Flavonoids are the most common and widely distributed group of plant phenolic compounds that are characterized by a benzo-ypyrone structure, which is ubiquitous in fruits and vegetables (Abu Baker et al., 2009). Total flavonoid can be determined in the sample extracts by reaction with sodium nitrite, followed by the development of coloured flavonoid–aluminium complex formation using aluminium chloride which can be monitored spectrophotometrically at 510 nm (Abu Baker et al., 2009). The hot-air dried of all samples contained the lowest amount of TFC as compared to the raw and other treated samples. The total flavonoid contents of hot-air and FIR treated rice bran, rice husk and ground rice husk were significantly decreased, while that of cellulase-treated was unchanged, compared with the control of each sample (Table 1).