Influence of infrared power on the production of raspberry powder during foam-mat drying

Drying is one of the traditional methods for increasing the shelf life of agricultural products. Therefore, using the suitable technology for processing of products, it is possible to reduce the processing time and improve the process conditions, high-quality products with the maintenance of the natural characteristics of the primary material. Black raspberry is an ideal product for processing in the industry due to anthocyanin content, phenolic compounds, and high antioxidant properties. The purpose of this study was to simulate mass and heat transfer phenomena during raspberry drying with the foam mat method by using a hot air-infrared combine dryer and assessing the qualitative and functional properties of the final product. Hot air- infrared test experiments were carried out with a constant foam thickness of 7 mm, at 60° C with a constant air velocity of 3 m / s and different infrared power 0, 400, 600, and 800 W. Ovalbumin powder was used as a foaming agent in concentrations of 0.5% (w / w) and methylcellulose as a foam stabilizer at 0.5% (w / v) concentration. Effect of infrared power on the moisture content of the powder, drying rate, effective moisture diffusion coefficient, water solubility index, water absorption index, bulk porosity of raspberry powder, were investigated. Finally, the validation of the data obtained from the simulation was done with the experimental data. The results showed that by increasing infrared power, drying rate and effective moisture diffusion coefficient increased. By increasing the infrared power from 0 to 600, the moisture content of the powder and WSI decreased by 16% and 28%, respectively. And with theincreasing infrared power from 600 to 800, their amount increased by 10%, and 21%, respectively. Also, with the increase of infrared power from 0 to 600, the water absorption index decreased by 15%, and with an infrared power increase from 600 to 800, its value increased by 10%. Increasing infrared power caused to WSI index first decreased and then increased.

Keywords:

Infrared , Foam mat drying , Moisture content , Raspberry