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A comparative experiment about the production of starch nanocrystals (SNCs) with/without glucoamylase enzymatic pretreatment by sulfate acid hydrolysis from waxy potato starch (WPS) was employed in the present study. The research focused on the enhancement of the preparation efficiency while improving the dispersion of SNCs at the same time. The enzymatic pretreatment resulted in the decrease of acid hydrolysis duration. The minimum size and best dispersibility of nanocrystals was obtained after 5 days of hydrolysis. X-ray diffraction confirmed the increase of crystallinity (from 33% to 50.8%) and the polymorphic transitions (B–A) for nanocrystals harvested at day 5. The structure of nanocrystals was characterized by FT-IR, which suggested the presence of sulfate ester on the surface of SNCs. Zeta potential and size distribution revealed the prominent stability and dispersibility of nanocrystals at pH 7.0. SEM and TEM revealed that SNCs had square shapes with particle sizes ranging from 50 to 100 nm. [ABSTRACT FROM AUTHOR]

Abstract: Pea starch nanocrystals (PSN) dispersion containing nanocrystals in a range of 30–80nm was prepared from native pea starch (NPS) granules by acid hydrolysis. Two series of films were prepared by blending poly(vinyl alcohol) (PVA) with NPS and PSN, respectively. The effects of NPS and PSN on the structure and properties of the resulting films were comparatively investigated by FTIR, XRD, SEM, and testing of light transmittance, tensile, and moisture uptake. The light transmittance (Tr), tensile strength (σ b), and elongation at break (ε b) of the PVA/NPS films were lower than that of PVA film and decreased with an increase in NPS content. However, the PVA/PSN nanocomposite films containing 5 and 10wt% of PSN content exhibited improved physical properties over the PVA film. The PVA/PSN films showed higher Tr, σ b, and ε b, and lower moisture uptake (Mu) than the corresponding PVA/NPS films with the same component ration. For example, the values of Tr, σ b, ε b, and Mu of the PVA/PSN film containing 10wt% of PSN content were 91%, 40MPa, 734% and 71%, respectively; while those of the corresponding PVA/NPS film were 69%, 35MPa, 579% and 73%, respectively. The results revealed that PSN, comparing with NPS, had much smaller sizes and dispersed more homogeneously in PVA matrix, resulting in stronger interactions with PVA. New applications of native pea starch and its nanocrystals as low-cost fillers were explored in this work, and PSN exhibited greater potential than NPS to improve the properties of PVA-based composites. [Copyright &y& Elsevier]