Effect of water content, droplet size, and gelation on fat phase transition and water mobility in water-in-milk fat emulsions

The effects of water content; 15, 30, and 40% (w/w), water droplet size; d(43) 15.0-19.6 mu m (larger) and d(43) 1.2-2.7 mu m (smaller), and sodium alginate (0.5%, w/w) induced water gelation on crystallization kinetics and water and fat proton relaxation were studied in water-in-milk fat emulsions during in situ cooling from 40 degrees C to 5 degrees C. Anhydrous milk fat (AMF) and commercial butter were employed as two separate fat sources. Although emulsions were crystallized faster than the bulk fat, the variations in the water fraction and droplet size did not show major influence on crystallization properties. Smaller droplet size induced significant (p < 0.05) reduction in water mobility with a minimal effect of the temperature. In AMF-based emulsions, gelation of water phase not only immobilized the water molecules but also enhanced the rate of fat crystallization. Globular fat and serum solids in butter-based emulsions showed to fasten the water proton relaxation.