Osmotic dehydration of tomato in ternary solutions: Influence of process variables on mass transfer kinetics and an evaluation of the retention of carotenoids

The objective of this work was to study the influence of temperature (20-40 degrees C, solution composition (0%salt/65%sucrose-10%salt/ 55%/sucrose) and agitation speed (0-1000 rpm) on the mass transfer kinetics of osmotically dehydrated tomato halves. The mass transfer kinetics were modeled using a first-order kinetic equation, by way of an empirical parameter (k) representing an overall mass transfer coefficient. Carotenoid retention was analyzed after 6 h of processing. The results showed that the overall mass transfer coefficients for water, NaCl and sucrose were positively influenced by the temperature and by an increasing solution salt content. The agitation speed had a significant influence on water loss, indicating that in this case, the mass transfer was not only governed by an internal mechanism, as appeared to be the case with the solutes. Osmotic dehydration apparently had no effect on the carotenoid content of the processed products, and can be considered to be an efficient method, allowing for water removal without changing the nutritive value. (C) 2007 Elsevier Ltd. All rights reserved.