3.2.1. Radical Scavenging Activity

The QUENCHER-DPPH and QUENCHER-ABTS methods were proposed for the first time to directly measure the RSA of the developed vegan egg-free mayonnaises containing blends of RRO with different cold-pressed oils and to compare their radical scavenging properties with that of commercial mayonnaises.

These analytical methodologies rely on the surface reaction phenomenon between mayonnaise samples with bound and free radical scavengers with organic DPPH radical and ABTS cation radical solutions. The QUENCHER method, as a cost-saving and extraction-free procedure, is highly relevant and recommended for the fat industrial laboratory to quickly control the antioxidant properties of emulsions.

The QUENCHER-DPPH and QUENCHER-ABTS results for all of the studied mayonnaise samples are presented in Figure 2.

**Figure 2.** Radical scavenging activity of 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; QUENCHER-DPPH—QUick, Easy, Novel, CHEap and Reproducible-2,2-diphenyl-1-picrylhydrazyl method; QUENCHER-ABTS—QUick, Easy, Novel, CHEap and Reproducible-2,2- azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) method. Bars with different letters (a–f) indicate significant differences between radical scavenging activity of mayonnaises (Tukey's post hoc test, *p* < 0.05).

It is noteworthy that the richest sources of hydrophilic and lipophilic antioxidants were traditional full fat mayonnaises (QUENCHER-ABTS = 3320 μmol TE/100 g and 2808 μmol TE/100 g for MT2 and MT1, respectively), while MT2 had a higher content of lipophilic antioxidants, as determined by the QUENCHER-DPPH test (828 μmol TE/100 g), than MT1 (DPPH = 692 μmol TE/100 g). In contrast, the store-bought plant-based mayonnaise (MV) revealed the lowest QUENCHER-DPPH (589 μmol TE/100 g) and QUENCHER-ABTS (1371 μmol TE/100 g) values (Figure 2). However, among aquafaba-based mayonnaises, samples containing blends of RRO with cold-pressed oils had similar DPPH results, whereas only the ABTS values for MRO and MSO did not differ significantly (Tukey's post hoc test, Figure 2). The lowest effectiveness of MLO to radical scavenging can be explained by the lowest DPPH (270 μmol TE/100 g) for CPLO among all cold-pressed oils (Table 4). It is worth noting that the addition of CPCO into the MCO sample caused a significant increase in QUENCHER-DPPH and QUENCHER-ABTS results. Moreover, nutritional yeas<sup>t</sup> and mustard had the highest radical scavenging properties (Table 4) which probably increased the RSA of aquafaba-based mayonnaise compared to commercially available MV mayonnaise.

For comparison, the methanolic extract of traditional mayonnaise had an RSA (DPPH = 267 μmol TE/100 g and ABTS = 856 μmol TE/100 g [51]) that was approximately three-fold lower than commercial samples measured by the QUENCHER procedure proposed in this study. Moreover, DPPH (78–134 μmol TE/100 g) and ABTS results (463–613 μmol TE/100 g) for methanol:water (70:30) extracts of vegan mayonnaises based on soy milk [52] were lower than our QUENCHER-DPPH values (589–828 μmol TE/100 g) and QUENCHER-ABTS values (1371–3320 μmol TE/100 g). The higher radical scavenging properties of mayonnaises determined by the QUENCHER procedure can be explained

as the proposed analytical method detects both the extractable and non-extractable compounds present in the analyzed samples.
