Exam Focus
- Recognize butter, butterscotch, or slick character associated with vicinal diketones while noting individual sensitivity.
- Evaluate whether the character is permitted, excessive, or inappropriate for the entered style.
- Connect possible yeast reduction, fermentation timing, contamination, or handling causes to conditional advice rather than certainty.
Core knowledge
- Vicinal diketones include diacetyl and 2,3-pentanedione; diacetyl commonly reads as butter, buttered popcorn, butterscotch, or slick mouthfeel.
- Sources include normal yeast metabolism, premature cooling or separation from yeast, insufficient maturation, Pediococcus or other microbes, and draft-line infection.
- Low diacetyl may be acceptable in some British and Czech styles, but it is a fault in many clean lagers and hop-forward beers.
Study application
Identify both sensory descriptor and likely cause, then decide whether the level fits the style.
BJCP Beer Judge Entrance Exam Notes
BJCP judging application
Record vicinal-diketone character by aroma, flavor, and any slick mouthfeel, then compare its intensity with the style guideline. Because similar impressions and multiple production paths exist, a judge should describe the evidence and suggest verification of fermentation completion or sanitation only as applicable possibilities.
Why It Matters
- Treating all diacetyl-like character as equally faulty ignores styles where a low level may be permitted.
- Sensitivity differences make careful panel comparison essential before the attribute drives a large score change.
Practical Sensory Exercises
Judge diacetyl in two contexts
Compare the same low butter-like descriptor against two styles with different permitted character. Write how the style-fit conclusion and advice change even though the sensory observation stays constant.
Key Terms
- Low diacetyl
- Low diacetyl may be acceptable in some British and Czech styles, but it is a fault in many clean lagers and hop-forward beers.