Tartaric acid

Chromatographically pure grade dichloromethane, methanol, and ethanol were purchased from Honeywell, USA. Analytical grade glucose, sodium hydroxide, sodium chloride, citric acid, malic acid, tartaric acid, and sodium dihydrogen phosphate were purchased from Beijing Chemical Reagent Company. Volatile standards and N-Alkanes (C6-C24) were purchased from Sigma-Aldrich. Yeast Zymaflore FX10, pectinase LAFASE HE GRAND CRU, and Lactobacillus B7 DIRECT 25HL were purchased from LAFFOTA, France.

Analytical grade reagents, including Milli-Q water, sodium hydroxide (NaOH), anhydrous sodium sulfate (Na₂SO₄), sodium chloride (NaCl), ammonium sulfate [(NH₄)₂SO₄], tartaric acid, and glucose, were purchased from Beijing Chemical Works (Beijing, China) and Shanghai Macklin Biochemical (Shanghai, China). Chromatographic grade reagents, including methanol, ethanol, and dichloromethane, were bought from Fisher (Fairlawn, NJ, USA) and Honeywell (Marris Township, NJ, USA). Reference standards of volatile compounds and C₆-C₂₄ n-alkanes were purchased from Sigma-Aldrich (St. Louis, MO, USA).

Four commercial yeast strains, ES488, CY3079, BV818 and VIC, were chosen because of their steady fermentation characteristics and excellent flavor enhancement according to the manufacturer instructions. The strains ES488 and CY3079 (Saccharomyces cerevisiae) were purchased from Enartis (Tracete, Italy) and Lallemand (Montréal, QC, Canada), respectively. Strains BV818 and VIC (Saccharomyces bayanus) were provided from Angel Yeast Co., Ltd. (Hubei, China). Pectinase and potassium metabisulfite were purchased from Enartis (Tracete, Italy). Water was purified through a Milli-Q purification system (Millipore, Bedford, MA, USA). Folin-Ciocalteu reagent was purchased from Beijing Sulaibao Tech Co., Ltd. (Beijing, China). Sodium hydroxide, sodium chloride, ammonium sulfate, aluminum nitrate, sodium sulfate, sodium carbonate, tartaric acid and ethanol were of analytical grade and purchased from Beijing Chemical Works (Beijing, China). The volatile standards used in this study were purchased from Sigma-Aldrich (St. Louis, MO, USA). These standards had a purity above 95%. The internal standard (4-methyl-2-pentanol) was obtained from Sigma-Aldrich (St. Louis, MO, USA) with a 98% purity.

Tartaric acid, glucose, methanol, methylene chloride, NaCl, and NaOH were of analytical grade and purchased from Beijing Chemical Works (Beijing, China). D-Gluconic acid lactone, polyvinylpolypyrrolidone (PVPP), and all monoterpene standards were purchased from Sigma-Aldrich (St. Louis, MO, USA). Glycosidase AR2000 was received from DSM Food Specialties Beverage Ingredients (Heerlen, Netherlands). Cleanert PEP-SPE (50 mg/6 mL) and Cleanert ODS-C18 (150 mg/6 mL) were purchased from Bonna-Agela Technologies (Tianjin, China).

Analytical-grade chemicals, including sodium chloride, sodium hydroxide, tartaric acid, anhydrous sodium sulfate, and glucose, were purchased from Beijing Chemical Works (Beijing, China). Chromatographic-grade reagents, including methanol, ethanol, dichloromethane, formic acid, acetonitrile, and acetic acid, were purchased from Fisher (Fairlawn, NJ, USA) and Honeywell (Marris Township, NJ, USA). Malvidin-3-O-glucoside and other reference standards of non-anthocyanin phenolic compounds were purchased from Sigma-Aldrich (St. Louis, MO, USA), ChromaDex (Irvine, CA, USA), and Extrasynthese (Genay, France). Reference standards of aroma compounds and C6-C24 n-alkanes were obtained from Fluka (Buchs, Switzerland) and Sigma-Aldrich (St. Louis, MO, USA). Cleanert PEP-SPE resins (1000 mg/12 mL) were purchased from Bonna-Agela Technologies Inc. (Tianjin, China).