Analytical rheology as a tool for the structural investigation of citrus pectin.

Rheological analysis of citrus pectin at pH 3 and 7 elucidates its structural dynamics, revealing distinct behaviors influenced by pH. At pH 3, pectin exhibits shear-thinning, with solvent-independent unified rheological profiles identifying three concentration regimes: 0.5%-1.5%, 2%-3%, and 3.5%-4%. These regimes, alongside Cox-Merz superpositions, outline the semi-dilute (c*) and concentrated (c**) transitions at 1.5%-2% and 3%-3.5%, respectively. Moreover, a Morris equation exponent of 0.65 indicates flexible, mobility-restricted macromolecules. Conversely, at pH 7, increased viscosities and Morris plot linearity for p = .1 suggest rigid chain behavior due to electrostatic repulsion among ionized acidic groups. This rigidity leads to concentration-dependent self-assembly structures that diverge from expected unified rheological profiles, a deviation amplified by heating-cooling cycles. This study clarifies the impact of pH on citrus pectin's rheology and emphasizes the intricate relationship between polymeric chain rigidity, self-assembly, and viscosity. By providing a refined understanding of these mechanisms, our findings contribute to the broader field of polysaccharide research, offering insights critical for developing and optimizing pectin-based applications in various industries.

Polysaccharide-coated quercetin-loaded nanoliposomes mitigate bitterness: A comparison of carrageenan, pectin, and trehalose.

The intense bitterness of quercetin poses a challenge to its utilization in the food industry. To address this issue, three anionic polysaccharides (carrageenan, pectin, and trehalose) were individually incorporated to fabricate polysaccharide-coated liposome nanocarriers. Electronic tongue analysis revealed a significant decreasing bitterness value (10.34 ± 0.07 mV, sensory score 1.8 ± 0.2, taste weak bitter) in quercetin-loaded nanoliposomes, compared with the bitterness value of quercetin aqueous solution (14 ± 0.01 mV, sensory score 7.3 ± 0.3, taste strong bitter). Furthermore, the polysaccharide-coated nanoliposomes exhibited an even greater capacity to mask the bitterness of quercetin, with carrageenan coated nanoliposomes demonstrating the most pronounced effect. The superior bitter masking ability of carrageenan coated nanoliposomes can be attributed to its high charge and viscosity. In sensory evaluations, gummy incorporated with carrageenan-coated nanoliposomes received the highest ratings, exhibiting enhanced overall palatability and antioxidant activity. This study offers insights into expanding the use of bitter nutrients in food applications and paves the way for more appealing and healthful food products.

Construction of metal-organic framework/cellulose nanofibers-based hybrid membranes and their ion transport property for efficient osmotic energy conversion.

The development of advanced nanofluidic membranes with better ion selectivity, efficient energy conversion and high output power density remains challenging. Herein, we prepared nanofluidic hybrid membranes based on TEMPO oxidized cellulose nanofibers (T-CNF) and manganese-based metal organic framework (MOF) using a simple in situ synthesis method. Incorporated T-CNF endows the MOF/T-CNF hybrid membrane with a high cation selectivity up to 0.93. Nanoporous MOF in three-dimensional interconnected nanochannels provides massive ion transport pathways. High transmembrane ion flux and low ion permeation energy barrier are correlated with a superior energy conversion efficiency (36 %) in MOF/T-CNF hybrid membrane. When operating under 50-fold salinity gradient by mixing simulated seawater and river water, the MOF/T-CNF hybrid membrane achieves a maximum power density value of 1.87 W m-2. About 5-fold increase in output power density was achieved compared to pure T-CNF membrane. The integration of natural nanofibers with high charge density and nanoporous MOF materials is demonstrated an effective and novel strategy for the enhancement of output power density of nanofluidic membranes, showing the great potential of MOF/T-CNF hybrid membranes as efficient nanofluidic osmotic energy generators.

Recent Advances in Functional Cellulose-based Films with Antimicrobial and Antioxidant Properties for Food Packaging.

