研究了单频25,kHz、40,kHz及双频25,kHz＋40,kHz超声处理对红薯淀粉结构及性质的影响．由扫描电镜分析图可知，超声处理能够使淀粉颗粒表面出现裂纹和不均匀孔洞，且双频超声作用效果最明显．由红外分析光谱可知，超声作用破坏了淀粉的结晶区和无定形区的相对大小，无定形结构部分增加，其尖峰衍射特征强度减弱，相对结晶度降低，与原淀粉相比，双频超声处理后的淀粉结晶度降低6.15%．Brabender 曲线表明，淀粉经超声处理后黏度降低，双频超声处理后的淀粉峰值黏度比原淀粉降低12.08%．超声处理后淀粉的透明度、溶解度均提高，其中双频超声处理30,min 时，透射比比原淀粉增加69.85%；双频超声处理60,min 时，溶解度比原淀粉增加26.83%．单频25,kHz、40,kHz和双频25,kHz＋40,kHz比较，双频超声处理对淀粉的结构和性质影响效果高于单频超声．%The effects of single frequency ultrasound of 25,kHz,40,kHz and dual-frequency ultrasound of 25,kHz+40,kHz on the structure and properties of sweet potato starch were investigated. After the ultrasonic treatment, many dents and holes were found by scanning electron microscopy on the surface of starch granules. FTIR analysis indicated that the ultrasounds didn’t change the crystal type of the starch,but damaged its crystal structure,and its crystallization index decreased. Com-pared with the controlled sample,the crystallization index of the starch treated with dual-frequency ultrasound decreased by 6.15%. Brabender curves showed that the viscosity of the starch could be reduced effectively by ultrasonic treatment,and the peak viscosity of the starch after dual-frequency ultrasound treatment was 12.08% lower than that of the controlled sample. In addition,the transmittance and solubility of the starch increased by ultrasound treatment. The starch being treated with dual-frequency ultrasound for 30,min showed the maximum transmittance,which increased by 69.85%. Treated with dual-frequency ultrasound for 60,min,its solubility increased by 26.83%. Compared with single frequencies of 25,kHz and 40,kHz,dual-frequency ultrasonic(25,kHz+40,kHz)treatment can bring about better changes in the structure and properties of starch than the single frequencies.
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