One of the new techniques in the drying of food is the application of infrared radiation that increases the drying rate, enhanced the final product quality, and decreases the costs of the process.
In this study, drying kinetic modeling of strawberry in an infrared dryer was investigated. The effect of radiation lamp power (150, 250 and 375 W) and distance of the lamp from the sample (5, 7.5 and 10 cm), on drying time, and moisture diffusion coefficients during the drying process of strawberry were evaluated. For measuring the weight of the samples during experimentation without taking them out of the dryer, the tray with samples was suspended on the digital balance. Standard models (Wang and Singh, Henderson and Pabis, Approximation of diffusion, Page, Modified Page –II, Newton, Midilli and Logarithmic) were fitted to experimental data to study the drying kinetics and fitting quality (coefficient of determination and standard error) of them was analyzed.
By increasing infrared lamp power from 150 to 375 W, the drying time of strawberry is reduced by 79.8%. Decreasing the distance of the lamp from a sample from 10 to 5 cm, 40.1 % of drying time is reduced. The effective diffusivity coefficient was increased by increasing heat source power and decreasing distance. Moisture effective diffusivity coefficient of strawberry was between 1.54×10-9 to 13.83×10-9 m2/s.
The effect of radiation lamp power and distance on the drying process of strawberry is significant. Modeling of strawberry drying process showed that all the models led to proper results, but in total, the Page model, compared to other studied models, with the biggest coefficient of determination (R2=0.999) and the smallest error (<0.011), had closer results to the experimental data.