Mass Transfer Characteristics of Cantaloupe Seed and Peel during Microwave and Convective Drying for Further Waste Valorization

Cantaloupe byproducts, seeds and peels are valuable waste products. Recently, these have been commercialized due to their health promoting effects in foods and cosmetics. This study investigated the drying behaviour of cantaloupe seeds and peels with two different drying techniques: convective hot-air drying (CD) and microwave drying (MWD). Drying experiments were carried out at air temperatures of 50-60-70\(\:℃\) for CD and at microwave power levels of 180-300-450 W for MWD. Increasing temperature and microwave power reduced the drying time. MWD shortened the total drying duration by up to 70–80% compared with CD. For both byproducts, the drying process occurred entirely in the ‘falling rate’ period, so internal moisture diffusion governed the mass transfer mechanism. Among the thin-layer models evaluated, the Midilli model provided the best goodness of fit for both seeds and peels (\(\:{R}_{adj}^{2}\)= 0.997–0.999 and RMSE = 0.002–0.018), whereas the Wang-Singh and Lewis models showed the weakest agreement with the experimental data. The effective moisture diffusivity values increased with temperature and power level and ranged from 4.2 \(\:\times\:\) 10 ^− 9 to 8.2 \(\:\times\:\) 10 ^− 9 m²/s for seeds and 2.0 \(\:\times\:\) 10 ^− 10 to 6.0 \(\:\times\:\) 10 ^− 10 m²/s for peels under CD, while 4.0 \(\:\times\:\) 10 ^− 10 to 7.8 \(\:\times\:\) 10 ^− 10 m²/s (seeds) and 1.0 \(\:\times\:\) 10 ^− 10 to 4.0 \(\:\times\:\) 10 ^− 10 m²/s (peels) were obtained under MWD. Peel samples consistently exhibited lower \(\:{D}_{eff}\) and higher activation energy than seeds. This shows peels’ higher resistance to moisture migration.