Abstract: The extrusion and quality properties of four different potato materials including potato, purple potato, sweet potato and purple sweet potato were systematically studied by using a texture analyzer, a rapid viscosity analyzer and a stability analyzer. The results showed that the extrusion properties of potato materials were significantly better than those of sweet potato materials. Potato exhibited the best extrusion properties as reflected by increased expansion degree, gelatinization degree and water solubility index and reduced volume density of extruded potato in contrast to other extruded samples. Correlation analysis showed that the extrusion properties of different potato materials were related to the differences in their major components. The firmness, consistency, trough viscosity, setback and ratio of setback to peak viscosity of potato materials were significantly lower than those of sweet potato materials, indicating that extruded potato had higher cooking degree and better taste. Furthermore, the quality of extruded potato was significantly better that of extruded purple potato (P < 0.05). The results of stability analyzer and stability index showed that the dispersion stability of potato materials especially potato was significantly better than that of sweet potato materials (P < 0.05). Therefore, the extrusion and quality properties of potato materials are superior to those of sweet potatoes and potato is the best of four potato materials.

Key words: potato materials, extrusion, extrusion properties, texture properties, pasting properties, stability