Physicochemical and nutritional properties of pigmented rice subjected to different degrees of milling

• Black rice possessed a thicker bran layer than red rice.
• The bran of MPB-10 red rice can be considered a potential source of ash material.
• 4% and 7% degree of milling (DOM) were needed, respectively, to reduce fat content in red and black rice.
• For pigmented rice up to 12% DOM, free phenolics were higher than bound phenolics.
• Non-milled red rice showed higher antioxidant activity than non-milled black rice.

Recent studies have reported the health benefits of pigmented rice cultivars due to the presence of bioactive compounds in the bran layer of caryopsis. This study evaluated the proximate composition, colour, total flavonoids, anthocyanins and proanthocyanidins contents, as well as the total phenolics and antioxidant activity of IAC-600 black rice cultivar and MPB-10 red rice lineage, as a function of degree of milling (DOM), at 0%, 4%, 7%, 10%, 12% and 15% of DOM. Black rice showed a thicker bran layer than red rice. Around 80% and 65% of the ash content of red and black rice, respectively, was distributed in the bran layer. 4% DOM reduced 47% of the fat content in red rice, while in order to reduce similar fat content in black rice, a 7% DOM was necessary. The total free phenolics were around 6- and 7-fold higher than bound phenolics for black and red rice, respectively. Although the non-milled black rice presented higher free and bound phenolics contents than non-milled red rice, the red rice showed higher DPPH and ABTS+ antioxidant activities.