Mucilagem da Pereskia aculeata Miller como agente espessante e emulsificante

Abstract

The hydrocolloids of Pereskia aculeata Miller (HOPN) have a thickening, emulsifying and stabilizing function. The objective of this work was to evaluate how concentration and temperature affect the rheological characteristics of HOPN and how the presence of sucrose, NaCl and pH affect the emulsifying and stabilizing function. For the rheological analysis the HOPN, gums were prepared at concentrations 1%; 2%; 3%; 4% and 5% (w/w). The analyzes were performed at 2°C; 12°C; 22 °C; 32°C and 42°C. The rheological tests were: shear rate (𝛿 = ̇ 0.1 to 300 s -1 ), oscillating dynamic shear (τ = 0.5% to 700%) (f = 1 Hz) and frequency sweep (f = 0.1 to 10 Hz) (τ = 1 %). The exponential and power law models and the Arrhenius model were used to evaluate the effect of concentration and temperature, respectively. A twolevel factorial was used to evaluate the effects of pH (4-7), sucrose concentration (0-15% w/w) and NaCl concentration (0-1% w/w) on the emulsifying and stabilizing properties through creaming, emulsifying and stability activity, electrical conductivity, zeta potential, rheology, particle size distribution and optical microscopy. The power law model best explained the rheological behavior of the gums, being characterized as pseudoplastic fluids. The HOPN concentration exerted a positive effect on the apparent viscosity (γ = 100 s -1 ) and temperature exerted negative effect explained by the exponential and Arrhenius models, respectively. The linear viscoelasticity region (LVE) exceeded 1 % deformation in all gums that were characterized as natural polymeric gel. The higher concentration of HOPN, the greater the deformability and structural resistance. Gums at a 1% concentration at 2°C do not present a defined behavior, gums with concentrations of 1% (at 12°C, 22°C, 32°C and 42°C), 2%; 3% and 4% (2°C, 12°C, 22°C) were characterized as concentrated solutions and those at 4% (32°C and 42°C) and 5% were characterized as gels. As for the emulsions, the presence of NaCl, the cream process was favored. In 7 days only emulsions with sucrose and sucrose and NaCl (pH = 7) did not undergo visible destabilization; the same was observed after thawing. The zeta potential values ranged from (-18.3 ± 1.2) mV to (-26.96 ± 0.12) mV, with the emulsions at pH 4 in the presence of NaCl presenting the lowest values. The emulsions were classified as pseudoplastic fluids with flow behavior explained by the Power Law. The values of mean diameter weighted by emulsion oil droplet surface ranged from (4.57 ± 0.08) μm to (6.32 ± 0.16) μm. It was concluded that HOPNs are efficient in forming emulsions and thickening solutions and the results presented are important for future HOPN applications in the food industry.