Effects of salts and sucrose on the rheological behavior, thermal stability, and molecular structure of the Pereskia aculeata Miller mucilage.

Abstract

The rheological behavior, thermogravimetric analysis (TGA), and atomic force microscopy (AFM) of the Pereskia aculeata Miller (OPN) mucilage treated with sodium chloride (NaCl), calcium chloride (CaCl2), and sucrose were evaluated. The experimental design was divided in a fractional factorial 25-1 for the screening of factors (OPN, sucrose, NaCl, CaCl2, and pH) and then in a 5 × 3 × 3 full factorial (OPN, sucrose, and NaCl). The model solutions used for the screening of factors presented shear-thinning behavior and the OPN mucilage concentrations were the factors that had significant effect on the apparent viscosity. Sucrose addition increased the thermal stability of the OPN mucilage solutions. OPN mucilage, sucrose, and NaCl were the variables with significant effect on thermogravimetric responses. The samples presented Newtonian behavior in 0-1.25% OPN mucilage concentrations and non-Newtonian behavior adjusted by power-law in 2.50-5.00% OPN mucilage concentrations with predominance of elastic behavior, contributing to the formation of stronger gels. The presence of sucrose in the systems containing OPN mucilage changed their rheological properties and salt additions caused reduction in viscosity. The AFM results provided a better understanding of the mechanism of OPN mucilage interactions in different solutions that justify the changes in viscosities.