Abstract: The properties of starch directly affect the appearance and eating quality of starch-based foods. In order to investigate the effect of high hydrostatic pressure (HHP) treatment on the properties of oat starch, changes in the morphological, textural, thermal and rheological properties of oat starch were determined after being treated under pressures of 100–600 MPa for 30 mins. The results showed that after HHP treatment at pressures of 100–300 MPa, the average particle size of oat starch granules decreased without significant changes in the surface morphology. In contrast, the particle size increased and the granule surfaces became rough, collapsed and adhered together after HHP treatment at 400–600 MPa. HHP treatment could significantly reduce the hardness, gumminess and chewiness of starch gels, and increase the resilience, springiness and cohesiveness. Differential scanning calorimetric (DSC) analysis indicated that starch gelatinization occurred after treatment at 500 or 600 MPa. The dynamic rheological studies revealed that the G’, G’’ and tan δ values of HHP treated starch paste were significantly higher than those of the original starch, indicating that this treatment enhanced the viscoelasticity of starch, and after treatment at 100 MPa, starch showed the best viscoelasticity. In the static rheological studies, both raw and treated starch were pseudo-plastic fluids. HHP treatment at 500 or 600 MPa reduced the thixotropy loop area and greatly improved the shear stability. This study will provide theoretical reference for research on the effect of ultrahigh pressure on starch properties.

Key words: high hydrostatic pressure; oat starch; morphological properties; thermal properties; rheological properties