2.2. Preparation of the anthocyanin-rich black rice extract
The unpolished black rice kernels were dried at 40 °C, ground with a high speed mill (DFT-200, Linda Machinery Co. LTD., Wenling, China) and passed through an 80 mesh screen sieve. Anthocyanins in black rice were extracted according to the modified method described by Prior et al. (2008). The dried black rice flour was extracted twice with ethanol/water/hydrochloric acid (50:50:0.5, v/v/v) by solid–liquid ratio (1:10) at 30 °C for 2 h. All extracts were combined and filtered through a Buchner funnel. The collected filtrates were subjected to vacuum evaporation at 35 °C to remove ethanol. The concentrated extracts were loaded on an AB-8 resin column to remove major impurities. The anthocyanins were washed with distilled water containing 1% hydrochloric acid and subsequently recovered with 70% ethanol containing 1% hydrochloric acid. The ethanol eluent was evaporated under vacuum at 35 °C to yield the anthocyanin-rich black rice extract. The yield of the extract from dried black rice flour is ∼1% (w/w).