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Chitosan (CS) was dissolved with the aid of ultrasound and hydrogen peroxide treatment. Then, sodium tripolyphosphate (TPP) was introduced as a crosslinker into CS solution from bottom to top. Finally, chitosan microflower (CSMF) was obtained by collecting the resulting precipitate and freeze-drying it. CSMF was characterized and the factors affecting its formation were studied. The results showed that the size of CSMF was 1–2 μm in diameter. The Fourier transform infrared (FTIR) spectrum of CSMF showed a vibration peak of phosphate group at 532 cm-1. The crystal form of CS changed from semi-crystalline structure to hydrated polycrystalline structure after conversion into CSMF. X-ray photoelectron spectroscopy (XPS) showed that CSMF produced C-N＋ bond, and thermogravimetric analysis (TGA) showed that the thermal stability of CSMF was slightly lower than that of CS. Also, it was found that pretreatment method, ultrasonic time, CS solution temperature and CS/TPP ratio (m/m) but not ultrasound power or hydrogen peroxide addition could affect the flower-shaped structure of CSMF. Furthermore, it was inferred that the formation mechanism of CSMF was related to that fact that after the degradation of CS into short- or long-chain CS within a certain molecular mass range, relatively longer and shorter degraded CS chains were crosslinked by TPP to respectively form the pedestal of the microflower structure and nanosheets which were self-assembled on the substate through the interaction between the –NH3+ and phosphate ions in the structure of CS.

Hydrophobic chitosan aerogels were prepared using chitosan as a matrix and 2,6-dimethyl-5-heptenal as a cross-linking modifier to graft n-octadecanethiol and were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The results showed that the surface of the hydrophobic chitosan aerogel had a three-dimensional porous structure. 2,6-Dimethyl-5-heptenal was successfully grafted via the Schiff base reaction. The proportion of elemental sulfur was 1.17% in the aerogel. In the surface contact angle test, the oil droplet contact angle was 0°, and the water droplet contact angle was 126°. The chitosan aerogel exhibited good hydrophobic properties. The loading of fat-soluble curcumin in the aerogel reached the maximum value of 70.5 mg/g after 40 min, and the optimal loading temperature was 27 ℃. The hydrophobic chitosan aerogel had a good sustained-release performance, and the sustained-release rate of curcumin in simulated intestinal fluid was up to 89.6%.

In order to study the feasibility of applying cassava starch-fatty acid complexes as a Pickering emulsion stabilizer, complex nanoparticles with complexing index (CPI) of 2.74%, 9.17% and 27.66% were prepared by mixing cassava starch paste containing 78.65% amylopectin at 95 ℃ and stearic acid followed by alcohol precipitation. The three complexes had an irregular spherical-like shape under field emission scanning electron microscopy (FESEM), and their average particle sizes, determined by a laser particle size analyzer, were 315.35, 348.19 and 427.60 nm, respectively. The X-ray diffraction pattern of each of the complexes showed two peaks at 13° and 21°, which were characteristics of the V type crystal structure, and the crystal content increase with increasing CPI. Their deconvoluted infrared spectra exhibited changes in short-range ordering at 1 047, 1 022 and 995 cm-1. The contact angle of the particles with the highest CPI was 60.30°. The three complex nanoparticles stabilized Pickering emulsions for more than seven days compared to less than two days with starch nanoparticles. The complex nanoparticles with CPI of 27.66% stabilized emulsions best. The addition of the complex nanoparticles with CPI of 27.66% at levels above 0.1 g/100 mL resulted in the formation of an emulsion with an oil-to-water ratio of 1:9 (V/V). The emulsion with this nanoparticle at 7 g/100 mL exhibited an improved stability for 60 days without creaming or phase separation. Moreover, no significant changes in the droplet size distribution were observed. The emulsion was stable at pH 5.6-9.0 and not affected by NaCl concentration in the range of 0.01-0.1 mol/L. The emulsion maintained its morphology well after being heated to 80 ℃. These results suggest that the complex nanoparticles are a potential Pickering emulsion stabilizer.

In order to better apply starch as a polymer material in the material industry, it is necessary to modify starch. In this study, cassava starch was used as raw material, and it was pretreated and acetylated in an anhydrous medium. By controlling the change in reaction time, acetylated starch with different degrees of substitution was prepared. And the effects of pretreatment on the physicochemical properties of acetylated starch particles, as well as the differences in physicochemical properties between high degree of substitution starch and low degree of substitution starch, were investigated through characterization methods such as X-ray diffraction, polarizing microscope, scanning electron microscope, contact angle measurement, and differential scanning calorimetry analysis. The results showed that pre-treatment could shorten the time required for acetylation of raw starch. The crystal diffraction peak of high degree of substitution acetylated starch disappeared, the polarized cross disappeared, and the morphology changed from circular to porous. It could be dissolved in organic solvents such as acetone. After 0.5 hours of acetylation reaction, the hydrophobic contact angle of pretreated starch could reach 69.006°±0.520°, the starch melting temperature decreased to 155 °C, and the decomposition temperature increased from 280 °C to 340 °C, enhanced the thermal stability of starch and possessed thermoplastic properties. This study can prepare acetylated starch with a degree of substitution of 2.5 within half an hour, which can be dissolved in organic solvents, providing new ideas for accelerating the application of starch in the material industry. [ABSTRACT FROM AUTHOR]