In situ microstructure evolution of heat-induced p-lactoglobulin (131,G) gels were investigated using confocal laser scanning microscopy (CLSM) at various gel preparation conditions: pH (2, 5, and 7), protein concentration (5%, 10%, and 15%), and salt concentration (NaCl 0, 0.1, and 0.3 M). Temperature-induced CLSM micrographs were used to measure several morphological features of the evolving protein clusters. The cluster area, perimeter, and circularity served as useful microstructural indices of BLG gels. Varying gelation conditions yielded BLG gels of different microstructures during heating. At pH 2 and 7, average area, and perimeter of protein clusters increased with protein content. Larger electrostatic repulsion provided microstructure with stranded clusters, whereas less electrostatic repulsion resulted in particulate clusters. The cluster size and shape were greatly affected by gelation pH; at pH 2 and 7, the average area, and perimeter increased with increasing salt content which provided particulate features to the gel microstructure. The combined effect of protein and salt content and pH is critical in imparting the gel its overall microstructure. (c) 2008 Elsevier Ltd. All rights reserved.