## 3 Results and Discussion
### The Microscopy Structure Analysis
It is mentioned here because based on the FTIR analysis, it was confirmed that samples B and L after the enzymatic hydrolysis had a similar course on the FTIR spectra. It can be evidence that the enzymatic hydrolyzates of \(\upiota\)-carrageenan were more favourable in milk ice cream than \(\upiota\)-carrageenan and its acid hydrolyzates. In the research by [PERSON] et al. [42], the ultrasound-assisted depolymerization of \(\upkappa\)-carrageenan was investigated. It was proven that the raw carrageenan average molecular mass was reduced by 89.32% while in the irradiated \(\upkappa\)-carrageenan it was only 41.98%. Such observations were connected with the fact that larger molecules present more resistance to flow and the same accumulate greater shear force, which leads to more frequent ruptures as the cavitation bubbles collapse than in the shorter polymer. Therefore, in our research, presumably, the effect of \(\upiota\)-carrageenan was similar even if the initial molecular mass of this polymer was higher than the obtained hydrolyzates [13]. Moreover, in the same research, [PERSON] et al. [42] noticed that after ultrasound treatment, \(\upkappa\)-carrageenan with a lower molecular mass revealed the retention of absorbance peaks with the decrease in the sulphate functional group and most of the peaks were retained, with one exception of a methylene peak. Cln our study, the chain of \(\upiota\)-carrageenan underwent changes by ultrasonic cavitations, which led to a similar effect on the IRI activity in ice cream as the hydrolyzates. Moreover, it generated information that hydrolyzates will be more stable and less vulnerable on the ultrasound treatment than pure \(\upiota\)-carrageenan. Nonetheless, further studies will be recommended to investigate the possible changes in the molecular structure of \(\upiota\)-carrageenan and its hydrolyzates after ultrasound treatment. Finally, the mechanism of ultrasound, such as inducing ice nucleation as well as increasing heat and mass transfer, is connected with the initial step of ice cream production. In our research, it was proven that ultrasound forces were so strong that they influenced the structure of ice cream even after a few months of storage and prevented excessive growth of ice crystals. The observation of the progress of the recrystallization process was also analysed based on images (Figures 4 and 5). To access this we used the overview of the appearance of ice crystals during storage after 24 h and 3 months of storage at \(-18\)\({}^{\circ}\)C (only representative photos were chosen to show in the paper, not including the photos after 1 month). Looking at the images, it may be noticed that the shape of the ice crystals was round and regular (Figure 4). The research by [PERSON] et al. [43] showed that in lactose solutions with the presence of whey proteins and \(\upkappa\)-carrageenan, after 48 h of ultrasound-assisted crystallization, the shape of crystals was mostly irregular, even with the tomahawk-like shape. Nonetheless, it is known that high ultrasound energies may be responsible for breaking crystals already formed and generating a disruption of agglomerates or even nuclei [44]. After 24 h of storage of ice cream, the changes between the samples treated with different sorts of homogenization were not visible. For example, in samples AH_24h (sample with acid hydrolyzes of t-carrageenanan and after traditional homogenization) and AU_24h (sample with acid hydrolyzes of t-carrageenanan and after ultrasound), the changes were connected with the size of ice crystals (which was confirmed in Table 4), but not in the appearance of crystals. A similar effect on the shape of the ice structure was noticed in frozen pork tissue [45] or in frozen mushrooms [39], that ultrasound treatment unified the shape and sizes of the ice crystals. Moreover, [PERSON] et al. [46] indicated that differences in the structure of ice crystals may depend on the ultrasonic power intensities.