The effect of ripening stage on raw and processed kiwifruit dynamic rheological behaviour.

GERSCHENSON L.N., ROJAS A.M. AND MARANGONI A.G.

New Orleans, USA.

Congreso; Institute of Food Technologists (IFT) Annual Meeting.; 2001

Institute of Food Technologists (IFT).

The effect of blanching and osmotic dehydration on the small deformation rheological properties and structure of kiwi fruit were determined. Kiwi fruit tissue behaved as an elastic solid with storage moduli (G’) dominating the viscoelastic response (G”/G’ » 0.2). Both storage (G’) and loss (G”) moduli were frequency independent and a clear linear viscoelastic range was evident. In general, G’ ad G” decreased upon blanching and osmotic dehydration due to tissue damage. Structural changes caused by blanching included swelling of the cell walls and increases in the extent of cell-cell separation in the middle lamella. For atmospheric osmotic dehydration, high levels of solutes were observed within the cells which lead to a reduction of freezable water. For unripe tissue, G’ and G” increased with vacuum dehydration and it seemed that both cell wall integrity and cellular turgor were preserved to a greater extent than in ripe processed tissue. When calcium was added to the osmoticum during osmotic dehydration under vacuum, no differences in dynamic rheological behaviour or tissue structure were detected. Ripening degree of raw vegetable used as foodstuff has a main effect on textural performance after processing.