YAMAMOTO CO., LTD.

Method of Grade Inspection

As a rule, the grade inspection is to be done in the following sequence;
1) Character,
2) Color (only for those for brewing sake),
3) Head rice
4) Damaged kernels, chalky kernels, foreign grains, foreign matter,
5) Grains of different type,
6) Moisture content
7) Test weight

Character: Character is the standard for those elements of quality that are difficult to express in numerical units, such as the test weight, consisting of nine items including degree of ripening of pericarp, grain maturity, hardness, uniformity of grain sizes, kernel form, and luster. The standard is set using a standard sample that has specific examples of those elements unique to each class.
Character affects quality and milling yield when brown rice is polished by the milling process. Nine inspection critereas are comprehensively evaluated.

Head rice: Head rice are those that have completed the maturing process and possess the grain shape that characteristically represents quality. The head rice has a well-developed and well-balanced body, large, translucent and lustrous. Head rice content in raw brown rice also affects the process of polishing brown rice, especially milling yield.

Damaged kernels, Chalky kernels, foreign grains and foreign matter:
1) Damaged kernels: Damaged kernels are those that are damaged either during the process of maturing or after harvesting by insects, mold, bacteria, and physical impediments, which include those that are sprouted, injured by microorganisms, have rotten sprouts, are damaged by insects, have a cracked belly, are odd-shaped, or colored brown, and broken grains.
The degree of damage of Damaged kernels affects milling yield and quality. Therefore, this is governed by the
standard for the ratio of their inclusion. Grains with minor damage and would not affect the quality and milling yield
are not considered Damaged kernels in the inspection.

2) Chalky kernels: Chalky kernels are basically immature grains. They are especially poor in terms of maturity,
translucency and luster, and are thin. They are defined separately from Immature grains in view of their
considerable influence on quality and milling yield.

3) Foreign grains in brown rice: These include any grains of another type (inclusion of glutinous brown rice in
non-glutinous brown rice, for example), paddy and wheat. It is very difficult to remove them completely in the
milling process. Therefore, the standard governs the ratio of their inclusion.

4) Foreign matter: These include anything other than grains, such as rachis branch, earth and sand, and stones.
As they can be removed before shipment relatively easily, the standard limits their presence quite severely.

Color:
This standard is unique to brown rice for brewing sake, in that the brown rice for brewing sake has a particular color of its own kind. Any inclusion of foreign grains other than those governed by foreign grains would seriously affect brewing.
Therefore, it is separately defined in the standard.

Moisture content:
This is expressed by the ratio of the weight of moisture evaporated by an oven method at 105℃ to the total weight of the sample. The standard limits are 15% or less in consideration of storage and management. Anything over this limit is treated as Off Grade, containing too much moisture.

Test weight:
This is an important item that is closely related to milling yield. It represents the degree of maturity of brown rice and is expressed by the weight of one liter of brown rice weighed with a Brauer Grain Balance. The lower limit of the test weight is defined for each grade.