Understanding Pre- and Post-Milling Crack Formation in Rice Grain

Abstract

HighlightsCracking and subsequent breakage of rice kernels reduces the marketability and profitability of rice.Pre-milling cracks in rice kernels cause breakage during milling, thereby reducing consumer acceptability.Three types of post-milling cracks reported are: surface, internal, and Hanasaki cracks.Post-milling cracks can be minimized throughout the supply chain.Abstract. Rice is consumed as intact grain, and any broken grains are discounted from the main marketable product. Breakage of rice mainly arises from cracks formed in the endosperm before or after milling. The cracks are formed by stress gradients that arise due to moisture absorption or desorption by grains. As a result of such stress, cracks mostly develop in a direction perpendicular to the length of the grain, making it less physically resistant to the stresses of milling, handling, and soaking processes. Until now, research into rice cracking has mainly focused on minimizing breakage during milling, and no significant knowledge is available on the impact and mechanisms of post-milling cracking and/or breakage and its effect on the downstream quality of rice. This article aims to review the existing information on the causes of rice cracking before and after milling. Keywords: Breakage, Crack, Drying, Glass transition temperature, Hanasaki, Head rice yield, Rice, Tempering.