Convective drying of feijoa (Acca sellowiana Berg): A study on bioactivity, quality, and drying parameters

Abstract

The impact of feijoa convective drying on the physicochemical characteristics, polyphenol content, antioxidant capacity, and anti-inflammatory activity, as well as the drying parameters (energy consumption and drying rate), were tested. Feijoa fruit slices were dried at 50, 60, and 70 °C, at air velocities of 0.5 and 1 m/s, and at thicknesses of 0.003 m and 0.005 m. The aqueous extracts were used for the determination of bioactivity. Anti-inflammatory activity was determined from the ability of the extracts to counteract and enhance the expression of pro- and anti-inflammatory genes in human THP-1 cells. The best operational drying parameters were found by means of response surface methodology and desirability function. High temperatures, high air velocities and thinner slices obtained the best results for colour, water activity, antioxidant capacity, anti-inflammatory activity and drying rate. Low temperatures, high air velocities, and thinner slices were suitable for the retention of polyphenols, vitamin C, and antioxidant capacity. The optimal conditions were 50.83 °C, 1 m/s air velocity, and 0.003 m thickness. The results indicate that convective drying is a suitable and cost-effective technique to generate functional ingredients while conserving biocompounds and biological activities.