Effects of blanching and freezing on the structure of carrots cells and their implications for food processing
1998
Prestamo, G. | Fuster, C. | Risueno, M.C.
Blanching and freezing effects are focused on the microscopic structure, whether the softening of frozen vegetables (carrots) is related to changes in pectic substances or to firmness. Under light and electron microscopy, in the frozen raw samples, some cells were disrupted, producing cavities. The cytoplasm was destroyed and enclosed in a very thin layer inside the cell, and the organelles attached to the plasmalemma had almost disappeared. The formation of a transparent region close to the plasmalemma was observed, as a result of the extraction of some altered materials (hemicellulose, cellulose, pectin). The cell walls in the blanched samples appeared quite different from those in the frozen samples. They did not display tissue disruption as in the frozen samples, but the organelles in the cytoplasm were also altered. We also report substantial vesicle formation (swollen walls) in the cell wall, and a dark granular material inside. When the blanched samples were also frozen, compartmentalization of the material inside was observed. The pectin content was higher in the frozen and frozen blanched samples than in the raw and blanched samples. The semithin and ultrathin structure was in accordance with the objective values obtained by Kramer/Shear cell, where the greatest damage occurred to the samples in the freezing process.
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