Abstract: As a perishable agricultural product with high moisture content,onion leads to serious losses due to germination and mould during storage. In order to complement the research on onion drying technology, cave drying technology, tunel drying technology was adopted to systematically investigate the effects of temperature（60 ℃, 70 ℃, 80 ℃）and air velocity（2 000, 2 500, 2 850 r/min）on the drying characteristics of onion. The drying curves and rate curves were plotted by real-time monitoring of the material quality changes, and the drying kinetic model was screened by combining the nonlinear fitting method. The results showed that the temperature regulation of drying rate was significantly higher than the wind speed, and the drying time was shortened from 180 min to 100 min when the temperature was increased from 60 ℃ to 80 ℃, with a decrease of 44.4%; the whole drying process was dominated by the decreasing-rate phase, and there was no obvious constant-rate period. The fitting results based on the Page model showed that the power index n decreased nonlinearly with increasing temperature（1.096 8~0.964 3）, the drying rate constant k increased exponentially（0.008 47~0.033 01 min^-1）, and the model coefficient of determination R²=1, which was a high degree of agreement between the predicted values in the validation tests and the measured values, confirming its strong explanatory power for the porous onion bulb structure. The study revealed the three-stage characteristics of onion drying: rapid evaporation of surface free water, diffusion dominance of bound water and cuticle blocking effect. This study provides theoretical basis and reliable mathematical model support for the optimisation of drying process of onion deep processing.

Key words: onion, tunnel drying, kinetic model, Page model