Time evolution of phase separating milk protein and amylopectin mixtures

Abstract

The time evolution of phase separating milk protein–amylopectin mixtures at pH 6.3 was studied by confocal scanning laser microscopy (CSLM). CSLM measurements revealed the formation of aggregate-like structures of protein particles. Two different procedures, 2-D Fourier transformation and morphological sieving, were used to analyse the CSLM images. Both procedures showed the existence of a characteristic length scale ( Λ) in the system, which evolved with time ( t) according to a power law, Λ∼ t α . The power-law exponent α depended on the amylopectin concentration in the mixture. At relatively low concentrations α≅0.2, which is compatible with theoretical predictions for ‘late stage’ coarsening. At relatively high amylopectin concentrations a much lower power of ca. 0.04 was observed, indicative of a very slow growth process. The slow growth may be explained from earlier work [Food Hydrocolloids 16 (2002) 127], which showed that at sufficiently high amylopectin concentrations a protein particle network develops with gel-like properties. The morphological sieving method in addition yielded information on the size of the protein-rich and amylopectin-rich domains in the CSLM images.