作为食品物理加工技术，扫频超声能产生一个更有利于改善空化效果的声场，提高了油脂得率，但由于空化效应的存在，导致油脂会发生一定程度的氧化，影响油脂黏度，因此，有必要对油脂氧化和流变特性进行研究。本文中采用压电膜传感器对花生油脂提取过程中本征频率为20 kHz、40 kHz和60 kHz的扫频超声场进行实时监测，根据国标检测油脂氧化性能，利用旋转流变仪测量油脂流变特性。研究发现：花生油脂提取的共振频率是40 kHz，对应的空化效应最显著；当本征频率小于40 kHz，电压峰值、频谱振幅覆盖范围和油脂氧化性能值随频率增加而增大、黏度减小；当本征频率大于40 kHz，电压峰值、频谱振幅覆盖范围和氧化性能值随频率增加而降低、黏度增大。共振频率对应的油脂黏度最小。该油脂是塑性流体，流动特性为宾汉流动，呈剪切稀化趋势。

Sweep frequency ultrasound is an important physical processing technique for food that can provide an acoustic field, which improves the cavitation effect and enhances the extraction yield of oils. However, oxidation may occur, and the viscosity is affected as a result of the cavitation effect. Therefore, it is necessary to study the oil oxidation and the rheological properties of this technique. In this study, a piezoelectric polyvinylidene fluoride (PVDF) sensor was used to monitor the sweep frequency ultrasonic fields with the eigenfrequencies of 20 kHz, 40 kHz, and 60 kHz during the entire process of oil extraction. The oxidative properties of the extracted oils were measured according to the national standards. The rheological properties of the samples were determined using a rotational rheometer. The results showed that the resonance frequency of the oil extraction was 40 kHz, and its cavitation effect was the most significant. When the ultrasonic eigenfrequency was less than 40 kHz, the peak voltage amplitude, frequency spectrum coverage range, and oxidative properties increased with the increment of eigenfrequency, and the viscosity decreased. The opposite effect was observed when the ultrasonic eigenfrequency was greater than 40 kHz, such that the voltage amplitude, frequency spectrum coverage range, and oxidative properties decreased with the increment of eigenfrequency, and the viscosity increased. The viscosity of the oils was the lowest at the resonance frequency. The extracted oils were plastic fluid with the flow characteristic of Bingham flow, and demonstrated a shear-thinning trend.

国家自然科学基金项目（31471698、21676125）；国家重点研发计划（2016YFD0400705-04）；中国博士后科学基金项目（2015M581746）；江苏省自然科学基金项目（BK20150492）；江苏省产学研合作项目（BY2016072-03）；江苏省博士后科学基金项目（1501105B）；江苏大学高级人才科研启动基金项目（14JDG159）