Investigation of Starch–Protein–Water Mixtures Using Dynamic near Infrared Spectroscopy

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Abstract
Dynamic near infrared (NIR) spectroscopy has been applied to the process of starch gelatinisation. A Rapid Visco-Analyser (RVA) was modified to allow NIR spectra to be recorded in real time as samples are heated and sheared. Analysis of the three-dimensional data obtained shows a major absorbance change at 1160 nm assigned to the stretch–bend combination mode of water and associated with the bonding of water molecules. There is also a major change in the 1400 nm region of the spectrum consisting of a combination of an absorbance change and a wavelength shift. The absorbance change at 1160 nm is shown to be associated with the gelatinisation of the starch granules, a process that occurs before pasting and gelation. The changes in the absorbance at 1160 nm also provide information on the interactions that occur when protein–starch–water mixtures are heated. The results obtained suggest that in excess water conditions, there is a complex interaction between gliadin, glutenin, starch and water which involves the initial ordering of water, increased ordering on stirring and the subsequent disordering of the water on heating, related to the presence of smaller protein molecules, occurring simultaneously with starch gelatinisation.