The Physical Properties and Crystal Structure Changes of Stabilized Ice Cream Affected by Ultrasound-Assisted Freezing

Abstract

In this study, the effect of ultrasound-assisted freezing with frequencies of 21.5 and 40 kHz, and a power of 2.4 kW in the chopped mode of milk ice cream in comparison to a standard freezer on the freezing course and formed crystal structure was examined. The first part of the research included the preparation of an ice cream mixture on the basis of skimmed milk with the addition of an emulsifier, locust bean gum, xanthan gum, ι-carrageenan and a reference mixture without stabilizer addition. Ultrasound-assisted freezing shortened the processing time of both stabilized and non-stabilized ice cream. Stabilized samples of milk ice cream exposed to ultrasound (US) at a frequency of 21.5 kHz were characterized by the most homogeneous structure, consisting of crystals with the smallest diameters among all of the tested samples, the size of which, after 3 months of storage at −18 °C, was 7.8 µm (for the reference sample, it was 14.9 µm). The ice recrystallization inhibition (IRI effect) in the samples after US treatment with a frequency of 40 kHz was also observed, regardless of the addition of stabilizers, which may suggest that sonication with these parameters could replace or limit the addition of these substances.