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

Abstract

To cite this version:Anne Rohart, Camille Michon, Jérôme Confiac, Véronique Bosc. Evaluation of ready-to-use SMLS and DWS devices to study acid-induced milk gel changes and syneresis. Dairy Science 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.

Rutin-Loaded Poloxamer 407-Based Hydrogels for In Situ Administration: Stability Profiles and Rheological Properties

“…The Brownian movement of the particles in the sample causes the deformation of the speckle image and a detector records the dynamics of the deformation to quantify the speed of movement of the particles. A fast movement of the particles causes a fast deformation of the speckle image, while a slow motion of the particles leads to a slow deformation of the speckle image [ 40 ]. Standard numerical algorithms were used to quantitatively characterize the deformation rate of the speckle image and to obtain statistical parameters such as the decorrelation curve that characterizes the speed of the particles in the fluid and the mean square displacement (MSD) as a function of the decorrelation time and different kinetic parameters such as the elasticity index (EI) and the solid-liquid balance (SLB) [ 41 ].…”

“…Standard numerical algorithms were used to quantitatively characterize the deformation rate of the speckle image and to obtain statistical parameters such as the decorrelation curve that characterizes the speed of the particles in the fluid and the mean square displacement (MSD) as a function of the decorrelation time and different kinetic parameters such as the elasticity index (EI) and the solid-liquid balance (SLB) [ 41 ]. The MSD value is determined from an autocorrelation function derived from the approach of Weitz and Pine and depends on the viscoelastic properties of the samples [ 40 ]. In a pure viscous fluid, the displacement of the particles increases linearly with time because they can move freely in the medium, while in a viscoelastic fluid, the particles are limited in their movement due to the polymeric network [ 39 , 40 ].…”

“…The MSD value is determined from an autocorrelation function derived from the approach of Weitz and Pine and depends on the viscoelastic properties of the samples [ 40 ]. In a pure viscous fluid, the displacement of the particles increases linearly with time because they can move freely in the medium, while in a viscoelastic fluid, the particles are limited in their movement due to the polymeric network [ 39 , 40 ]. The MSD plot of a viscoelastic sample could be broken down into three regions with respect to the decorrelation time.…”

“…The MSD plot of a viscoelastic sample could be broken down into three regions with respect to the decorrelation time. At the very short decorrelation time, the particles are totally free to move in the medium, so the MSD curves increase linearly; at intermediate decorrelation times the particles interact with the polymeric “cage”, and the MSD slope decreases and reaches a plateau (this phase is related to the elasticity of the sample); finally, at longer decorrelation times, the particles escape from the “cage” and the MSD grows linearly again [ 39 , 40 ].…”

“…The elasticity index (EI) is the inverse of the MSD value and identifies the elasticity of a sample. It is computed from the plateau of the MSD curves at intermediate decorrelation timescales according to the equation: where 6δ 2 (nm 2 ) is the mean value of MSD at intermediate decorrelation times, d (μm) is the mean particle diameter measured by laser diffraction, and d e is the diameter of a model particle used for calibration (1 μm) [ 40 ]. Lower MSD plateau values mean a smaller cage and, therefore, a stronger degree of elasticity of the systems [ 39 , 40 ].…”