Geles pécticos semideshidratados dietéticos de manzana. Simulación numérica considerando contracción volumétrica

CICUTTIN, SABRINA RITA; GINER, SERGIO ADRIÁN

ITAL, Campinas, SP, Brasil

Simposio; Simposio Brasileiro sobre desenvolvimento de novos produtos alimenticios. Alimentos funcionais e para fins especiais; 2006

Instituto de Tecnología de Alimentos, Estado de Sao Paulo, Brasil

Abstract The objective of this work was to find a reduced calorie formulation of apple pectic gels (laminates) and to develop a mathematical model that describes heat and mass transfer in a shrinking product . The laminates are novel foods based on a mixture of apple puree and added sugar in acidic medium to cause a gelation process assisted by the fruit natural pectins, and by the drying-induced sugar concentration. In this work we found a low-calorie formulation for the apple laminate, where the added sugar was replaced by polidextrose. The product was dehydrated up to a final moisture of 0.5 dec., b.s., value for which the gel is already formed and the aw is of 0.85, which would not inhibit growth of pathogenic bacteria. The finished product contains 159.4 kcal in 100g, which means a reduction by 42.54% of the energy value compared to the conventional formulation. To know the relationship between moisture content and water activity, the desorption isotherm of the low calorie formulation was experimentally determined, which was accurately predicted by the Halsey model. As the product shrinks during drying we found a correlation of the diffusion coefficient which, besides accounting for the effect of temperature, also incorporates that of moisture content. Then, a heat and mass transfer mathematical model was proposed for apple laminate dehydration, which considered product shrinkage . The numerical solution was solved in a finite difference numerical method. Predictions were satisfactorily compared with drying curves, so the model can be used for basic process design.