| Improved methods were developed for fixing and staining milkfat globules (MFG) and casein micelles (CM) in dairy whipping cream (CREAM). These methods were used to study the microstructure of MFG, CM and foam cells in CREAM by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).;SEM emulsion specimens were embedded in agarose gel; exposed to glutaraldehyde and osmium tetroxide (OsO$sb4$) vapors; treated with tannic acid and guanidine-HCL mordants; fixed with imidazole-buffered OsO$sb4$ (O), ferricyanide OsO$sb4$ (FO), or tricomplex OsO$sb4$ (TO); partially dehydrated, treated with 1% $rho$-phenylenediamine, critical point dried, mounted on aluminum stubs and examined by SEM without metal coating.;TEM emulsion specimens were prepared by the same procedure except that after the $rho$-phenylenediamine en bloc treatment, they were infiltrated with propylene oxide, embedded in EPON 812, ultra-thin sectioned, stained with uranyl acetate and lead citrate, and examined by TEM. SEM and TEM foam specimen procedures were similar to their respective emulsion specimen procedures, except that specimens were treated with a second mordant, thiocarbohydrazide, just prior to post-mordant fixation and staining.;The FO post-mordant method preserved MFG microstructure best for SEM. The TO method provided the best microstructural details of CM adsorbed onto MFG and the best resolution of individual MFG and CM by SEM. The FO method was best for preserving MFG emulsion microstructure for TEM, but the TO method preserved the spherical shape of individual MFG best for TEM. The FO method provided the best contrast to foam microstructure, whereas the TO method provided excellent resolution and visualization of MFG and foam microstructure for SEM. Although the FO method preserved MFG and CM in foam microstructure well, the TO method preserved the rigidity of individual MFG best for TEM. By comparison of SEM and TEM for determining the emulsion and foam microstructure, SEM provided the external details and three dimensions of emulsion and foam microstructures in whipped cream and TEM provided more internal details of emulsion and foam microstructures than SEM did. |
