3.2.3. Microstructure

Previous studies clearly demonstrated that the size of oil droplets (ODs) is one of the most essential parameters influencing mayonnaise stability, texture, and taste [54]. Mayonnaises characterized by small ODs usually possess significantly increased viscosity and stability. The size of ODs depends on the homogenization approach, including its duration and intensity, mayonnaise composition, and ingredient viscosity [55].

In our studies, the CLMS images revealed differences in the size of ODs between analyzed emulsions (Figure 3A–G). The largest ODs were observed for MV and smallest ODs were found for MT1 and MT2. Recently, it was reported that aquafaba-emulsifying properties caused the presence of larger ODs compared to the egg-yolk-based mayonnaise [23,30]. The size of ODs likely depends on the size of emulsifier molecules which in the egg yolk are much smaller compared to aquafaba [30]. He et al. [30] demonstrated that the average of ODs size (*d*43) of mayonnaise analogue prepared using freeze-dried or spraydried aquafaba was significantly larger, at 222 ± 9 μm<sup>2</sup> and 97.3 ± 16 μm2, respectively, compared to egg yolk based mayonnaise (9.02 ± 1 μm2). Our results seem to confirm that the addition of plant-based proteins, such as pea protein, results in larger average areas of ODs (101.40 μm2) in cases of MV when compared to egg yolk-based mayonnaise MT1 and MT2, where the average areas of ODs were 4.47 μm<sup>2</sup> and 4.44 μm2, respectively. We also cannot exclude that the larger size of ODs in MV might be the result of low oil content (35%) in comparison to MT1 and MT2 (around 70%).

The use of equal amounts of aquafaba—23.70% and different oil composition was accompanied by the presence of significantly larger ODs in MCO (45.28 μm2) and in MLO (56.75 μm2). In turn, ODs in MRO and in MSO showed an average area of 15.96 μm<sup>2</sup> and 14.29 μm2, respectively (Figure 3H). The observed variations in ODs size between the analyzed mayonnaises could reflect the differences in their lipidic composition.

**Figure 3.** (**A**–**G**) Representative images of oil droplets (ODs) stained with Nile red. (**H**) The data point-box plot showing a mean area of ODs quantified with imaging software (ImageJ). A statistical analysis was performed by a one-way analysis of variance (ANOVA) with Tukey's post hoc test (*p* < 0.05). Different letters (a–c) indicate significant differences with *p* < 0.05 between aquafaba-based mayonnaises with blends of refined rapeseed oil and cold-pressed rapeseed oil (MRO), cold-pressed sunflower oil (MSO), cold-pressed linseed oil (MLO), and cold-pressed camelina oil (MCO); MT1— commercial egg yolk mayonnaise from producer 1; MT2—commercial egg yolk mayonnaise from producer 2; MV—commercial vegan mayonnaise.
