Characterization of the mucilage extracted from the edible fronds of bird's nest fern (Asplenium australasicum) with enzymatic modifications

Abstract

The mucilage extracted from the Asplenium australasicum (bird's nest fern) edible fronds with single/dual enzymatic modification was characterized. Protein content and sugar composition analysis revealed that both trichloroacetic acid and proteinase treatment could effectively remove the proteinaceous matter of mucilage, accompanied with an increase in carbohydrate content. Furthermore, the lateral portion of the proteinaceous matter bound with larger size polysaccharide may contain short segments of glucose. The four glycoside hydrolase studied, including galactanase, mannanase, arabinanase and xylanase, all diminished the levels of glucose, arabinose and rhamnose significantly, but to a different extent, particularly for sample with xylanase treatment. After the removal of protein with proteinase, some physical properties of A. australasicum mucilage were improved, for instance, solubility, turbidity and intrinsic viscosity, though the interfacial activity and average molecular weight decreased. Moreover, after dual enzymatic modification, the intrinsic viscosity and moisture holding capability of A. australasicum mucilage were further increased. This is possibly due to the production of mucilage with higher purity and less branched polysaccharide chains by structural modification that leading to more intermolecular interactions and higher hydration capacity. Among the dual enzymatic modification studied, proteinase + xylanase treatment was most effective in terms of structural modification.