The effect of high power airborne ultrasound and microwaves on convective drying effectiveness and quality of green pepper

•Application of ultrasound in combined convective-microwave drying.•Airborn ultrasound as assist in drying of green pepper.•Analysis of drying effectiveness and the quality of drying products.•Mathematical modelling of convective-ultrasound drying of green pepper.•Improvement of drying effectiveness by heating, vibration and synergistic effects. The effectiveness of hybrid drying based on convective drying with application of ultrasound and microwave enhancement is the main subject of the studies. The drying kinetics, energy consumption as well as the quality aspect of green pepper is analysed. It was shown that hybrid drying methods shorten significantly the drying time, reduce the energy consumption and affect positively the quality factors. Each of the analysed aspects depend on combination of the convective-ultrasound-microwave drying programs. Besides, based on the drying model elaborated earlier by one of the authors, the effects of ultrasound on convective drying assessed by such phenomena as “heating effect”, “vibration effect” and “synergistic effect” are presented.