To elucidate the mechanism of the color deepening phenomenon involving aged red rice samples, the
time-dependent changes in the color and chemical composition of four different samples (freshly
harvested, as well as those stored for 1, 2, and 5 years) were studied. A detailed study of the color change
was carried out by obtaining the reflectance spectra of the samples. To investigate the underlying chemical
changes, each sample was extracted with an appropriate solvent and analyzed by high-performance
liquid chromatography, Folin–Ciocalteu assay, phloroglucinolysis, and mass spectrometry. A similar color
change was induced via the photoirradiation of a fresh red rice sample. It is suggested that the chemical
modifications of proanthocyanidins are responsible for the color change observed in red rice.
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