Recent advances in nanocellulose based hydrogels: Preparation strategy, typical properties and food application.

Nanocellulose has been favored as one of the most promising sustainable nanomaterials, due to its competitive advantages and superior performances such as hydrophilicity, renewability, biodegradability, biocompatibility, tunable surface features, excellent mechanical strength, and high specific surface area. Based on the above properties of nanocellulose and the advantages of hydrogels such as high water absorption, adsorption, porosity and structural adjustability, nanocellulose based hydrogels integrating the benefits of both have attracted extensive attention as promising materials in various fields. In this review, the main fabrication strategies of nanocellulose based hydrogels are initially discussed in terms of different crosslinking methods. Then, the typical properties of nanocellulose based hydrogels are comprehensively summarized, including porous structure, swelling ability, adsorption, mechanical, self-healing, smart response performances. Especially, relying on these properties, the general application of nanocellulose based hydrogels in food field is also discussed, mainly including food packaging, food detection, nutrient embedding delivery, 3D food printing, and enzyme immobilization. Finally, the safety of nanocellulose based hydrogel is summarized, and the current challenges and future perspectives of nanocellulose based hydrogels are put forward.

Low gelatin concentration assisted cellulose nanocrystals stabilized high internal phase emulsion: The key role of interaction.

Low concentrations of gelatin (0.02-0.20 wt%) were applied to regulate the surface and interface properties of CNC (0.50 wt%) by forming CNC/G complexes. As gelatin concentration increased from 0 to 0.20 wt%, the potential value of CNC/G gradually changed from -44.50 to -17.93 mV. Additionally, various gelatin concentrations led to micromorphology changes of CNC/G complexes, with the formation of particle interconnection at gelatin concentration of 0.10 wt%, followed by network structure and enhanced aggregation at gelatin concentration of 0.15 and 0.20 wt% respectively. The water contact angle (25.91°-80.23°) and interface adsorption capacity of CNC/G were improved due to hydrophobic group exposure of gelatin. When gelatin concentration exceeded 0.10 % at a fixed oil phase volume fraction (75 %), a high internal phase emulsion (HIPE) stabilized by CNC/G can be formed with a good storage stability. The rheological and microstructure results of HIPE confirmed that low gelatin concentration can assist CNC to form stable emulsion structure. Especially, the auxiliary stabilization mechanism of various gelatin concentration was different. CNC/G-0.10 % and CNC/G-0.15 % stabilized HIPE mainly depended on the enhanced interface adsorption and network structure, while CNC/G-0.20 % stabilized HIPE mainly relied on enhanced interface adsorption/accumulation due to weak electrostatic repulsion and aggregate granular morphology of CNC/G-0.20 %.

Preparation and physicochemical properties of nanocellulose lightweight porous materials: The regulating effect of gelatin.

The composite lightweight porous material (TOCNF-G-LPM) based on TEMPO-oxidized cellulose nanofibril (TOCNF) and gelatin were facilely prepared by ambient pressure drying using glutaraldehyde as crosslinking agent. The influence of gelatin addition on the physicochemical properties of TOCNF-G-LPM was investigated. The long-size entangled structure of TOCNF maintained the skeleton network of TOCNF-G-LPM while gelatin can adjust the characteristics of highly porous network (porosity of 98.53%-97.40%) and light weight (density of 0.0236-0.0372 g/cm3) with increasing gelatin concentration (0.2-1.0 wt%). The results of scanning electron microscopy (SEM) and confocal laser scanning microscope (CLSM) indicated that the internal structure of TOCNF-G-LPM became more ordered, uniform and denser as gelatin concentration increased. Introducing gelatin decreased water and oil absorption properties, but improved the thermal, mechanical properties and shape recovery ability of TOCNF-G-LPM at appropriate addition. Furthermore, TOCNF-G-LPM showed no significant effect on the growth and reproduction of Caenorhabditis elegans (C. elegans), confirming a good biocompatibility.