Abstract
In recent years, ultrasonic pretreatment technology has been widely used in the aquatic product preservation industry. Among these technologies, dual-frequency ultrasonic refrigeration is the most common. However, in practical applications, selecting the frequency is relatively simple, and there has been less research on power selection. In this paper, the specific frequency (up and down 20 kHz, around 40 kHz), using different powers of (a) 200 W, (b) 300 W, and (c) 400 W processing, ultrasonic intermittent mode with 30 s on/30 s off cycle, and an ultrasonic processing time of 10 min was examined; the control group (CK) comprised samples without ultrasonic treatment. The samples were stored at 4 °C and then placed in a Polyethylene (PE) bag. The changes in microbiological parameters, physicochemical indices, and protein indices of the samples were monitored every two days. The results show that 400 W ultrasonic treatment can significantly inhibit the growth of TVC during storage. The rate of increase in pH, TVB-N, and TBA values decreased significantly compared with the other groups. Compared with the CK group, the shelf life of the 400 W treatment group was extended by 6 days. Therefore, the 400 W pretreatment method based on orthogonal double frequency has strong application potential for effectively extending the shelf life of refrigerated large yellow croaker.