Physical, textural, morphological, and bioactive properties of convective dried autumn olive fruits (Elaeagnus umbellata)

Autumn olive (Elaeagnus umbellata) is a good source of natural antioxidants and compounds associated with protective effects on health. The current study investigated the possible impacts of the convective drying process on textural, morphological, phenolic compounds, and antioxidant properties of autumn olive berries. Fruits were dried at four different temperatures (50, 60, 70, and 80 °C) and three air velocities (0.5, 1.0, and 1.5 m/s). The effects of drying on the microstructure, color, shrinkage, total phenolic substance, total flavonoid, lycopene content, antioxidant activity (DPPH and FRAP values), and individual phenolic compounds were studied. Drying and rehydration kinetics and modeling were done. The analysis showed that the most suitable model for the drying kinetics of autumn olive fruits was Midili and Weibull for the rehydration kinetics. The total phenolics, FRAP, DPPH, and lycopene values of autumn olive fruits were determined as the best temperature for convective drying at 80°C and 70°C. The highest gallic acid, catechin, benzoic acid, salicylic acid, ellagic acid, and quercetin-3 glucoside were preserved in fruits dried at 80 °C and 1 m/s air velocity. Furthermore, the dried autumn olive at 80 °C and 1.5 m/s air velocity provided high hardness, chewiness, and gumminess, respectively. The current study observed that the fruits dried at 60 ℃ contain the highest values of flavonoids. The samples processed by drying were much more hardness, gumminess, and chewiness. In contrast, the fresh autumn olive fruits were higher cohesiveness, springiness, and resilient values. The result of drying air velocities revealed no significant effects on textural properties, antioxidant activity, individual phenolic compounds, and total color change (p<0.05). It was determined that the highest rehydration capacity was in fruits dried at high temperatures (70 and 80 ℃). These results indicate that the best drying temperature for autumn olive fruits at 80 ℃.