Potassium metabisulfite

Hydrochloric acid, sodium hydroxide, glacial acetic acid, ferric chloride hexahydrate, ortho-phosphoric acid (≥85%), acetonitrile, sulfuric acid, L-(+)-tartaric acid, D-fructose, and 0.1 N sodium hydroxide were purchased from Fisher Scientific (Santa Clara, CA, USA). Sodium chloride, bovine serum albumin (BSA), (-)-epicatechin (≥90%), (+)-catechin (≥98%), caffeic acid (≥98%), malic acid (≥99%), and quercetin-3-glucoside (≥98%) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Potassium metabisulfite (≥97%), sodium dodecyl sulfate, and ammonium dihydrogen phosphate (>98%) were purchased from Acros Organics (Geel, Belgium). Triethanolamine was purchased from Aqua Solutions, Inc. (Deer Park, TX, USA). Commercial malvidin-3-O-glucoside chloride (oenin) (≥95%) and malvidin-3,5-O-diglucoside chloride (malvin) (≥95%) were provided by Extrasynthese (Genay, France). Milli-Q water used for the preparation of solutions was obtained from a Barnstead MicroPure Water Purification System (Thermo scientific^®, Waltham, MA, USA).

Acetonitrile, D-fructose, ferric chloride hexahydrate, glacial acetic acid, hydrochloric acid, L-(+)-tartaric acid, ortho-phosphoric acid (≥85%), sodium hydroxide, sulfuric acid, and 0.1 N sodium hydroxide were purchased from Fisher Scientific (Santa Clara, CA, USA). Bovine serum albumin (BSA), caffeic acid (≥98%), (+)-catechin (≥98%), (−)-epicatechin (≥ 90%), malic acid (≥99%), quercetin-3-glucoside (≥98%), and sodium chloride were purchased from Sigma-Aldrich (St. Louis, MO, USA). Ammonium dihydrogen phosphate (>98%), potassium metabisulfite (≥97%), and sodium dodecyl sulfate were purchased from Acros Organics (Geel, Belgium). Commercial malvidin-3-O-glucoside chloride (oenin) (≥95%) and malvidin-3,5-O-diglucoside chloride (malvin) (≥95%) were provided by Extrasynthese (Genay, France). Triethanolamine was purchased from Aqua Solutions, Inc. (Deer Park, TX, USA). Milli-Q grade water (18.2 MΩ cm resistivity) used for the preparation of reagent, solutions, and high-performance liquid chromatography with diode array detector (HPLC-DAD) mobile phase was obtained from Barnstead MicroPure Water Purification System (Thermo scientific^®, Waltham, MA, USA).

Hydrochloric acid, sodium hydroxide, glacial acetic acid, ferric chloride hexahydrate, ortho-phosphoric acid, acetonitrile, sulfuric acid, and 0.1 N sodium hydroxide were purchased from Fisher Scientific (Santa Clara, CA, USA). Sodium chloride, methylcellulose, bovine serum albumin (BSA), (−)-epicatechin, and (+)-catechin were purchased from Sigma-Aldrich (St. Louis, MO, USA). Potassium metabisulfite, sodium dodecyl sulfate, and ammonium dihydrogen phosphate were purchased from Acros Organics (Geel, Belgium). Triethanolamine was purchased from Aqua Solutions, Inc. (Deer Park, TX, USA).
Twenty-four commercial wines from Vitis vinifera and interspecific cold-hardy hybrids including two ‘Cabernet sauvignon’, two ‘Pinot noir’, five ‘Marquette’, ten ‘Frontenac’, and five ‘Petite pearl’ cultivars were purchased in a liquor store, and they were provided by wineries from Iowa and Montana. Table 1 is the list of commercial red wines including vintage, variety, and origin.