The value of milled rice in the market is determined by a number of physical and chemical characteristics, and the consumers, which varies within a country, and between the countries.
Milling degree or colour: The degree of milling or amount of the brown rice removed affects the colour of white rice and often the price. Under-milled rice absorbs water poorly, does not cook well, and is normally cheaper.
Head rice or broken percentage: Milled rice, having 75-80 % head rice (whole kernels), also includes broken kernels. High head rice yield is one of the most important criteria for measuring milled rice quality. High-quality rice normally has less than 5% broken.
Whiteness or translucency: This characteristic is a combination of varietal physical characteristics and the degree of milling. During milling, the whitening and polishing process greatly affects the whiteness of the grain and its transparency.
Chalkiness: Grain appearance is affected by the amount of chalkiness or white belly. Chalkiness is caused by interruption of the final grain filling. Though chalkiness disappears upon cooking (and has no direct effect on cooking and eating qualities), excessive chalkiness often downgrades the quality and reduces milling recovery.
Gelatinization temperature or cooking time: Environmental conditions such as temperature during ripening influence gelatinization temperature. There is normally a preference for rice with intermediate gelatinization temperature.
Amylose content or stickiness: The amylose content of rice usually ranges from 15–35%. High-amylose rice has high volume expansion, the grains cook dry, are less tender, and become hard upon cooling. Low-amylose rice cooks moist and sticky. Intermediate-amylose rice (21–24%) is preferred in most rice-growing areas of the world.
Gel consistency: Gel consistency measures the tendency of the cooked rice to harden on cooling. Varieties with a softer gel consistency are preferred if rice is to be consumed after cooling, or if cooked rice with higher degree of tenderness is desired.