Effect of Ultrasound-Assisted Freezing on the Crystal Structure of Mango Sorbet

Abstract

In this study, the effect of ultrasound-assisted immersion freezing (UAF) of mango sorbet in comparison to conventional freezer freezing, on freezing course and created crystal structure, was studied. The scope of work included the preparation of a sorbet mixture prepared on the basis of frozen mango fruit with the addition of locust bean gum (LBG), guar gum and a commercial mix of carrageenan without the addition of stabilizers, and freezing it using a conventional freezer and ultrasound-assisted freezing equipment, with variable operating parameters (21.5 kHz and 40 kHz—continuous or chopped mode). Then, the freezing time and the crystal structure of the frozen samples (a microscopy analysis) were examined. US-assisted freezing reduced the time of the process for stabilized samples of the sorbet. It was also proven that, proper stabilization with the combination of US treatment results in the formation of favorable crystal structure. Stabilized sorbet subjected to US action at a frequency of 21.5 kHz in chopped mode was characterized by the most uniform crystal structure, consisting of crystals with the smallest diameters among all the tested samples; the equivalent diameter was 9 µm, while for the stabilized control it was 25 µm.