RHEOLOGICAL PROPERTIES OF ACID MILK GELS .2.. EFFECT OF COMPOSITION, PROCESS AND ACIDIFICATION CONDITIONS ON PRODUCTS FROM RECOMBINED MILKSUSING THE MICROFLUIDIZER

The effects of eight factors (solids content, fat content, fat type, o rder of heating, severity of heat treatment, homogenization pressure, acidification temperature and concentration of glucono-delta-lactone ( GDL)) on the theological properties of acid milk gels prepared from re combined milks homogenized by microfluidization have been studied. The gelation time (time at which G' and G '' began to increase) was reduc ed by low level of solids, low level of fat, high heat treatment, high incubation temperature and high concentration of acidulant. Heating t he milk after homogenization, high heat treatment and high incubation temperature increased the gelation pH (the pH of the sample at gelatio n time). The theological properties (elastic modulus, viscous modulus and phase angle) were influenced by level of solids, level of fat, hea t treatment and incubation temperature. High level of solids and fat, high heat treatment and low incubation temperature increased both elas tic and viscous moduli, but only level of fat and incubation temperatu re influenced phase angle. Incorporating olive oil instead of milk fat and varying homogenization pressure had no significant effects on gel initiation or viscoelastic properties. As compared to the high pressu re valve homogenizer, the microfluidizer produced smaller particles an d a narrower size distribution, but the theological properties of the acid gels were very similar.