Method 2 (Rapisarda et al., 1994). An aliquot of juice (2 mL)
was diluted up to 25 mL with a pH 1 solution (125 mL of 0.2
M KCl and 375 mL of 0.2 M HCl). A second aliquot (2 mL)
was diluted up to 25 mL with a pH 4.5 buffered solution (400
mL of 1 M CH3CO2Na, 240 mL of 1 M HCl, and 360 mL of
H2O). Absorbance of the solutions was measured at 510 nm.
Concentration of anthocyanins was calculated by the equation