The impact of parboiling on physical structure, physicochemical properties and zinc status of Zn-fortified germinated brown rice

The structural and physicochemical properties, cooking quality and zinc retention ratio of Zn-fortified germinated brown rice were investigated with different parboiling times (4-20 min). The brown rice grains exhibited visually more yellowish-brown colour and cracks on the surface with the germination and longer parboiling, and the micrographs clearly displayed wrinkles after these processes. Germination and the increase of parboiling time exacerbated the disruption of microstructure and the decrease in relative crystallinity and enthalpy change. The relaxation time (T2) increased in Zn-fortified germinated brown rice and parboiled samples compared to brown rice. Cooking time of Zn-fortified germinated brown rice was reduced from 36 min to 27 min with longer parboiling. Parboiling treatment longer than 4 min improved the palatability. There was no significant difference of Zinc retention ratio at different parboiling times. Sixteen min parboiling was recommended to obtain the brown rice product, which requires a short cooking time with desired palatability, as well as acceptable colour and zinc content. Overall, parboiling is an effective technique to modify the physical structure and physicochemical properties and improve cooking quality of Zn-fortified germinated brown rice.