Characterization of antioxidant compounds of red and white rice and changes in total antioxidant capacity during processing

Abstract

Although most rice cultivars have whitish kernel, some varieties have a red testa. Aim of this work was to compare the total antioxidant capacity (TAC) and the antioxidant chemical composition (namely tocols, gamma-oryzanols, and polyphenols) of red and white rices. In addition, the effect of milling and cooking on antioxidants was investigated in both rices. Dehulled red rice showed a TAC more than three times greater than dehulled white rice and its high TAC was essentially characterized by the presence of proanthocyanidins (PA) and associated phenolics. Milling caused a significant loss of TAC, even if red rice maintained a higher TAC. Cooking caused a further loss of antioxidants, but when there was a full uptake of cooking water by the grains ("risotto") this loss was limited. Thus, the consumption of whole or partially milled rice cooked as risotto would be preferred to preserve its nutritional properties.

Phytochemical profiles and antioxidant capacity of pigmented and non-pigmented genotypes of rice (Oryza sativaL.)

“…These findings are consistent with those reported by Huang and Ng (2011) even though the levels of tocols vary depending on the genotype and the environmental conditions. Meanwhile, no clear trend in the contents of Ts and T3 was observed between nPR and PR, which is consistent with previous findings (Finochiaro et al 2007;Min et al 2011). Some of the PR analyzed in this study had a lower content of total vitamin E than the nPR, indicating that the color of rice does not relate to the total tocols content (Min et al 2011).…”

“…However, the data are in agreement with those reported by De Mira et al (2009) and Min et al (2011), who also determined higher concentrations of free phenolics in PR than bound phenolics. This may be due to the fact that PR is rich in anthocyanins that are not esterified to other cellular components (Finochiaro et al 2007). …”

The influence of extraction methods on composition and antioxidant properties of rice bran oil

“…The chemical composition (tocols, γ-oryzanol), and antioxidant properties of white, red, and brown rice bran were compared with the unique extraction method (Aguilar-Garcia et al, 2007;Finocchiaro et al, 2007). However, all previous studies have shown that the phytochemical composition and the ability of the antioxidant of rice varieties depend on many factors, majorly, cultivars, and extraction methods.…”

Effects of Salt Stress after Late Booting Stage on Yield and Antioxidant Capacity in Pigmented Rice Grains and Alleviation of the Salt-Induced Yield Reduction by Exogenous Spermidine

“…Regulation of flavonoid pathway branch is regulated by complex network of signals triggered by internal metabolic cues and external signals including abiotic stress factors (Abeynayake et al, 2012). Flavonoid pigments particularly anthocyanins and proanthocyanidins have been reported to be highly correlated with antioxidant capacities of colored rice grains (Finocchiaro et al, 2007;Min et al, 2012). Anthocyanin accumulation can be induced by biotic and abiotic stressors, such as UV-B irradiation, drought, cold, toxic metals in soils and pathogens attack (Chalker-Scott, 1999).…”