Effect of blanching/osmotic dehydration combined methods on quality and stability of minimally processed strawberries

The combined effect of blanching [steam (S) or microwave (MW)] and osmotic dehydration at atmospheric pressure (OD) or pulsed vacuum treatments (PVOD) , on some physiochemical and quality parameters of strawberry (a(w), pH, co lor, firmness, polyphenoloxidase enzyme activity and microstructure), as we ll as on microbial stability of processed samples, was analyzed. Pulsed vac uum osmotic dehydration with 65 Brix sucrose solution of strawberry, carrie d out after steam blanching treatment was the most effective in a(w) depres sion due to the highest sucrose gain during osmotic treatment. This implies the highest loss of firmness and color changes, but at the same time it in duce the greatest microbial stability. CryoSEM observations shows that, ste am treated samples suffer a great degree of cell decompartmentation near th e fruit skin, as compared with the well preserved cells in MW treated sampl es. Differences in microstructural features observed between OD and PVOD tr eated samples were not reflected on the measured mechanical parameters. (C) 2000 Published by Elsevier Science Ltd.