Infrared Spectroscopy as Applied to Glycinin Film and Gel Formation Kinetics

Abstract

Secondary structural changes of glycinin during film and gel formation were studied by infrared spectroscopy. Two complementary data treatments—i.e., principal component analysis and two-dimensional correlation spectroscopy—were applied to the infrared spectra in order to determine the time evolution of conformational changes. Kinetic curves, assessed by taking scores of the first principal components into account, revealed more pronounced changes in the case of film formation. The development of aggregates in film and gel, through intermolecular β-sheets, was identified by an increase of the absorbance band at around 1620 cm−1. Two-dimensional infrared correlation spectroscopy made it possible to observe a decrease in both α-helices and disordered structures prior to the appearance of aggregates. Changes in intramolecular β-sheets took place in a second step. The more drastic changes observed in the case of film formation were believed to result from dehydration and aggregation coupled phenomena.