The packaging of food plays a crucial role in food preservation worldwide. However, traditional packaging systems are passive layers with weak efficiency in protecting the food quality. Therefore, packaged foods are gradually spoiled due to the oxidation and growth of microorganisms. Additionally, most of the commercial packaging films are made of petroleum-based materials which raise environmental concerns. Accordingly, the development of eco-friendly natural-derived active packaging systems has increased the attention of scientists. Cellulose as the most abundant polysaccharide on earth with high biocompatibility, no toxicity, and high biodegradability has extensively been applied for the fabrication of packaging films. However, neat cellulose-based films lack antioxidant and antimicrobial activities. Therefore, neat cellulose-based films are passive films with weak food preservation performance. Active films have been developed by incorporating antioxidants and antimicrobial agents into the films. In this review, we have explored the latest research on the fabrication of antimicrobial/antioxidant cellulose-based active packaging films by incorporating natural extracts, natural polyphenols, nanoparticles, and microparticles into the cellulose-based film formulations. We categorized these types of packaging films into two main groups: (i) blend films which are obtained by mixing solutions of cellulose with other soluble antimicrobial/antioxidant agents such as natural extracts and polyphenols; and (ii) composite films which are fabricated by dispersing antimicrobial/antioxidant nano- or microfillers into the cellulose solution. The effect of these additives on the antioxidant and antimicrobial properties of the films has been explained. Additionally, the changes in the other properties of the films such as hydrophilicity, water evaporation rate, and mechanical properties have also been briefly addressed.

Engineered cellulose nanofibers membranes with oppositely charge characteristics for high-performance salinity gradient power generation by reverse electrodialysis.

Reverse electrodialysis (RED) using nanofluidic ion-selective membrane may convert the salinity difference between seawater and river water into electricity. However, heterogeneous modification reactions of cellulose commonly leads to the inhomogeneous distribution of surface charges, thereby hampering the improvement of cellulose-based nanofluidic membranes for energy conversion. Herein, RED devices based on cellulose nanofibers (CNF) membranes with opposite charge characteristics were developed for the generation of salinity gradient power. Anion-CNF membrane (A-CNF) with varying negative charge densities was synthesized using 2,2,6,6-Tetramethylpiperidine 1-oxy radical (TEMPO) oxidation modification, whereas cation-CNF membrane (C-CNF) was prepared through etherification. By mixing artificial seawater and river water, the output power density of CNF RED device is up to 2.87 W m-2. The output voltage of 30 RED units connected in series may reach up to 3.11 V, which can be used to directly power tiny electronic devices viz. LED lamp, calculator, etc. The results of this work provide a feasible possibility for widespread application of ion exchange membranes for salinity gradient energy harvesting.

Polysaccharide-based nanoassemblies: From synthesis methodologies and industrial applications to future prospects.

Polysaccharides, due to their remarkable features, have gained significant prominence in the sustainable production of nanoparticles (NPs). High market demand and minimal production cost, compared to the chemically synthesised NPs, demonstrate a drive towards polysaccharide-based nanoparticles (PSNPs) benign to environment. Various approaches are used for the synthesis of PSNPs including cross-linking, polyelectrolyte complexation, and self-assembly. PSNPs have the potential to replace a wide diversity of chemical-based agents within the food, health, medical and pharmacy sectors. Nevertheless, the considerable challenges associated with optimising the characteristics of PSNPs to meet specific targeting applications are of utmost importance. This review provides a detailed compilation of recent accomplishments in the synthesis of PSNPs, the fundamental principles and critical factors that govern their rational fabrication, as well as various characterisation techniques. Noteworthy, the multiple use of PSNPs in different disciplines such as biomedical, cosmetics agrochemicals, energy storage, water detoxification, and food-related realms, is accounted in detail. Insights into the toxicological impacts of the PSNPs and their possible risks to human health are addressed, and efforts made in terms of PSNPs development and optimising strategies that allow for enhanced delivery are highlighted. Finally, limitations, potential drawbacks, market diffusion, economic viability and future possibilities for PSNPs to achieve widespread commercial use are also discussed.

Morphology-induced differences in adsorption behaviors and strength enhancement performance for fiber networks between quaternized amylose and amylopectin.

Cationic starch is the most widely used paper strength additive for papermaking wet end applications. However, it remains unclear how differently quaternized amylose (QAM) and amylopectin (QAP) are adsorbed on the fiber surface and their relative contribution to the inter-fiber bonding of papers. Herein, separated amylose and amylopectin were quaternized with different degrees of substitution (DS). After that, the adsorption behaviors of QAM and QAP on the fiber surface, the viscoelastic properties of the adlayers and their strength enhancement to fiber networks were comparatively characterized. Based on the results, the morphology visualizations of the starch structure displayed a strong impact on the adsorbed structural distributions of QAM and QAP. QAM adlayer with a helical linear or slightly branched structure was thin and rigid, while the QAP adlayer with a highly branched structure was thick and soft. In addition, the DS, pH and ionic strength had some impacts on the adsorption layer as well. Regarding the paper strength enhancement, the DS of QAM correlated positively to the paper strength, whereas the DS of QAP correlated inversely. The results provide a deep understanding of the impacts of starch morphology on performance and offer us some practical guidelines in starch selection.

