Measurement of the Sol–Gel Transition Temperature in Agar

  • R. Medina-Esquivel
  • Y. Freile-Pelegrin
  • P. Quintana-Owen
  • J. M. Yáñez-Limón
  • J. J. Alvarado-Gil
Article

Abstract

Aqueous solutions of agar show a sol–gel transition temperature in the range from 32°C to 47°C depending on colloid concentration; however, the width of the transition and the subsequent process occurring after it, are not well understood. In this work the sol–gel transition of agar is studied by a simple optical method. It consists of the illumination of the sample using a non-coherent light source and the monitoring of transmitted light using a photodiode. It is shown that during the sol–gel transition, the transmitted light decays over a broad range of temperature. Simultaneously, it is possible to observe that fluctuations in the transmitted light decrease along the sol–gel transition, and at a specific temperature, they become very small. Based on these observations, the sol–gel transition temperature for three different concentrations of agar (0.5, 1.5, and 2.5% w/v) is determined. These results are compared with the sol–gel transition temperature values provided by the conventional rheological method.

Keywords

Agar Gelling Light transmission Sol–gel transition 

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Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  • R. Medina-Esquivel
    • 1
  • Y. Freile-Pelegrin
    • 2
  • P. Quintana-Owen
    • 3
  • J. M. Yáñez-Limón
    • 1
  • J. J. Alvarado-Gil
    • 3
  1. 1.CINVESTAV-Unidad QuerétaroQueretaroMexico
  2. 2.Departamento de Recursos del MarCINVESTAV-Unidad MéridaMeridaMexico
  3. 3.Applied Physics DepartmentCINVESTAV-Unidad MéridaMeridaMexico

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