Optimization of Ultrasonic-assisted Cleaning of Seedless Green Raisins by Response Surface

Aiming at the problem that seedless green raisins easily browned by raisin processing enterprises, the ultrasonic-assisted cleaning process was adopted. Based on single factor experiments, the alcohol content, temperature and time of the cleaning agents were selected as the influencing factors, and browning index BI value was as the index. The response surface method was designed to obtain the optimal conditions for the ultrasonic-assisted cleaning process of seedless green raisins. The raisins cleaned under the best cleaning conditions were dried with a heat pump.The results showed that the optimal condition were alcohol degree 44%vol, temperature 9℃, and time 90 s. The BI value of seedless green raisins was only 33.43, which was 26.98% lower than that of traditional tap water spray cleaning. The optimal temperature for heat pump to dry raisins was 50℃. Under these conditions, the BI value of seedless green raisins was 23.69, which was slightly lower than the unwashed seedless green raisins for 28.52% at the same temperature.