Bitterness-masking assessment of luteolin encapsulated in whey protein isolate-coated liposomes.

An unacceptable bitter taste limits the application of luteolin in healthier food systems. In this study, a bitterness-masking assessment was performed on whey protein isolate-coated liposomes loaded with luteolin (WPI-coated liposomes) using an electronic tongue and human sensory test. The physical properties of the WPI-coated colloidal nanocarrier were characterized by zeta potential, average diameter, distribution, and morphology analyses. The results indicated that WPI-coated nanocarrier systems exhibited a uniformly dispersed distribution and spherical morphology. After the comparison of the bitterness value, the bitterness-reducing effect of 5% WPI-coated liposomes was the most significant and reduced the bitterness of luteolin by 75%. Raman spectroscopy and X-ray diffraction analysis demonstrated that the decoration of WPI on the liposomes reduced the free motion of lipid molecules. This promoted the ordering at the polar headgroup area and hydrophobic core of the lipid bilayer, which explained why luteolin-loaded liposomes (uncoated liposomes) and WPI-coated liposomes could reduce the bitterness of luteolin from the perspective of bitter molecular groups. Combined with the Raman spectral data, the bilayer rigidity of 5% WPI-coated liposomes was positively responsive to the stabilization of uncoated liposomes against storage and resistance ability against surfactants. It was proven that the emergence of the surface modification of the WPI coating enhanced the stability of uncoated liposomes. These results may contribute to the use of WPI-coated liposomes as prospective candidates for effective delivery of the bioactive bitter substance in nutraceuticals and functional foods.

Effects of the Structure and Molecular Weight of Alkali-Oxygen Lignin Isolated from Rice Straw on the Growth of Maize Seedlings.

The abundant and low-cost features of lignin in combination with its natural activities make it a fascinating biopolymer for valorization, especially, in agriculture as an active plant growth regulator. However, the structure-activity relationship of lignin in regulating plant growth and metabolism remains unclear. In this work, rice-straw-based low-molecular-weight (LWM, 1860 Da) and high-molecular-weight (HMW, 6840 Da) alkali-oxygen lignins are structurally and comparatively investigated to understand their effects on the growth and metabolism of maize seedlings. The results indicate that LMW lignin at 150 mg·L-1 displays early growth stimulation in maize. Under the optimal concentration of LMW lignin (25 mg·L-1), the growth of maize shoot is ∼83% higher than that of the control one. Furthermore, LMW lignin also has a positive effect on the upregulation of photosynthetic pigment, carbohydrate, and protein synthesis. In contrast, HMW lignin shows an overall inhibitory effect on the above-mentioned biochemical parameters. Based on the structural characterization, LMW lignin contains a higher syringyl/guaiacyl ratio (0.78) and carboxyl content (1.64 mmol·g-1) than HMW lignin (0.43 and 1.27 mmol·g-1, respectively), which demonstrates that methoxyl and carboxyl content of lignin may play a decisive role in seedling growth.

Enhanced osmotic energy conversion through bacterial cellulose based double-network hydrogel with 3D interconnected nanochannels.

Hydrogel with 3D networks have shown great potential for ion transportation and energy conversion. However, the micron size pores of hydrogel greatly limit the ion selectivity and energy conversion performance. Here, we report a bacterial cellulose (BC) derived hydrogel membrane with double-network (DN) and tailored ion transport channels by rationally filling acrylic acid (AAc)-co-acrylamide (AAm)-co-methyl methacrylate (MMA) polymers into BC hydrogel micropores. Fabricated AAM/BC DN hydrogel membrane displays a unique hierarchical interconnected porous structure and 3D cation transport channels. From the results, the maximum power density reached up to 7.63 W·m-2 at 50-fold salinity gradient under alkaline conditions (pH 11). Interestingly, the power density of 45.5 W·m-2 was achieved through acid-base neutralization reaction. Furthermore, hydrogel successfully obtained a power density of 28.4 W·m-2 from a mixed system of paper black liquor wastewater/seawater. The results of this investigation suggested the enormous potential of BC-based nanofluidic membrane in sustainable osmotic energy conversion.

Design of metallic phase WS2/cellulose nanofibers composite membranes for light-boosted osmotic energy conversion.

