Characterization of yogurts made with milk solids nonfat by rheological behavior and nuclear magnetic resonance spectroscopy.

The effect of adding milk solids nonfat (MSNF) on the physical properties and microstructure of yogurts was investigated. The physical properties of fat free yogurt, fat free with MSNF yogurt, whole fat yogurt, and whole fat with MSNF yogurt were analyzed using shear viscosity, viscoelasticity, and texture analysis. The two yogurts with MSNF had higher consistency coefficient (K), storage modulus (G'), yield stress, and hardness. To gain insight into the multiphase system, nuclear magnetic resonance (NMR) and brightfield microscope images were acquired. The addition of MSNF significantly modified NMR relaxation time; T(1) values were reduced significantly. Brightfield microscope images showed that the size of the protein network of the two yogurts with MSNF added was greater than that of the two yogurts without MSNF added. The microstructural information supported the physical information. The results showed that the increase in MSNF contributed positively to strengthening the physical/mechanical properties of yogurt.