The Surface Coverage of Fat on Food Powders Analyzed by Esca (Electron Spectroscopy for Chemical Analysis)

ES.A (electron spectroscopy for chemical analysis) was used to estimate the fat coverage on different spray-dried food powder surfaces. The method presented here represents a new way of estimating the actual surface coverage of fat on a food powder. The ESCAmethod is illustrated with three different series of experimen ts. The results obtained with the ESCA-technique are combined with the results obtained from the conventional free fat extraction technique for different spray-dried powders. In the first series , emulsion s containing different ratios of protein to fat were spray-dried. An increase in the amount of fat in the emulsion gives an increased surface coverage of fat. Powders with a high fat content shows a high free fat level, indicating a continuous network of fat in side the particles. Secondly, the effect of heat treatment on the ability of bovine serum albumin to encapsulate fat has been investigated . The results show that albumin treated at high temperature encapsulates the fat less completely than the albumin treated at low temperature. Finally, emulsions containing oil phases with different melting points were spray-dried and analyzed. Powders with a high melting fat show very well encapsulated fat with only a minor surface coverage of fat. Powders with a qualitatively different distribution of fat can be identified by comparing the surface coverage of fat estimated by ESCA with the free fat measurements

Colloidal structures in media simulating intestinal fed state conditions with and without lipolysis products

Purpose. To study the ultrastructure of biorelevant media and digestion products of self-nanoemulsifying drug delivery system (SNEDDS) at high level BS/PL conditions. Methods. Cryogenic transmission electron microscopy (Cryo-TEM) was employed to visualize the colloid structures in the biorelevant media and lipolytic products generated during hydrolysis of a SNEDDS formulation. Their electrical properties were investigated by measuring their zeta-potential values. Results. In the biorelevant media, vesicles (either unilamellar or multilamellar) and bilayer fragments are visualized. Occasionally, vesicles with an internal deformed structure are recognized, suggesting surface tension or uneven lateral stress. Visualization studies of the intermediate colloidal phases produced during digestion of a SNEDDS using the in vitro lipolysis model revealed the formation of similar structures as previously reported. The zeta-potential of the media was negatively charged and decreased from -23 to -35 mV with increasing surfactant/lipid load. Lower zeta-potential values (-16 mV) obtained for the structures formed during the lipid hydrolysis of the SNEDDS were probably due to the presence of calcium, which shields the surface, thereby reducing the charge. Conclusions. The diversity of these vesicles in terms of size, lamellarity, and internal organization advocate their important role during lipid digestion in the gastrointestinal milieu