27 CFR § 19.719 - Spirits made unfit for beverage use in the production process.
If an alcohol fuel plant makes spirits unfit for beverage use before the spirits are removed from the production process, for example by the in-line addition of materials or by the addition of materials to receptacles where spirits are first deposited, the proprietor must determine the quantity and proof of the spirits produced for purposes of the production records by:
(a) Determining the proof of each lot of spirits by procuring a representative sample of each lot, prior to the addition of any materials for rendering the spirits unfit for beverage use, and then proofing the spirits; and
(b) Determining the quantity (proof gallons) of spirits produced by subtracting the quantity of materials added to render the spirits unfit for beverage use from the quantity of fuel alcohol (in gallons) produced and multiplying the resulting figure by the proof of the spirits divided by 100.