Effect of microwave-vacuum, ultrasonication, and freezing on mass transfer kinetics and diffusivity during osmotic dehydration of cranberries

The objectives of this study were (i) to evaluate moisture loss (ML), solids gain (SG), moisture loss rate (d(ML)/dt), solids gain rate (d(SG)/dt), effective moisture diffusivity (D-eM ), and effective solids diffusivity (D-es) during osmotic dehydration (OD), ultrasound-assisted osmotic dehydration (UA-OD), and osmotic dehydration of whole cranberries, preceded by microwave-vacuum pretreatment (MV + OD) or freezing/thawing treatment (F + OD ) and (ii) to use a mathematical model to predict moisture content MI infinity and solids content SG(infinity) in equilibrium state and the distribution of moisture and sucrose in whole cranberries during dehydration. Microwave-vacuum and OD treatments produced cranberries with the highest values of ML and SG (39.7 and 8.4 g 100 g fresh fruit(-1) , respectively), d(ML)/dt and d(SG)/dt (76.9 and 8.5 h(-1), respectively), D-eM and D-es (6.1 and 3.7 x 10(-10) m(2) s(-1), respectively). Azuara's and Peleg's models adequately described the OD kinetics of whole cranberries in terms of ML and SG. The results indicate that the equilibrium values of ML infinity and SG(infinity) were not reached under the conditions specified in the present study.