Rheological behavior and antioxidant activity of a highly acidic gum from Althaea officinalis flower

Abstract

Chemical composition, rheological properties and antioxidant activities of Althaea officinalis flower gum were studied as a new source of thickening agent for application in food systems. The isolated gum comprised mainly carbohydrates (52.6 ± 0.8%), uronic acids (37.5 ± 0.5%), and proteins (7.1 ± 0.1%). Rhamnose (57.7%) was the major sugar; the polysaccharide backbone was chiefly composed of 1,2-linked rhamnose. The average molar mass of the polysaccharide was 33.3 × 106 g/mol. Rheological behavior was determined as a function of concentration (0.5–5.0% w/v) and temperature (5.0–50 °C). Polysaccharide solution steady-shear flow behavior was pseudoplastic and well-described with the Carreau model (R2 = 0.99). The degree of pseudoplasticity (N) of the solutions increased with increased concentration and decreased with increased temperature. Frequency sweeps indicated weak gel behavior at higher concentrations or lower temperatures. Moderate DPPH radical scavenging activity and ferric reducing power was observed for the extracted polysaccharide.