ABSTRACT
Biological materials (fruits, vegetables, poultry, fish, and
meat) are immersed into an osmotic concentrated solution.
Cellular structure is semipermeable. Two countercurrent
flows take place: small amounts of solute (sugar, salt, and
alcohol) enter the food from the osmotic solution by differ-
ences in solute concentration. Water travels simulta-
neously from the food to the solution, by differences in
osmotic pressure.[1-3] Vitamins and minerals migrate from
the solid. Some acids are eliminated from the fruits,
improving their sweetness and softness. Diffusion controls
solute gain (SG) by the solid. Mixed internal-external flow
controls water loss (WL).[1,3] Cellular membranes trans-
form from semipermeable to permeable state, changing
their structure. A dehydration front moves from the solid
surface to its center. Water is transported: 1) from the core
of the material to the dehydration front; 2) through the
front; and 3) through the material.[4] Common osmotic
dehydration (OD) products are semisweet dried fruits,
ready-to-eat medium shelf-life fruits and vegetables, and
pretreated material for other meals. Usual process parameters
are[1-9] temperature: 18-50C, solution concentration: 10-70 Bx, immersion times: 1-12 hours, fruit-to-syrup ratios: 1:1 to 1:30, WL: 20-70%, SG: 3-25%, geometry:
cubes, slices, and spheres, size: 2-10 mm long, and diffu-
sion coefficients (D) range for water and solids: 10-9 to
10-11 m2/sec.
