Grain quality

Grain quality is a term that refers to the quality of grain. However, what constitutes quality depends on the use of the grain. For instance in ethanol production, the chemical composition of grain such as starch contents is important, in food and feed manufacturing, properties such as protein, oil and sugar are significant, in milling industry soundness is the most important factor to consider and for seed producer, the high germination percentage (viability of seed) and seed dormancy is the important feature to consider, for consumers the properties like color and flavor will be important.

Overall quality of grain is affected by several factors includes, growing practices, time and type of harvesting, postharvest handling, storage management and transportation practices. The properties of grain quality can be summarized into ten main factors (i) Uniform moisture contents, (ii) High test weight, (iii) No foreign material, (iv) Low percentage of discolored, broken and damaged kernels, (v) Low breakability, (vi) High milling quality, (vii) High protein and oil content, (viii) High viability, (ix) No afaltoxin (mycotoxin), and (x) No presence of insects and molds.

Grain quality is characterized into two main factors (i) intrinsic factors, and (ii) extrinsic factors. The intrinsic factors of grain includes, color, composition, bulk density, odor, aroma, size and shape.

Color is an important primary factor for characterization and grading, trade, and processing of grain. It is a common criterion used in wheat trade.

The main compositions of grain are carbohydrates (energy), protein, lipids, mineral, fiber, phytic acid, and tannins. It varies significant depends on the type of grain, genetics, varieties, agricultural practice, and handling of the grain. Grain composition plays a significant role in grading and marketing of grains.

Bulk density is defined as the ratio of the mass to a given volume of a grain sample including the interstitial voids between the particles.

Size and shape are important factors in grain quality and grading; it varies between grain to grain and between varieties of the same species. It is commonly used in rice grading and key factors in milling industry.

The extrinsic factors include: age, broken grain, immature grain, foreign matter, infected grain and moisture content.

Grain grading and specification system assures that a particular lot of grain meets the required set standards customer. In many countries grading of grain depends on four main properties; (i) bushel (test) weight (ii) moisture contents (iii) broken foreign material or the percentage fragments example broken corn foreign materials (iv) damaged kernels (i.e. total and heat damaged).

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