Abstract:

To maximize anthocyanins yield from black rice extracted with ethanol solution, one-factor-at-a-time and orthogonal array design methods were used to examine the optimal values of 5 main technological parameters. Cyanidin-3-glucoside was served as the reference substance for the quantification of anthocyanins. Subsequently, the crude anthocyanin extract obtained was purified by macroporous resin absorption. Results showed that an optimal anthocyanins yield was achieved through extracting the material with a 10-fold (mL/g) volume of a mixture composed of absolute ethanol, water and hydrochloric acid (50: 50:0.5, V/V) for 1 h 3 times each time at 50 ℃. Among 9 macroporous resins tested, AB-8 exhibited the best compromise between high adsorption and high desorption rates so as to be used to purify the crude anthocyanin extract from black rice. In the purification, the optimal elution solvent was 80% aqueous ethanol and the optimal values of flow rate for sample loading onto AB-8 and elution solvent flow rate were 1.0 and 2.0 BV/h, respectively. The purified anthocyanin extract was determined to have 22.59% anthocyanins content (the value in the crude anthocyanin extract 3.448%) with a 6.02-fold enrichment, which demonstrated an effective purification.

Key words: black rice, macroporous resins, anthocyanins, extraction, purification