Parboiling consists of soaking the paddy, then steaming it, and finally redrying it before milling. During soaking and steaming, the starch swells and becomes gelatinized. When the grain dries, the endosperm hardens and becomes resistant to breakage during milling. Parboiled rice has a different taste and texture than rice that has not been parboiled. Those accustomed to it seem to prefer it. Those who are used to eating the unparboiled product do not take readily to parboiled rice.
--Robert F. Chandler, Jr., 1979, Rice in the Tropics: A Guide to the Development of National Programs, p. 79