Adsorption of proteins at the solution/air interface influenced by added non-ionic surfactants at very low concentrations for both components. 1. Dodecyl dimethyl phospine oxide

Adsorption of Proteins at the Solution/Air Interface Influenced by Added Nonionic Surfactants at Very Low Concentrations for Both Components. 2. Effect of Different Surfactants and Theoretical Model

“…At the C 12 DMPO addition concentration of 10 −2 mmol/L, the time necessary to attain the equilibrium is by a factor of about 30 longer than that for the bubble. These results support the applicability of the present method which is based on a bubble formed in a large volume of the studied solution, which was used also in ref 12, and indicate the reliability of the results in what regards the adsorption equilibrium. Figure 2 shows the dynamic surface tension curves of the individual BCS solution at a bulk concentration of 10 −5 mmol/ L (curves 1 and 1* were obtained for two different samples) and seven mixed solutions at different C 14 DMPO concentrations in the range from 2 × 10 −5 to 5 × 10 −3 mmol/L.…”

“…Added surfactants influence the interfacial properties of the proteins and their surface activity, rheological behavior, and adsorption dynamics. The effects caused by the additions of nonionic surfactants were studied in a number of publications − using various surfactants. The influence of added surfactants was studied for β-lactoglobulin, lysozyme, and β-casein.…”

“…It was noted in ref that in all known studies the protein concentration was high enough (equal or above 10 –4 mmol/L), and therefore no noticeable influence of the additions of nonionic surfactant at very low concentrations could be detected. In ref , it was reported that at C 12 DMPO concentrations between 10 –4 and 10 –3 mmol/L the surface tension decrease of the mixtures amounts to about 3–5 mN/m as compared with the experimental values measured for both individual β-lactoglobulin and β-casein solutions, and with the theoretical data calculated using the model for the protein/surfactant mixture. It should be noted that in this model the values of the equilibrium adsorption constants were the same as those for the individual solutions.…”

“…It should be noted that in this model the values of the equilibrium adsorption constants were the same as those for the individual solutions. The studies in ref at quite low concentrations of the surfactants and proteins in their mixed solutions were performed with the buoyant bubble profile tensiometry. It was found that because of a significant acceleration of the diffusional fluxes of surfactants and proteins to the surface of a spherical bubble the time to reach adsorption equilibrium becomes dramatically reduced.…”

Adsorption of Proteins at the Solution/Air Interface Influenced by Added Nonionic Surfactants at Very Low Concentrations for Both Components. 3. Dilational Surface Rheology

“…For mixtures of non-ionic surfactants with more flexible proteins like β-casein (BCS) there is a sharp maximum in the dilational elasticity. Experimental results on the dilational rheology of protein/non-ionic surfactant mixtures were reported in 13-17 ; some of these results and the relevant theoretical models of the corresponding surface layers were discussed previously 18,19 . The influence of the addition of the non-ionic surfactants C 12 DMPO, C 14 DMPO, С 10 ОН and С 10 ЕО 5 at concentrations from 10 −5 to 10 −1 mmol/L to BCS and BLG solutions, respectively, at a fixed concentration of 10 −5 mmol/L on the surface tension were studied in 19 .…”