Recycle a measured portion of acidic stillage or backset into a new mash to help control pH and stabilize fermentation conditions while preserving yeast selection and other flavor-active variables as separate decisions.
Sour mash is a fermentation-control loop, not a sour-tasting whiskey style.
Process definition
Recycle a measured portion of acidic stillage or backset from a prior distillation into the next mash to help condition acidity and stabilize fermentation conditions while keeping yeast, nutrients, temperature, timing, and other flavor-active variables explicit.
Inputs
Fresh grain and water, cook and conversion plan, measured backset, yeast or starter, nutrient plan, and target fermentation range.
Sequence
- Characterize the fresh mash and the available backset.
- Add a recorded proportion at the intended stage.
- Measure the resulting acidity or pH rather than relying on the name of the process.
- Inoculate and manage fermentation under the house yeast, nutrient, temperature, and time plan.
- Record fermentation behavior, contamination indicators, yield, and sensory consequences.
- Preserve lot-to-lot backset and fermentation records.
Governing variables
Backset composition, proportion, timing, grain bill, water chemistry, conversion, yeast strain, nutrients, temperature, vessel, sanitation, fermentation time, and distillation handoff.
Evidence
Risen and Cowdery establish the bounded American definition; Hannush supplies historical Tennessee cases. SRC-107, chapter 3, printed pp. 70–71 / PDF sheets 95–96, independently describes acidic spent mash as fermentation-environment control.
Evidence boundary
SRC-107's exact minimum proportion and favorable flavor claim are secondary-review assertions and are not promoted as universal American-whiskey rules.
Review gate
Hannush Source Audit — 28 September 2026
Hannush PDF118–119 and225–227 describe historical practices and meanings. Fermented-mash transfer and modern acidic stillage/backset are not interchangeable accounts.
The supplied capture lacks endnotes, bibliography and index, and has confirmed interior gaps. All available457 sheets were read; this is not full-source completion. Fresh source review and limitations
