## 3 Results
### Color and \(\beta\)-Carotene Content  
The concentration of carrot puree influenced the degree of color variation observed, regardless of the ultrasound treatment employed. An increase in brightness, redness, and yellowness was observed in the samples (Figure 3). The relationships obtained in the presented studies were also given for carrot puree [53], tomato juice [38], and pineapple juice [26], while the opposite results were presented for orange juice (extract 9.23 \({}^{\circ}\)Brix) [40]. Such a discrepancy in the results may be related to the different chemical composition of  
Figure 2: Influence of the sonication and carrot puree concentration on the flow viscosity curves measured at 20 \({}^{\circ}\)C. Description of the colors and lines on the graph: marron—carrot puree without US treatment; green—carrot puree with US treatment at a frequency of 21 kHz; royal blue—carrot puree with US treatment at a frequency of 35 kHz; continuous line—dedicated to carrot puree with 9 \({}^{\circ}\)Brix; dashed line—dedicated to carrot puree with 12 \({}^{\circ}\)Brix; dotted line—dedicated to carrot puree with 21 \({}^{\circ}\)Brix. the juice and the presence of other pigments. After sonication, lightness could decrease with an increase in the content of soluble substances in the juice. Figure 3: Influence of the US treatment and concentration on the (**a**) color coefficients of carrot pure; (**b**) total color difference in carrot pure. a, b, c, d, e, f, g—Means with the same letter separately for each color coefficient are not significantly different; red dashed line for value 2; blue dashed line for value 3.5. Colors for bars on the graph: marron—without US treatment—0 kHz; green—21 kHz; royal blue—35 kHz. The most significant changes in color values a* and b* were observed following ultrasonic treatment at 35 kHz. In contrast, the least significant changes were noted in brightness at the same setting. Similar correlations for low-concentrated juices were obtained for orange juice [40], tomato juice [38], and carrot juice [53]. The application of ultrasound decreased brightness for purees 9 and 21 \({}^{\circ}\)Brix, while it increased in a concentration of 12\({}^{\circ}\)Brix. Minor changes in the values were observed for the redness parameter (a*), except for the 21 \({}^{\circ}\)Brix pure, for which a notable increase was evident. In contrast, yellowish decreased with ultrasound treatment at 9 and 12 \({}^{\circ}\)Brix concentrations, while an increase was observed at 21 \({}^{\circ}\)Brix. The yellowish coefficient (b*) values in carrot puree increased as the juice concentration increased. When the low-frequency US was applied, the yellowness coefficient decreased in the 9 \({}^{\circ}\)Brix carrot puree (Figure 3a). Statistically significant increases in the b* chromaticity coefficient were observed in carrot puree treated with higher-frequency ultrasonic waves compared to untreated juices (Figure 3a). The sonication of tomato juice at 20 kHz for a period of 10 min resulted in a reduction in the values of the b coordinate [38]. In contrast, an increase in b* coordinate after sonication was observed in orange juice extract with 9.23 \({}^{\circ}\)Brix [40] and in pineapple juice [26]. According to [PERSON] et al. [27], changes in chromaticity factors a* and b* can be linked to synchronized changes in the luminosity value (L*). They also suggested that during the ultrasound process, the disruption of the carotenoid-protein complex may intensify the orange color of the juice. [PERSON] et al. [26] made a similar observation, suggesting that sonication can release intercellular contents, which may impact the product's color. No consistent trend was observed in the changes to the individual color determinants. The total color difference (\(\Delta\)E) was calculated to assess the overall changes. It was found that, except for the 21 \({}^{\circ}\)Brix concentration at 35 kHz, the color difference in juices sonicated at 21 kHz could not be detectable even by a trained expert.