pH differential method (Maran et al. 2013a) was used to
estimate the total monomeric anthocyanin content (TMAC)
of the extracts. The method was based on the anthocyanin
structural transformation that occurs when pH changes.
Aliquots of the extracts were diluted with pH 1.0 and 4.5
buffers using potassium chloride (0.025 M) and sodium acetate
(0.4 M) respectively, and then placed in the dark conditions
for 1 h. The absorbance of each solution was recorded
using a spectrophotometer (Shimadzu UV-1800, Kyoto,
Japan) calibrated with distilled water as the blank at the
wavelength of 530 and 700 nm. Difference in absorbance
between pH values and wavelengths was calculated using
the formula