14A-4

J. F. VéLEZ-RUIZ¹, C. Kosegarten-Conde, and A. Lopez-Malo. (1) Chemical and Food Engineering Department, Universidad de las Américas-Puebla, Sta. Catarina Mártir, Cholula, Puebla, PUEBLA, 72820, Mexico

Drying of food materials is used as a means of improving product stability, storability, and distribution. On the other hand, the osmotic dehydration as a pretreatment technology offers many advantages over other concentration methods, such as low-temperature application processing, better sensory attributes of the food product, and lower operational costs.

Research was conducted to find the influence of process variables on the drying of osmotic dehydrated pineapple rings. We used three water activities (0.97, 0.98 and 0.99), three drying temperatures (65, 75 and 85 °C), and two air velocities (low and high).

The osmotic dehydration process of pineapple rings (1 and 2 cm of thickness) with 1:4 fruit:syrup ratio at room temperature, was observed and measured during several hours in order to get a defined sugar content and/or water activity. A time of 350 to 400 min was needed to reach constant values of water loss and sugar gain. After the osmotic concentration treatment, the drying experimental runs for pineapple samples showed a drying curve with only a falling rate period, in contrast to the fresh pineapple, that exhibited two process rates: a brief constant rate period and a falling rate period; the first one was ignored for modeling purposes.

From the drying, the mass transfer and effective diffusion coefficients were evaluated depending of the process conditions. Two models, Fick law and Generalized curve, were utilized to fit the experimental results, with very good agreement.

As expected, higher water activities, air temperatures, and air velocities favored the drying process of osmotic dehydrated samples. Good quality attributes, color, and rehydration rate were observed for all samples osmotically pretreated.