of fermentation compounds from yeast on the quality of hop aroma, hitoshi takemura et al. , kirin
How can two breweries with same hop conditions result in beers of different hop aroma intensities?
Hypothesis 1: Biotransformation of hop oils by yeast?
Hypothesis 2: Do other yeast based compounds (esters) affect the perception of hops?
Testing 1: Results from GCMS does not support, as linalool levels are the same in “lower” beer (linalool is a typical indicator compound of hop aroma).
Testing 2: added esters and higher alcohols to beer (at ppm, and ppb levels, respectively) and tested by expert panel. Esters seemed to have no effect on hop fruity flavor, while higher alcohols (especially 1-pentanol, 1-heptanol) showed a suppression effect on hop fruity flavor. This supports hypothesis 2. Next, fermentation temperature (17, 21oC) and yeast pitching levels were tested. Again, put in front of small trained panel: temperature had a larger effect (higher temp leads to lower hop fruity flavor), and pitching rate had a less robust effect (higher pitching rate showed lower hop fruity character). Questions from audience: does aeration affect? Didnt test. Did you propagate yeast from same source? Yes. Were the spiked samples representative of normal beers for higher alcohol content? Yes (eg. 10-20ppb heptanol).
TALK 2: Aroma and Harvest maturity of hops, Daniel Sharp, OSU grad student
How does harvest time affect aroma chemistry, with Cascade and Willamette hops in particular? (hop oil in hops, not beer).
Hops from two farms, 2 years (2010, 2011), 3 harvest dates (early, trad., late). In triplicate. Extraction via ASBC steam distillation method, detected by HPLC and GC-FID. Harvest timeline: difficult to time the harvesting as “traditional” harvest time is usually a guessing game. Yearly climate differences also uncontrollable. Sample-sample variation between hop collection was large (three collections from whole hop field for each farm/variety).
Hop Storage Index: Very little difference due to harvest time.
Alpha acids: drop in the cascades at late harvest.
Cascade: (i cant keep up, moving too fast!).
Willamette: most terpenes increased over whole study, even into late harvest.
Sensory: only on cascade, difference test. Difference noted, so consumer acceptance test was performed. Trad harvest were preferred. Descriptive: late had more onion and garlic
Essential oil increases past harvest date for willamette, cascade stays constant or drops a bit.
?s: Bob Foster: Did you control kilning temps? Yes, 120F. Practical considerations for farmers? Need to nail down good useful predictor. Pellets vs whole? Used Whole. Did you look at dry matter content with harvest dates? No patterns, all over the place. Glycosides? No, Shellhammer will speak to that.
TALK 3: Patricia Aron, MillerCoors (and OSU)
Phenolic profiling of lager beers during aging in relation to hopping technology.
Some background on hop polyphenols, beer stability.
Hypothesis: hopping regime affects the phenolic profile over aging …(ack, too fast!). Focussing of flavonoids.
Method: 12p base wort, lager, Chelan hops. Accelerated aging (6 weeks). Hop treatments: control- no iso’s and no hop polyphenols; pellet- iso’s and hop polyphenols; spent- no iso’s with hop polyphenols; extract-alpha acids only.
Many analysis methods, broad and specific. Chock-a-block with chemistry, but it’s too fast too keep up with here. Increase in total polyphenols in aging, then a drop off as it ages further. More specific analysis of flavanoids/proanthocyanidins: spent hop beers were the highest (expected, due to the nature of the spent hop product). Spent hop beer saw the lowest increase of aldehydes over aging of the treatment beers. Methional (potato!) was the dominant aldehyde found in aging. no significantly different in trans-2-nonenal. Kettle hopping (pellets) did not augment proanthocyanidin content in beers. Hopping regime did not affect loss of iso-alpha acid content over aging. Brewing with hop products did not affect the antioxidant potential of beers by ESR (odd).
?s: what is the standard or definition for “spent hops”? There isn’t. Are you confident in your analysis of proanthocyanidins? Difficult, some material is not susceptible to acid cleavage. Does freezing/thawing have an effect? Dunno, but maybe.
TALK 4: Contributions to hop aroma from the water-soluble fraction of hops. Tom Shellhammer, Oregon State
Used spent hop material (after supercritical CO2 extraction) in lager beer, analyzed with sensory and instrumental. Simcoe, Centennial, Citra, Cascade. Very low level of residual alpha acids (highest was 0.5%, ~98% of the alphas were removed in extraction). Also very very low in residual hop oils. 1g/L hop addition, 5min into 60min boil.
3 finished beers: One with pellets (normal), one with hop extract (like Miller), one with spent hop material (water soluble materials). BU range: 18-37 (pellets), 12-15 (spent). Alcohol, 4% by weight. Spent hop beer showed surprising amount of linalool (order of magnitude). Principal Component Analysis showed spent and pellet beers in their own clusters, with the extract varieties separating out from each other.
Sensory: Spent hop beer aroma showed lower hop aroma intensity, as anticipated.
Summary: evidence that spent hop beers produce aromas that are noticeable and significant, and dependent on variety (particularly Simcoe).
?s: how was sensory performed on finished beers? Randomized, 5 reps minimum, difficult to control temperature due to randomization. Does the flavor result in a desire to brew with spent hop products? Didn’t look at preference or hedonics, but unofficial tastings showed surprising acceptance.
Please excuse any typos or shorthand, it’s late and my BAC is approx 0.2%, and I don’t have the energy to proofread.