United States Grade Standards for Milled Rice

Milled rice is classed by kernel size and shape — long grain, medium grain, and short grain — with provision for mixed rice, and separately for specialty types. Classing matters commercially because these types cook differently and are not substitutable: a long grain kernel stays separate, a shorter kernel holds together, and buyers select accordingly. Within its class, a lot is then graded on measured factors.

The standard covers rice at defined stages, and the terms are not interchangeable: rough rice is the grain with the hull still on; brown rice has been hulled but retains the bran layers; milled rice has had the bran removed. Milled rice, the subject of this page, is graded on criteria that only make sense once the kernel is white and visible.

The grading factors reflect what buyers of milled rice can see and what milling has done to the kernel:

• Broken kernels — separated by size into defined fractions rather than counted as one factor
• Chalky kernels — opaque, soft kernels that break more readily and cook unevenly
• Damaged and heat-damaged kernels
• Colour and seeds — off-colour kernels, red rice, and foreign seeds
• Degree of milling — how completely the bran layers have been removed

Broken kernels are the defining factor of the rice trade. Whole kernels command the premium, brokens are a lower-value product with their own market, and head rice yield — the proportion of whole kernels a mill recovers — is the number that determines whether a lot of rough rice was worth buying. Breakage originates largely before the mill: fissures form in the kernel from moisture cycling in the field and in drying, and the mill merely reveals them.

Chalkiness is a related and instructive factor. Chalky areas are regions of loosely packed starch that scatter light, and they arise chiefly from high temperature during grain filling. They are structurally weak, so they raise breakage, and they are visible, so they carry an appearance penalty as well. Degree of milling is different in kind from all of these: it is not a defect but a processing choice — mill more and the rice is whiter but more of the kernel is lost — which is why it is assessed against reference standards rather than judged as damage.

A grade describes the physical and visual condition of milled rice. It says nothing about cooking behaviour beyond what class implies, and nothing about the aroma, amylose content, or varietal identity that much of the rice market actually trades on — a fragrant variety is bought by name and by test, not by grade. It is also not a food-safety determination.

A grade applies to the lot the sample represents, drawn and handled under prescribed procedures. Rice adds a specific reason for care: brokens and whole kernels segregate readily during handling, so a sample taken carelessly will misrepresent the very factor the grade turns on. Sampling method, sample size, and lot definition follow official procedure rather than party agreement.