Wort Nitrogen and Yeast Strain Drive Thiol Release, Flavor Expression, and Fermentation Performance in Beer
Bibliographic record
Abstract
Polyfunctional thiols (PFTs) contribute potent tropical and fruity aromas to beer at ng/L levels, but their release from cysteinylated and glutathionylated precursors depends on yeast activity and fermentation conditions. This study examined the effects of yeast strain and wort free amino nitrogen (FAN) on thiol biotransformation, fermentation performance, and sensory expression using beers brewed at pilot scale with Cascade hops across three FAN levels (110, 240, 360 mg/L) and five yeast strains, including an IRC7-knockout strain. Low wort FAN significantly enhanced thiol release (up to 3× more 3SH and 4MSP), yet wort prepared with medium or high FAN resulted in greater tropical aroma intensity and was associated with elevated esters. Sensory profiles varied with FAN and yeast strain, revealing off-flavors (diacetyl & sulfur/egg) at FAN extremes. The IRC7-knockout strain surprisingly maintained thiol production similar to its parent, suggesting alternative enzymatic pathways for thiol release. These findings highlight FAN’s role in modulating volatile profiles and fermentation kinetics, offering practical strategies to optimize hop aroma and flavor balance in beer.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".