Evaluation of drying, physical, and bioactive compounds of processed Rosa pimpinellifolia L. fruit by convective drying

Black rosehip (Rosa pimpinellifolia L.) is a bioactive-rich fruit of increasing industrial interest; however, the combined effects of convective drying conditions on its physicochemical quality, rehydration behavior, and bioactive retention remain insufficiently studied. Therefore, this study aimed to determine the changes in physical and bioactive properties of the fruits during convective drying, including color (L*, a*, b*, ΔE), shrinkage, moisture and rehydration behavior, and the retention of key bioactive compounds. For this purpose, various temperatures (50, 60, 70, and 80 °C) and air velocities (0.5, 1.0, and 1.5 m/s) were used. Additionally, the rehydration process was conducted at three temperatures: 20, 40, and 60 °C. The process included rehydration kinetics (Rk) and modeling. Midilli-Kucuk and Peleg, as well as Vega-Gálvez, showed promise as suitable models for drying and Rk, respectively. In case of rehydratation, dry fruits absorb water the fastest at 60 °C. Additionally, at 60 °C and 0.5 m/s, dried fruits exhibited the highest rehydration capacity. Notably, total color change (ΔE) and shrinkage values were affected by temperature and air velocity (p < 0.05). The highest ΔE value occurred at 60 °C and 0.5 m/s, while the lowest was at 80 °C at 1.5 m/s. Mechanically, the maximum and minimum shrinkage occurred at 50 °C and 60 °C, respectively, at speeds of 1.5 m/s and 0.5 m/s. Considering antioxidant retention (TPC, TAC, DPPH, FRAP, ABTS), drying at 70 °C and 1.5 m/s was optimal, providing the best balance between quality and bioactive preservation, with losses of 34.58% for total phenolics and 64.24% for anthocyanins compared to fresh fruit.