Residue Specific Hydration of Primary Cell Wall Potato Pectin Identified by Solid-State 13C Single-Pulse MAS and CP/MAS NMR Spectroscopy

Hydration of rhamnogalacturonan-I (RG-I) derived from potato cell wall was analyzed by C-13 single-pulse (SP) magic-angle-spinning (MAS) and C-13 cross-polarization (CP) MAS nuclear magnetic resonance (NMR) and supported by H-2 SP/MAS NMR experiments. The study shows that the arabinan side chains hydrate more readily than the galactan side chains and suggests that the overall hydration properties can be controlled by modifying the ratio of these side chains. Enzymatic modification of native (NA) RG-I provided samples with reduced content of arabinan (sample DA), galactan (sample DG), or both side chains (sample DB). Results of these samples suggested that hydration properties were determined by the length and character of the side chains. NA and DA exhibited similar hydration characteristics, whereas DG and DB were difficult to hydrate because of the less hydrophilic properties of the rhamnosegalacturonic acid (Rha-GalA) backbone in RG-I. Potential food ingredient uses of RG-I by tailoring of its structure are discussed.