Preparation,Characterization And Applization Of Starch Spherulites

A new method has been developed to prepare starch spherulites,there are three main steps:enzymatic hydrolysis,acid hydrolysis and recrystallization at cryogenic temperature.First,the a-amylase and amyloglucosidase were mixed in different proportions for enzymatic pore-forming to obtain porous starch;after that,the residues obtained by hydrolyzing the porous starch 2 d by sulfuric acid(3.16 mol/L)were dissolved in boiling water,the precipitate was centrifuged,the supernatant frozen at-20 ? overnight and thawed at room temperature.Then the precipitate was washed with distilled water,collected by suction filtration and dried at room temperature.Multiple analysis techniques involving high performance anion exchange chromatography(HPAEC),scanning electron microscope(SEM),light microscopy,wide-angle X-ray diffraction,attenuated total reflectance ATR-FTIR spectroscopy,laser confocal micro-Raman(LCM-Raman)spectroscopy,and differential scanning calorimetry(DSC)were applied to study the morphology and structure of the starch spherulites.These spherulites showed the spherical shape with a smaller size(?2 ?m),a smoother and denser surface and two symmetrical orifices(uncrystallized holes),but there were particles aggregation and surface adhesion.After crystallization,a typical B-type structure was observed for all products.Comparing with native starch,the short-range ordered structure of spherulites were better.High relative crystallinity and large enthalpy suggested that the the quantity of double helical and crystallites was significantly enhanced,but the crystal of spherulites was unstable,imperfect and inhomogenous because of low gelatinization temperature,weak birefringence and expanded transition temperature.Amylopectin from different spherulites showed similar chain length distribution profiles,and a shoulder at DP 6-24 was found in all samples.And there were no significant difference in morphology and structure of spherulites when pretreatment with different ratio of two enzymes in the first step.Soybean oil-in-water(O/W)Pickering emulsions were prepared using spherulites as particle stabilizers.The emulsifying stability of the starch spherulites was determined from photographs that were taken 120 d after emulsification.Results indicated that pH of emulsion system<6.0 and NaCl had obvious effect on the cream volumes and emulsifying stability.And emulsions which were prepared using octenyl succinic anhydride(OSA)modified spherulites as particle stabilizers had good emulsifying stability.The in vitro enzymatic digestibility of starch spherulites was evaluated.We found that the digestive process of the starch spherulites was different from the native starch.But the resistant starch content of starch spherulites was concentrated on 19.90-30.05%after 120 minutes,compared with the native starch,there was no significant difference.So the starch spherulites were prepared in this experiment can be used as a resistant starch.