Spectrophotometric investigation of gel formation in water solution of agar

The temperature and concentration dependences of the transmission spectrum of an aqueous solution of agar are investigated. Measurements taken in the heating and cooling modes show strong thermal hysteresis in the spectral properties. Analysis of the results suggests that the formation of a gel network occurs in a much narrower temperature range than its collapse. The study of the temperature dependence of transmittance indicates that the association bispirals by cooling the solution and responsible for the formation of network occurs at temperature about [Formula: see text]C. A breakdown of these associates by heating of the gel begins at [Formula: see text]C and covers a wide temperature range. The gel point [Formula: see text] and the gel melting point [Formula: see text] increase with increasing polymer concentration, but for [Formula: see text] this dependence is stronger. Growth of turbidity (light scattering) of gel by increasing of agar concentration is due to the increasing of number and size of gel associates.