Structural and Physicochemical Properties of Starch Isolated from the Rhizome of Drynaria roosii: A Novel Source

Drynaria roosii, a traditional Chinese medicine, is a large epiphytic fern that belongs to the family Polypodiaceae. It is a novel starch plant resource with commercial value. The physicochemical properties of starch isolated from the rhizome of D. roosii are investigated for the first time and compared with those of other commercial starches, including Pteridium aquilinum (L.) Kuhn, Triticum aestivum L., and Manihot esculenta Crantz. The rhizome of D. roosii contains total starch and apparent amylose contents of 17.26% and 30.01%, respectively. The starch from D. roosii has a unimodal distribution, large particles with elliptical or spherical to irregular shape, C-B-type crystal pattern, and no single-helix structure. The swelling power, solubility, pasting temperature, and breakdown and setback viscosities are the lowest, and the resistant starch contents in native, gelatinized, and retrograded starches are the highest. The amylopectin of the starch from D. roosii exhibits lower proportions of short chains with DP 6-24, higher proportions of longer chains with DP 25-100, and average chain length than those of the other three starches. These findings have great significance to broaden the understanding of Polypodiaceae starch, which has great potential for utilization in food industries.