In this work, gelatin was used as a model polymer to
compare some of the methods of determining Tgel . Gelatin is
a protein that forms thermoreversible gels through the formation
of hydrogen bond stabilized triple helices as gelatin solutions
are cooled.1 In this work, a commercial grade of Type
A ~acid process pigskin! gelatin with a Bloom strength of
250 ~Cangel Inc., Toronto, Ontario! was used in all experiments.
Gelatin concentrations used for rheological measurements
were 1.3%, 2.5%, 5.0% and 10.0% ~w/v!. Gelatin solutions
included 0.1 M NaCl, 0.02% sodium azide to inhibit
the growth of bacteria, and the pH was adjusted to 7.0. Suspensions
were heated to 60 °C for 10 min to dissolve the
gelatin. Samples were stored at 4 °C until needed and gels
were melted at 60 °C for 5 min before measurements were
taken.