该研究对干燥前的花椰菜进行超声波预处理，探究了不同水平的超声预处理条件对花椰菜干制品品质的影响，分析了其热风干燥过程中的水分状态及分布。在单因素实验的基础上，以色泽、复水比、维生素C含量和DPPH自由基清除能力为响应值，选取超声时间、超声频率和超声功率密度进行三因素三水平的响应面中心组合设计实验，获得花椰菜干制品品质较佳的超声条件。结果表明，花椰菜超声波预处理最优工艺为：超声时间6.00 min，超声频率80 kHz，超声功率密度0.22 W/cm2。此条件下花椰菜干制品b*值为30.58，复水比2.97，Vc含量为311.78 mg/100 g，DPPH自由基清除能力为17.20 μmol Trolox/g。低场核磁共振（LF-NMR）结果发现，花椰菜热风干燥过程中首先脱除的为自由水，其次为半结合水及部分结合水；且超声波处理后提高了花椰菜中氢质子自由度，能够加快其干燥过程中水分脱除速率。因此，响应面中心组合设计实验和LF-NMR技术可用于花椰菜干制品预处理工艺优化和干燥过程水分变化分析，改善干制品品质，提高生产效率。

In this study, ultrasonic pretreatment of cauliflower was used before drying, and the effects of different levels of ultrasonic pretreatment conditions on the quality of dried cauliflower products were explored. Meantime, the moisture status and distribution of cauliflower during hot air drying were analyzed. Based on single-factor experiments, taking color, rehydration ratio, vitamin C content and DPPH free radical scavenging capacity as response values, ultrasonic time, ultrasonic frequency and ultrasonic power density were selected to perform a three-factor three-level response surface center combination design experiment. And the ultrasonic conditions with better quality of dried cauliflower products were obtained. The results showed that the optimal process for ultrasonic pretreatment of cauliflower was ultrasonic time 6.00 min, ultrasonic frequency 80 kHz, ultrasonic power density 0.22 W/cm2. Under these conditions, the b* value of the dried cauliflower product was 30.58, the rehydration ratio was 2.97, the Vc content was 311.78 mg/100 g, and the DPPH free radical scavenging ability was 7.20 μmol Trolox/g. The results of low-field nuclear magnetic resonance found that free water was firstly removed during the process of hot air drying of cauliflower, followed by semi-bound water and partially bound water. After ultrasonic pretreatment, the degree of freedom of hydrogen protons in cauliflower was increased, so the water removal rate could be accelerated during the drying process. Therefore, to improve the quality of dried cauliflower products and reduce drying time, the response surface center combined design experiment and LF-NMR technology can be used to optimize the pretreatment process of dried cauliflower products and analyze the moisture changes during drying.

江苏省重点研发计划（现代农业）重点项目（BE2018382）