Abstract
This study analyzed the effects of thermal pre-treatments such as convective drying (P-CD), water (BL_W), and microwave blanching (M_BL) and osmotic enrichment pre-treatments with juices from pomegranate (PG), chokeberry (CH), and sea buckthorn (SB) on microwave-vacuum-dried (MVD) carrot properties. Convective drying (CD) and freeze-drying (FD) were used as a comparative method. The dry matter content and water activity of MVD carrots were varied, but in many cases, the values were comparable to those of FD-dried carrots. Pre-enrichment in CH juice significantly reduced the values of the color parameters L*, a*, and b*, regardless of the drying method. The smallest changes were observed in microwave pre-blanching (M_BL). The lowest loss in carotenoid content was observed in CD-dried carrots (14-34 mg/100 g d.m.). Blanching and enrichment in SB juice allowed significant retention of these compounds. As a result of drying carrots, the total phenolic content (TPC) increased. Compared to the raw material, the TPC content in dried carrots increased 3-9 times. Drying using the FD and MVD methods gave a similar effect of increasing the TPC content, including a greater effect after enrichment in CH juice. The highest average antioxidant activity against the DPPH• and ABTS•+ radicals was recorded for FD-dried carrots (6.9 and 30.0 mg Trolox/g d.m.). SB juice contributed to a significant increase in the total vitamin C content, even by 89.1%, compared to raw carrots. Applying osmotic pre-enrichment in PG juice increased the sugar content in dried FD and CD samples by 37.4-49.9%, and in MVD by 21-59%.