Characteristics of thin-layer infrared drying of apple pomace with and without hot air pre-drying

Thin-layer infrared drying characteristics of apple pomace, with and without hot air pre-drying, were studied with a laboratory scale infrared dryer. Moreover, ten commonly used mathematical models were used to fit experimental data. Logarithmic model and Page model were most adequate in describing thin-layer drying of fresh and pre-treated apple pomace respectively. The values of average effective diffusivity in drying the pre-treated apple pomace were about 1.3 times of that in the fresh apple pomace with the initial moisture content of 40% (wet basis).The values of activation energy of moisture diffusion were about 30 kJ/mol for the fresh and pre-treated apple pomace respectively. Infrared drying, combined with hot air pre-drying, can save 20% of drying time to remove the same amount of remained moisture as compared to the infrared drying alone. The above findings might be used for operation of drying apple pomace.