Soaking, heating and high hydrostatic pressure treatment degrade the flavonoids in rice bran
Guanghe Zhao, Mengqi Hu, Xiwen Lu, Ruifen Zhang
Abstract
In this study, the phenolic profiles, antioxidant activity and overall structure of rice bran were analyzed following successive treatments of soaking, heating and high hydrostatic pressure. Compared with untreated rice bran, the samples that underwent these treatments exhibited decreased flavonoid contents and increased amounts of phenolic acids. However, in contrast to the decrease in flavonoid contents, the in vitro antioxidant activity of rice bran did not change according to the same trend. Morphological and structural analyses based on scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) proved the progressive structural destruction of rice bran induced by the successive treatments mentioned above. These results suggested that some flavonoids might convert to phenolic acids during these treatments because of the structural destruction of rice bran. In view of the functional differences of phenolic acids and flavonoids, appropriate treatments should be chosen according to the specific use of rice bran.