Phase change in amylose-water mixtures as seen by Fourier transform infrared

Abstract

The phase content of amylose–water mixtures (0.7/0.3 w/w) has been analyzed by transmission Fourier transform infrared (FTIR) spectroscopy in the 1175–950 cm−1 region. Spectra are obtained under three different conditions: (a) as a function of temperature (T) from 25 to 97°C; (b) at room temperature (RT), after slow cycles of T; and (c) at RT after quenching. Tmax, the maximum temperature in the cycle, ranges from 50 to 120°C. The quality of the seven‐band spectra allows for an unambiguous determination of each band area. Unexpectedly, slow cooling after different Tmax brings about wide changes in the spectra while quenching does not. Two jumps in the absorbance are found: one at 70°C and the other above 105°C. Previous work on slow calorimetry of amylose–water mixtures suggests that these temperatures correspond to the beginning and the end of the same physical phenomena that takes place slowly between these two temperatures—namely the dissolution of the strained network phase. The spectra have two distinct regions, the low wavenumber region (1078–950 cm−1) and the high wavenumber region (1175–1078 cm−1). A distinct gain in the integrated absorbance of the 1175–1078 cm−1 region at the expanse of that of the 1078–950 cm−1 region when Tmax increases is interpreted as a change from strained to unstrained environments. A nonequilibrium state between the chains is a strained environment. In light of the 13C NMR evaluation of the change of molecular order with T, the observed changes of the ir spectra could correspond to a transformation of a network of double helices into freer chains, possibly single helices. The present in‐depth analysis of equilibrium or near equilibrium states by FTIR can serve to understand, through in situ spectra, molecular mechanisms during the gelation/crystallization of amylose and other gel‐forming polymers. © 2001 John Wiley & Sons, Inc. Biopolymers 58: 305–318, 2001

A Study of the Deformation, Network, and Aging of Polyethylene Oxide Films by Infrared Spectroscopy and Calorimetric Measurements

“…The IR spectra reveal important changes due to the treatment, such as band displacement and change of intensity or position of the base-line related to the sample. For polyolefins, PET [31] and amylose [32,33], the integrated absorbance permits to determine (with some assumptions), the ordered, the disordered, and the strained fractions in a sample. For amylose pastes [32,33], the combination of FTIR and calorimetric analyses illustrates conformation modifications with thermal treatment.…”

“…For polyolefins, PET [31] and amylose [32,33], the integrated absorbance permits to determine (with some assumptions), the ordered, the disordered, and the strained fractions in a sample. For amylose pastes [32,33], the combination of FTIR and calorimetric analyses illustrates conformation modifications with thermal treatment. Bands were tentatively assigned to simple and double helices, whose respective content was treatment dependent [32,33].…”

“…For amylose pastes [32,33], the combination of FTIR and calorimetric analyses illustrates conformation modifications with thermal treatment. Bands were tentatively assigned to simple and double helices, whose respective content was treatment dependent [32,33]. The sensitivity of some bands of the IR spectra to sample history has been investigated in mixtures of polymers [34].…”

Multi‐scale structural and digestion properties of wheat starches with different amylose contents

“…Bernazzani et al . () and Zhou et al . () suggest the band at 1022 cm −1 increases with the less organised structure of the starch, whereas the band at 1047 cm −1 (composed of two overlapping bands at 1040 and 1053 cm −1 ) is related to the more organised structure of the starch.…”

“…This difference in the absorbance intensity might be related to their corresponding molecular organisation in the starch granules. Bernazzani et al (2001) and Zhou et al (2010) suggest the band at 1022 cm À1 increases with the less organised structure of the starch, whereas the band at 1047 cm À1 (composed of two overlapping bands at 1040 and 1053 cm À1 ) is related to the more organised structure of the starch. Thus, the overall starch structural organisation could be reflected by the ratio of 1047/ 1022 cm À1 , which represents the most characteristic of crystalline and amorphous regions in starch.…”