The study of the secondary cell wall, which is the most
extensive part of the wood fiber, showed that the cellulose
fibrils consist of highly ordered cellulose chains, which are
embedded in a matrix of hemicelluloses and lignin. Pure
hemicelluloses are also present between the cellulose fibrils
and the matrix [3]. Pores in the matrix are small, and permit
the transfer of water, salts, and small organic molecules
only. Although the hemicelluloses are at least partly watersoluble,
they cannot diffuse out of the cell wall because of
their molecular size.
Because the hemicelluloses are embedded in the cell
wall, their isolation is difficult. Methods for the isolation of
hemicelluloses from wood are too numerous to be completely
reported here, but the most important methods will
be described. They can be roughly divided into methods
using a high-energy input, which involve the formation of
organic acids from the wood itself to dissolve the hemicelluloses,
and methods where chemicals are added for the
dissolution and the temperature is then usually only modestly
raised.
The study of the secondary cell wall, which is the most
extensive part of the wood fiber, showed that the cellulose
fibrils consist of highly ordered cellulose chains, which are
embedded in a matrix of hemicelluloses and lignin. Pure
hemicelluloses are also present between the cellulose fibrils
and the matrix [3]. Pores in the matrix are small, and permit
the transfer of water, salts, and small organic molecules
only. Although the hemicelluloses are at least partly watersoluble,
they cannot diffuse out of the cell wall because of
their molecular size.
Because the hemicelluloses are embedded in the cell
wall, their isolation is difficult. Methods for the isolation of
hemicelluloses from wood are too numerous to be completely
reported here, but the most important methods will
be described. They can be roughly divided into methods
using a high-energy input, which involve the formation of
organic acids from the wood itself to dissolve the hemicelluloses,
and methods where chemicals are added for the
dissolution and the temperature is then usually only modestly
raised.
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