Fatty acids and fatty alcohol esters as novel markers of authenticity and extraction method of commercial avocado oil

Abstract

The lack of regulations on avocado oil authenticity enabled producers to blend it with cheaper oils without declaring it on the label. This study explored fatty acids (FA) and fatty alcohol esters (FAE) as innovative markers of avocado oil purity and extraction method. Only 40 % of the samples met the FA standards. Regarding FAE, extra virgin samples showed a maximum concentration of 2674.12 ± 570.98 mg total FAE·kg^-1 oil, significantly higher than the 640.98 ± 220.06 mg total FAE·kg^-1 oil observed in refined samples, making FAE novel markers of extraction method. Furthermore, a canonical discriminant analysis using Wilk's statistic (Λ = 0.008, F _{126, 1028.2} = 8.87, p < 0.0001), based on fault concentrations (high, medium, low) of the allegedly pure samples, revealed that the high- and medium-fault clusters aligned closely with declared blends containing canola or safflower oils. FA and FAE are promising molecules to detect adulteration in avocado oil.

Keywords: Avocado oil identity; Food adulteration; Food fraud; Food quality.

Graphical abstract

Fig. 1

Piled concentrations of the fatty alcohol esters (FAE) of the extra virgin (a) and the refined (b) samples of avocado oil. Each column represents the distribution of the mean FAE values of each brand; the standard error (SE) bars are for the mean total FAE. Significance differences (α ≤ 0.05) for each group (extra virgin and refined) were obtained by one-way ANOVA (n = 6) and Fisher's LSD test. The samples were arranged alphabetically, based on their ID; the ones with Y1 were tested in study one (2021), and the ones with Y2 were tested in study two (2023).

Fig. 2

Distribution of the main (a) and minor (b) fatty acids (FA) in the avocado oil samples, based on their concentration of faults, using the standards of the Mexican Norm NMX-F-811-SCFI as a reference. Each column in each FA represents the mean concentration values, with their corresponding standard error (SE) bars, of FA per category: high faults (6–14) (n = 54), medium faults (2–5) (n = 36), and low faults (0–1) (n = 60); the significant differences (α ≤ 0.05) were evaluated by one-way ANOVA and Fisher's Least Significant Difference (LSD) test.

Fig. 3

Principal component analysis (PCA) of the avocado oil samples, grouped based on their concentration of faults, with fatty acids (FA) and fatty alcohol esters (FAE) (a) and FA only (b) as variables. In the legend: High (6–14 faults); Medium (2–5 faults); Low (0–1 faults). Abbreviations: PC1 and PC2: Principal Components one and two; IDs of samples: EXV: extra virgin; REF: refined; Y1: year one (2021); Y2: year two (2023).

Fig. 4

Three-dimensional plots with avocado oils and samples labeled as blends, using the discriminant functions from Model 1, which considers fatty acid (FA) profiles and fatty alcohol ester (FAE) profiles. The plots have accumulated variance explained of 0.91 (a), 0.88 (b), and 0.78 (c). In the legends of the plots: High faults (6–14); Medium faults (2–5); Low faults (0–1); Mix A: avocado + safflower + sunflower oils; Mix B: avocado + coconut + safflower oils; Mix C: avocado + olive + canola oils; Mix D: avocado + coconut + canola oils; and Mix E: avocado + olive oils.

Fig. 5

Three-dimensional plots with avocado oils and samples labeled as blends, using the discriminant functions from Model 2, which only considers fatty acid (FA) profiles. The plots have accumulated variance explained of 0.91 (a), 0.90 (b), and 0.76 (c). In the legends of the plots: High faults (6–14); Medium faults (2–5); Low faults (0–1); Mix A: avocado + safflower + sunflower oils; Mix B: avocado + coconut + safflower oils; Mix C: avocado + olive + canola oils; Mix D: avocado + coconut + canola oils; and Mix E: avocado + olive oils.