Effects of Freeze-Drying on Sensory Characteristics and Nutrient Composition in Black Currant and Sea Buckthorn Berries

Fresh berries contain numerous components that can undergo complex changes during the drying process. This study aims to investigate the effect of freeze-drying on the sensory and chemical properties of black currant and sea buckthorn berries. Freeze-drying was performed at a shelf temperature of 35–55 °C with a step of 5 °C and durations of 18, 20, 22, and 24 h. Comparing the final freeze-dried berries with their fresh counterparts, it was observed that at a shelf temperature of 50 °C and a drying time of 18 to 20 h, there was a minimal loss in the content of vitamins, organic acids, and carbohydrates. However, based on organoleptic evaluations, the best results were achieved after drying for 20 h. Furthermore, the preservation of citric and malic acids in black currant berries, along with citric, tartaric acids, and sucrose in sea buckthorn berries, was only at 45.6% when the freeze-drying time was extended to 22 h. Considering the physical and chemical properties of listed freeze-dried berries, the optimal parameters were identified as a shelf temperature of 50 °C and a drying time of 20 h. The findings from this study serve as a foundation for selecting appropriate freeze-drying parameters for various types of berries.