APPLICATION OF Bromelia balansae Mez PEEL AQUEOUS EXTRACT AS AN ANTIOXIDANT IN A LIPID SYSTEM

Bromelia balansae Mez, commonly known as caraguatá, contains significant concentrations of phenolic compounds that may contribute to protection against oxidative processes. This potential motivated the evaluation of an aqueous fruit peel extract in oil-in-water (O/W) emulsions. The peel flour was subjected to aqueous extraction under orbital agitation in a shaker incubator. The resulting extract was analyzed for total phenolic content and antioxidant capacity using the ferric reducing antioxidant power (FRAP) assay. The extract was incorporated into O/W emulsions homogenized using an ultrasonic probe. A control formulation and a formulation containing butylated hydroxytoluene (BHT) as a reference antioxidant were also prepared. The components were added at a ratio of 50:45:5 (sunflower oil: water:Tween 20). The concentrations of the natural antioxidant, expressed in terms of total phenolic compounds, and the synthetic antioxidant BHT were adjusted to 200 mg kg⁻¹. Physical stability was evaluated based on the creaming index, while oxidative stability was assessed by measuring the hydroperoxide index over eight days of storage at room temperature and 40 °C. The peel extract contained 33.60 mg GAE g⁻¹ of total phenolic compounds and exhibited an antioxidant capacity of 930.92 µmol TE g⁻¹. The presence of bioactive compounds, particularly phenolics, may account for the high reducing capacity observed in the FRAP assay. The emulsion containing the extract exhibited 100% physical stability throughout the eight-day storage period at both temperatures, with no creaming observed. This stability may be associated with an increase in viscosity promoted by the extract. At room temperature, the hydroperoxide value increased from 0.848 to 2.569 meq O₂ kg⁻¹ in the extract treatment, whereas the final values for the BHT and control treatments were 1.375 and 1.475 meq O₂ kg⁻¹, respectively. At 40 °C, the final values were 6.169, 2.734, and 6.348 meq O₂ kg⁻¹ for the extract, BHT, and control treatments, respectively. This behavior may be related to the polar paradox, which suggests that antioxidant effectiveness depends on the polarity and distribution of antioxidant compounds within a system. Predominantly polar phenolic compounds may exhibit antioxidant activity in aqueous media but may not accumulate sufficiently at the oil–water interface, where lipid oxidation can be initiated and propagated. In addition, interactions among extract constituents may influence their antioxidant activity. Although the extract exhibited substantial phenolic content and FRAP activity, these properties did not translate into effective oxidative protection in the emulsions. Under accelerated storage at 40 °C, the extract, at the concentration and under the conditions tested, did not delay lipid oxidation. Further studies should investigate different extract concentrations and emulsion formulations to determine whether its protective effect can be improved.