Structural and physicochemical properties of lotus seed starch nanoparticles

Lotus seed starch (LS) was enzymatically hydrolyzed by pullulanase, β-amylase and α-amylase to obtain three types of starch nanoparticles (SNPs): P-SNPs, β-SNPs and α-SNPs, respectively. The structure and physicochemical properties of lotus seed starch nanoparticles (LS-SNPs) were systematically studied by Laser particle size analysis, Scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectrometry, Nuclear magnetic resonance (NMR) and Gel permeation chromatography (GPC). The results showed that compared to LS (10,466.7 ± 230.9 nm), the D [3,2] of P-SNPs were (334.7 ± 16.2), which indicated that LS was decomposed into LS-SNPs with low degree of polymerization. P-SNPs showed the highest efficiency, with 81.74% of samples reaching the nanoscale. The particle size order was LS > β-SNPs (α-SNPs) > P-SNPs. XRD results showed P-SNPs had the highest crystallinity 65.07%. During preparation of LS-SNPs, crystal region was destroyed, and double helix structure became stronger, but no new functional groups were introduced. P-SNPs had the smallest amorphous area and also showed a minimal molecular weight and the broadest molecular weight distribution. P-SNPs had the smallest particle size and the highest crystallinity, so P-SNPs were the best of all LS-SNPs.