Rheological properties and microstructure of acid milk gels as affected by fat content and heat treatment

Gels were made from recombined milks containing 0, 1.5 or 3.5% fat that were heated at 75, 80 or 90 degrees C for 30 min, followed by acidification with glucono-delta-lactone at 30 degrees C. The rheological and microstructural properties of acid gels were investigated using dynamic low-amplitude oscillatory rheology and confocal scanning laser microscopy (CSLM). Heating milks, at temperatures greater than or equal to 80 degrees C, increased the storage moduli (G') and decreased the gelation time. Recombined milks containing high fat (3.5%) had higher G' than gels made from low-fat or skim milk. Milk heat treatment resulted in gels with a cross-linked microstructure. Recombined fat globules appeared to be embedded in the protein matrix.