Evaluation of ready-to-use SMLS and DWS devices to study acid-induced milk gel changes and syneresis

Abstract

The aim of this study was to examine the potential of ready-to-use multi-speckle diffusing wave spectroscopy (MS-DWS) and static multiple light scattering (SMLS) devices to follow the acid-induced gelation of milk, as well as to detect the appearance of gel syneresis. These light-scattering techniques, MS-DWS and SMLS, have been used in comparison to the classical rheology to study acid milk gel formation and syneresis detection. A systematic study of the effects of heat treatment of milk on the formation of acid gels was conducted. Results obtained by DWS and rheology showed excellent correlation in good agreement with the existence of a link between particle dynamics measured by DWS and the macroscopic viscoelastic response of the gel. Moreover, both light scattering techniques showed ability to detect gel shrinkage due to their high sensitivity to particle mobility. DWS allowed evidencing wheying-off along the tubes’ glass walls, while SMLS performed well in detecting syneresis on gel surface or confined in localized zones of the glass walls. The results were discussed in light of a proposed model considering gel syneresis as regards of gel properties. Light-scattering techniques proved to be very efficient tools to detect syneresis in acid milk gels and thus can be of great interest in preventing this mechanism.