Parboiling involves partial boiling of the paddy before milling in order to increase its nutritial value, to change the texture of cooked rice, and reduce the breakage in milling.
Parboiling is done in three steps: Soaking, steaming and drying.
Parboiling causes a gelatinization of the starch during the boiling and during cooling the amylase molecules re-accociate with each other and form a tightly packed structure. The kernels are harder and appear glassier after the parboiling process. The parboiling process moves micro nutrients contained in the bran, which is usually removed in the whitening process in the rice mill, to the endosperm. Parboiled rice is therefore more nutritious than white rice.
Parboiling also mends little cracks that might have developed in the endosperm during postharvet processing and therefore head rice recoveries of parboiled rice are higher.
Parboiled rice takes less time to cook and is firmer and less sticky when cooked.