Identification and Semi-quantification of Polysaccharides in Complex Food Matrices by NMR
Despite the extensive use of polysaccharides as food structuring ingredients, the analytical toolkit to identify and quantify these biopolymers in complex food matrices is surprisingly small. NMR has a track record in revealing the overall structure of intact polysaccharides and this encouraged us to explore its potential for analytical assessment of polysaccharides in complex food matrices. A critical first step was the isolation of polysaccharides from the food matrix. Next we optimized the experimental conditions for obtaining well resolved high-resolution NMR spectra. Within the acquired 1D and 2D heteronuclear NMR spectra mixtures of up to 4 polysaccharides of different structural classes could be resolved. By making use of spectral assignments from the literature and a home-built (1D/2D) NMR spectral library a semi-quantitative assessment of the identified polysaccharides could be made. Whereas for relatively simple compositions we could rely upon interactive 1D spectral fitting, we needed to deploy quantitative 2D NMR approaches for more complex ones. The ability of NMR to indentify and semi-quantify polysaccharides in complex food matrices makes it a complementary technique in the current toolkit for analytical assessment of polysaccharide mixtures in food matrices.