26 USC 5384 - Amelioration and sweetening limitations for natural fruit and berry wines

(a) In general 
To natural wine made from berries or fruit other than grapes, pure dry sugar or liquid sugar may be added to the juice in the fermenter, or to the wine after fermentation; but only if such wine has not more than 14 percent alcohol by volume after complete fermentation, or after complete fermentation and sweetening, and a total solids content not in excess of 21 percent by weight; and except that the use under this subsection of liquid sugar shall be limited so that the resultant volume will not exceed the volume which could result from the maximum authorized use of pure dry sugar only.
(b) Ameliorated fruit and berry wines 

(1) Any natural fruit or berry wine (other than grape wine) of a winemakers own production may, if not made under subsection (a) of this section, be ameliorated to correct high acid content. Ameliorating material calculations and accounting shall be separate for wines made from each different kind of fruit.
(2) Pure dry sugar or liquid sugar may be used in the production of wines under this subsection for the purpose of correcting natural deficiencies, but not to such an extent as would reduce the natural fixed acid in the corrected juice or wine to five parts per thousand. The quantity of sugar so used shall not exceed the quantity which would have been required to adjust the juice, prior to fermentation, to a total solids content of 25 degrees (Brix). Such sugar shall be added prior to the completion of fermentation of the wine. After such addition of the sugar, the wine or juice shall be treated and accounted for as provided in section 5383 (b), covering the production of high acid grape wines, except that
(A) Natural fixed acid shall be calculated as malic acid for apple wine and as citric acid for other fruit and berry wines, instead of tartaric acid;
(B) Juice adjusted with pure dry sugar or liquid sugar as provided in this paragraph shall be treated in the same manner as original natural juice under the provisions of section 5383 (b); except that if liquid sugar is used, the volume of water contained therein must be deducted from the volume of ameliorating material authorized;
(C) Wines made under this subsection shall have a total solids content of not more than 21 percent by weight, whether or not wine spirits have been added; and
(D) Wines made exclusively from any fruit or berry with a natural fixed acid of 20 parts per thousand or more (before any correction of such fruit or berry) shall be entitled to a volume of ameliorating material not in excess of 60 percent (in lieu of 35 percent).