3.2.2. Oxidative Status

The oxidative status of the oil phase of each mayonnaise sample was evaluated by characteristic values such as PV, AnV, TOTOX and AV (Table 5).


**Table 5.** Oxidation parameters of mayonnaises.

*n* = 3; SD—Standard Deviation; Different letters (a–g) within the same column indicate significant differences between oxidation parameters (PV—peroxide value; AnV—anisidine value; TOTOX—total oxidation index;AV—acid value) 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 (Tukey's post hoc test, *p* < 0.05).

The PV shows the degree of peroxidation and measures the amount of total peroxides, whereas the content of aldehyde carbonyl bonds formed during secondary lipid oxidation is evaluated as AnV. PV and AnV measurements are commonly used together to determine the total extent of oxidation by the TOTOX index. Moreover, AV is an important variable for the quality of the fat-based product because it reveals free fatty acid content affecting its oxidative ageing.

As can be seen, PV results were significantly different in different mayonnaise samples (Tukey's post hoc test, Table 5). The lowest amount of primary oxidation products was in MT2 (PV = 0.82 mEq O2/kg), while vegan mayonnaise (MV) had the highest PV = 4.61 mEq O2/kg. This can be explained by the highest amount of total antioxidants in the MT2 sample (QUENCHER-DPPH = 828 μmol TE/100 g and QUENCHER-ABTS = 3320 μmol TE/100 g, Figure 2), which most effectively inhibited harmful oxidation reactions. However, the highest PV for MV can be attributed to the lowest antioxidant potential (QUENCHER-DPPH = 589 μmol TE/100 g and QUENCHER-ABTS = 1371 μmol TE/100 g), preventing the peroxidation in polyunsaturated fatty acids of the oil phase. Moreover, the addition of CPLO with a high level of unsaturated fatty acids (MUFA = 33.8% and PUFA = 49.7%, Table 3) sensitive to peroxidation raised the susceptibility of mayonnaise to oxidation. Thus, MLO had a high level of PV (2.27 mEq O2/kg) and AnV (2.95) in its fat phase (Table 5). Meanwhile, the presence of resistant SAFA (7.0–10.6%) to degradation processes and a high percentage of MUFA (29.1–64.6%) in CPRO, and CPSO improved the oxidative stability of MRO and MSO samples (PV and AnV ranged between 1.43–1.90 mEq O2/kg and 1.12–1.39, respectively).

Unexpectedly, low amounts of primary (PV = 1.19 mEq O2/kg) and secondary (AnV = 1.55) oxidative products in the oil phase of MCO with the highest content of PUFA (73.8%, Table 3) can be explained by the high radical scavenging properties of CPCO (DPPH = 387 μmol TE/100 g and ABTS = 706 μmol TE/100 g, Table 4) and MCO (QUENCHER-DPPH = 690 μmol TE/100 g and QUENCHER-ABTS = 2121 μmol TE/100 g, Figure 2). The antioxidant compounds in cold-pressed oils may act as antioxidants and prevent or delay the lipid oxidation of mayonnaises.

For comparison, the effect of cold-pressed black cumin oil (CPBCO) on the oxidative stability of traditional mayonnaise was evaluated. At the end of storage for 4 weeks at 20 ◦C, mayonnaise with 20% of CPBCO had a lower content of primary oxidation products (PV = 17.66 mEq O2/kg) than the control sample (36.07 mEq O2/kg) [10]. Moreover, substituting egg yolk with milk protein and adding high levels of fish oil to the mayonnaise samples raised the PV results to approximately 75 and 25 mEq O2/kg at 20 ◦C and 2 ◦C of storage, respectively [19].

It is noteworthy that the best stability revealed the MT2 sample with the lowest TOTOX index (2.40), which combines the amount of primary with secondary oxidation products. In contrast, the MV sample containing the lowest total antioxidants level (QUENCHER-DPPH = 589 μmol TE/ 100 g and QUENCHER-ABTS = 1371 μmol TE/100 g, Figure 2) was characterized with the highest TOTOX value = 12.29 (Table 5).

Additionally, aquafaba-based mayonnaises had a significantly lower AV (0.11–0.26 mg KOH/g) than commercial mayonnaise samples (AV = 0.49–0.52 mg KOH/g).

Similarly, commercial mayonnaise revealed higher AV (5.39 mg KOH/g) than samples made with lemon juice and a mix of lemon juice and vinegar (AV = 1.68–3.37 mg KOH/g), which can be explained by non-specific reactions during AV measurements [53].
