Fig. 4.

Total polyphenol content and DPPH free radical scavenging capacity in grape juice mixed with thickening or gel-forming agents after in vitro digestion. To determine the total polyphenolic content, the colorimetric Folin-Ciocalteu method was used. The calibration curve was constructed using gallic acid. The total phenolic compound amount was determined by comparison to the curve, and the results are expressed as mg equivalents of gallic acid/g of sample. A 70% ethanol solution was used as the control solution. Control, 20% grape juice with no addition of hydrocolloids; CMC, 1% carboxymethyl cellulose; LBG, 1% locust bean gum; AA, 0.5% or 0.8% agar agar; KG, 0.5% or 0.8% konjacglucomannan; HS, 0.5% or 0.8% hot & soft plus. The results are expressed as mean±SD of at least three independent experiments. Different letters (a–d) represent significant differences (P < 0.05) among all groups by ANOVA.