Introduction

Lipid oxidation in food products such as mayonnaise results in the appearance of rancidity and deterioration, making these products unfit for human consumption. Mayonnaise is an oil-in-water emulsion with a low pH and an oil content between 65 and 85% (^{Mattia et al., 2015}).

One of the most effective alternatives to delay lipid oxidation in this product is the addition of antioxidants such as butyl hydroxyanisole and butylated hydroxytoluene. However, their use in food has been restricted due to their adverse effect on enzymes in human organs (^{Bakkali et al., 2008}). This has motivated the development of formulations with antioxidants obtained from natural sources (^{Amorati et al., 2013}; ^{García et al., 2014}; ^{Gavilanez & Rojas, 2024}). This is how mayonnaise has been made with poly ε-caprolactone nanoparticles loaded with thyme essential oil (^{Passos et al., 2019}), tocopherol, rosemary essential oil, and Ferulago angulata (Schlecht) Boiss extract (^{Alizadeh et al., 2019}) and microencapsulated phenolic compounds from lemon waste (^{Shaygannia et al., 2021}).

Although various research has been done on using natural antioxidants in the formulation of mayonnaise, the actual effect of these phytochemical compounds should continue to be studied in depth. Although they show antioxidant activity in vitro and in vivo, they could not favor the preservation of the product. Thus, for example, it has been reported that gallic acid showed a pro-oxidant activity in mayonnaise, possibly due to its ability to reduce metal ions to their most active form, such as Fe³⁺ to Fe²⁺ (^{Jacobsen et al., 2014}).

Spray-drying has been used earlier to microencapsulate oregano essential oil (MOEO) (^{Rojas-Molina et al., 2022}; ^{Plati et al., 2021}). However, other wall materials were used in these studies, which differed from maltodextrin-gum Arabic combinations. Considering the above, this work aimed to estimate the kinetic parameters of the variation of the peroxide index (PI) and shelf life of mayonnaise with microencapsulated oregano (Origanum vulgare L.) essential oil as a natural antioxidant during its accelerated storage.

Methodology

The emulsion consisted of 7% m/m of oregano (O. vulgare) essential oil, 9.3% m/m gum Arabic, 18.7% m/m maltodextrin, and 65% deionized water (35% m/m total solids feed). According to ^{Rojas-Molina et al. (2022}), the microcapsules were obtained by spray drying.

The mayonnaises of each treatment (10 kg) were prepared under the same conditions. Ethylenediaminetetracetic acid was dissolved in an aliquot of the control treatment formulation oil (T1) and then mixed with the rest. The MOEO was added with the soybean oil during the emulsion formation to obtain concentrations of 0.26 and 0.44% for the treatments T2 and T3, respectively. The determination of the maximum concentration of MOEO to be used in the formulation of mayonnaise, without affecting the color, odor, and taste, was carried out through an acceptance/rejection test in group sessions with 10 semi-trained judges. The concentration of MOEO varied between 0 and 1.0% (m/m).

All the solid ingredients (white sugar, common salt, starch, citric acid, Guar gum, xanthan gum, mustard flour) were mixed for about 1 min, except the MOEO, to facilitate its homogenization during emulsification. Chlorinated water was then added and mixed for 2 to 3 min until the paste was homogenized due to the hydration of the starches. The eggs were then added, and, at the end, the refined soybean oil at 12 °C and the pasteurized white vinegar were slowly incorporated, homogenizing the mixture until the emulsion was obtained.

The mayonnaises were packed in the presence of air in the headspace of 270 g glass jars with a metallic twist off top (Ø = 63 mm) and then stored at 35, 45, and 55 ºC for a variable time, depending on the formulations and temperatures, until the samples were considered objectionable.

A sample was dissolved in a mixture of ethanol/petroleum ether with an ethanolic hydroxide of potassium (AOAC, 2012) to determine the titratable acidity (% m/m acetic acid). The PI (meq O₂/kg of oil) was determined by an iodometric method with a visual endpoint detection after treating the mayonnaise to separate the oil from the emulsion (ISO 3960, 2017). The parameters of the Arrhenius model (k and Ea) for the variation of the PI during the storage were estimated. The temperature acceleration factor (Q₁₀) was also determined according to ^{Nascimento et al. (2013}).

ANOVA was performed with the Statistica program (v. 7, 2004, StatSoft. Inc., Tulsa, USA), and when a significant difference was detected (p ≤ 0.05), Duncan's multiple range test was applied.

PI during storage was subjected to linear regression analysis as a function of time. The ANOVA's R² and the lack of fit test were used to choose the best-fit kinetic model, with a significance level of 5%.

Results and discussion

The kinetics of the variation in IP during accelerated storage of mayonnaise sauces showed a better fit, in all cases, for a pseudo-zero-order reaction, with adjusted R² values between 0.8945 and 0.9791. Table 1 presents the results of the variance analysis of the kinetic models of this variation in mayonnaise sauces.

