Catechin

Cabernet Sauvignon grapes were harvested in September 2020 in a vineyard located in Qinhuangdao (Hebei, China). Black chokeberries were harvested in the same period in an orchard located in Haicheng (Anshan, Liaoning, China). The active dry yeast (commercial model number: RW) was purchased from Angel Yeast (Yichang, Hubei, China). Catechin was obtained from the Shanghai McLean Biochemical Technology Co. Ltd., Shanghai, China. Gallic acid was obtained from the Tianjin Guangfu Fine Chemical Research Institute. Chlorogenic acid, epiCatechin, rutin hydrate, astragaloside, caffeic acid, quercetin, isoquercitrin and myricetin were obtained from the Chengdu Manchester Biotechnology Co. Ltd., Chengdu, China. The hydrocarbon mixture (C7-C40 alkanes) standard was obtained from the Shanghai Anpel Laboratory Technology Co. Ltd., Shanghai, China. Acetophenone, isopentyl acetate, benzyl alcohol, benzaldehyde, benzoic acid, 2,4-di-tert-butylphenol and 2-nonanone were obtained from the Beijing Tanmo Quality Inspection Technology Co. Ltd., Beijing, China.

All chemicals used were of analytical grade. Potassium hydrogen phthalate, phenolphthalein, sodium hydroxide, anthrone, sucrose, ethyl acetate, gallic acid, aluminum chloride, concentrated sulfuric acid, sodium nitrite, anhydrous ethanol and sodium carbonate were purchased from Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China). Catechin, ascorbic acid and oxalic acid were purchased from Shanghai McLean Biochemical Technology Co., Ltd. (Shanghai, China). Folinphenol was purchased from Beijing Soleibao Technology Co., Ltd. (Beijing, China). 2, 6-dichlorophenol indophenol was purchased from Shanghai Yuanye Biotechnology Co., Ltd. (Shanghai, China). The quality attributes were measured repeatedly three times.

The total flavonoid content was determined by the protocol described previously (Kim et al., 2003 (link)). The absorbance of flavonoids was determined at 506 nm using a visible spectrophotometer (PE Lambda-6, Waltham, MA, USA). Based on the linear equations (y = 1.2051x−0.0066 (R² = 0.9988, SEE (the sum of squares due to error) = 0.0119)) from catechin (purity >97.50%, Macklin Inc, Shanghai) standard solutions of different concentrations, flavonoid concentrations were calculated. Spectrophotometric analysis was performed to determine the content of total phenolics/polyphenols using Folin-Ciocalteu’s phenol reagent (Kim et al., 2003 (link)). The absorbance of polyphenols was also determined using a PE Lambda-6 spectrophotometer at 765 nm, and the polyphenol content was calibrated using a linear equation (y = 7,1266x + 0.0095 (R² = 0.9993, SEE = 9,070)) from gallic acid (purity >99.00%, Macklin Inc, Shanghai) reference solution. As a percentage of the sample’s dry mass, the final content of flavonoids or phenols was obtained.