Characterization of plasma protein gels by means of image analysis

In this study, image analysis is presented as a powerful tool to analyse changes in the microstructural properties of protein gels. Several methods were used to elucidate changes in plasma protein gels induced by changes in the pH conditions, visually noticeable but difficult to assess objectively. Fractal analysis was used to measure the degree of self-similarity, lacunarity analysis to study the distribution of pores within the protein network and the spatial variability of SEM images to describe the compactness of the gel. It was found that the lacunarity measurements and the cut-off of the autocorrelation functions complemented the fractal dimension (D-f) and the average pore size, the most used parameters in describing the microstructure of protein gels. Correlations between macroscopic properties and microstructural attributes revealed that an increase in textural attributes, such as hardness, springiness and cohesiveness, and in the capacity of gels to retain water, entailed an increase of Df and the compactness of gels, but a decrease in the pore size and the heterogeneity of gaps. (C) 2006 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.