Effects of Different Treatment Methods on Improving the Quality of Purple Sweet Potato Noodles
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Abstract:
In this study, the changes of cooking loss rate, microstructure, rheological properties and resistant starch content of purple sweet potato flour were investigated to explore the effects of steaming, aging and freezing treatment on the quality of purple sweet potato noodle. The results showed that the cooking loss rate, resistant starch content, microstructure and rheological properties of purple sweet potato noodle prepared by extrusion changed under different treatment conditions including steaming, aging and freezing. The content of resistant starch gradually increased from 3.01% to 4.02% under 2 to 4 h aging treatment, but it remained unchanged with the further increasing of aging time. In the first 3 to 5 min, the content of resistant starch increased from 3.41% to 4.82% with the increase of steaming time, however, it decreased from 4.82% to 2.40% when the steaming time increased from 5 min to 11 min. Under different treatment conditions, the surface microstructure of purple sweet potato powder changed obviously, suitable steaming, aging or freezing treatment improved the microstructure of purple sweet potato noodle, but overtreatment also led to deterioration of the microstructure. The storage modulus and loss modulus of untreated purple sweet potato noodle were obviously higher than those of treated purple sweet potato noodle, and the storage modulus was obviously higher than the loss modulus, and the elastic modulus was dominant. Therefore, suitable steaming, aging and freezing treatment can effectively improve the whole quality of purple sweet potato noodle.
