Characterization of Nubet and Franubet barley starches

Franubet, a mutant of Nubet, had grains of smaller weight, less starch, but greater protein content than did Nubet. Nubet starch had simple granules with bimodal granule size distribution (diameters of 9–22 and 1.2–4 μm for the A and B granules, respectively), whereas Franubet starch had smaller (diameters of 1–4 μm) and irregular-shaped granules, and some displayed compound starch granules. There were no significant differences in X-ray diffraction pattern and amylose content, but Nubet starch had a greater phosphorous (0.045%) and bound lipid (0.61%) content than Franubet starch (0.026 and 0.47%, respectively). Franubet amylopectin (AP) had similar proportions (4.0%) of chains with DP 6–9 and larger proportions (21.5%) of chains with DP >37 than did Nubet AP (4.2 and 19.7%, respectively). Franubet starch showed lower onset gelatinization temperature (52.8 °C) and smaller enthalpy change in melting of amylose–lipid complex (0.5 J/g) than did Nubet starch (54.6 °C and 1.0 J/g, respectively). Franubet starch displayed a lower pasting temperature, less final and setback viscosity but greater peak and breakdown viscosity, which could be attributed to its lower lipid and phospholipid content.