Abstract
ABSTRACTHydrocolloid powders from Pereskia aculeata Miller were obtained by using drying in a vacuum oven and freeze-drying at different concentrations (0.5–3.0 g of hydrocolloids/100 g of aqueous phase) to produce oil-in-water emulsions. The rheological characteristics of the emulsions and their microstructures were determined. The freeze-dried hydrocolloids and higher hydrocolloid concentrations resulted in emulsions with higher viscosities. The drying method and hydrocolloid concentration influenced the thixotropic behavior, and the resulting emulsions exhibited shear-thinning behavior. Microstructural analysis showed that with increasing freeze-dried hydrocolloid concentration, the emulsions had droplets with lower average diameters and greater uniformity, suggesting greater system stability.
Highlights
An emulsion is conventionally defined as a thermodynamically unstable system that consists of two immiscible liquids such as oil and water, which destabilize over time by various physicochemical mechanisms such as creaming, flocculation, coalescence, phase inversion, and Ostwald ripening
Based on the fitting performed, the power law model yielded the best coefficients of determination (R2 > 0.94) and good results for the root mean square error (RMSE)
Shear stress as a function of shear rate and curves adjusted by power law for emulsions prepared with OPN hydrocolloids (0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 g OPN/100 g aqueous phase) that were (a) vacuum oven-dried and (b) freeze-dried
Summary
An emulsion is conventionally defined as a thermodynamically unstable system that consists of two immiscible liquids such as oil and water, which destabilize over time by various physicochemical mechanisms such as creaming, flocculation, coalescence, phase inversion, and Ostwald ripening. Emulsifiers and thickeners contribute to the structural and textural properties of foods through their aggregation and gelation behavior. Of these materials, proteins are known for their emulsifying capacity (EC) and foaming ability. Proteins reduce the interfacial tension between immiscible liquids due to their adsorption at the interface They can form films at the droplet surface, providing electrostatic repulsion between the droplets. Polysaccharides are used as stabilizers, thickeners, and gelling agents because of their water retention and thickening properties.[4,5] The properties of protein–polysaccharide biopolymer complexes such as hydration (solubility and viscosity), structuration (aggregation and gelation), and interfacial phenomena (foaming and emulsifying) can be exploited in the formulation of new foods. Food colloids contain charged colloidal particles, i.e., oppositely charged polysaccharides and proteins, which interact and form particulate dispersions, foams, gels, and emulsions.[6]
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