A comparative review of protein and starch characteristics and end-use quality of soft and hard wheat

Abstract

Hardness of wheat endosperm is a physical property that depends on the genetic makeup of the grain and varies amongst different types/varieties. It is associated with proteins, particularly 14–15 kDa friabilins, which exist in higher amounts at the surface of starch in soft wheat grains while either absent or occur in smaller quantities on granules of hard wheat varieties. The storage proteins in hard wheat flours exhibit a higher proportion of polymeric proteins, β-sheets and β-turns. Soft wheat starches show lower crystallinity, amylose-lipid complex content and proportion of A-type granules (disk or lenticular-shaped granules with diameter >10 µm) while higher gelatinisation temperatures, swelling, breakdown susceptibility and retrogradation than hard wheat starches. Flours from hard and soft wheat also differ for processing and end-use quality based on differences in dough rheological properties, solvent retention capacities and particle size.

Keywords

• Hard vs soft wheat
• Protein secondary structure
• Polymeric vs monomeric proteins
• Rheology
• Starch properties