Parboiling is the hydrothermal treatment of paddy before milling. Three important steps in parboiling are illustrated in Figure 5.1:
1. Soaking (sometimes called steeping) paddy in water to increase its moisture content to about 30%
2. Heat-treating wet paddy, usually by steam, to complete the physical-chemical changes; and
3. Drying paddy to a safe moisture level for milling.
Parboiling is an age-old process in parts of Asia, Africa, and to a limited extent today, in some European countries and America. It is done to improve the milling recovery of paddy, to salvage poor quality or spoiled paddy, and to meet the demands of certain consumer preferences. The process causes certain changes in the milled rice: physical, chemical and aesthetic.