Effect of Temperature and Acidification Rate on the Fractal Dimension of Acidified Casein Aggregates

¹ Laboratoire de Physico-Chimie et Génie Alimentaires, Ecole Nationale Supérieure d'Agronomie et des Industries Alimentaires, Institut National Polytechnique de Lorraine, 2, Avenue de la Foret de Haye, 54500, Vandoeuvre Lès Nancy, France

The influence of temperature and acidification rate on the fractal structure of acidified casein aggregates was studied by scattering and turbidimetric techniques. The angular dependence of static light scattering was used to determine the fractal dimension of pH-induced casein aggregates. The casein particles were aggregated in 50-fold diluted reconstituted milk under various acidification rates and temperatures. First, temperature was fixed at 20°C as acidification rate was increased from 0.7 to 19.5 10^–5 upH·s^–1 (units of pH per second). The fractal dimensions for the casein aggregates obtained were constant and equal to 2.38. When the temperature was increased from 10 to 40°C and acidification rate was fixed around 3.8 10^–5 upH·s^–1; the fractal dimension values decreased then from 2.44 to 2.11. These results are discussed in relation to experimental and theoretical results on colloid aggregation.

Key Words: acid coagulation • casein aggregates • fractals • temperature

Submitted on June 17, 1996
Accepted on July 11, 1997

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