β‐Cyclodextrin‐Mediated Removal of Soy Phospholipids from the Air–Water Interface

Binding of soy phosphatidylcholine (PC) and phosphatidylinositol (PI) with β‐cyclodextrin (βCD) was studied using a spread monolayer technique at the air–water interface. First, surface pressure (π) versus surface concentration (Γ) isotherms of both PC and PI were characterized by forming spread monolayers on an aqueous subphase. PC and PI monolayers reached saturation at Γ of 1.98 and 3.24 μmol/m2, respectively, at 25 °C. Subsequently, desorption of PC or PI from the spread monolayer in the presence of 2–14 mM βCD in the subphase was studied by measuring changes in π of monolayer. This desorption was indicative of a complex formation between βCD and PC or PI. The amount of PC or PI bound to βCD was determined by converting the net change in π to Γ by using π–Γ isotherms. From the saturated monolayers at the air water‐interface, approximately 30% of PC and 50% of PI could be removed by 14 mM βCD. It was calculated that the free energy change required to transfer a PL from the monolayer at air–water interface to the aqueous phase in presence of βCD was decreased by 6–7 kcal/mol. Hydrolysis of PC in the monolayer by phospholipase A2 (PLA2) improved extraction efficiency of βCD. By incorporating 2.29 μM PLA2 and 10 mM βCD in subphase, up to 80% of PC monolayer could be desorbed from the air–water interface. These results are discussed in terms of the potential use of βCD to remove PLs bound to soy protein.