APPLICATION OF ULTRASOUND DURING THE PRETREAMENT AND THE CONVECTIVE DRYING OF PINEAPPLE. INFLUENCE ON DRYING KINETICS.

JEFFERSON LUIZ GOMES CORRÊA; MERCEDES CAROLINA RASIA; JOSE VICENTE GARCIA-PEREZ; ANTONIO MULET; JUAN ANDRES CÁRCEL

Concordia

Congreso; International Conference of Food Innovation. Food Innova 2014; 2014

Universidad Nacional de Entre Ríos. Universitat Politecnica de Valencia

Brasil is the second largest producer of pineapple. The fruit is consumed not only as a fresh fruit but also processed in different ways. It is the case of convective drying, the most common drying technique, wich provides a product with large shelf life that can be preserved at ambient temperature. However, this process involves the exposure of the food to high temperature for a long time with consequent degradation of quality characteristics as nutrient contents, color and texture. The use of ultrasound, during a pretreatment or even during the convective drying, could increase drying rate by reducing external and internal mass transfer resistances and, therefore, reduce the impact of processing in quality. In this work, the influence of a pretreatment in distilled water (20 and 40 min at 25 °C) on convective drying of pineapple slices (2 cm diameter, 0.5 cm thickness) was studied. The pretreated samples were dried (40 °C and 70 °C, 1 m s-1) until to achieve an initial moisture loss of 85% . During drying, the mass of samples was monitored each 5 minutes. Both, pretreatment and drying were carried out with (1500 W, 40kHz and 75kW, 21.7kHz respectively) and without ultrasound application. All conditions tested were experimentally determined by triplicate. The drying kinetics were modeled by using a diffusive model. The results showed that the application of ultrasound on both the pretreatment and the convective drying increased the effective diffusivity identified. However, there was no clear relationship between the time of ultrasound exposure in the pretreatment and effective diffusivity.