Applications of physical and chemical treatments in plant-based gels for food 3D printing.

Extrusion-based three-dimensional (3D) printing has been extensively studied in the food manufacturing industry. This technology places particular emphasis on the rheological properties of the printing ink. Gel system is the most suitable ink system and benefits from the composition of plant raw materials and gel properties of multiple components; green, healthy aspects of the advantages of the development of plant-based gel system has achieved a great deal of attention. However, the relevant treatment technologies are still only at the laboratory stage. With a view toward encouraging further optimization of ink printing performance and advances in this field, in this review, we present a comprehensive overview of the application of diverse plant-based gel systems in 3D food printing and emphasize the utilization of different treatment methods to enhance the printability of these gel systems. The treatment technologies described in this review are categorized into three distinct groups, physical, chemical, and physicochemical synergistic treatments. We comprehensively assess the specific application of these technologies in various plant-based gel 3D printing systems and present valuable insights regarding the challenges and opportunities for further advances in this field.

Tailoring the optical and mechanical properties of cellulose nanocrystal film by sugar alcohols and its pH/humidity-responsive behavior.

Cellulose nanocrystals (CNC) have gained widespread attention in intelligent food packaging because of their iridescent optical properties. Here, we report a CNC composite film employing CNC, sugar alcohols (e.g., maltol, erythritol, mannitol, sorbitol, and xylitol) and natural pigment anthocyanins, which has a special iridescent color that can be used as a pH and humidity sensor. The effects of five sugar alcohols with different addition ratios on the structural, optical, and mechanical properties of the CNC films were investigated. The results demonstrated that the addition of sugar alcohol made composite films exhibiting a red-shift of λmax, a more uniform color in visual observation, and a larger pitch. Among them, the CNC-mannitol composite film with a ratio of 10:1 exhibited the best mechanical properties, possessing a tensile stress strength of 57 MPa and toughness of 137 J/m3. Subsequently, anthocyanins were incorporated to this composite film, which showed a marked color change along with the pH from 2 to 12 and exhibited a reversible color change from red to transparent upon a relative humidity change from 35 % to 85 %. Overall, such multi-environment-responsive iridescent films with excellent mechanical properties have a great potential for use in intelligent food packaging applications.

Synthesis and characterization of cellulose nanocrystal-Fe composite nanoparticles and their digestion behavior in simulated gastric fluid.

Cellulose nanocrystals (CNC) exhibit great potential as a food emulsifier or functional material template. Herein, CNC-Fe nanoparticles were successfully prepared via an in situ chemical reduction approach. Zeta potential measurements, low-field nuclear magnetic resonance spectroscopy, and atomic force microscopy showed that Fe(III) ions were adsorbed onto CNC when FeCl3 was added to a CNC dispersion. Micromorphological analysis revealed small (diameter = 10.0 ± 2.4 nm) spherical nanoparticles synthesized on the surface of aggregated CNC after the reduction of the Fe(III) ions. Fourier transform infrared spectroscopy revealed an intense peak at 779 cm-1 in the CNC-Fe nanoparticles, which was attributed to FeO stretching vibrations. X-ray photoelectron spectroscopy indicated that the valence state of Fe in CNC-Fe nanoparticles was predominantly ferrous. The synthesized CNC-Fe nanoparticles demonstrated excellent colloidal stability in a dispersion for 21 d and complete, rapid, and spontaneous dissolution in vitro simulated gastric fluid. Our results highlight the potential use of CNC as a template for loading Fe into nanoparticles for Fe fortification in food.

Effects of lipid type and toxicological properties on the digestion of cellulose nanocrystals in simulated gastrointestinal tract.

This study aimed to understand the impact of different oil types on the cellulose nanocrystals (CNCs) to modulate lipid digestion and the in vitro gastrointestinal toxicity of CNCs in food systems. We explored the ability of CNCs to modulate lipid digestion in a simulated gastrointestinal system and monitored the gastrointestinal fate of CNC-based emulsions with different oil types. Finally, a small intestine epithelial model was used to evaluate the influence of cytotoxicity. The results suggested that the addition of 0.6 wt% CNCs in the high-fat food model reduced the hydrolysis of free fatty acids (FFAs) from triglycerides by 37.8% after the small intestine phase. CNCs showed the best effect in reducing lipid digestion in emulsions with high unsaturation triglycerides. In addition, the toxicology results suggest that 0.6 wt% CNCs had only a slight effect on reactive oxygen species and cytotoxicity, and no significant change in cell-layer integrity.

Studies into interactions and interfacial characteristics between cellulose nanocrystals and bovine serum albumin.

This study investigates the interactions between cellulose nanocrystals (CNCs) and bovine serum albumin (BSA) under different pH conditions. A multiscale technique was employed to characterize the CNCs and BSA at pH 7 and pH 3. ζ-Potential measurement and UV-vis spectroscopy demonstrated strong interactions between CNCs and BSA at pH 3, whereat they have opposite charges. Interfacial tensiometry showed a deficiency in the surface activity of the CNCs and indicated that BSA dominated the interface behavior in their complex. Quartz crystal microbalance with dissipation revealed that the sequential adsorption of BSA and CNCs produced viscoelastic bilayers at pH 3, and the mass adsorbed was âˆ¼ 28 times that adsorbed at pH 7. Molecular dynamics simulations indicated that the key interactions between the two materials were produced between the hydrophobic CNC surface and the BSA domain IIA region. These results provide interesting insights into the design of complex food emulsions and fluid interfaces.

Nanocellulose: a promising green treasure from food wastes to available food materials.

