Colloidal and rheological behavior of aqueous dispersions of buriti tree (mauritia flexuosa) gum

Abstract

The temperature, concentration and pH variables influence the aqueous dispersion of the gum properties. In this context, the aims of this research were to characterize the gum obtained from the buriti tree (Mauritia Flexuosa) trunk exudate, as well as to evaluate the colloidal and rheological behavior of the aqueous dispersions of this gum. Thus, the centesimal composition, absolute zeta (ζ) potential as a function of pH (1.2 to 4.0), particle size distribution, as well as the rheological properties of the gum at different temperatures (15, 20, 25, 30, and 40 °C) and concentrations (4, 5, 8, and 10% (m/v)) were studied. In addition, the Newton, Power Law, and Herschel-Bulkley models were fitted to the rheological data. Buriti tree gum (BG) was found to have 10.43% moisture, 5.05% ashes, 0.68% lipids, 3.09% proteins, and 80.76% carbohydrate. The aqueous dispersion of the gum (1%) had a ζ value of -17.1 mV with a tendency for greater stability at pH < 4 and polydisperse particle size distribution (45 nm to 648.1 nm diameter) with PDI (polydispersity index) of 1. The aqueous dispersion with 4 and 5% gum had typical Newtonian fluid behavior and became pseudoplastic at concentrations of 8 and 10%. The Herschel-Bulkley model had the best fit to the rheological data (r2 > 0.99). Gum dispersion viscosity decreased with higher temperature and lower concentration. The activation energy (Ea) value for gum dispersion ranged from 9.07 to 17.35 kJ/mol.

Fatty acid profile and rheological behavior of annatto seed oil (Bixa orellana), cupuassu seed fat (Theobroma grandiflorum), and their blends

“…The rheological curves of shear stress versus shear rate of the pure samples and their blends are presented in Figure 2. All samples showed a linear relationship between shear stress and shear rate, i.e., they exhibited Newtonian fluid behavior (Silva et al, 2017). It can be noted that, for a constant strain rate, there is a decrease in shear stress values with increasing temperature (Figure 2).…”

Structural and Thermal Characteristics of Buriti Tree Gum (Mauritia flexuosa)

“…The buriti ( Mauritia flexuosa L.), which belongs to the Arecaceae family, is an abundant palm in the mesoregion of Baixo Tocantins, in the State of Pará-Brazil, and is very important for economic extraction and subsistence, due to the use of its fruits and leaves [ 5 ]. The buriti trunk produces a gum exudate, which protects the palm from threats and microbial attacks [ 2 , 6 , 7 ]. Materials such as this contain polysaccharides with complex molecular structures, whose origin, size, types of chemical bonds, number of branches and side chains, and spatial conformation govern interactions with water molecules and other molecules [ 7 ].…”

“…Silva et al [ 6 ] investigated the rheological and colloidal properties of aqueous dispersions of buriti gum, which presented a Newtonian behavior in low concentrations (4–5% w / v ) and a tendency toward a pseudoplastic behavior, in concentrations of 8 and 10% w / v of gum. The dispersions showed intermediate colloidal stability at pH < 4.0 and greater dispersibility in water at higher pH values.…”

“…The results obtained by Silva et al [ 6 ] for buriti gum already help us understand and identify applications for the product; however, explaining the molecular structure and information on the thermal stability of the gum is important to guide its technological use. Furthermore, understanding the molecular structure of this gum is important for designing studies involving interaction with other compounds as well as improving the properties of products that allow multiple applications, such as the sulfation of arabinogalactans for medicinal use [ 21 , 22 , 23 ].…”