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Blends of xanthan gum (XG), guar gum (GG) and carboxymethyl cellulose (CMC) were prepared according to a simplex-centroid design (7 points) and used at 0.5% (wt/wt) in O/W emulsion formulations. Results demonstrated that interaction among XG, GG and CMC had positively influenced the droplet characteristics and flow behaviour of the prepared emulsions. There were significant ( p < 0.05) decreases in droplet size ( d [3,2] = 5.84–7.00 μm) of the emulsions containing binary blends (at 1:1 ratio) of XG:GG and XG:CMC as well as ternary blend of XG:GG:CMC (at 1:1:1 ratio) when compared to that of emulsion containing XG alone ( d [3,2] = 11.41 μm). Regression modelling revealed that synergistic effect of ternary XG:GG:CMC blend was stronger than that of all the binary blends as evident in the yield stress and apparent viscosity of the respective emulsions. Both responses were proven to be best fitted with a special cubic model ( R 2 > 0.94) while coefficient of consistency was successfully fitted with a quadratic model ( R 2 = 0.94). The models are useful for predicting the respective responses to any blend combination of the components. In this study, ternary synergism was believed to be occurred through a specific mechanism whereby CMC might have formed its own network interpenetrating with the network from a well-known XG-GG or GG-CMC synergisms that finally resulted in more complex network structure which positively influenced the properties of the prepared emulsions. [ABSTRACT FROM AUTHOR]

Abstract: Droplet size distribution and thermal behavior of concentrated oil-in-water emulsions based on soybean oil (SBO)/palm kernel olein (PKO) blends were investigated. The emulsions were prepared using 70% (wt./wt.) oil blends of SBO/PKO as dispersed phases and stabilized by egg yolk. An increase in PKO level (0–40% wt./wt.) in the oil dispersed phase volume fraction caused significant increases (p <0.05) in volume-weighted mean diameter (d 4,3). The DSC data suggested that crystallization of the emulsions was induced by a ‘template effect’ of yolk constituents via a surface heterogeneous nucleation. Emulsions with 0–20% (wt./wt.) PKO levels in the dispersed phase demonstrated a good cool–heat stability even after three successive thermal cycles (from 50°C to −70°C at 10min/°C). After the first thermal cycle, emulsions with 30% and 40% PKO levels in the oil dispersed phase were destabilized due to strong coalescence and crystallized via volume-surface heterogeneous nucleation. The unstable emulsions were attributable to high level of saturated triacylglycerols from PKO, with high droplet size characteristic, causing them to be more prone to partial coalescence. [Copyright &y& Elsevier]

Abstract: Droplet characteristics, flow properties and stability of egg yolk-stabilized oil-in-water (O/W) emulsions as affected by the presence of xanthan gum (XG), carboxymethyl cellulose (CMC), guar gum (GG), locust bean gum (LBG) and gum Arabic (AG) were studied. The dispersed phase (40%) of the emulsions was based on soybean oil/palm kernel olein blend (70:30) that partially crystallized during extended storage at 5°C. In freshly prepared emulsions, the presence of XG, CMC, GG and LBG had significantly decreased the droplet mean diameters. XG, LBG, GG and CMC emulsions exhibited a shear-thinning behavior but AG emulsion exhibited a Bingham plastic behavior and control (without gum) emulsion almost exhibited a Newtonian behavior. Both control and AG emulsions exhibited a severe phase separation after storage (30 days, 5°C). The microstructure of stored XG emulsion showed the presence of partially coalesced droplets, explaining a large increase in its droplet mean diameters. Increases in droplet mean diameters and decreases in flow properties found for stored GG and LBG emulsions were attributed to droplet coalescence. Nevertheless, the occurrence of droplet coalescence in these emulsions was considered to be small as no free oil could be separated under centrifugation force. Increases in flow properties and excellent stability towards phase separation found for stored CMC emulsion suggested that CMC could retard partial coalescence. Thus, the results support the ability of CMC, GG and LBG in reducing partial coalescence either by providing a sufficiently thick continuous phase or by acting as a protective coating for oil droplets. [Copyright &y& Elsevier]