THE RESPONSE OF SOME PROPERTIES OF FRUITS TO VACUUM IMPREGNATION

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Abstract
The behavior of several fruits (three varieties of apples, strawberry, kiwi‐fruit, mango and peach) during vacuum impregnation (VI) treatments was studied by using specially designed equipment and methodology to determine deformation and impregnation levels in fruit samples. The coupling of the Hydrodynamic Mechanism (HDM) and the Deformation‐Relaxation Phenomena (DRP) was analyzed throughout the two typical steps of VI process (first period at vacuum pressure and second period at atmospheric pressure). VI experiments were carried out over different lengths of time under vacuum (t1) and at atmospheric pressure (t2) duration in order to obtain kinetic information on the coupled HDM and DRP. Nevertheless, neither the duration of t1 or t2 was observed to have an influence on the deformation and impregnation levels in the examined time scales. The effective porosities (ɛe) of the fruits that were studied were determined and compared with the fruit porosity (ɛ) obtained from density data. In almost all cases the ratio ɛe/ɛ was lower than 1, which indicates that only a fraction of fruit pores was available to HDM action. DRP affects the volume fraction of impregnated liquid in all cases.