Rice is used as wholegrains. Hence any breakage of the grain during milling is undesirable. The primary reason why rice breaks during milling lies not in the milling process but in the defects in the grain that enters the mill. The main factor is cracks in rice. The rice grain is mechanically strong, but it is susceptible to moisture stress and develops fissures upon rapid hydration or dehydration either in the field or in the process of drying. There is a critical moisture content only below which cracking occurs. This is related to the glass transition temperature (Tg), below which the material is glassy, i.e. brittle, and above which it is rubbery, i.e. more malleable. Moisture acts as a plasticiser for starch and lowers the Tg, which is why wet grain does not crack. Cracking can be avoided during drying by hot tempering to resolve the moisture gradient before cooling. Milling machinery affects rice breakage only to the extent of the defective/damaged grains. Gentle milling protects some defective grains from failing, while harsh milling leads to failure of more or all of them.