A new sight separation for collecting starch nanocrystals with small size and high crystallinity based on the hydrolysis mechanism

Adsorption behavior of cationic dyes on starch nanocrystals: Kinetic, isotherm, and thermodynamic insights from single to multi-component systems

The adsorptive potential of starch nanocrystals (SNCs) was evaluated for the elimination of methylene blue (MB), crystal violet (CV), and malachite green (MG) from aqueous media in single, binary, and ternary dye systems using batch mode experiments. SNCs were extracted using mild acid hydrolysis to remove the amorphous parts of native granular starch, and they were characterized using different physicochemical methods, such as FESEM, XRD, FTIR, BET, TGA, and pHZPC. The results revealed that the optimal pH for dye removal in both single and mixed dye systems was found to be 9.0. The equilibrium time increased from 5 to 20 min when the system was changed from single to binary, and then further increased to 30 min when the system was changed to ternary. The equilibrium data for single-dye systems exhibited a good fit with the Langmuir isotherm model (R2 > 0.98, SEE <3.52 mg g-1), whereas for binary and ternary dye mixtures, the extended Langmuir model provided an accurate representation of the experimental data (R2 > 0.99, SEE <1.33 mg g-1). Among the single, binary, and ternary systems, the highest adsorption capacities were observed for MB, MB in the (MB + MG) binary system, and MB in the (MB + CV + MG) ternary system. The respective adsorption capacities were recorded as 79.55 mg g-1, 61.91 mg g-1, and 43.59 mg g-1. The adsorption of dyes onto the SNCs was inherently spontaneous and endothermic, and adhered to the pseudo-second-order kinetic model in single dye systems as well as mixed dye systems. It can be concluded that the SNCs are capable of being utilized for five consecutive cycles in the adsorption-desorption process for single dye systems and three consecutive cycles for mixed dye systems. This suggests that the SNCs have potential as a sustainable and efficient option for dye removal in mixture systems.

High-efficiency preparation of starch nanocrystals with small size and high crystallinity by ethanol-acid penetration and dry-heating pretreatment

Ethanol-acid penetration and drying-heating treatment was developed to shorten the preparation time and improve the quality of starch nanocrystals (SNCs). After treatment by optimized parameters, including 40 % ethanol solution, 10.6 mM chloric acid, and heating time of 1.5 h or 2.0 h, the starches exhibited weakened internal structure and relatively complete crystalline structure. Compared with the regular preparation of only acid hydrolysis, the regular final yield (8.5 % after 5 days) was reached in 48 h and 12 h of the starch heated at 1.5 h and 2.0 h, respectively. The micromorphology, molecular weight, and crystalline structure evaluation demonstrated that the collected nanoparticles were indeed SNCs with smaller size and higher relative crystallinity than regular SNCs. Further analysis found that the SNCs had better crystalline lamellae, higher thermal stability, and lower proportion of phosphorus and sulfur atoms than regular SNCs. This provided a potential method for the high-efficiency preparation of SNCs.

Pickering emulsions stabilized by starch nanocrystals prepared from various crystalline starches by ultrasonic assisted acetic acid: Stability and delivery of curcumin

Ultrasonic assisted acetic acid hydrolysis was applied to prepare starch nanocrystals (SNCs) from native starches with different crystalline structures (A, B, and C types). The structure properties, morphology, Pickering emulsion stability and curcumin deliver capacity of both SNCs and native starches were investigated and compared. Compared with native starches, SNCs showed smaller size and higher crystallinity. The size of SNCs varied with different crystalline types, with C-type starch exhibiting the smallest SNCs (107.4 nm), followed by A-type (113.8 nm), and B-type displaying the largest particle size (149.0 nm). SNCs-Pickering emulsion showed enhanced stability with smaller emulsion droplets, higher static stability, and denser oil/water interface. SNCs-Pickering emulsions displayed higher curcumin loading efficiency (53.53 %-61.41 %) compared with native starch-Pickering emulsions (13.93 %-19.73 %). During in vitro digestion, SNCs-Pickering emulsions proved to be more proficient in protecting and prolonging the biological activity of curcumin due to their smaller size and better interfacial properties. These findings demonstrated the potential of SNCs for application in Pickering emulsion and delivery of bioactive components.