Effect of process variables on the drying of guava pulp by cast-tape drying

Cast-tape drying (CTD) is a relatively new technique for dehydration and production of food powders. A solution or suspension is spread over a flexible support heated by water or steam. This study investigated the effect of flexible support type (polyester film - Mylar* or fiberglass coated with Teflon*) and pulp layer thickness (2 mm and 3 mm) on drying rate and temperature of guava pulp processed by CTD. All drying curves presented constant-rate period, which was 2.1 greater using 2 nun thick-pulp than 3 mm thick-pulp, for both Mylar* and Teflon*. Using same pulp thickness, similar drying rates and evaporative capacities were observed for both flexible supports. Guava pulp was less sticky on Teflon* than on Mylar* support and that is an advantage. Therefore, cast-tape drying can be used for production of guava powder with high drying rates and evaporative capacities.