Nuclear　magnetic　resonance　was　used　to　study　water　proton　transverse　relaxation　in　oat　β-glucan　aqueous　solutions　during　storage.　The　molecular　weights　of　the　samples　ranged　from　112　to　494　kDa.　The　polysaccharide　structure　was　identified　by　IR,　GC–MS,　NMR　spectroscopy,　and　high　performance　anion　exchange　chromatography.　In　1%　solutions,　494　kDa　β-glucan　formed　stable　solution　phase.　Aggregates　were　generated　in　the　solution　of　low　molecular　weight　polysaccharide.　The　transverse　relaxation　time　of　water　associated　with　the　aggregate　microphase　was　about　15　ms.　The　majority　of　the　solution　was　bulk　water,　with　a　relaxation　time　of　800–1600　ms.　The　proton　exchange　rate　was　about　103　s−1,　calculated　from　two-site　exchange　model.　The　proportion　of　β-glucan　in　the　aggregate　microphase　increased　from　0　to　over　80%　of　the　total　β-glucan　during　storage　of　112　kDa　samples.　In　the　4%　solutions,　the　evolution　of　water　proton　relaxation　associated　with　the　gel　network　can　be　explained　by　the　fractal　structure　theory.　The　relaxation　behavior　suggested　the　growth　and　syneresis　of　the　gel　network　during　the　gelation　of　the　low　molecular　weight　β-glucan　solutions.　©　2017　Elsevier　Ltd