NMR characterization of structure and moisture sorption dynamics of damaged starch granules

Among the many biopolymers that constitute food products, starch is one of the most common. Starch granules are often damaged in the milling process, which affects the final product quality, mainly due to changes in water adsorption properties. In this work, the crystallinity degree of wheat starch samples as a function of the mechanical damage is determined by low field H-1 NMR. We also introduce the use of single-sided NMR to determine granular swelling, water distribution and sorption dynamics of the samples. Results show that the crystallinity of the samples decreases with the milling. We also observed that swelling index and sorption capacity values are higher in the milled samples than in the native starch. Our experiments show how single-sided NMR is a valuable tool to provide information on dynamic processes not only in starch, but also in many carbohydrate polymeric samples with the additional benefit of spatial resolution.