The influence of food emulsifiers on fat and sugar dispersions in oils. I. Adsorption, sedimentation

Abstract

The adsorption isotherms of several emulsifiers to fat and sugar crystals dispersed in oils have been determined. Further, the influence of the emulsifiers on the interactions between the crystals has been estimated in sedimentation experiments, where an increased sediment volume due to adsorption corresponds to an increased adhesion between the crystals and vice versa. Most of the emulsifiers examined adsorb weakly to fat crystals and form tight monolayers, resulting in increased adhesion between the crystals at high concentrations. On the other hand, loosely packed layers are formed at low concentrations, and a decreased adhesion is observed. Unsaturated monoglycerides and phospholipids cause a decrease in adhesion for all concentrations examined.The emulsifiers adsorb more strongly to sugar crystals than to fat crystals and form tightly packed monolayers with hydrocarbon chains directed to the oil. The crystals are then stabilized sterically the adhesion between them is weaker and the sediments are more compact. At low concentrations, the opposite behavior often occurs. Monoglycerides interact in a specific way with sugar and cause increased adhesion between the crystals for all concentrations examined. Phospholipids reduce the adhesion between sugar crystals, resulting in much denser sediments. Saturated monoglycerides in amounts over the solubility limit tend to precipitate as a network between fat or sugar crystals, which causes bulky sediments and results in better stability against oiling out.

Soybean-based Surfactants and Their Applications

“…The competitive adsorption of lecithin to displace proteins adsorbed at the oil/water interface may cause a change in the interactions between the proteins and fat crystals and thus affect the mechanical strength of the interfacial film [Ogden & Rosenthal, 1997], while the competitive adsorption of lecithin to displace proteins adsorbed at the surface of fat crystals may facilitate the coalescence of fat globules and thus destabilise the emulsions [Melsen & Walstra, 1989]. The adsorption of lecithin may also change the polarity of fat crystals [Johansson & Bergenståhl, 1992;Rousseau, 2000]. Usually, low-molecular-weight surfactants are effective at generating emulsions with smaller droplets because of their fast adsorption to the newly created interfaces, but they may not be effective at providing long-term stability to the emulsions.…”

Ultrasonic Attenuation Measurements of the Mixing, Agglomeration, and Sedimentation of Sucrose Crystals Suspended in Oil

“…The degree of agglomeration can be followed by measuring the particle size of the particles directly or inferred from apparent viscosity measurements [1,5] or from sedimentation measurements [4]. For studies of agglomerates formed by weak adhesion, sedimentation experiments are more suitable than rheological measurements as the forces applied to the aggregate during measurement are less [6].…”

“…For example, Chevalley [3] showed that the presence of 3-4% water increases the viscosity of molten chocolate markedly as compared to the typical moisture concentrations of 0.5-1.5%. Emulsifiers can assist the dispersion of fine particles by adsorbing at the surface and providing some steric repulsion [4].…”

Studying model suspensions using high resolution synchrotron X-ray microtomography

“…When a small proportion of a secondary immiscible liquid such as water or glycerol is added to a suspension of this kind, it can lead to behavioural changes from a fluid-like material to a paste-like material (Koos and Willenbacher, 2011;Johansson and Bergenståhl, 1992). This transformation has been ascribed to the formation of liquid bridges between the solid particles by the secondary liquid thereby modifying the rheological properties of the suspension such as its yield stress and viscosity which can increase several-fold Willenbacher, 2011, 2012; chemical engineering research and design x x x ( 2 0 1 6 ) xxx-xxx mechanisms are responsible for the movement of a secondary liquid phase in a suspension including gravity, capillary and diffusion effects (Ghosh et al, 2004).…”