4.9. DMACA Staining and PA Determination

DMACA staining and PA determination were followed as in Pang et al. [23]. Total soluble PA content was calculated spectrophotometrically after reaction with DMACA reagent (0.2% wt/vol DMACA in methanol-3N HCl) at 640 nm by Spectrophotometer (Unico, UV/VIS 2802PC, Princeton, NJ, USA with (+)-catechin (Solarbio, 154-23-4, Beijing, China) as standard. For total insoluble PA analysis, Absorbance values were converted into PA equivalents using a standard curve of procyanidin B1 (4852-22-6, MYM, Beijing, China).