27 C.F.R. § 24.192
In preparing still wine or still hard cider for the production of effervescent wine, sugar and acid of the kinds and within the limitations prescribed in §24.182 may be added with yeast or yeast culture to acclimate the yeast and to facilitate the process of secondary fermentation or to correct the wine. Fruit syrup, sugar, wine, wine spirits, and acid may be used in preparing a finishing dosage for effervescent wine provided the dosage does not exceed 10 percent by volume of the finished product. Where the proprietor desires to use more than 10 percent by volume finishing dosage, the proprietor shall file for a formula approval under §24.80. The fruit syrup, wine spirits and wine used will come from the same kind of fruit as the wine from which the effervescent wine is made. In the production of effervescent wine, taxpaid wine spirits or wine spirits withdrawn tax-free may be used. Tax-free wine spirits may only be used in the production of effervescent wine that is a natural wine. In the refermentation and finishing of a sparkling wine or sparkling hard cider, the acids and materials specifically authorized in §24.246 may be used.
27 C.F.R. §24.192
Sec. 201, Pub. L. 85-859, 72 Stat. 1383, as amended (26 U.S.C. 5382 )
Approved by the Office of Management and Budget under control number 1512-0059