Food Structure


The effect of blanching, post-harvest refrigerated (4C) storage and enzyme treatment with poly-galacturonase on the microstructure of Spartan apple juice was examined by thin sectioning and negative staining transmission electron microscopy. Particles were categrized as granules (3-54 nm), spheres (20-368 nm) and aggregates (12-2519 nm). Enzyme treatment with polygalacturonase significantly decreased granule size (P < 0.01). Storage of apples significantly decreased both granule size (p < 0.01) and aggregate length (p < 0.05) and also resulted in a web-like aspect in the microscopic appearance of juice particulate. The web-like aspect of the particulate was removed either through enzyme treatment with polygalacturonase or by blanching. Blanching of puree significantly increased granule (p < 0.05) and sphere size (p < 0.01) while significantly decreasing aggregate length (p < 0.01). In addition, blanching stabilized suspended particulate by what appeared to be the formation of a protective colloid which prevented particle aggregation through electrostatic repulsion.

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