Novel Method for Characterizing Short-Range Molecular Order in Noncrystalline Starch by ¹³ C CP/MAS NMR

Quantifying short-range molecular order in noncrystalline starches has considerable importance for understanding the functionality of starchy products. In this study, a novel ¹³C CP/MAS NMR spectroscopic method was developed to provide the quantitative assessment of short-range molecular order in noncrystalline starches. Spectral components (i.e., subspectra) of ordered phases in noncrystalline starches were subtracted from the subspectra of amorphous starches that were calibrated by multiplying with a scale factor. After peak fitting of the subspectra of ordered phases of noncrystalline and amorphous starches, the band at 95 ppm in the C1 region was identified as a characteristic of short-range order in noncrystalline starches. The relative peak area (RPA) at 95 ppm was negatively correlated with water content and is thus proposed as a relatively quantitative metric for estimating the proportion of short-range order of noncrystalline starches. This newly developed method will help to better understand the structure-functionality of starchy materials.