Elaboração e caracterização de emulsões com óleo de pequi estabilizadas por proteína de ervilha e carboximetilcelulose

Abstract

Protein-based emulsions have emerged as promising alternatives to conventional systems stabilized by artificial surfactants, especially given the growing demand from the food industry for natural ingredients and clean labels. Pequi oil (Caryocar brasiliense), abundant in the Brazilian Cerrado, is rich in bioactive compounds such as carotenoids, unsaturated fatty acids, and phenolic compounds, which confer antioxidant and anti-inflammatory properties. In this context, the present work aimed to develop and characterize oil-in-water (O/W) emulsions for the encapsulation of pequi oil, aiming at the protection of its bioactive compounds. Pea protein isolate (PE) and the protein-carboxymethylcellulose complex (PE-CMC) were used to stabilize the systems. The study was conducted in two stages. Initially, the emulsions were optimized using a Central Composite Rotational Design (CCRD 2²), considering the concentrations of PE and CMC as independent variables, and centrifugal stability (CS), emulsifier activity and stability index (EAI), contact angle (CA), and homogenization quality as response variables, with the aim of maximizing system stability. In the next step, a Completely Randomized Design (CRD) in a 5 × 2 factorial scheme was applied, evaluating the effect of pH (3, 4, 5, 6, and 7) and the type of stabilizer (PE and PE–CMC) on the behavior of the emulsions. In the first step, the optimal formulations corresponded to emulsions containing 3.41% PE and 3.41% PE combined with 0.5% CMC. In the next step, the results showed a significant interaction between pH and the type of stabilizer, directly influencing the stability of the system. Emulsions stabilized solely with PE exhibited high physical instability, characterized by pronounced flocculation and phase separation, especially at pH 4, 5, and 6, due to the low solubility of the protein under these conditions. In contrast, PE–CMC emulsions showed greater stability across the evaluated pH range, maintaining system integrity, although phase separation was observed at pH 3 and 4, attributed to the formation of insoluble complexes. This superior performance was associated with the combination of electrostatic and steric stabilization mechanisms promoted by CMC, resulting in a more robust interfacial barrier. PE–CMC emulsions also demonstrated greater efficiency in retaining the bioactive compounds of pequi oil, although this efficiency was affected by pH, similarly to the other systems. The freeze-thaw cycle was the only stress condition in which PE–CMC emulsions did not perform satisfactorily. It is concluded that systems stabilized with PE and PE-CMC constitute effective strategies to improve the stability and functionality of emulsions containing pequi oil, with pH-dependent behavior, promoting the protection of bioactive compounds against environmental and processing stresses.