Characterization of the mucilage isolated from the edible fronds of bird's nest fern (Asplenium australasicum)

Abstract

With the increasing attentions in exploiting natural additives for food industry, the mucilage isolated from the young fronds of Asplenium australasicum (J. Sm.) Hook under diverse extraction conditions was investigated for their physicochemical properties. It was observed that the yields of the mucilage were generally raised with increasing citric acid concentration, extraction temperature and time. Chemical analysis revealed that the mucilage was composed mainly of anionic polysaccharides and proteins (4.7–20.7%), depending on the extraction conditions. Furthermore, in comparison with some commercial food hydrocolloids reported in the literatures, A. australasicum mucilage showed significant surface activity, as evidenced by a pronounced reduction (about 29–36%) on the surface tension of water and excellent emulsion stability in a model oil-in-water type emulsion. The surface tension of A. australasicum mucilage solution decreased with increasing mucilage concentration to a certain point (0.075–0.1%), but remained fairly constant as the mucilage concentration was further increased up to 0.5%. Moreover, the emulsifying activity of A. australasicum mucilage was pH and oil/water volume ratio dependent. These results suggest that the acid-extracted mucilage from the young fronds of A. australasicum is a potential natural thickener and emulsification stabilizer.