Comparative studies on physicochemical properties of total, A- and B-type starch from soft and hard wheat varieties

Starch from soft wheat and hard wheat varieties was evaluated for physicochemical properties, including pasting and retrogradation properties, swelling power and solubility, and granule morphology. Grain hardness index of soft and hard wheat varieties ranged from to 25 to 35, and 71 to 82, respectively. Soft wheat varieties showed a larger proportion of total starch (TS) and A-type starch (AS), and a smaller proportion of B-type starch (BS). The amylose content of starch from hard wheat varieties was significantly higher than that from soft wheat varieties. Starch from soft wheat varieties exhibited higher pasting viscosity, transmittance, swelling power, and smaller crystallinity as compared to starch from hard wheat varieties. BS from hard wheat exhibited the lowest average breakdown and setback viscosity, hardness, adhesiveness, and fracturability. AS exhibited the highest pasting viscosity, better transparency, gel properties, freeze-thaw stability, swelling power, clearer "Maltese cross", and higher crystallinity, whereas BS exhibited the highest gelatinization temperature, better gel stability and solubility. The study might broaden the recognition of starch from different wheat varieties, and provide a theoretical basis for wheat breeding and the potential utilization of different types of wheat starch and flour.