DETERMINATION OF THE DEGREE OF BRANCHING IN NORMAL AND AMYLOPECTIN TYPE POTATO STARCH WITH H-1-NMR SPECTROSCOPY - IMPROVED RESOLUTION AND 2-DIMENSIONAL SPECTROSCOPY

Starch from genetically modified potatoes was found to be highly branc hed compared with normal potato varieties through the use of H-1-NMR s pectroscopy. The average chain length, blue-value, and the wavelength at maximum absorptivity clearly show that the new potato varieties pro duce amylopectin starch. Correlation between the degree of branching a s determined by H-1-NMR and starch-iodine complexation, expressed as b lue-value, was good and the NMR-method gives low standard deviation. F or the first time, the anomeric proton, H-1, of a (1-->4)-alpha-linked D-glucose residue and the H-1 of the glucose residue of a non-reducin g end have been assigned separate chemical shifts in starch. Assignmen ts were made as determined From two-dimensional homonuclear and H-1-C- 13 heteronuclear spectroscopy (COSY, HM6C, and HMBC). The molecular we ight in degraded starch and pullulan were determined by means of NMR-s pectroscopy. These results were in accordance with determinations by s ize exclusion chromatography and with the known molecular weights of p ullulan standards.