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

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.

Cold extraction method of chia seed mucilage (Salvia hispanica L.): effect on yield and rheological behavior.

Chia seeds (Salvia hispanica L.) when immersed in water, produce a highly viscous solution due to the release of mucilage, high molecular weight complex carbohydrates with wide application in the food industry. Thus, this study involve development of method for extracting mucilage from chia seed based on mechanical process and low temperature. The method involve extraction by cold pressing and drying by freeze-drying, which was compared to the traditional hot extraction method. The chia seed mucilage cultivated in Brazil was extracted successfully using the previously mentioned extraction method. Rheological analysis including thixotropy, flow curve and frequency sweep of mucilage was done. Microstructure was examined by scanning electron microscopy. The optimal process at 27 °C gave yield of 8.46%. The rheograms showed that the apparent viscosity decreased with increase in shear rate and this effect was most notable in the dispersions obtained by cold extraction and with high concentrations. The gum obtained using CE presented higher values for thixotropic behavior. The storage modulus (G') was consistently higher than the loss modulus (G″) and the data indicated formation of 'weak gel' structure of the dispersions. SEM indicated macroscopic fibrous structure of mucilage obtained through cold extraction process, indicating that the macromolecular network formed by fibrous material contained in mucilage maintained its structure in the process of deep freezing and freeze-drying.