Effect of infused CO2 in a model solid food on the ice nucleation during ultrasound-assisted immersion freezing

•Carbon dioxide was infused into model solid food (gelatin gel).•Infusion of CO2 (ICO) in gelatin gel samples facilitated nucleation to occur.•ICO sample nucleated at temperature closer to ultrasound application with shorter delay.•ICO treatment was in favor of ultrasound-initiated nucleation. To understand the mechanism of ice nucleation induced by ultrasound in solid food matrix, the effect of infusion of CO2 (ICO) in a model solid food system (gelatin gel) on the dynamic nucleation of ice during ultrasound-assisted immersion freezing (UIF) was investigated. The results showed that the content of absorbed CO2 in a gelatin gel samples increased with ICO-treated time increase and a great number of micro bubbles were observed in the samples by light microscope. The nucleation temperatures of the samples with/without ICO treatment increased by the application of ultrasound. In addition, there was a better correlation between the nucleation temperature and the ultrasound onset temperature for the samples infused with CO2. Moreover, compared to the samples without ICO treatment, the nucleation delay was shorter and nucleation temperature was closer to ultrasound irradiation temperature. It can be concluded that cavitation and ultrasonic irradiation parameters are factors affecting the nucleation of model solid food and CO2 infusion can be used to initiate the nucleation of solid samples during UIF.