Apple Pectic Gel Produced by Dehydration

• Autores: Leiva Díaz, Evangelina; Giannuzzi, Leda; Giner, Sergio Adrián
• Año de publicación: 2009
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Química; Fruit leather; Hot-air drying; Non-isothermal drying
• Institución: Universidad Nacional de La Plata

A novel, flexible sheet-like food formed by the high methoxyl pectin–sugar–acid gelation during drying of apple puree was investigated to characterize drying-related properties. Product volume was reduced by 68% over the process, and this shrinkage was successfully modeled by assuming the volume reduction equal to the volume of water evaporated. The sorption isotherm at 25 °C was determined, and a new expression for the moisture content, W, as a function of water activity, aw, of the type W=C₁ exp (C₂ a^C3_w)resulted as the most accurate for this J-shaped isotherm. The drying kinetics was studied at 50, 60, and 80 °C in a tray dryer. No constant drying rate period was found, and the drying curve was divided in high- and low-moisture zones. For high moistures, an internal–external mixed control diffusive model coupling mass and heat transfer was applied to obtain a mass transfer Biot number of 2.1. In the low-moisture zone, a diffusive, isothermal drying model for strict internal control was utilized. Diffusivities varied around 1 × 10–9 m²/s for high moistures and were about ten times lower at low moistures, although the activation energies were comparable (15,259 and 16,800 J/mol, respectively). The drying time at 60 °C was 6.67 h. The product scored four points out of five in a sensory evaluation of general acceptability.
Centro de Investigación y Desarrollo en Criotecnología de Alimentos