The cooked rice samples were immediately dried using a vacuum freeze dryer (ALPHA1-4, Marin Christ Inc., Osterode, Germany). After drying, they were stuck on a specimen holder using a silver plate and coated with a thin film of gold (10 nm) in a vacuum evaporator. The resultant specimens picked from the central endosperm of rice kernel were observed and photographed using a scanning electron microscope (Quanta-200, FEI Company, Eindhoven, Netherlands) at an accelerating voltage of 5.0 kV.