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.
McKenzie, D. L. and Beveridge, T.
"The Effect of Storage, Processing and Enzyme Treatment on the Microstructure of Cloudy Spartan Apple Juice Particulate,"
Food Structure: Vol. 7
, Article 10.
Available at: http://digitalcommons.usu.edu/foodmicrostructure/vol7/iss2/10