WATER SORPTION, DRYING AND ANTIOXIDANT PROPERTIES OF DRIED TOMATO PRODUCTS

This work is focused on some properties of various dried tomato products (tomato pulp, tomato halves and insoluble solids-rich tomato), useful to optimize drying processes. Adsorption and desorption isotherms at 20degreesC of these products were measured and modelled by the Guggenheim-Anderson-de Boer (GAB) equation. Insoluble solids-rich tomato was the least hygroscopic of all tomato products. Tomato products were air-dried in a pilot plant and the drying kinetics was modelled. The mass transfer equation for drying of thin slabs, modified to include shrinkage of samples during drying, was successfully applied to experimental data. Apparent water diffusivity values ranged from 2.3 x 10(-9) to 9.1 X 10(-9) m(2)/s as a function of the structure of tomato products. The lycopene and ascorbic content and the antioxidant activity of hydrophilic and lipophilic extracts were measured both on fresh and dried tomato products. Interesting properties of insoluble solids-rich tomato were evidenced: it had the highest lycopene content (ca. 12,000 mg/kg dm) and lipophilic antioxidant activity (ca. 400I(50), mug dm) of all tomato products.