2.3. Visual phase diagrams
Visual j-carrageenan/KCl and j-carrageenan/Na-CN/KCl phase
diagrams were constructed in order to establish the appropriate
concentrations of salt and biopolymers for gel formation. In order
to construct the visual phase diagrams, the biopolymer stock solutions
were diluted to the desired concentration at 50 C, and 4 mL
of each solution mixed with 4 mL of each KCl solution. For the
j-carrageenan/KCl phase diagram, the polysaccharide concentration
varied between 0.5% and 3% (w/v) and the KCl concentration
from 0.1% to 3% (w/v). For the j-carrageenan/Na-CN/KCl diagram,
the same salt concentration was used and the j-carrageenan/Na-
CN ratio varied between 0.2 and 5.0, with a total biopolymer concentration
(protein + polysaccharide) of 3% (w/v). These mixtures
were stirred and placed into a temperature – controlled chamber
(model TE-391, Tecnal, Brazil) at 10 C. After 24 h of storage, the
gel formation was visually evaluated. From these data it was possible
to construct the sol–gel transition diagrams and to set up
some of the conditions for microgel preparation.