ULTRASTRUCTURAL AND TEXTURAL CHANGES IN PROCESSED CARROT TISSUE

Processed carrot tissues were studied using a transmission electron microscope (TEM) and an Instron Universal Testing Instrument. Carrot slices were evaluated raw, after thermal processing and after freezing and thawing. Cell walls of carrot tissues, frozen and thawed, were intact and dense. The middle lamella lost pectic materials. Overall, frozen and thawed cells were not so closely pressed as those of raw tissues. In thermally processed carrots the cell wall and the middle lamella were less densely stained compared to raw or frozen-thawed carrots. Thermally processed carrots exhibited significantly smaller modulus of deformability and stiffness and toughness values than raw carrots. There were no significant differences between the modulus of deformability and stiffness values for frozen-thawed and thermally processed carrots. Toughness values were, however, significantly lower for the thermally processed in comparison with the frozen-thawed carrots. Instrumental texture measurements indicated that different areas of carrot tissue behave differently to thermal processing.