Chitosan nanoparticles (NPs) exhibit great potential in drug-controlled release systems. A controlled hydrodynamic cavitation (HC) technique was developed to intensify the emulsion crosslinking process for the synthesis of chitosan NPs. Experiments were performed using a circular venturi and under varying operating conditions, i.e., types of oil, addition mode of glutaraldehyde (Glu) solution, inlet pressure (Pin), and rheological properties of chitosan solution. Palm oil was more appropriate for use as the oil phase for the HC-intensified process than the other oil types. The addition mode of water-in-oil (W/O) emulsion containing Glu (with Span 80) was more favorable than the other modes for obtaining a narrow distribution of chitosan NPs. The minimum size of NPs with polydispersity index of 0.342 was 286.5 nm, and the maximum production yield (Py) could reach 47.26%. A positive correlation was found between the size of NPs and the droplet size of W/O emulsion containing chitosan at increasing Pin. Particle size, size distribution, and the formation of NPs were greatly dependent on the rheological properties of the chitosan solution. Fourier transform infrared spectroscopy (FTIR) analysis indicated that the molecular structure of palm oil was unaffected by HC-induced effects. Compared with ultrasonic horn, stirring-based, and conventional drop-by-drop processes, the application of HC to intensify the emulsion crosslinking process allowed the preparation of a finer and a narrower distribution of chitosan NPs in a more energy-efficient manner. The novel route developed in this work is a viable option for chitosan NP synthesis.

• Investigated anti-solvent crystallization of sucrose. • Measurement of supersaturation level of anti-solvent crystallization. • Abegg Stevens and Larson model was used to calculate crystallization kinetics. • Lower activation energy of crystallization in an ultrasonic field.

Hydrodynamic cavitation is an effective method for chitosan degradation, of which the mechanism directly determines the molecular weight distribution of degradation products. In this study, based on the Monte Carlo simulation and experimental results, the mechanism of chitosan degradation with hydrodynamic cavitation and molecular weight distribution of products were analyzed. The results showed that the algorithm established in the simulation could effectively analyze degradation mechanism and the factors that influenced degradation mechanism and molecular weight distribution of products. The degradation with hydrodynamic cavitation was caused by chemical and mechanical effects, of which the former dominated the degradation process. The outlet and inlet angles and throat length of the cavitator had major and minor influences on the degradation pattern, respectively. The chemical effect led to random cuts resulting in wide distribution of the products, while the mechanical effect led to central cuts resulting in narrow distribution of the products. With more central cuts, the slide-shaped molecular weight distribution curve of degradation products was gradually transferred into a bell-shaped curve. These results provide instructions for researches on the molecular weight distribution of chitosan products degraded with hydrodynamic cavitation.

The combination of polyphenols and protein can improve the functional characteristics of protein. How to effectively promote the binding of polyphenols to protein is still a difficult topic. In this study, hydrodynamic cavitation (HC) was used to induce the fabrication of complexes between soy protein isolate (SPI) and different polyphenols (tannic acid (TA), chlorogenic acid (CGA), ferulic acid (FA), caffeic acid (CA), and gallic acid (GA)). The effect of HC on the interaction between polyphenols and SPI was investigated, and the structural and functional properties of the formed complexes were characterized. The results showed that HC treatment led to SPI structure stretching, which increased the binding level of polyphenols, especially that of TA (increased from 35.08 ± 0.73% to 66.42 ± 1.35%). The increase in ultraviolet-visible absorption intensity and quenching of fluorescence intensity confirmed that HC enhanced the interaction between polyphenols and protein. HC treatment reduced the contents of free sulfhydryl and amino groups in SPI-polyphenol complexes and altered their Fourier transform infrared spectroscopy, indicating that HC treatment promoted the formation of C-N and C-S bonds between SPI and polyphenols. Circular dichroism spectroscopy indicated that HC treatment altered the secondary structure of SPI-polyphenol complexes, inducing an increase in α-helix and random coil contents and a decrease in β-sheet content. Regarding functional properties, HC treatment improved the emulsification and antioxidant activity of SPI-polyphenol complexes. Therefore, HC is an effective technique for promoting the binding of polyphenols to protein.

Chitosan degradation was investigated using a combination of jet cavitation and impinging stream. Different operating parameters such as the initial concentration (1-5 g L(-1)), initial pH (3.2-4.8), solution temperature (30, 40, 50, 60, and 70°C), inlet pressure (0.1-0.45 MPa), and treatment time (0-120 min) were optimized to achieve the maximum degradation of chitosan. After the optimization of jet cavitation parameters, chitosan degradation was carried out using venturi tubes of different structures (the fluidic generator). The efficiency of the jet cavitation degradation was improved significantly by combining with impinging stream. The structures of the degradation products were characterized by Fourier-transform infrared spectroscopy and X-ray diffraction. This study has conclusively established that a combination of jet cavitation and impinging stream can be effectively used for the complete degradation of chitosan.

In this paper, the hydroxyl radical yield of a cavitation bubble and its influencing factors in the process of chitosan degradation with hydrodynamic cavitation in a single-hole orifice plate was investigated by a numerical simulation method. The hydroxyl radical yield of the cavitation bubble was calculated and analyzed by the Gilmore equation as the dynamic equation combined with the mass transfer equation, heat transfer equation, energy balance equation, and the principle of Gibbs free energy minimization. The influence of geometric parameters of the orifice plate and operating parameters on the formation of hydroxyl radicals was investigated. The results showed that the hydroxyl radicals produced at the moment of cavitation bubble collapse increased with the increase of the initial radius (R₀), upstream inlet pressure (P₁), downstream recovery pressure (P₂), downstream pipe diameter (d_p), and the ratio of the orifice diameter to the pipe diameter (β). The simulation results provide a certain basis for the regulation of hydrodynamic cavitation degradation of chitosan.