# Critical Review of Techniques for Food Emulsion Characterization
## 3 Techniques for Emulsion Characterization
### Microscopic Analysis
However, to account for any changes that may have occurred in the structure of the emulsion during microscopic evaluation, it is necessary to verify the obtained data with other analytical methods such as droplet size analysis. One of the most promising techniques for emulsion imaging that may open new perspectives in understanding the behavior of these complex systems is atomic force microscopy (AFM). This technique allows direct visualization of emulsion interfacial films (Figure 7) and analysis of their tightness, integrity, morphology, and structure. This can provide crucial insights into emulsion stability and separation phenomena, as well as the behavior of molecules at the droplet interfaces [89]. For example, AFM can be utilized to examine the competitive adsorption of various emulsifier molecules at the oil-water interface [90]. [PERSON] et. al. used AFM to visualize the gradual displacement of milk protein \(\beta\)-lactoglobulin from an air-water interface by the water-soluble surfactant Tween 20 [90]. AFM has also been used to study the formation and arrangement of multi-layer films at the oil-water interface, providing a deeper understanding of the stabilization mechanisms in more complex interfacial layers. Recent technological advancements in AFM have allowed the visualization and quantification of interfacial interactions at a nanoscale level [91]. By utilizing nano-structured probes for scanning material surfaces at sub-nanometric and atomic resolution, AFM can provide information on the surface interaction forces as well as micro/nano-structured surface topography [92]. One of the significant limitations of AFM analysis of emulsion droplets is that it can be time-consuming and labor-intensive. Since, in most studies on emulsions _via_ AFM, the imaging is performed under dry conditions (in the air mode), the droplets need to be deposited on a solid matrix by the Langmuir-Blodgett technique [93] and dehydrated before observation [88]. The process of depositing air-water or oil-water interfacial films onto a solid matrix is not only highly intricate and difficult but may also alter the native emulsion structure. However, the transfer process of air-water interfacial films is more convenient and operable compared to oil-water interfacial films. This has led to a greater focus on visualization studies of air-water interfacial films, while the oil-water interfaces are less often explored. Therefore, there is an urgent need for new techniques that allow for the direct _in situ_ visualization of nanodroplet interfaces in liquid nanemulsions. The use of surface force apparatus in conjunction with atomic force microscopy can provide novel insights into the complexities of emulsion stabilization mechanisms [94]. Another downside of AFM lies in the fact that it does not provide information on the internal structure or composition of emulsion droplets, as it primarily focuses on surface topography. AFM measurements on nanodroplets present certain limitations due to their deformable soft surfaces. Such surfaces may present challenges in accurately measuring their mechanical properties and surface roughness and can be easily damaged during the probing process.