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Milling Degree of Rice
Definition
- Milling Degree is usually defined as the extent to which the bran layers of rice have been removed during milling.
- Milling removes the germ and the bran layers which include the outer pericarp of the rice kernel, the aleurone layer, and some of the starchy endosperm.
How measured
- Visually-See FGIS designations below
- Color--typically, the higher the milling degree, the whiter the kernel. There are several different commercial ways of measuring the whiteness-Satake milling meter, Kett whiteness meter, and commercial color meters (Hunter, Minolta, etc.)
- Surface Lipid content-most of the lipid in the kernel is in the germ and bran. As milling degree increases, the surface lipid content is reduced. Surface lipids are extracted and quantitatively measured.
Significance
Milling degree affects processing properties of rice.
- Undermilled rice still has bran attached to the kernel. This can reduce water absorption, adds fiber, protein, and lipids (thus reducing % starch). This would affect applications such as cooking time, kernel to kernel interactions (stickiness versus separateness), color of the rice and interactions with other ingredients.
- Higher lipid content would affect how a rice kernel would pick up spices or seasoning coating.
- Highly milled rice will have a higher starch content and lower lipids and protein than a rice milled to a lower milling degree. This affects starch pasting properties and the effect can be seen in a higher curve run on an RVA (Rapid Visco Analyser).
Industry specifications for Milling Degree
At the current time, there is no one way to specify milling degree. Different suppliers use different methods as described above. An experienced supplier can help one select the correct rice for an application.
FEDERAL GRAIN INSPECTION SERVICES (FGIS) OF USDA MILLING DEGREE DESIGNATIONS
§ 868.305 7 CFR Ch. VIII (1-1-03 Edition)
§ 868.305 Interpretive line samples.
Interpretive line samples showing the official scoring line for factors that are determined by visual observation shall be maintained by the Federal Grain Inspection Service, U.S. Department of Agriculture, and shall be available for reference in all inspection offices that inspect and grade rice.
[42 FR 40869, Aug. 12, 1977; 42 FR 64356, Dec. 23, 1977, as amended at 47 FR 34516, Aug. 10, 1982. Redesignated at 54 FR 21406, May 18, 1989 and 60 FR 16364, Mar. 30, 1995]
§ 868.306 Milling requirements.
The degree of milling for milled rice;
i.e., "hard milled," "well-milled," and "reasonably well-milled," shall be equal to, or better than, that of the interpretive line samples for such rice. [67 FR 61250, Sept. 30, 2002]
Most US rice falls into the category of well-milled which means that all of the bran and germ have been removed during milling. Only a minimal amount of the endosperm (starchy area) has been removed.
Hard-milled means rice has been milled longer and removed more of the bran and outer endosperm layer. It will typically be stickier than well-milled rice. Its protein level may be lower also.
Reasonably well-milled rice will have the germ and most of the bran removed, but may still have bran streaks (patches of bran that have not been removed) on the kernels.
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