Table 1 Analysis of variance of kinetic models of lipid oxidation of mayonnaise sauces. 

Note. *T1: control treatment; T2: treatment with adding oregano EO microcapsules at 0.26% m/m; T3: treatment with adding oregano EO microcapsules at 0.44% m/m. **Estimated by determining the peroxide index (PI) expressed as O₂ in meq kg^-1; t: time expressed in days.

Table 2 shows the models for estimating the shelf life of the mayonnaise sauces for each treatment. A high significance of the linear models for estimating the shelf life is observed, with a confidence level of 95.0% and adjusted R² values of 0.939, 0.994, and 0.914 for T1, T2, and T3, respectively.

Table 2 Models for estimating the shelf life of mayonnaise sauce 

Note. T1: control treatment; T2: treatment with adding oregano EO microcapsules at 0.26% m/m; T3: treatment with adding oregano EO microcapsules at 0.44% m/m. t: shelf life (d), T: temperature (ºC).

These values indicated that the adjusted models explain more than 91.4% of the variability in estimating the shelf life of the mayonnaise sauce. Table 3 shows the specific rate constants and lifetime of the different treatments

Table 3 Specific rate constant and shelf life of mayonnaise sauces. 

Note. T1: control treatment; T2: treatment with adding oregano EO microcapsules at 0.26% m/m; T3: treatment with adding oregano EO microcapsules at 0.44% m/m.; k: specific rate constant.; Considering rejection for a limiting peroxide index of 10 meq/kg (NC 50, 2015).

During accelerated storage, the protective effect of microencapsulated oregano EO was observed, with an increase of 34, 8, and 11 days at 35, 45, and 55 ºC, respectively, in the treatment with the addition of oregano EO microcapsules at 0.44% m/m compared to the control batch and considering the product objectionable when it reached a limit value of the IP equal to 10 meq/kg (NC 50, 2015). This represents an increase in durability of 45, 24, and 42% m/m for 35, 45, and 55 ºC, respectively. The rate constant generally increased with temperature, so the highest formation of peroxides occurred at 55 ºC.

These rate constants can be used to determine the influence of temperature variations through the acceleration factor Q₁₀ (^{Pedro & Ferreira, 2006}). This factor indicates the number of times the rate of a deterioration reaction changes when the temperature is varied by 10 ºC and is a practical and reliable way of predicting the effect of variations in storage temperature on food.

A tendency was found for the T3 treatment to be more susceptible to temperature variation in the range of 35 to 45 ºC (Table 4). However, when the higher temperature range (45 to 55 ºC) is analyzed, the opposite behavior is observed and could be related to the presence of microencapsulated EO.

Table 4 Q₁₀ values for the variation of peroxide index in mayonnaise sauce. 

Note. T1: control treatment; T2: treatment with adding oregano EO microcapsules at 0.26% m/m; T3: treatment with adding oregano EO microcapsules at 0.44% m/m.Values estimated through the relationship between shelf life (Ɵ) at a temperature (T) and shelf life at T+10 °C.

Figure 1 presents the graphs using the Arrhenius equation for the three studied temperatures. The Arrhenius equation was established by the relationship of ln k and 1/T, where the ordinate at the origin is ln A and the slope is -Ea/R.

Figure 1 Arrhenius models for the variation of the peroxide index in mayonnaise sauces stored at 35, 45, and 55 ºC. a) control treatment; b) treatment with the addition of oregano EO microcapsules at 0.26% m/m; c) treatment with the addition of oregano EO microcapsules at 0.44% m/m. 

The activation energy of chemical reactions in foods is usually between 24,000 and 150,000 J/mol. Ea values higher than 65,000 J/mol are related to the high susceptibility of the attribute to deterioration due to increased temperature (^{Touati et al., 2016}). As seen in Table 5, the Ea values for the variation of the IP were between 13,886.84 and 22,243.38 J/mol. As a trend, as the concentration of microencapsulated EO increased, Ea decreased, with treatment T3, with 0.44% m/m EO, having the lowest Ea. This is also related to the highest Q₁₀ value found for that treatment.

Table 5 Arrhenius equations for the variation of the peroxide value in mayonnaise sauces. 

Note. T1: control treatment; T2: treatment with adding oregano EO microcapsules at 0.26% m/m; T3: treatment with adding oregano EO microcapsules at 0.44% m/m. T: temperature (K); k: rate constant (meq O₂/kg/d).

Conclusions

Mayonnaise, with 0.44% MOEO, presented the highest stability during accelerated storage in terms of delaying the increase in the PI, which indicates the deterioration of this type of product. Adding the MOEO did not affect (p > 0.05) the product's sensory attributes. However, the judges reported its influence on the typical odor and flavor compared to the control mayonnaise. The variation of the PI in the mayonnaises was adjusted, in all cases, to a zero-order reaction. Linear models were obtained to estimate the shelf life of mayonnaise for each treatment.