Evaluation of non-starch polysaccharides and oligosaccharide content of different soybean varieties (Glycine max) by near-infrared spectroscopy and proteomics

A total of 832 samples of soybeans were screened by near-infrared (NIR) reflectance spectroscopy, to identify soybean samples with lower content of oligosaccharides and non-starch polysaccharides (NSP). Of these, 38 samples were identified based on variation in protein content and agronomic value, and submitted to high-resolution NIR spectroscopy. Based primarily on the NIR data, twelve samples were further selected for chromatographic characterization of carbohydrate composition (mono-, di- and oligosaccharides and NSP). Their soluble proteins were separated by 2-dimensional gel electrophoresis (2DE). Using partial least square regression (PLSR), it was possible to predict the content of total NSP from the high-resolution NIR spectra, suggesting that NIR is a suitable and rapid non-destructive method to determine carbohydrate composition in soybeans. The 2DE analyses showed varying intensities of several proteins, including glycinin G1 precursor. PLSR analysis showed a negative correlation between this protein and insoluble NSP and total uronic acid (UA).