SEM images of rice branThe SEM imag

SEM images of rice bran

The SEM images of the raw bran, the ohmically treated bran and the steamed bran are presented in Fig. 3(a–d). In this study, only the aleurone layer was scanned because of its high content of phenolic compounds and anthocyanin pigments. The SEM images of OHM (Fig. 3c and d) revealed a smooth surface, whereas a corrugated surrounding surface of the aleurone cell was found in the steaming method (Fig. 3b). Similar results were observed in the extraction of essential oils from Thymus valgaris L. using ohmic-hydro distillation as studied by Gavahian, Farahnaky, Javidnia, and Majzoobi (2012). These phenomena may be due to the rate of heat transfer and the transfer's generation of heat within the bran. The heat from OMH transfers very rapidly and evenly inside the bran. A sufficient moisture content of the bran (having adequate electrical conductivity) allows the passage of electric current through the rice bran cell membrane. The heating occurs in the form of internal energy transformation (from electric to thermal) within the bran (i.e. aleurone cell and surrounding surface area) and rapidly penetrates other surrounding areas. In addition, the electric energy of OHM was responsible for the breakdown of the rice bran cell membrane (Nair et al., 2012). This event may be one of the reasons for the sudden eruption of the aleurone cell. In contrast, the heat transfer of the steam method was slow because the transfer was by conduction and convection only ( Goullieux and Pain, 2005 and Knirsch et al., 2010).

SEM images of aleurone layer of the rice bran fraction: (a) raw bran (RB), (b) ...