Milling and thermal treatment induced changes on phenolic components and antioxidant activities of pigmented rice flours.

Processing methods involved in value addition
to pigmented broken rice, a milling by-product may affect
the nutraceutical qualities. Hence the effect of pulverisation
and toasting on nutraceutical content in brown rice
flours of red and black rice varieties were studied. Plate
milling reduced soluble, bound and total polyphenols in
red, but increased in black; increased insoluble polyphenols
and oryzanol, and reduced anthocyanin in both varieties;
antioxidant activity is reduced in red, but increased in
black. Toasting caused reduction of soluble, insoluble and
total polyphenol, anthocyanin and antioxidant activity in
both varieties with an increase in bound polyphenols, and
retention of flavonoids and oryzanol. HPLC characterization
of phenolics showed changes on processing in content
of catechin, caffeic, vanillic, protocatechuic and ferulic
acid. It can be concluded that processing impacts the
phenolic components of pigmented broken brown rice flour
and this information is useful for functional food industry.