Characterization of the Microstructure of Phase Segregated Amylopectin and β-Lactoglobulin Dry Mixtures

Abstract

The microstructure of phase-segregated amylopectin (AP) and β-lactoglobulin (βlg) mixtures formed during drying from solutions with different concentrations and different polysaccharide and protein ratios have been studied using atomic force microscopy (AFM) and transmission electron microscopy (TEM). AFM was used as the main technique and TEM was used to confirm the results. Systems with only one of the components, AP or βlg, displayed even structures. When the polysaccharide and the protein were in the same system they phase segregated with a sharp boundary between the phases. According to the type of surface morphology of the phase-segregated samples, they were grouped into: domains wetting the airwater surface and domains appearing to be immersed in the solid film. The size range of the domains varied widely from about some nanometers to about a few micrometers which was determined by kinetic reasons or by restrictions given by the film structure of the sample. The two phase systems were AP-continuous phase at AP to βlg ratios above about 1:3 and βlg-continuous phase at ratios below about 1:6. Between these ratios, the systems appeared more or less bicontinuous. The morphology as well as its position in the phase diagram suggested a spinodal phase separation. Phase separation was also observed in the metastable region (AP to βlg ratio 3:1), although the domains were smaller and less developed and it was interpreted as binodal phase separation.

Characterization of chitosan–whey protein films at acid pH

“…Similar phase-separated systems have been reported for other polysaccharide-protein dried films (Quiroga & Bergenståhl, 2007;Silva et al, 2007).…”

Confocal Raman microscopy for mapping phase segregation in individually dried particles composed of lactose and macromolecules

“…Phase segregation as a consequence of drying has been observed in thin dried films using AFM, for instance in thin films formed from protein and starch [28]. Further, SEM micrographs of the cross-sections of HPMC/corn starch dried films revealed a polymer phase segregation [29].…”

Atomic Force Microscopy-Based Screening of Drug-Excipient Miscibility and Stability of Solid Dispersions

“…They allow for studying phase separation directly and on molecular length scales, which results in much shorter observation times. The capability of AFM to study de-mixing mechanisms over time and in the presence of various environmental factors was already demonstrated on solid drug dispersions ( 21 ), polymer blends ( 22 ), glass ( 23 ), food ( 24 ), and probably many other materials. Because the samples can also be fractured, or sectioned with a microtome, bulk and surface evolution can accurately be differentiated ( 25 , 26 ).…”