Encapsulation of Capsaicin in Oil-In-Water Nanoemulsion: Optimization by a Mixture Design and Its Application in...

In this research work, a mixture design was applied to optimize the encapsulation of capsaicin in oil-water-nanoemulsion using almond gum, pea protein isolate, and citrus pectin as independent variables. Therefore, results indicated that the cubic, special cubic, and quartic models were the most adequate to describe the variation of responses as a function of independent variables. Therefore, the pea protein isolate showed the highest effect on mean droplet size, polydispersity index, ξ-potential, and antioxidant activities. However, the almond gum was the most significant component in whiteness and plastic viscosity (p < 0.05). Moreover, the rheological properties of the nanoemulsions demonstrated that are non-Newtonian fluids with pseudoplastic (shear thinning) behavior and are well-fitted by the Casson model. Remarkably, all the nanoemulsions exhibited antioxidant activities, in which the almond gum and pea protein isolate combination indicated the highest activities (IC₅₀). Also, the formulated nanoemulsions exhibited more sensitivity to the Gram-positive bacteria (Listeria monocytogenes and Staphylococcus aureus). Thus, the statistical data revealed that the mixture of almond gum (16.13%), pea protein isolate (73.45%), and citrus pectin (10.42%) was proven to be the optimum condition. Besides, these findings indicated that there are no significant differences between optimal conditions and those obtained in practice (p > 0.05). Under these conditions, the experimental values of mean droplet size, polydispersity index, ξ -potential, whiteness index, plastic viscosity, creaming index, encapsulation yield, and the inhibitory concentration at 50% were 3.58 nm, 12.13%, -30.53 mV, 78.65, 0.12 Pa·s, 1.96%, 94.06%, and 23.01 μg/mL, respectively. Furthermore, encapsulated capsaicin was used to Merguez preservation and the results revealed that pH, color parameters, TVB-N, TBARS amounts, textural properties, and their shelf life were improved over a storage time of 30 days at 4°C. Hence, the findings are encouraging and allow considering the use of capsaicin nanoemulsions based on almond gum for the enrichment of food, cosmetic, and pharmaceutical products.