Abstract: In order to improve the freeze, heat and shear stability of sweet potato starch, the effects of freezing temperature and sodium alginate on the particle size, crystalline structure, surface morphology, gelatinization and thermal properties of sweet potato starch granules were investigated. The results indicated that the particle size of starch granules decreased with decreasing the freezing temperature from ?20 to ?80 ℃. The surface morphology transformed from few big holes into many pits. After adding sodium alginate, the holes on the surface of starch granule gradually diminished and even disappeared. Adding sodium alginate strikingly increased the relative crystallinity and peak temperature and significantly decreased the breakdown value of frozen starch. The above results suggested that sodium alginate could protect starch granules from freeze damage and increase its heat and shear stability, which will provide theoretical reference for further research to improve the quality of frozen starchy foods.

Key words: sweet potato starch; freezing treatment; sodium alginate; microstructure