Infrared spectroscopy with heated attenuated total internal reflectance enabling precise measurement of thermally induced transitions in complex biological polymers

Anal Chem. 2013 Apr 16;85(8):3999-4006. doi: 10.1021/ac303552s. Epub 2013 Mar 26.

Abstract

We report an improved tool for acquiring temperature-resolved fourier transform infrared (FT-IR) spectra of complex polymer systems undergoing thermal transitions, illustrated by application to several phenomena related to starch gelatinization that have proved difficult to study by other means. Starch suspensions from several botanical origins were gelatinized using a temperature-controlled attenuated total reflectance (ATR) crystal, with IR spectra collected every 0.25 °C. By following the 995/1022 cm(-1) peak ratio, clear transitions occurring between 59 and 70 °C were observed, for which the midpoints could be determined accurately by sigmoidal fits. The magnitude of the change in peak ratio was found to be strongly correlated to the enthalpy of gelatinization as measured by differential scanning calorimetry (DSC, R(2) = 0.988). An important advantage of the technique, compared to DSC, is that the signal-to-noise ratio is not reduced when measuring very broad transitions. This has the potential to allow more precise determination of the gelatinization parameters of high-amylose starches, for which gelatinization may take place over several tens of °C.

MeSH terms

  • Amylose / chemistry*
  • Calorimetry, Differential Scanning
  • Crystallization
  • Hot Temperature
  • Kinetics
  • Phase Transition
  • Polymerization
  • Signal-To-Noise Ratio
  • Spectrophotometry, Infrared / methods*
  • Spectroscopy, Fourier Transform Infrared / methods*
  • Starch / chemistry*
  • Thermodynamics

Substances

  • Starch
  • Amylose