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Title: Grain hardness: a major determinant of Wheat Quality (A Review)

item Morris, Craig

Submitted to: Food Science and Technology International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/21/2010
Publication Date: 12/21/2010
Citation: Pasha, I., Anjum, F.M., Morris, C.F. 2010. Grain hardness: a major determinant of Wheat Quality (A Review). Food Science and Technology International. 16:511-522.

Interpretive Summary: Wheat is unique among all the cereal grains grown in many parts of the world as a staple food, and is used to make numerous products. The term wheat quality is complex and cannot be expressed in terms of a single property. Wheat quality depends on several milling, chemical, baking and rheological dough properties. The quality of wheat is the result of factors such as seed stock, effects of soil, climate, and kernel components. It may also be defined in terms of its suitability for a particular purpose or use. The variation in kernel texture (hardness or softness) is inherited and is controlled by a single locus referred to as Hardness (Ha). This locus comprises three genes which are the Pin a, Pin b and Gsp-1 gene, the latter encodes a protein called grain softness protein (GSP). The soft wheats possess the dominant or wild type form (Ha), while hard wheats have the recessive or mutated form (ha). The durum wheats lack the D-genome and represent a harder class of wheat. It is now known that both Pina and Pinb genes have various different alleles in hexaploid wheats. To date, almost 17 Pina and 25 Pinb alleles have been found in common wheat and related species.

Technical Abstract: Wheat quality is a complex term and depends upon intended use for specific products. The major determinants of wheat quality are grain hardness, protein content and gluten strength. Endosperm texture in wheat is the single most important and defining quality characteristic, which determines wheat classification and affects milling, baking and end-use quality. Various methods used for grain hardness measurement are classified into different groups based on grinding, crushing, abrasion or indentation. The most widely used methods for texture measurement are PSI, NIR hardness, SKCS, pearling index, SDS-PAGE and PCR markers. The protein is a functional component of wheat grains affecting end-use quality. The friabilin, i.e.15 kDa, is an endosperm specific protein associated with starch granules of cereal grain and is directly related to grain softness. Friabilin is composed of a mixture of different polypeptide puroindolines (PIN) a and b. The distinction between soft and hard classes of wheat is governed by the hardness (Ha) locus located on chromosome 5DS with additional modifying genes contributing to variation within classes. Numerous PIN allelic variations have been reported now and their relation to end product quality has been established. In this review, the effort has been made to elaborate the importance of grain hardness in wheat quality.