###### Abstract  
HTST (high-temperature short-time) pasteurization and UHT (ultra-high-temperature) sterilization are techniques commonly used in the dairy industry. Although the use of these methods in fruit and vegetable processing is also well known, the multitude of diverse food matrices determines the need to test and adjust process parameters in order to obtain the best quality of the final product. HTST and UHT are methods that provide effective inactivation of microorganisms and enzymes. Despite the fact that UHT and HTST are thermal processes that cause degradation of bioactive ingredients or color change, in many cases, these two methods are superior to traditional pasteurization, which uses significantly longer exposures to high temperatures. Therefore, this article aims to review the effect of HTST and UHT processing on the quality of juices, nectars and beverages, taking into consideration the quality characteristics, like the presence of microorganisms, pH, titratable acidity, total soluble solids, turbidity, color parameters, contents of bioactive components, antioxidant activity, enzymatic activity and volatile compounds. The impacts of HTST and UHT methods on various food products are discussed, including the food matrix, preservation parameters and the mechanism of interaction. The ability to modify the processing parameters can allow for the selection of adequate preservation parameters for individual products and better results than other unconventional methods, such as HPP (high-pressure processing) or PEF (pulsed electric field). Based on the cited literature, it can be concluded that pH, titratable acidity and TSS most often experience slight changes. As for the other parameters considered, it is extremely important to choose the right temperature and duration for a specific food matrix. HST; UHT; thermal preservation of food; liquid food; bioactive compounds; phenolics; antioxidant capacity; vitamin C; enzyme activity; volatiles profile +
Footnote †: journal: Medical  
a 2-10% decrease in the antioxidant capacity of peach beverage, with negligible changes in total phenolic content and total flavonoid content [7]. Pasteurization (95 \({}^{\circ}\)C/3 min) led to reductions in individual anthocyanin contents of unclarified (39-51%) and clarified (11-18%) crude black mulberry juice [8]. [PERSON] and [PERSON] [9] indicated absolute color differences in pomergnate juice of \(\Delta\)E = 4.19 and \(\Delta\)E = 6.29 after heating at 95 \({}^{\circ}\)C for 2 and 3 min, respectively. Because of changing consumer needs, including the search for products with high contents of bioactive ingredients and highly rated organoleptic quality, recently, intensive studies have been conducted on the use of modern preservation methods [3; 10; 11; 12; 13; 14; 15]. Also, because of numerous negative reports on the effects of heating on the quality of fruit and vegetable products [12; 16; 17; 18; 19], further research is needed to optimize preservation parameters in order to obtain the best possible quality. Two modern and still improving methods of food preservation are HTST (high-temperature short-time) pasteurization and UHT (ultra-high-temperature) sterilization. Thanks to the better heat exchange and much shorter exposition time for heating than traditional pasteurization, HTST and UHT allow for obtaining a better quality final product [20]. The aim of the paper is to review the effects of HTST and UHT processing on the quality of juices, nects and beverages, taking into account quality characteristics such as the presence of microorganisms, pH, titratable acidity, total soluble solids, turbidity, color parameters, content of bioactive components, antioxidant activity, enzymatic activity and volatile compounds. This article can serve as a significant compendium of knowledge for use in work on food processing and scientific research design.