Impact of mixed-linkage (1→3, 1→4) β-glucans on physical properties of acid-set skim milk gels

The effects of concentration and molecular structure of barley β-glucans on physical properties of skim milk gels acidified at 42 °C by glucono-δ-lactone (GDL) and reaching a final pH of 4.8 were investigated. Incorporation of β-glucans (0.5–2.0%, w/w) into skim milk aqueous dispersions (10%, 12% and 14%, w/w) resulted in weakening of the protein network upon acidification as shown by reduction of the storage modulus (G′) values of the composite gels, compared with control (free of β-glucan) formulations. However, dynamic rheometry and large deformation measurements (texture profile analysis) revealed that this weakening effect could be reduced or eliminated by using β-glucans with certain molecular features that either promote development of a high viscosity medium (high molecular weight) or formation of a secondary gel network structure (low molecular weight and/or high trimer/tetramer ratio) by the polysaccharide itself. Despite the fact that inclusion of β-glucans at low concentrations increased the levels of spontaneous syneresis, using high β-glucan concentrations or polysaccharide preparations with the aforementioned structural characteristics resulted in milk gels with significantly lower serum separation compared to control formulations.