Raman Spectroscopic Determination of the Degree of Cationic Modification in Waxy Maize Starches

ABSTRACT

Waxy (essentially amylose-free) maize starch was chemically modified to varying degrees by treatment with 3-chloro-2-hydroxypropyltrimethyl ammonium chloride (CHPTAC), and the degree of cationic modification was determined by a standard wet chemistry method. FT-Raman spectra of the modified starches were taken, and a characteristic Raman band ∼761 cm⁻¹ was found. This 761 cm⁻¹ Raman band's intensity depended on the level of cationic modification of the starch. The ratio of intensity of the ∼761 cm⁻¹ band to a ∼715 cm⁻¹ C-C stretch Raman band (used as an internal standard) was plotted versus the amount of cationic modification derived by titration analysis, and a linear fit was obtained with a correlation of 0.998. The FT-Raman spectroscopy method presented here demonstrates a rapid non-destructive way to determine the level of cationic modification of waxy maize starch, and should be suitable for use with cationic modified starches of any amylose content.

Keywords::

• FT Raman spectroscopy
• cationic modification
• modified starch