Structural characterization and rheological properties of the water extracted mucilage of Basella alba and the starch/aqueous mucilage blends

Abstract

Basella alba is a succulent plant, and its stem and leaf contain significant amount of mucilage. However, researches about Basella alba mucilage are quite limited. Therefore, the objective of this study is to characterize the structural and rheological properties of the water extracted mucilage from the leaf and stem of Basella alba, including chemical compositions, monosaccharide compositions, intrinsic viscosity, molecular size distribution, and steady shear and dynamic shear rheological properties. Furthermore, rheological properties of starch/aqueous mucilage blends with various mixing ratio were also characterized. Results showed that the mucilage of Basella alba was comprised of 38–39 molar% of galactose, 28–36% of arabinose, 4–11% of galacturonic acid, and 3–5% rhamnose, with a weight average molecular weight of about 1.9-2.4 × 106. The intrinsic viscosity of leaf and stem mucilage solutions were found to be 2.48 and 9.20 dl/g, respectively. 2–6% of mucilage solutions showed slight shear thinning behavior, with a flow behavior index in the range of 0.58–0.85. Dynamic shear results revealed that 2–6% of mucilage solutions showed significant fluid properties, with a loss tangent value in the range of 1.1–3.4. However, as mixing with wheat starch under various proportions, significant synergistic effect was observed, particularly for the starch/aqueous mucilage ratio of 1.8/0.2 or 1.7/0.3, as evidenced by a significant increase in viscosity, storage modulus, and decrease in loss tangent to lower than one (0.2–0.3). On the contrary, no synergistic gelation occurred when adding mucilage to tapioca starch solutions. Gelation was even suppressed when adding mucilage to potato starch solutions. This discrepancy may be related to the differences in the nature of different starches. These information would be useful for future application.