title: Interaction of Quillaja bark saponins with food-relevant proteins.
abstract: The surface activity and aggregation behaviour of two Quillaja bark saponins (QBS) are compared using surface tension, conductometry and light scattering. Despite formally of the same origin (bark of the Quillaja saponaria Molina tree), the two QBS show markedly different ionic characters and critical micelle concentrations (7.7·10(-6) mol·dm(-3) and 1.2·10(-4) mol·dm(-3)). The new interpretation of the surface tension isotherms for both QBS allowed us to propose an explanation for the previous discrepancy concerning the orientation of the saponin molecules in the adsorbed layer. The effect of three food-related proteins (hen egg lysozyme, bovine β-lactoglobulin and β-casein) on surface tension of the saponins is also described. Dynamic surface tension was measured at fixed protein concentrations and QBS concentrations varying in the range 5·10(-7)-1·10(-3) mol·dm(-3). Both dynamic and extrapolated equilibrium surface tensions of the protein/QBS mixtures depend not only on the protein, but also on the QBS source. In general, the surface tension for mixtures of the QBS with lower CMC and less ionic character shows less pronounced synergistic effects. This is especially well visible for β-casein/QBS mixtures, where a characteristic maximum in the surface tension isotherm around the molar ratio of one can be noticed for one saponin product, but not for the other.
authors.affiliation: Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Kezwon
authors.affiliation: Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland. Electronic address: kamil.wojciechowski@ch.pw.edu.pl.
authors.forename: Kamil
authors.initials: K
authors.lastname: Wojciechowski
mesh_terms: D000327:Adsorption; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry; D002364:Caseins / Q000737:chemistry; D002417:Cattle; D002645:Chickens; D005502:Food; D007477:Ions; D007782:Lactoglobulins / Q000737:chemistry; D008823:Micelles; D008892:Milk / Q000378:metabolism; D008970:Molecular Weight; D009113:Muramidase / Q000737:chemistry; D024301:Plant Bark / Q000737:chemistry; D011506:Proteins / Q000737:chemistry*; D062605:Quillaja Saponins / Q000737:chemistry*; D013499:Surface Properties; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry; D014197:Trees
chemical_list: D001672:Biocompatible Materials; D002364:Caseins; D007477:Ions; D007782:Lactoglobulins; D008823:Micelles; D011506:Proteins; D062605:Quillaja Saponins; D013501:Surface-Active Agents; C421864:hen egg lysozyme; D009113:Muramidase
keywords: QBS; lysozyme; surface tension; β-casein; β-lactoglobulin