Development and characterization of chitosan-stabilized pepper oleoresin emulsions: antimicrobial, antioxidant, and cytotoxic properties

The present study investigated the formulation and stabilization of Pepper Oleoresin (PO) oil-in-water emulsions using Tween-80 (TW80) and Chitosan (CH) employing ultrasonication. PO emulsions were formulated with various surfactant concentrations (1% to 4% w/w of TW80). The CH concentration varied from 0.005% (CH1) to 1% w/w (CH9) in the PO-TW80 emulsions. The average droplet size, zeta potential, viscosity, density, and morphology were analyzed to understand the emulsion stability. The PO emulsion with 4% w/w TW80 exhibited a homogenous emulsion with nano-sized droplets of around 165 ± 5.9 nm and a zeta potential value of −29 mV. The PO emulsion with TW80 (4% w/w) exhibited good stability (up to 6 months) at room temperature (25 °C ± 2) as the concentration of CH increased (0.005% to 1% w/w). Stable PO emulsions were obtained at 4% w/w TW80 and 1% w/w CH9 with nano-sized droplets around 362.5 ± 18.82 nm and a zeta potential of +45 mV. The interaction between TW80 and CH was confirmed through Isothermal Titration Calorimetry (ITC) and FTIR analysis. In addition, the PO-TW80-CH9 (1% w/w CH) emulsion inhibited the ABTS free radicals (>85%). It also exhibited cytotoxic activity toward MDA-MB-231 cells and displayed antimicrobial effects. The results suggest that the combination of TW80 and CH could serve as an efficient emulsifier system for stabilization of oleoresin emulsions for food and pharmaceutical applications.