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Cooling effects on a model rennet casein gel system: part I. Rheological characterization
Qixin Zhong1, Christopher R Daubert, Orlin D Velev
1Department of Food Science, North Carolina State University, Raleigh, North Carolina 27695, USA.
Langmuir : the ACS Journal of Surfaces and Colloids
|August 25, 2004
Summary
Slower cooling rates during rennet casein gelation result in stronger gels. Controlling cooling schemes manipulates casein gel microstructure and properties by influencing floc size.
Area of Science:
- Food science
- Colloid and surface chemistry
- Materials science
Background:
- Casein network structure evolves through molecular, particle, floc, and network stages during cooling.
- Rennet casein flocs exhibit fractal characteristics, with fractal dimension and floc size impacting gel rheology and microstructure.
Purpose of the Study:
- To investigate the gelation of a model rennet casein system under varying cooling rates.
- To understand the relationship between cooling rate, casein floc structure, and resulting gel properties.
Main Methods:
- Dynamic rheological tests were employed to monitor casein structure formation during cooling.
- Cooling was performed from 80 to 5 degrees C at rates of 0.5, 0.1, 0.05, and 0.025 degrees C/min.
Main Results:
- Slower cooling rates led to the development of stronger rennet casein gels.
- Fractal dimensions remained consistent across different cooling rates, suggesting stable colloidal interactions.
- Variations in rheological properties were attributed to differences in floc size, with more numerous, smaller flocs promoting gelation at higher temperatures and stronger networks.
Conclusions:
- Cooling rate is a critical factor in controlling rennet casein gelation and microstructure.
- Manipulating cooling schemes, particularly by favoring smaller, more numerous flocs, allows for targeted control over gel strength and texture.
- This research offers a method for optimizing casein gel properties through controlled cooling processes for applications with fixed chemical compositions.