A mass balance approach was used quantify select polyphenols in pre- and post-fermentation products resulting from the fermentation of Vitis vinifera cv. Grenache noir and Airén. For Grenache noir, the overall mass recovery was 102.7%. The main products were wine (78.3%), pomace (8.5%), lees (4.2%), and rachises (3.4%). Pomace was a rich source of all identified polyphenols. Lees sorbed significant amounts of gallic acid, catechin, epicatechin, malvidin-3-O-glucoside, malvidin-3-acetylglucoside, quercetin-3-O-glucoside, and quercetin. An approximately 200% increase in the total amount of gallic acid occurred during fermentation. For the Airén grapes, the overall mass recovery was >90%. The pomace, rachises, juice solids after settling, and lees constituted ∼50% of the total mass of products obtained; pomace alone accounted for 40% of the total product mass. Over 90% of the total amount of gallic acid, catechin and epicatechin and ∼50% of the quercetin-3-O-glucoside were found in the pomace
