Abstract
The changes of the alginate and of the wakame (Undaria pinnatifida) fronds through boiling were chemically, physically, and histologically examined. The results obtained were as follows :
1) When the fronds were boiled for 60 minutes, about 35 percents of the alginate were effused from the fronds into boiling fluid.
Only a minute portion of the effused alginate was precipitable by the 0.012 N CaCl2 solution in the presence of 0.5 N MgCl2. On the contrary, about half or more of the alginate retained in the fronds was precipitable in the same solution.
2) From observation with a scanning electron microscope, there was found a little change in the tissue of the outer layer of the fronds, while there was observed remarkable disintegration in the tissue of the inner layer of the fronds by 60 minutes of boiling.
3) The contraction of the molecular size of Na-alginate by boiling was found by an examination of the mean diameter of the molecules computed from viscosity, gel filtration, and sedimentation rate of Na-alginate aqueous solution. It was suggested from the index of the shape of molecules (Kagawa et al.) that the winding of the molecular chains was intensified through boiling. From these results it is speculated that depolymerization occur on an alginate molecule by boiling, and the contraction of the alginate molecules is attributed to the changes of the shape of the molecule through boiling.
