title: Infrared spectroscopy with heated attenuated total internal reflectance enabling precise measurement of thermally induced transitions in complex biological polymers.
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.
authors: King's College London, School of Medicine, Diabetes and Nutritional Sciences Division, Biopolymers Group, London, Franklin-Wilkins Building, 150 Stamford Street, London, SE1 9NH, United Kingdom.
authors: Frederick J
authors: FJ
authors: Warren
authors: Benjamin B
authors: BB
authors: Perston
authors: Paul G
authors: PG
authors: Royall
authors: Peter J
authors: PJ
authors: Butterworth
authors: Peter R
authors: PR
authors: Ellis
mesh_terms: D000688:Amylose / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D006358:Hot Temperature; D007700:Kinetics; D044367:Phase Transition; D058105:Polymerization; D059629:Signal-To-Noise Ratio; D013055:Spectrophotometry, Infrared / Q000379:methods*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013213:Starch / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D013213:Starch; D000688:Amylose