The Impact of Vacuum and Convective Drying Parameters on Kinetics, Total Phenolic Content, Carotenoid Content and Antioxidant Capacity of Kiwiberry (Actinidia arguta)

Abstract

This study aimed to investigate the impact of convective and vacuum drying performed at different temperatures on the content of bioactive components of kiwiberry. Dried fruits obtained from Geneva and Weiki cultivars were analyzed for total carotenoid content, total phenolic content (TPC), and antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays. The secondary goal was to establish drying kinetics and to find the best-fitting model for the drying process. The results showed that the highest total carotenoid content was found in Geneva fruits dried by vacuum method and was equal to 39.55–90.27 µg/g dry matter (d.m.). Considering free radical scavenging activity, the best results were also achieved for vacuum dried Geneva cultivar. These samples exhibited EC50 equal to 0.16–0.51 mg d.m./mL and 0.05–0.24 mg d.m./mL as evaluated using DPPH and ABTS assays, respectively. Vacuum drying method usually better preserved the phenolic content of kiwiberry—samples dried at 50 °C did not differ significantly from fresh material. Generally, the shortest drying time was observed for the samples dried at 70 °C regardless of the drying method. Changing the temperature during drying from 80 to 50 and 60 °C did not cause expected benefits regarding chemical property preservation. In most cases, the Midilli et al. model represented the best fit to describe obtained drying kinetics.