Insights into structure and function of high pressure-modified starches with different crystalline polymorphs

The effect of high pressure (HP) treatment at 200-600 MPa for 30 min on properties of three starches with different polymorphs was investigated. HP treatment altered greatly the morphology of wheat starch, especially at 400 MPa or higher. The crystallinity of wheat starch decreased from 22.6% for native starch to 3.4% for starch after treatment at 600 MPa. The short-range molecular order as measured by FTIR and Raman spectroscopy decreased with increasing treatment pressure. HP treatment had little effect on structural properties of potato and yam starches, except for yam starch after treatment at 600 MPa. HP treatment decreased the pasting viscosities of wheat starch except for the treatment at 200 MPa, which increased the peak, trough and final viscosities by 6.7, 11.1 and 5.7%, respectively. The peak viscosity of potato and yam starches was increased respectively by 14.0 and 11.3% after HP treatment at 600 MPa. HP treatment at 600 MPa enhanced greatly the final digestion percentages of wheat and yam starch by 20 and 26.4%, but had little effect on potato starch. The above results showed that wheat starch was more susceptible to the effects of HP treatment than did yam and potato starches, and that C-type yam starch behaved more likely the B-type potato starch to HP treatment.