27 C.F.R. § 24.305
A proprietor who sweetens natural wine with sugar or juice (unconcentrated or concentrated) under the provisions of this part shall maintain a record of sweetening by transaction date. The record will contain the following:
(e) The gallons and degrees Brix of the wine produced by sweetening.
(Sec. 201, Pub. L. 85-859, 72 Stat. 1381, as amended (26 U.S.C. 5367))
(Approved by the Office of Management and Budget under control number 1512-0298)