The effect of heat treatment at 90, 100, 110 and 120 ℃ for 20 min to sweet potato flour on dough properties and characteristics of sweet potato-wheat bread was investigated. The lightness (L*) and a* of sweet potato flour samples after heat treatment were increased, while the b* were decreased significantly, as well as the particle size, volume and area mean diameter ( p < 0.05). A slight change of the microstructures of sweet potato flour was observed, where the number of irregular granules increased as the temperature increased from 90 to 120 ℃. Compared with sweet potato flour samples without heat treatment and with heat treatment at 90, 100 and 120 ℃, the gelatinization temperature and enthalpy change of sweet potato flour at 110 ℃ were the lowest, which were 77.94 ℃ and 3.67 J/g, respectively ( p < 0.05). After heat treatment, gas retention of the dough with sweet potato flour increased significantly from 1199 ml without heat treatment to 1214 ml at 90 ℃ ( p < 0.05). In addition, specific loaf volume of sweet potato-wheat bread with sweet potato flour after heat treatment increased significantly, which was the largest at 90 ℃ (2.53 cm/g) ( p < 0.05). Thus, heat treatment at 90 ℃ to sweet potato flour could be potentially used in wheat bread production.

The effect of high hydrostatic pressure (HHP, for 20 min at 25°C to sweet potato flour (SPF) on dough properties and characteristics of sweet potato-wheat bread was investigated. The particle size of SPF after HHP was decreased significantly. The obvious rupture was observed in granules of SPF after HHP at 300 and 400 MPa by scanning electron microscopy (SEM). After HHP, significant differences on endothermic peak temperatures (T P ) of SPF were observed by differential scanning calorimetric (DSC), of which the enthalpy change (DH) had a slight increase, expect that at 200 MPa. Gas retention of dough with SPF after HHP increased markedly from 1199 (0.1 MPa) to 1246 ml (100 MPa). Specific loaf volume of bread with SPF at 400 MPa was increased significantly, while the hardness and chewiness were reduced. Thus, SPF treated with HHP at 400 MPa could be potentially used in wheat bread production.Keywords Bread, dough properties, high hydrostatic pressure, sweet potato flour.Effect of HHP on sweet potato bread I. Carballo P erez et al.Effect of HHP on sweet potato bread I. Carballo P erez et al.1093