In some seasons, cracking of the rice grain is a significant problem. Most cracking occurs in the field and seems to be related to changes in grain moisture or to moisture cycles after the rice matures. Hot sunny days that dry the grain are commonly followed by humid or dewy nights that wet the grain. The changes in grain moisture over a 24-hour period can lead to cracking. Cracking may also result from rain on dry grain and storage of grain with variable moisture levels.
Rough handling of grain during harvest operations and during drying and processing will also cause the grain to crack.
Cracking decreases head rice yield because cracked grains often break during milling. Most markets require whole or unbroken grain, therefore cracked grain can reduce payments received by the grower and the miller.
Cracking also decreases the cooking quality of the grain. Grains that are cracked but remain intact during milling are deemed visually undesirable. Further, during cooking the starch leaches out of cracked grain and collects as a sticky layer on the bottom of the rice cooker. If rice is cooked by the rapid boil technique, the starch leaches from the rice into the cooking water.