Formation of beta-lactoglobulin aggregates during thermomechanical treatments under controlled shear and temperature conditions

Tailoring of heat-induced whey protein aggregates is a constant concern for the dairy industry. In this study, an original laboratory-scale device was used to study the effect of process and composition variables on B-lactoglobulin aggregation. Experiments were carried under processing-like conditions: high protein concentration (2-10% w/w), high heating (1 degrees C s(-1)) and cooling (2 degrees C s(-1)) rates, concentrated ionic environment (2.2-11 mM of CaCl2) and shear (0-400 s(-1)). Different holding times (0-240s) and temperatures (67-95 degrees C) have been tested. The use of two distinct granulometric methods (laser granulometry and Focused Beam Reflectance Measurement) enabled monitoring of the kinetics of aggregate formation with information on size and concentration. The process conditions have an important influence on the functional properties of the suspension: the median volume diameter goes from less than 2 gm for short time and static heat treatment up to 80 gm for long time. Applying shear during heat treatment decreases the concentration of small aggregates (1-10 mu m) and increases the concentration of large aggregates (20-200 mu m). Using the quantitative characterization of temperature and time impact, it is possible to select the optimal temperature to maximize denaturation and minimize size. With the beta-lg solution used in this study, the optimal temperature is around 88 degrees C