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Rheological and microstructural analysis of Rennet Casein gel

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Cooling is a final process during process cheese production and is therefore critical when determining the texture and functional properties of the product. It is well established that a slower cooling yields a firmer cheese.

However, there is a lack of quantitative description of this operation, and the mechanism behind the observation is needed to better control the cooling process.

The rheological data for process cheese cooled at different rates was quantified and was consistent with the industrial observation.

To illustrate physical changes during cooling, Rennet Casein gels were studied as the first step in understanding the cooling effects on process cheese texture and microstructure.

A similar trend in storage modulus to process cheese was observed when the casein gels were cooled at different rates. To explain this behaviour, a schematic illustration was used as the physical bases for microstructure of colloidal gels that can result in different rheological properties.

Fractal dimension, floc size, and floc order in the protein network were treated as three possible variables. The theory developed by Shih et al. (1990) was used to determine the floc fractal dimension, and a confocal laser scanning microscope observed the floc size and order.

The results showed that the floc fractal dimension and size were not significantly different when casein gels were cooled at different rates.

However, the cooling did impact floc arrangement in the protein network.

A higher order at a slower cooling rate resulted in a higher storage modulus, a smaller limit of linear viscoelastic range, and an increase in gelation temperature.

The rheological data were consistent with the microscopic images and the hypothesised variables sufficiently explained the physical changes in casein gels during cooling at different rates.

More details are available at Rheology Solutions.

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