Dosage effect of waxy null alleles on starch and processing characteristics of durum wheat

New potential food applications have emerged from the recent development of full and partial waxy durum wheat. We have evaluated agronomic performances, milling yield, semolina and starch properties, and pasta cooking quality in near isogenic full waxy, partial waxy 4A, partial waxy 7A, and non-waxy durum lines grown in a replicated trial in two locations in North Dakota. Full waxy durum lines contained negligible levels of amylose, although partial waxy lines did not significantly differ in their amylose concentrations from the normal type. During milling, full waxy lines yielded lower semolina than the others, and semolina had lower gluten strength and higher starch damage than the normal and partial waxy lines. Waxy starch properties were similar to those reported for waxy starch originated from other crops: waxy starch swelled to a greater extent and produced a more viscous solution at a lower temperature. It was also more resistant to retrogradation and freeze-thaw cycles. Pasta from full waxy lines had a duller appearance, cooked faster, and was softer than pasta from non-waxy and partial waxy lines, although the waxy trait did not affect the water absorption of the pasta. We suggest that much of the decrease in waxy pasta firmness may be due to increased cooking loss, higher starch damage, and lower starch retrogradation.