COMBINED TECHNIQUES IN AIR-DRYING OF FRUI T - PRETREATMENTS IN SOLUTIONS CONTAINING ETHANOL

Ethanol plays different roles in foods, affecting not only their micro bial and chemical stability but also their sensorial and physical prop erties, such as water vapour pressure and, consequently, water activit y (a(w)). In this research the influence of ethanol impregnation on dr ying rate and quality of dried apples were evaluated. Before drying, a pple cubes were dipped in aqueous solutions of ethanol at different le vel of concentration, for different times. Fruit pieces, raw or pre-tr eated, were air-dried in a cabinet and in a suction-flow pi lot plant under standardised process conditions. In all dried samples, water con tent, colour, microbial load and residual content of ethanol were dete rmined. The results showed that pre-treatments in ethanol solutions re markably increase the drying rate and cause a reduction of polyphenolo xidase activity, resulting in a lower level of browning in pre-treated dried apple cubes. Moreover in samples dipped in solutions with conte nts of ethanol of 20 and 40% by weight, it has been detected a residua l ethanol value lower than 4%.