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, color, firmness, polyphenoloxidase enzyme activity and microstructure), as well as on microbial stability of processed samples, was analyzed. Pulsed vacuum osmotic dehydration with 65 Brix sucrose solution of strawberry, carried out after steam blanching treatment was the most effective in a(w) depression 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 induce the greatest microbial stability. CryoSEM observations shows that, steam treated samples suffer a great degree of cell decompartmentation near the fruit skin, as compared with the well preserved cells in MW treated samples. Differences in microstructural features observed between OD and PVOD treated samples were not reflected on the measured mechanical parameters. (C) 2000 Published by Elsevier Science Ltd.