Spectrum Characteristics and Stability of Anthocyanin Pigment from Hulless Barley (<i>Hordeum vulgare</i> ssp. <i>vulgare</i>)

Anthocyanins are natural colorants which have recently received worldwide attention due to their extensive range of colors, innocuous and beneficial health effects. In this study, anthocyanin pigment isolated from purple hulless barley were subjected to spectral (pH 1~12) and stability analyses (pH 1, 3 and 5). The pigment exhibited red, green or yellow-brown color depending on pHs, and the most reddish (517 nm) and bluish color (582 nm) was around pH 1 and pH 8~9, respectively. The light irradiation and heating (50 and 95 °C) tests indicated that the pigment was more stable at lower pH than at higher pH, and the light and heat could accelerate its color degradation. After 15-day storage under darkness, about 6.8, 7.6, 8.6, 10.4, 11.1 or 17.6% additional anthocyanin residual was respectively observed in the pigment solution (pH 3) in the absence of added 0.25 M KCl, NaCl, CaCl2, MgCl2, ZnCl2 or AlCl3. These results suggested small metal ions, especially highly charged ions had protective effects on storage stability of anthocyanin pigment.