APPARENT MASS DIFFUSIVITIES IN FRUIT AND VEGETABLE TISSUES UNDERGOINGOSMOTIC PROCESSING

Apparent mass (water and solute) diffusivities were measured during os motic processing of model fruit (apple) and vegetable (potato) tissues . Among process parameters, temperature had the largest positive effec t on moisture (D-w) and soluble solids (D-ss) diffusivity. Increased c oncentration gave increased mositure and decreased solute diffusivitie s. The dehydration efficiency index (D-w/D-ss ratio) increased with co ncentration but measured or remained constant with temperature. Using the right size of osmotic solute it was possible to maintain satisfact ory moisture diffusivities with nearly zero net solute uptake. Freeze/ thaw-induced tissue damage caused a dramatic decrease in dehydration e fficiency. Both moisture and solute diffusivities followed Arrhenius k inetics with activation energies (E(a)) ranging between 21.2 and 29.7 kJ mol(-1) K-1. Cell level explanations on response differences are at tempted. (C) 1997 Elsevier Science Limited.