Surface composition of nanoencapsulated food ingredients by X-ray photoelectron spectroscopy (XPS)

Nano-delivery systems, as the techniques to encapsulate bioactive compounds, represent an efficient tool to overcome limitations associated with their direct utilization in food formulations. Beside physiochemical properties of nanoparticles (e.g., particle size and zeta potential), surface characterization can provide crucial information about nanocarriers. X-ray photoelectron spectroscopy (XPS) is one of the professional surface analysis techniques with a high sensitivity and accuracy. XPS is mainly used for characterizing the surface of nanocarriers according to elemental analysis, chemical composition, and determination of molecular binding states. It is based on electron bombardment of the sample surface by X-ray beams, emission of produced photoelectrons from the surface with certain energy values, and finally, the kinetic energy and number analysis of the photoelectrons. This chapter briefly reviews XPS in terms of principles and instrumentation. Also, potential applications of XPS for encapsulation systems and nanostructures as well as in the food industry are highlighted. In this regard, the relevant studies have been considered.