Particle stability in dilute fermented dairy drinks: formation of fluid gel and impact on rheological properties.

摘要

Fluid gels are known to be highly shear-thinning materials that demonstrate yield stress. In this study, the rheological properties of gellan and gellan-pectin fluid gels in fermented dairy drinks were evaluated using viscometric measurements. Both gellan- and gellan-pectin-containing solutions showed the rheological properties of fluid gels, resulting in stabilization of particles; however, no evidence of a fluid gel was observed with pectin alone or in the absence of hydrocolloids. Unlike pectin, gellan gum was capable of creating significant values of yield stress and accordingly stabilized colloidal particles and solid particles added to the fermented dairy drink. However, pectin improved stability in combination with gellan. The origin of fluid gel formation was assumed to be both permanent interactions occurring between gellan and proteins, forming hairy particle gels, and transient interactions between the particle gels. The significance of yield stress values for particle stability was demonstrated and 2 methods, including an infinite apparent viscosity method and a conventional Bingham approach, were employed to calculate values for yield stress. Both methods showed good potential for future use, due to their simplicity, reasonable results and also the wide availability of the instrument applied.