Microwave‐assisted forced convection drying effect on bioactive compounds of the Canadian blueberry leaves (Vaccinium corymbosum)

Abstract

Canadian blueberry leaves (Vaccinium corymbosum) are a potential source of polyphenols (catechins) and antioxidants (FRAP and PT). In this study, the technique of drying by microwave-assisted forced convection was carried out to find the optimal conditions which would allow obtaining the highest polyphenol content under control parameters such as microwave power (100, 300, and 400 W), hot air velocity (0.5 and 2.0 m/s), leaf size (whole and fractional), and temperatures (50, 60, and 70°C). It was found that 30 W/g microwave powers and a 60°C temperature for the process in whole leaves were the optimal conditions that allowed obtaining the highest content of polyphenols (>10 mg/gdb (+) catechin) and antioxidant capacities (100–150 mg GAE/gdb), more than in fractional leaves. It was observed that different hot air velocities did not affect the concentration of the polyphenol’s contents; this was verified using the factor mixture analysis technique. Practical applications The MWFC process allows the preservation of antioxidants in Canadian blueberry leaves (Vaccinium corymbosum). These leaves have high antioxidant capacity for nutraceutical and pharmaceutical uses. This leaf, with high polyphenol content, can be used to obtain extracts in infusions and human food through the mixture of this leaf with multiple powdered products traditionally consumed or food supplements. This research presents the optimal conditions for the preservation of antioxidant compounds in dried Canadian blueberry leaves.