The synthesis of novel functional materials from abundant food waste resources has great application potentials and ecological benefits. Nanocellulose is a renewable and sustainable polymer that possesses a modifiable surface, excellent mechanical strength, and high aspect ratio, and it is nontoxic. These unique properties garner nanocellulose a promising prospect for multi-various applications including the food industry. This review presents the structural characteristics and advances in the extraction approaches of nanocellulose, with an emphasis in recent progress on the various applications of nanocellulose in the field of food industry. Finally, the environmental and human health issues related to the production of nanocellulose are evaluated. The scheme to extract and produce nanocellulose from food wastes provides a platform for the sustainable utilization of waste biomass. These nanocelluloses exhibit excellent performances in green food packaging materials, emulsion stabilizers, dietary fiber, nutrition delivery and food three-dimensional (3 D) printing hydrogels. To ensure the security and regulatory issues, validated standards to characterize the structure and evaluate its toxicity are still indispensable to achieve the commercialization of nanocellulose in the food industry.

Facile extraction and characterization of cellulose nanocrystals from agricultural waste sugarcane straw.

BACKGROUND: Sugarcane straw is an available but largely ignored lignocellulosic biomass to obtain cellulose nanocrystals (CNCs) with highly crystalline, tunable surface chemistries and a wide-ranging adaptability. Herein, we utilized sugarcane straw to obtain pure cellulose via purification processes, followed by subsequent preparation of CNCs via sulfuric acid hydrolysis. The properties of the purified fibers and obtained CNCs were assessed by their composition, morphology, chemical structure, crystallinity and thermal stability. RESULTS: After the purification process, alkali-treated fibers (ATFs) contained 886.33 ± 1.25 g kg-1 cellulose, and its morphological analysis revealed a smooth and slender fibrous structure. The CNCs obtained by treatment with 64 wt% sulfuric acid at 45 °C for 60 min were isolated in a yield of 21.8%, with a diameter and length of 6 to 10 nm and 160 to 200 nm, respectively. Moreover, crystallinity index of these CNCs reached 62.66%, and thermal stability underwent a two-step degradation. Short-term ultrasonication after hydrolysis was employed to enhance isolation of the CNC particles and improve the anionic charge with higher value -38.00 mV. CONCLUSION: Overall, isolation and characterization results indicated the potential for CNCs preparation using sugarcane straw, in addition to offering a fundamental understanding of this material and indicating potential applications. © 2021 Society of Chemical Industry.

Cellulose nanocrystals produced using recyclable sulfuric acid as hydrolysis media and their wetting molecular dynamics simulation.

Cellulose nanocrystals (CNCs) were successfully produced with good nanoscales and dispersibility, using a recycled sulfuric acid (H2SO4) hydrolysis process. This method, at the cost of an overall 25% increase in the hydrolysis time, could significantly reduce the dosage of H2SO4 by approximately 40% without affecting the per-batch yield and performance of CNCs. The obtained CNCs with an average diameter of 6.0-6.5 nm and an average length of 126-134 nm, were successfully applied in the preparation of oil-in-water (O/W) Pickering emulsions via high-pressure homogenization. The emulsions exhibited good storage stability when the concentration of CNC was 1.0 wt%. Further, understanding the wetting behaviors of surface modified CNCs with solvent is critical for the functional designing of Pickering emulsion. Hence, we gained insights into the wetting of hydrophobic and hydrophilic surfaces of sulfate modified CNCs with water and organic solvent (hexadecane) droplets, using molecular dynamic simulation. The results showed that both surfaces had hydrophilic as well as lipophilic properties. Although the sulfate-grafted surface was more hydrophilic than unmodified CNC, substantial local wetting heterogeneities appeared for both solvents. It provides a deeper understanding of the interfacial interactions between modified CNCs and solvent molecules at the molecular level.

Rheological behavior and particle alignment of cellulose nanocrystal and its composite hydrogels during 3D printing.

Cellulose nanocrystal (CNC) has tremendous potential in chemical, material, and food fields as an attractive green bioresource. We formulated viscoelastic hydrogels composed of anisotropic CNC using an extrusion-based 3D printing technology. We explored the rheological properties and printability of CNC hydrogels with different concentrations (0.5-25 wt%), and quantified the shear-induced self-assembly behavior of CNC during printing. The results showed that 20 wt% CNC hydrogels exhibited optimal print resolution and fidelity, with a high degree of orientation (72 %-73 %) of CNC alignment along the printing direction. It provides quantitative guidelines for the development of 3D printable materials with particle orientation. Furthermore, we prepared two composite hydrogels for 3D printing by blending CNC with high/low methoxy pectin (HMP/LMP). The results revealed that two hydrogels had favorable print fidelity at suitable ratios (CNC: HMP = 2:8, CNC: LMP = 10:5). This provided flexible and sustainable choices for the development of medical tissue engineering.

Genotypic and environmental variation in cadmium, chromium, lead and copper in rice and approaches for reducing the accumulation.

The field scale trials revealed significant genotypic and environmental differences in grain heavy metal (HM) concentrations of 158 newly developed rice varieties grown in twelve locations of Zhejiang province of China. Grain Pb and Cd contents in 5.3% and 0.4% samples, respectively, were above the maximum permissible concentration (MPC); none of samples had Cr/Cu exceeding MPC. Stepwise multiple linear regression analysis estimated soil HM critical levels for safe rice production. Low grain HM accumulation cultivars such as Xiushui817, Jiayou08-1 and Chunyou689 were recommended as suitable cultivars for planting in slight/medium HM contaminated soils. The alleviating regulator (AR) of (NH4)2SO4 as N fertilizer coupled with foliar spray of a mixture containing glutathione (GSH), Si, Zn and Se significantly decreased grain Cd, Cr, Cu and Pb concentrations grown in HM contaminated fields with no effect on yield, indicating a promising measurement for further reducing grain HM content to guarantee safe food production.