Independent corroboration that sour mash is a feedback-control practice operating on the next fermentation environment, not a flavor style.
Step five of the production diagram, positioned between cooking and yeast addition.
Broom defines sour mash or backset as acidic spent liquid from distillation that is added to the fermenter to adjust fermentation pH and help control bacterial infection.
p. 19 (PDF sheet 23)
Kentucky & Tennessee Production — Backset/Sour Mash/Setback
Printed p. 19 / PDF sheet 23 visually verified against the user-supplied PDF on 2026-08-25. The book's separate universal-sour-mash statement was not operationalized.
Verified paraphrase from The World Atlas of Whisky, printed p. 19 / PDF sheet 23.
Evidence
Broom describes acidic spent distillation liquid as an input returned to the fermenter to adjust pH and help manage bacterial infection.
Context
The passage is step five of the production diagram. A separate universal-sour-mash sentence was not operationalized.
Annotation
Independent corroboration for the bounded definitional Claim about feedback control.