2.3. Sample preparation
Randomly selected caryopsis from each coloured cultivar was
milled using an ultra centrifugal mill (Iwatani, Osaka, Japan).
Milled rice powder (2.0 g) was soaked in 1% HCl methanol or 80%
methanol, and sequentially extracted for 6 h at room temperature
with shaking. The total volume of extract was adjusted to 50 ml
with 1% HCl methanol or 80% methanol. Samples extracted with
1% HCl methanol were used for the ORAC assay or the HPLC.
Samples extracted with 80% methanol were used for measurement
of phenolic content. Endosperm samples of the coloured rice
cultivars, polished to 90% by a rice polisher (Panasonic, Tokyo,
Japan), were analysed using the ORAC assay, and the extraction
method employed was the same as for caryopsis. All extracted
samples were stored at 80 C until use.