## 1 Introduction
Ultrasound is an emerging technology developed to minimize processing time, maximize quality, and ensure the safety of food products [16; 17]. In the food industry, sonication is used for inactivating microorganisms [18], creating the viscosity of juice through the emulsification process [19], and as a pre-step before freezing, drying, and extraction processes [17; 20; 21] in food products such as fruit juices, mayonnaise, and tomato ketchup [22; 23]. Ultrasound techniques have emerged as an energy-efficient and straightforward technology in food processing. These are classified into two main categories: low-power ultrasound (high-frequency) and high-energy ultrasound (high-power and high-intensity) [17; 24; 25]. Low-power ultrasound is used for the non-destructive quality control of fresh fruits and vegetables during the pre- and post-harvest stages and in the processing of cheese, fat-based products, and aerated and frozen foods. In contrast, high-energy ultrasound can disrupt foods' physical, mechanical, or chemical properties, thereby enhancing their processing, preservation, and safety [26; 27; 28]. The process primarily relies on acoustic cavitation, whereby ultrasound waves create and collapse bubbles in liquids. This generates mechanical forces, localized heating beneficial for sterilization, and highly reactive radicals that facilitate chemical reactions such as pesticide degradation and enzymatic cross-linking [17; 24; 25]. Several studies have explored the impact of ultrasound on various fruit and vegetable juices. While some research suggests a minimal effect on their physical properties, others have identified significant changes in specific parameters. Extensive research has been conducted on tomato juice and its concentrated puree, revealing that ultrasonic treatment can alter their viscosity and consistency. Additionally, studies have shown that ultrasound treatment can affect the viscosity of carrot puree. One study indicated that the viscosity of carrot juice gradually increased with longer ultrasound treatment time [16]. However, another study suggested that the viscosity of carrot juice remained relatively unchanged under different treatment conditions (changed US power), indicating that the impact of ultrasound on viscosity may depend on specific treatment parameters [29]. Ultrasound treatment significantly influences the color stability of carrot puree, particularly after longer treatment durations, resulting in observable changes in the lightness parameters of carrot tissue [30]. Moreover, ultrasound treatment has been found to increase the turbidity of apple juice, potentially affecting its visual appearance and color stability [31]. Furthermore, ultrasound treatment has been shown to impact the nutritional content of carrot puree. Studies have revealed that ultrasound treatment could enhance the total carotenoid content, total soluble solids, total sugars, and ascorbic acid contents of carrot products, indicating a positive effect on nutritional quality [16; 29; 32]. However, the impact of ultrasound treatment on carotenoid content was found to be variable, with some studies reporting a decrease in carotenoid content under specific treatment conditions [29]. Current research on carrot puree's rheological and physical properties is somewhat limited, and there appears to be a gap in data concerning carrot purees treated with ultrasound. As a result, this study seeks to examine the effects of two ultrasonic frequencies (21 and 35 kHz) on carrot purees' rheological and physicochemical properties. This study assumes that a product with repeatable and designed functional and nutritional features will be obtained due to sonication. The scope of this study includes an analysis of the effect of sonication and its frequency on the rheological properties and activation energy of the tested carrot puree, which were considered functional features. Additionally, it examines color and carotenoid content, which are functional properties that can characterize the nutritional value of the tested samples.