CHARACTERIZATION OF WHEY PROTEIN-POLYPHENOL INTERACTIONS BY DYNAMIC LIGHT SCATTERING

M. VON STASZEWSKI; JAGUS, R.J.; A.M.R. PILOSOF

Atenas

Congreso; 11th. International Congress on Engineering and Food; 2011

National Technical University of Athenas, School of Chemical Engineering

Many drinkable dairy products added with green tea polyphenols have been launched by food industriesbecause epidemiological studies suggest an association between the prevention of diseases and theconsumption of polyphenol-rich beverages or foods. However, polyphenols have a significant affinity forproteins that leads to formation of soluble complexes, which can grow in size and even form sediments.The aim of this work was to study the binding of green tea polyphenols to b-lactoglobulin,caseinomacropeptide and a-lactalbumin in a pH range between 3.0 and 6.0 by means of dynamic lightscattering.Whey proteins and polyphenol aqueous solutions were prepared in citrate buffer (pH 3.0, 0.01M), acetatebuffer (pH 4.5, 0.01M) or phosphate buffer (pH 6.0, 0.01M). Dynamic light scattering experiments werecarried out in a Zetasizer Nano-Zs (Malvern Instruments, Worcestershire, UK) provided with a He–Ne laser(633 nm) and a digital correlator, Model ZEN3600. Measurements were carried out at a fixed scattering angleof 173º. The assay was carried out in triplicate.The intensity size distributions for all the mixed samples were monomodal and the peaks shifted to highersizes as compared to pure proteins. It is noticeable that the particle size measured by light scattering changedwith pH. Close to the isoelectric point of each protein the aggregation potential of polyphenols and the size ofthe complexes formed were the highest. Although the initial binding of polyphenols to whey proteins isessentially a non-selective hydrophobically driven interaction, the insolubility of the complex formed is mostlikely determined by surface charge effects. At the isoelectric point of the proteins, complexation proceeds upto form big particles that can easily precipitate.Controlling the interactions between whey proteins and green tea polyphenols would therefore provide a toolto improve the development new functional foods.