Hard Vitreous Kernel
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Vitreous kernel count is a way to characterize grain quality by observing the optical properties of the grains. The appearance of the grain correlates with the level of
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
(at least up to protein content of 12.5%.) When the protein content is high enough, the protein binds the
starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diet ...
granules inside the grain and creates a glassy ("vitreous") appearance. The lack of protein opens air-filled voids in between the starch granules that create light-colored (" mottled") patches, also known as ''yellow berry''. Hard Vitreous Kernel (HVK) is a visible sign of the kernel hardness, and its specification is used internationally as a primary way to grade the
durum wheat Durum wheat (), also called pasta wheat or macaroni wheat (''Triticum durum'' or ''Triticum turgidum'' subsp. ''durum''), is a tetraploid species of wheat. It is the second most cultivated species of wheat after common wheat, although it repres ...
. During the
milling Milling may refer to: * Milling (minting), forming narrow ridges around the edge of a coin * Milling (grinding), breaking solid materials into smaller pieces by grinding, crushing, or cutting in a mill * Milling (machining), a process of using ro ...
process, yellow berry content disintegrates into very small particles, creating tiny mill "fine fractions" or ''fines'' that are considered to be of inferior quality for making
dough Dough is a malleable, sometimes elastic paste made from flour (which itself is made from grains or from leguminous or chestnut crops). Dough is typically made by mixing flour with a small amount of water or other liquid and sometimes includes ...
. The higher vitreous count corresponds to better-quality grain with higher output of
semolina Semolina is the name given to roughly milled durum wheat mainly used in making pasta and sweet puddings. The term ''semolina'' is also used to designate coarse millings of other varieties of wheat, and sometimes other grains (such as rice or ma ...
from milling. For example the Australian wheat grain classes ADR1 and ADR2 are required to have the count of 80% and 70% respectively. The causes of low vitreous kernel count can be genetic (low-protein
cultivar A cultivar is a kind of Horticulture, cultivated plant that people have selected for desired phenotypic trait, traits and which retains those traits when Plant propagation, propagated. Methods used to propagate cultivars include division, root a ...
) or environmental (lack of nitrogen in nutrition, disease). The count is expressed as a percentage and is measured by comparing the grains with the photographic standards. Despite the widespread use of the metrics, the details of evaluation greatly differ by country: in 1973, while counting the same sample, the experts from 17 different countries came up with results ranging from 48% to 98% of vitreous kernels. Optical recognition systems were still being developed for the task as of the late 2010s. The ''kernel hardness index'' method that measures the force necessary to crush the grain is suggested as an alternative. However, while it can distinguish between the vitreous grains and the starchy ones, the grains with the intermediate level of the protein (''piebalds'', non-vitreosus per the Canadian grading standards), have almost the same hardness as the vitreous ones.


See also

* Grain quality#Vitreousness


References


Sources

* * * * Wheat production {{agriculture-stub