Investigation of surface properties of quince seed extract as a novel polymeric surfactant

In recent years, there is a growing trend from both academia and the industry towards the use of “clean-labeled” ingredients obtained from renewable resources. Proteins and polysaccharides, in particular, are becoming increasingly popular as alternatives to already well-established synthetic surfactants. Quince seeds are a relatively novel hydrocolloid source that has recently raised interest among researchers due to their strong surface activity and viscosity-enhancing properties. This study investigates quince seed extract's surface properties (dynamic surface tension and dilatational surface rheology) and how they differ with varying concentrations (between 0.01% and 1%), pH's (3, 7, 9, and 11), and ionic strengths (0.1, 0.3, 0.5 M NaCl). By QSE addition alone, equilibrium surface tension could be lowered to ∼36 mN/m, which is lower than the lowest ST that can be achieved with many other surface active biopolymers. Critical aggregation concentration (CAC) was identified as 0.165% w/v, meaning a relatively low extract concentration was sufficient to provide complete surface coverage. Dynamic surface tension curves revealed almost instantaneous polymer adsorption for concentrations over 0.01% w/v, which demonstrates the strong potential of the gum as a foaming agent. As solution pHs get further from the isoelectric point of QSE proteins, the rate of adsorption of QSE molecules onto the interface and the equilibrium surface pressures increased. Surface properties were also significantly affected by the ionic strength of the medium, with eq. STs decreasing with increasing QSE concentration. pH and ionic strength induced conformational changes in the interfacial layer and also led to local minima and maxima in dilatational elastic and loss modulus within ranges studied. Considering these findings, QSE is a very promising natural alternative to other polymeric surfactants and stabilizers currently used in the food, cosmetic and pharmaceutical industries.