Abstract

This study aimed to determine the effect of CO2 laser microperforation (LMP) pre-treatment in terms of pore density and pore size on the time required for apple (Granny Smith) slices to reach a water activity below 0.4 by means of different dehydration techniques: osmotically dehydration followed by conventional hot air-drying (OD/CD) or refractance window (TM) technology (OD/RW (TM)) or just drying by means of refractance window (TM) technology (RW (TM)). Furthermore, a suitable mathematical model for the diffusion phenomenon was implemented. CO2 laser microperforation was performed on the apple slices in order to reach different pore radius and densities. Apple slices were osmotically dehydrated with a 45 degrees Brix solution at 40 degrees C before the conventional and refractance window (TM) treatments, and others were directly dried with a RW (TM). The drying procedures were performed at 70 degrees C to reach a water activity (a(w)) below of 0.4. The drying time, color change, soluble solid content, and diffusion coefficients (D-eff) were determined. Compared to non-microperforated samples, increasing the pores density from 2.86 to 7.94 pores/cm(2) and the pores size from 100 to 300 mu m, drying time was reduced in the range of 10 to 60%. The D-eff ranged from 5.76 x 10(-10) to 11.07 x 10(-10) m(2)/s for the Fick's second law model and from 0.21 x 10(-10) to 5.94 x 10(-10) m(2)/s(alpha) for the anomalous diffusion model and showed super-diffusive behavior (alpha > 1). Laser pre-treatment favored anomalous diffusion behavior during drying. Collectively, RW (TM) showed promising results by significantly reducing the control drying time by over 50%.