Optimization extraction of anthocyanins from purple corn (Zea mays L.) cob using tristimulus colorimetry

Optimization of the conditions for extracting anthocyanins from the cob, a byproduct of purple corn (Zea mays L.), was investigated in this paper. A full factorial design (22 × 32) was used. The factors studied were type of solvent: ethanol or methanol; solvent/water mixture: 100, 90, 80% v/v; type of acid: citric acid or acetic acid; and concentrations of acid: 0.25, 0.5, 1% v/v. Tristimulus colorimetry was employed to evaluate the yield and quality of anthocyanins extracts. The results showed that the maximum yield (5.90 mg/g dw) was obtained with the combination of 80% (v/v) methanol and 1% (v/v) citric acid, and that the relatively high chroma (C* = 23.60) and hue angle (h = 16.63) values of the anthocyanins extract were observed under the same conditions. Eight kinds of anthocyanins in the cob were detected by HPLC–DAD, most the anthocyanins were non-acylated.