In this study, polyphenols extracted from apple waste were blended with modified nanocellulose and modified microcrystalline cellulose to produce composite films based on water chestnut starch. Thermogravimetric analysis indicated that the addition of polyphenols from apple residue could enhance the heat endurance of the water chestnut starch film. The study findings suggested that the incorporation of M-NCC led to a 24.35% boost in the tensile strength of the finished films, while that with M-MCC increased by 55.17%. The hydrophobic properties were improved due to the introduction of non-polar carbon chains and hydrophobic ester groups, resulting in respective increases in the surface contact angle of 22.66% and 24.94%. The incorporation of polyphenols from apple residue led to a 16.05% increase in the water solubility of the starch film, and the incorporation of M-NCC and M-MCC resulted in a decrease in the water solubility of the composite films by 19.04% and 30.79%, respectively. Moreover, the DPPH free radical scavenging rates of the films containing apple polyphenols (P, PN, and PM) were increased by 164.7%, 163.3%, and 134.7%, demonstrating excellent antioxidant properties. These findings suggested that the combination of apple pomace polyphenols and cellulose nanocrystals offered an optional approach for preparing food packaging films.
Starch nanoparticles (SNPs) have been recognized as potentially efficient adsorbents for polyphenols. However, their actual adsorption in complex systems such as fruit pomace extract is significantly lower than theoretical predictions and their adsorption capacity is inferior to traditional materials such as macroporous adsorbent resins, which limits their industrial application. Aiming to enhance the adsorption of apple pomace polyphenols, this study used sodium alginate (SA) modifies SNPs to create a cornstarch-based composite system (SA-SNPs). The optimal modified addition of sodium alginate was 0.3 g (g starch) −1 , under this condition, the nanoparticles obtained exhibited the smallest particle size (154.60 nm) and the best adsorption performance (33.97 mg g −1 in 90 min). The SA-SNPs reached the adsorption equilibrium at 180 min, which significantly enhanced the equilibrium adsorption amount of the polyphenols (from 2.68 to 37.02 mg g −1 ). The adsorption process was found to follow the pseudo-second- order kinetic model and the Langmuir isotherm model, which included membrane diffusion, intra-particle diffusion, and equilibrium phases. The adsorption amount initially increased and then continued to decrease with the increase in temperature, and the whole process was exothermic and spontaneous (ΔH° = −52.394 kJ mol −1 , ΔG° < 0 kJ mol −1 ). Additionally, SA-SNPs loaded with polyphenols demonstrated better protection of polyphenol DPPH radical-scavenging activity during storage, enhanced stability, and optimal colon-targeted sustained-release properties in complex physiological environments. This work presents a new approach to improving the adsorption capacity of SNPs and developing high-performance natural edible separation materials.
Jifan Zhang,Yuxi Li,Yuqing Dai,Tao Lin,Haojian Shao,Yi Liu,Xunyong Liu
The efficient reuse of agricultural wastes such as apple pomace has always been a research focus because it increases the economic added value of apple pomace and reduces environmental pollution . Using cellulose, the main component of apple pomace, is an important way to reuse apple pomace resources. Cellulose is widely used as a good adsorption material to remove dyes from water. However, the effective adsorption sites of cellulose are few, and the binding force between adsorption functional groups and dyes is weak, resulting in the unsatisfactory adsorption performance of cellulose. To solve these problems, first, cellulose from apple pomace was oxidized to easily modified dialdehyde cellulose (DAC), and a series of factors was optimized to obtain DAC with high aldehyde content. Second, an HPEI-DAC hydrogel with a three-dimensional porous structure characterized by FTIR, XPS and SEM was prepared by crosslinking hyperbranched polyethyleneimine (HPEI) containing many amine groups with DAC. Because of its special topological structure and increasingly stronger adsorption sites, the HPEI-DAC hydrogel exhibited good adsorption performance for methyl orange (MO). The effects of the DAC/HPEI ratio, synthesis temperature, pH value and HPEI-DAC dosage on the adsorption property of HPEI-DAC for MO were studied. The HPEI-DAC hydrogel exhibited an adsorption capacity as high as 416.72 mg/g for MO. For the MO adsorption process , the adsorption kinetics and equilibrium data were consistent with the pseudo-second-order and Langmuir isotherm models, respectively. Moreover, the HPEI-DAC hydrogel could be easily regenerated and showed good reusability. After six cycles of adsorption/desorption, the adsorption capacity of the HPEI-DAC hydrogel remained at the initial value of 70 %. Therefore, the HPEI-DAC hydrogel can be considered a good adsorption material for treating azo dye wastewater.
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