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 tha t were heated at 75, 80 or 90 degrees C for 30 min, followed by acidif ication with glucono-delta-lactone at 30 degrees C. The rheological an d microstructural properties of acid gels were investigated using dyna mic low-amplitude oscillatory rheology and confocal scanning laser mic roscopy (CSLM). Heating milks, at temperatures greater than or equal t o 80 degrees C, increased the storage moduli (G') and decreased the ge lation time. Recombined milks containing high fat (3.5%) had higher G' than gels made from low-fat or skim milk. Milk heat treatment resulte d in gels with a cross-linked microstructure. Recombined fat globules appeared to be embedded in the protein matrix.