Abstract
A technology has been developed for producing dry functional vegetable powders from carrot, beetroot, and pumpkin pomace using combined methods: convective drying, ultrasound pretreatment, and vacuum-microwave drying. A comparative analysis was conducted to evaluate the effects of different drying techniques on particle size distribution, flowability, hydration properties, color, thermal stability, retention of bioactive compounds (β-carotene, betalains, carotenoids), and overall functional-technological characteristics of the powders. It was established that vacuum-microwave drying provides the best results: minimal moisture content (5.2–6.1%), low water activity (0.28–0.33), high flowability (Carr’s index 23.7–30.4), excellent dispersibility and solubility, as well as maximum retention of thermolabile compounds (carotenoids/betalains retention up to 90–95%). Ultrasound pretreatment significantly enhances mass transfer, reduces particle size, and improves powder quality during subsequent convective drying; however, it remains inferior to the vacuum-microwave method across all key indicators. Optimal parameters for vacuum-microwave drying were determined for each type of raw material, ensuring maximum nutrient preservation with minimal processing time. The resulting powders demonstrate high thermal stability up to 200 °C and are suitable for fortification of functional food products. The study results confirm the high potential of combined drying technologies applied to secondary vegetable raw materials for the production of natural functional ingredients with extended shelf life.