Abstract:

This study aimed to develop an ultrasonic-assisted desulfurization technology for sulfited Chinese olive. Effect of ultrasonic power on desulfurization rate and effects of frequency in single-frequency ultrasonic mode on desulfurization rate, L value and hardness of sulfited Chinese olive were evaluated, and desulfurization effects of single- and dual-frequency ultrasonic modes were compared. Moreover, three environmental conditions for ultrasonic treatment such as temperature, water refresh cycle and pH adjustment of deionized water were optimized using response surface analysis (RSA). The desulfurization rate presented a positive relationship with the ultrasonic power, but a negative relationship with ultrasonic frequency within the range of 25 kHz to 60 kHz. The desulfurization effects of various ultrasonic powers declined as the following order: 25 kHz ＞ 40 kHz＞ 60 kHz. However, the dual-frequency ultrasonic mode (combination of any two of 25 kHz, 40 kHz and 60 kHz) did not show synergistic but only simple superposition effect. RSA indicated that under the ultrasonic parameters of 25 kHz and 250 W, the temperature, pH value and interaction between them had significant effects on the content of sulfur dioxide. The environmental conditions for ultrasonic treatment were 60 ℃, water refresh per 6 h and pH adjusted to 3.

Key words: sulfited Chinese olive, desulfurization, ultrasonic frequency, ultrasonic power