Study on Effect of Inductively Coupled Ar/O2 Plasma in E- and H-Mode on Riceberry Rice by SEM/EDS

Abstract

Riceberry brown rice is regarded as a source of various nutrients; often richer than white rice. Non-thermal plasma has recently been gaining a role for improving properties of cereal grains, especially brown rice. A number of methods of plasma treatment has been proposed including discharges as capacitive coupled plasma (CCP) and inductive coupled plasma (ICP). ICP has two operation modes as capacitive (E-mode) and inductive (H-mode) discharge with rather distinct characters. In this study we have focused on using ICP Ar/O2 plasma in both E-and H mode for plasma treatment on riceberry brown rice. The input power for plasma generation were set to 50 and 250 W for E-and H-mode, respectively. Plasma in H-mode was having higher plasma density than that in E-mode, as observed in the optical emission spectrum. The surface morphology of riceberry brown rice before and after Ar/O2 plasma treatment was evaluated using a scanning electron microscope without or with an energy dispersive spectroscopy (SEM and SEM/EDS). It has been found that the bran layer was richer in elemental compositions than the endosperm. The surface of rice sample was found to be etched and more porous after plasma treatment. The Ar/O2 plasma in H-mode was observed to offer higher effect. The surface contact angle was found to decrease from 120.1o ± 0.9o in untreated samples to 79.3o ± 0.6o and 99.2o ± 0.8o in plasma treated samples on E-and H-mode, respectively.