THE RESPONSE OF SOME PROPERTIES OF FRUITS TO VACUUM IMPREGNATION

The behavior of several fruits (three varieties of apples, strawberry, kiwifruit, mango and peach) during vacuum impregnation (VI) treatment s was studied by using specially designed equipment and methodology to determine deformation and impregnation levels in fruit samples. The c oupling of the Hydrodynamic Mechanism (HDM) and the Deformation-Relaxa tion Phenomena (DRP) was analyzed throughout the two typical steps of VI process (first period at vacuum pressure and second period at atmos pheric pressure). VI experiments were carried out over different lengt hs of time under vacuum (t(1),) and at atmospheric pressure (t(2)) dur ation in order to obtain kinetic information on the coupled HDM and DR P. Nevertheless, neither the duration of t(1) or t(2) was observed to have an influence on the deformation and impregnation levels in the ex amined time scales. The effective porosities (epsilon(e)) of the fruit s that were studied were determined and compared with the fruit porosi ty (epsilon) obtained from density data. In almost all cases the ratio epsilon(e)/epsilon was lower than I, which indicates that only a frac tion of fruit pores was available to HDM action. DRP affects the volum e fraction of impregnated liquid in all cases.