The breakage susceptibility of raw and parboiled rice: A review

• The intensity of dehulling and milling impacts the level of rice breakage.
• Fissures, chalkiness, immaturity and rice kernel dimensions determine rice kernel breakage.
• Parboiling can increase the head rice yield.
• The extent of starch gelatinization and kernel fissuring determine the breakage susceptibility of parboiled rice.

Rice (Oryza sativa L.) is one of the most important cereals in the world. Before it is consumed, it is common to remove the hull, bran and germ from the rough rice kernel which is either parboiled or not. During such processing, rice kernels are subjected to mechanical stresses which cause some rice grains to break. A main challenge of the rice industry is to minimize the quantities of broken rice. We here review the factors impacting the breakage susceptibility of rice kernels. Their tendency to break is primarily determined by fissures, chalkiness, immaturity and rice kernel dimensions, properties which are both cultivar and rice grain history dependent. The intensity of processing of any given rice feedstock determines the actual level of broken rice kernels. If performed properly, parboiling, a three-step hydrothermal treatment consisting of soaking, heating and drying of rough rice, substantially reduces the level of broken kernels.