Analysis of particles collisions in a newly designed rotating dryer and its impact on the Camu-Camu (Myrciaria dubia) pulp drying

Abstract

Camu-Camu (Myrciaria dubia) is a native fruit from the Amazon region, which is still little known by most people, but that has been arousing great interest from the scientific community due to its significant concentrations of important bioactive compounds. In this work, the drying of Camu-Camu pulp was investigated using an alternative system: a rotary drum with an inert bed. In this nonconventional rotary dryer the surface contact between hot air and the pasty material is enhanced by the presence of a bed of inert particles inside the drum, in addition it prevents loss of material on the walls and drum structure. The inert bed had particles of three different diameters: 25.40 mm; 19.05 mm and 12.70 mm, including the binary combinations among them. DEM (discrete element method) simulations were performed to evaluate the effect of the different particles bed, as well as the operational variables (rotation speed, filling degree and inert fraction) on the collisional force and the number of collisions. An optimization study using the desirability function was performed to find the best inert mixture. The highest experimental yield was 86.66%, which was obtained using a combination of the biggest particles (high collisional force) and smallest particles (high number of collisions). The product quality was evaluated in terms of bioactive compounds content (ascorbic acid, total phenolic content, total flavonoid content and antioxidant capacity). The results showed that this nonconventional system presented a good performance to obtain the powder of Camu-Camu fruit with a good quality.