| Abstract
| - A study is presented on the structure of rennet(-induced) casein or skim milk gels at three pH values(5.3, 6.0, and 6.65) and temperatures (20, 25, and 30 °C). The structure was examined by confocal scanninglaser microscopy and permeametry. Deconvolution was applied to the microscopic images. A fractal scalinganalysis has been applied to the images and permeametry results. In this analysis, the fractal dimensionality(Df), lower cutoff length (R0), and apparent pore size (P) of the linear scaling regime were calculated fromthe microscopical data. The Df and apparent pore size were also calculated from the permeametry data.During aging of the gels, a coarsening of the structure was observed; the pore size increased and theclusters became more compact. This was reflected in the fractal parameters: R0 and P increased duringgel aging. Their values are generally high (0.5−1.5 and 5.0−15 μm, respectively) compared to data obtainedby computer simulations. The Df value is also high (∼2.2−2.6), which is an indication of slow aggregationor rearrangements during aggregation. The gel aging effects are probably mainly due to rearrangementssuch as particle fusion and strand fracture, which rates increase with increasing temperature, and evenmore pronouncedly, with decreasing pH.
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