Spray drying of tomato pulp in dehumidified air: I. The effect on product recovery

Abstract

This work investigates the performance of a modified spray dryer for tomato powder preparation by spray drying of tomato pulp. A pilot scale spray dryer (Buchi, B-191) with cocurrent operation and a two-fluid nozzle atomizer was employed for the spray drying process. The modification made to the original design consisted in connecting the spray dryer inlet air intake to an absorption air dryer. Samples of tomato pulp with a 14% constant total solids concentration were used. Sixty-four different experiments were conducted keeping constant the feed rate, the feed temperature and the atomizer pressure, and varying the compressed air flow rate, the flow rate of drying rate and the air inlet temperature. Data for the residue remaining on the walls and for the product collected in the receiving vessel were gathered. Analysis of experimental data yielded correlations between product recovery and the variable operating conditions. The modified spray drying system was proved advantageous over the standard laboratory spray dryer. Preliminary air dehumidification reduced residue accumulation, allowing the product to be dried at lower air outlet temperatures.