Dynamic Surface Tension and Surface Dilatational Elasticity Properties of Mixed Surfactant/Protein Systems

Abstract

We present the study on dynamic surface tension and surface dilatational elasticity properties of dilute aqueous systems of pentaglycerol fatty acid esters (pentaglycerol monostearate, C 18 G 5 , and pentaglycerol monooleate, C 18:1 G 5 ), whey protein, sodium caseinate, and mixed surfactant and protein at room temperature. The adsorption kinetics at the air-liquid interface has been studied by bubble pressure tensiometer and the oscillation bubble (rising drop) method. It has been shown that the dynamic surface tension curve basically presents two-regions; namely induction region and rapid fall region. During the induction time the adsorption is the diffusion-controlled process of amphiphilic surfactant or protein molecules from the bulk of the solution to the interface. Whey protein and sodium caseinate showed longer induction time 10000 ms compared to the surfactant systems, where induction time was estimated to be 1000 ms. However, in both the protein and surfactant systems, the induction time goes on decreasing with increasing the concentrations. The similar behavior was observed in the mixed system, and lower surface tension values were observed at higher concentrations. The fitting of the experimental data to the theoretical equation shows the presence of two relaxation mechanisms of widely different time scale for the adsorption of surfactant or protein molecules at the interface. The relaxation time strongly varies with the concentrations following the power law, and at fixed concentration it was the highest for whey protein and the lowest for C 18:1 G 5 system. The surface dilatational elasticity determined within the frequency range of 0.1 to 1 cycle/s supports the dynamic surface tension data.

Spontaneous Emulsification of Triolein Induced by Mixed Micellar Solutions of Sodium Polyoxyethylene Alkyl Ether Sulfate and Dodecyldimethyl Amine Oxide

“…It is well known that E mainly depends on the kinetics of the surfactant molecules Table 2 Dynamic interfacial tension parameters of the AES/DDAO systems. between the bulk solution and interface i.e., the Marangoni effect 28,30,31 and this effect supports this result. These results confirm that E values can be decreased by increasing dγ t /dt max values, and then the oil/water interface is easily expanded.…”

Effects of Buttermilk Powders on Emulsification Properties and Acid Tolerance of Cream

“…Phospholipids, casein, and whey proteins in a cream act as emulsifying components (Walstra and others 2006). Whey proteins are abundant in the skimmed milk fraction of cream, and their ability to adsorb onto surfaces is weaker than that of casein (Britten and Giroux 1991; Shrestha and others 2008), and hence they can not greatly influence the properties of the fat globule surface. Casein causes aggregation at low pH, and hence can not be responsible for this result.…”

“…Casein and whey proteins cover the surface of fat globules when they are homogenized and increase their surface area (Cano‐Ruiz and Richter 1997). Casein decreases surface tension faster than whey protein (Shrestha and others 2008) and exhibits good emulsification properties; however, casein is aggregated at around pH 4.6 (Walstra and others 2006). On the other hand, whey proteins are soluble at around pH 4.6 (Walstra and others 2006) and are thus utilized to improve the acid tolerance of an emulsion.…”

Chemical analysis in a drop: a dynamic surface tension detector for polymer and protein characterization

“…The surface tension at the air−liquid interface is directly proportional to the product of the maximum pressure drop measured and the radius of the capillary. The time‐dependent surface tension of globular proteins has been studied using the PDM and the interaction of proteins with small−medium organic molecules has been studied by the ADSA technique and the bubble pressure method . Recently, the PDM with drop‐shape analysis was applied to investigate the characteristic relaxation times and elasticity of interfacial layers from the protein HFBII hydrophobin, an amphiphilic protein produced by filamentous fungi, widely used in the stabilization of foams and emulsions .…”