Raman spectroscopic determination of the degree of succinate in modified waxy maize starches

Abstract

Waxy (essentially amylose-free) maize starch was chemically modified to varying degrees by treatment with succinic anhydride, and the degree of substitution was determined by a standard wet chemistry method. FT-Raman spectra of the modified starches were obtained, and indicated a characteristic ~1730 cm-1 C=O stretch Raman band whose intensity was dependent on the degree of succinylation. The ratio of intensity of the ~1730 cm-1 band to a ~940 cm-1 C-C stretch Raman band (used as an internal standard) was plotted against the degree of succinylation determined by titration, and a linear fit was obtained with a correlation of 0.998. Hence FT-Raman spectroscopy represents a rapid non-destructive method to determine the degree of succinylation of modified waxy maize starch, and should be suitable for use with succinylated starches of any amylose content.