An investigation on the influence of pH and ionic strength on the adsorption and interfacial dilatational properties at the oil-water interface of pumpkin (Cucurbita pepo) seed protein hydrolysate

• Main Authors: Bučko Sandra Đ., Katona Jaroslav M., Petrović Lidija B., Milinković Jelena R., Fraj Jadranka L., Spasojević Ljiljana M., Miller Reinhard
• Format: Article
• Language: English
• Published: Serbian Chemical Society 2018-01-01
• Series: Journal of the Serbian Chemical Society
• Subjects: natural surfactants; enzymatic hydrolysis; oil-water interface; interfacial dilatational rheology; dilatational elasticity
• Online Access: http://www.doiserbia.nb.rs/img/doi/0352-5139/2018/0352-51391800042B.pdf
• ISSN: 0352-5139; 1820-7421

Pumpkin (Cucurbita pepo) seed protein hydrolysate (PSPH) was obtained by enzymatic hydrolysis of pumpkin seed protein isolate using pepsin. Influence of pH (3, 5 and 8) and ionic strength, Ic (0–1 mol dm-3), on the adsorption kinetics of PSPH (diffusion rate constant, kdiff, and adsorption rate constant, kads), interfacial pressure (π) and interfacial dilatational properties (dilatational elasticity, E′, and viscosity, E″) of the oil–PSPH solution interfaces was investigated at different PSPH concentrations (c = 0.0014–14 g dm-3). It was found that PSPH adsorbs to the interface at c ˃ 0.0014 g dm-3, regardless of pH and ionic strength, as evidenced by the increase in interfacial pressure. The kdiff and kads value were found to be the highest at pH 3 and the lowest at pH 5 at the corresponding concentrations. The dilatational properties of the interfaces, which were investigated at different oscillation frequencies, ν, 0.01–0.2 Hz, showed that the E′ of the oil–PSPH solution interfaces is much higher than its E″. Moreover, E′ increases with increasing PSPH concentration at pH 5 and 8, and with increasing Ic, regardless of the pH, while E″ changes only minimally. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 46010]