Appendix: Electron microscopy: principles and applications to food microstructures

Latest advances in imaging techniques for characterizing soft, multiphasic food materials

“…The resulting image is very similar to a conventional optical microscopy micrograph (albeit without colour) but with much higher magnification; this enables rapid and easy interpretation (Groves & Parker, 2013).…”

“…Electron microscopy is a key technique in the characterization of structure at the molecular, nano-and microscale in different areas of science, including food. It can provide surface and internal features of samples, and reveal the role of single biomolecules such as proteins, fat crystals and polysaccharides in multiphasic systems such as emulsions, gels, foams (Groves & Parker, 2013). While conventional light microscopes have limited resolution due to the use of visible light radiation, described by the Abbe equation (Eq.…”

“…Contrast is thus generated and measured by a detector from the opposite side of the beam generator. The internal structure of nano-sized objects can be analysed with a resolution of 0.07 nm, the highest resolution capable with microscopic techniques (Groves & Parker, 2013). The superior resolution of TEM compared to SEM stems from the higher accelerating voltage (100 keV), which provides an electron beam with smaller wavelength and thus higher resolving power.…”

“…In addition to coating (as described for SEM) samples must be cut into thin slices (100 nm) to allow enough electrons to reach the detector during TEM measurements. Sectioning is usually carried out by ultramicrotomy, which is a costly and complex operation (Groves & Parker, 2013). This requirement on sample thickness has inherent consequences for the kind of structures can be successfully imaged, .e.g.…”

Physicochemical characteristics, protein hydrolysis, and textual properties of surimi during fermentation withActinomucor elegans

“…SEM has been widely applied in food analysis as it gives a 3D view of the sample and makes the differences in structure easily understood [24]. As shown in Fig.…”