Difference in mechanical properties of acid gels from LTLT and UHT milks revealed by nonlinear behavior

Abstract

This study investigated nonlinear rheological properties of the acid gel of milk prepared from low-temperature long-time (LTLT) and ultra-high-temperature (UHT) pasteurized milk. By measuring shear stress as a function of strain throughout the gelation process, we aimed to distinguish nonlinear characteristics of these two milk gels. The differential shear modulus, measured at various stages of the gelation, revealed differences in the fracture behavior of two acid gels. Acid gel from the UHT milk that were more brittle and less deformable compared to those from LTLT milk. Our results indicate that while the linear shear modulus reaches a steady state, the nonlinear shear modulus of the UHT milk gel continues to increase over time. This suggests that UHT milk gels possess evolving structural characteristics that are reflected only in nonlinear viscoelasticity. These findings highlight a difference in the mechanical properties of gels between UHT and LTLT milk.