negative for phase separation to occur. There are, however, several
exceptions to this rule, for instance because DH may depend on
temperature. For many polysaccharides, the temperature effect seems to
be fairly small.
This brings us to the question about the applicability of the Flory–
Huggins theory for food polymers. For polyelectrolytes, the theory is
invalid, unless ionic strength is very high. In Section 7.3 the solubility of
proteins will be discussed. Very few polysaccharides are simple homo-
FIGURE6.17 Solubility of a homopolymer according to the Flory–Huggins
theory. Variables are the excluded volume parameterb(or the polymer–solvent
interaction parameterw), the net volume fraction of polymerj, and the polymer-to-
solvent molecular volume ratioq. Solid lines denote binodal, the broken line
spinodal decomposition. Critical points for decomposition (phase separation) are
denoted by. See text.