D.N. Pinder

Dynamic light scattering investigation of sodium caseinate and xanthan mixtures.

Aqueous solutions of sodium caseinate and xanthan at pH 7 and containing 0.1 M NaCl, and their mixtures were investigated using dynamic light scattering. Sodium caseinate solutions showed a bimodal distribution of relaxation rates; with the aggregate peak distribution predominating. Xanthan solutions showed a single distribution at low concentrations (< or =0.06 wt.%) and a bimodal distribution at higher concentrations. The sodium caseinate-xanthan mixture modes were independent of the total biopolymer concentration, and behaved as a superposition of sodium caseinate solution alone and xanthan solution alone. This indicates that there is no interaction between xanthan and sodium caseinate in the range of concentrations considered in this study.

Monitoring of flocculation and creaming of sodium-caseinate-stabilized emulsions using diffusing-wave spectroscopy.

Diffusing-wave spectroscopy (DWS) has been used to study the stability of sodium-caseinate-stabilized emulsions. The emulsions underwent creaming as a result of depletion flocculation when excess sodium caseinate was added. The creaming process was monitored over a 3-h period and each autocorrelation function was collected for 2 min to ensure adequate signal-to-noise ratio. The temporal variation of average particle size times the coefficient of viscosity of the continuous phase was derived from the backscattering measurements, and the variation of the scattering mean free path length with time was found from the backscattering and transmission measurements. It was confirmed that the creaming process was delayed at high oil concentrations, presumably due to the formation of oil droplet networks.

Dynamic light scattering investigation of guar/dextran mixtures in aqueous solutions

Dextran and guar solutions and their mixtures were investigated by dynamic light scattering. The measurements have shown that dextran solutions present a major fast decay mode and another slower decay mode. Solutions of guar alone and dextran/guar mixtures have shown up to four different modes. The large number of modes may be caused by the aggregation of guar molecules. Although guar/dextran form very complicated mixtures, partly because of the aggregation of guar, an attempt is made to interpret these measurements within the framework of the theories of ternary polymer solutions.

Diffusing‐Wave Spectroscopy of Gelling Dairy Systems

Conventional diffusing‐wave spectroscopy (DWS) was combined with a CCD‐camera based diffusing‐wave spectroscopy (MSDWS) to study acid induced skim milk gels. This allowed the measurement of intensity autocorrelation functions from 10−6 to 3×103 s, giving access to both fast and slow dynamic modes of these gels.