Osmotic energy reserves in estuaries, coupled with the ubiquitous solar energy, could be harnessed through emerging nanofluidic membranes to reduce the energy crisis. Herein, we mixed WS2 with high concentration of metal phase and cellulose nanofiber (CNF) to fabricate composite membranes by vacuum filtration. Incorporated CNF as space charge donors increases the ion flux through the enlarged interlayer spacing in the WS2/CNF composite membrane. By simulating seawater and river water, the power density of the composite membrane reached to 1.99 W m-2. Furthermore, due to the photoelectric characteristics of WS2, the composite membrane exhibits photoresponsivity, which generated a photocurrent of 177 nA through illumination. Taking the advantage of the optoelectronic properties of the composite membrane, the power density under illumination is twice than that of the dark state. Based on the results, this material design strategy can enhance the ion transport in nanofluidic membranes for efficient generation of clean energy.

Ion transport property, structural features, and applications of cellulose-based nanofluidic platforms - A review.

Mimicking the cellular machineries-based ion transport phenomenon for multipurpose applications of the nanofluidic devices has inspired scientific community. Owing to this phenomenon, various artificial nanofluidic systems are highly desirable for energy-environment associated fields including energy storage and conversion, biosensing, and desalination of seawater. Nevertheless, high cost and low efficiency hamper the development of nanofluidic devices in the respective fields. Pertinently, cellulose-based nanofluidic devices rectified the ionic transport property and offer an efficient and sustainable platform for harvesting osmotic energy. Recently, the design strategies of cellulose-based nanofluidic materials provided a more targeted material design for specific applications. Herein, we briefly introduce the structural aspects of cellulose, review the structural features and ion transport properties of cellulose-based nanofluidic materials, and highlight their applications as osmotic energy generators, sensors, transistors, flexible electronic skins, and bio-detection devices. In summary, the challenges and future perspectives of cellulose-based nanofluidic materials are described.

Increased ion transport and high-efficient osmotic energy conversion through aqueous stable graphitic carbon nitride/cellulose nanofiber composite membrane.

Increased attention has evoked on the utilization of renewable energy, particularly osmotic power as a potential solution to the energy crisis and environmental pollution. Herein, we fabricate graphitic carbon nitride (g-C3N4)/cellulose nanofiber (CNF) composite membranes with tailored lamellar nanochannels for capturing osmotic energy from salinity gradients. Composite membranes exhibiting charge-governed ion conductivity were prepared via co-homogenization of g-C3N4 with CNF and vacuum filtration. Ion conductivity was efficiently modulated by fine-tuning the charge density through controlling the weight content of CNF in the composite membranes. Higher ion conductivity of 0.014 S cm-1 at low concentrations (<10-2 M KCl) was achieved due to the increased charge density of the lamellar nanochannels and the excellent aqueous stability of the membranes. We demonstrate the potential of the composite membranes in nanofluidic osmotic energy conversion, displaying thermo-enhanced power output performance. This work could inspire new designs of cellulose-based nanofluidic devices for improved osmotic energy conversion.

Mixed pretreatment based on pectinase and cellulase accelerates the oil droplet coalescence and oil yield from olive paste.

Commercial enzymatic pretreatment is being classically used for enhancing the oil extraction yield in the olive oil industry in China. Nevertheless, the mechanism is not yet clearly defined. The aim was to study the action of pectinase and cellulase for improving the oil yield from the aspects of oil droplets coalescence and rheological properties changes of olive paste during malaxation process. From confocal laser scanning microscopy imaging, the bound oil droplets were released and gradually coalesced into larger droplets, eventually formed a continuous oil phase with enzymatic pretreatment. Furthermore, the mixed enzymatic pretreatment effectively decreased viscosity of the olive pastes and promoted the depolymerization and solubilization of pectic polymers involved in the cell-cell adhesion, thus further enhanced the oil extraction yield from 7.15 % to 11.68 % (w/w). Finally, the mixed enzymatic pretreatment improved the droplet release and coalescence, reduced the viscosity of olive paste, and increased the oil yield.

Current understanding and optimization strategies for efficient lignin-enzyme interaction: A review.

From energy perspective, with abundant polysaccharides (45-85%), the renewable lignocellulosic is recognized as the 2nd generation feedstock for bioethanol and bio-based products production. Enzymatic hydrolysis is a critical pathway to yield fermentable monosaccharides from pretreated substrates of lignocellulose. Nevertheless, the lignin presence in lignocellulosic substrates leads to the low substrate enzymatic digestibility ascribed to the nonproductive adsorption. It has been reported that the water-soluble lignin (low molecular weight, sulfonated/sulfomethylated and graft polymer) enhance the rate of enzymatic digestibility, however, the catalytic mechanism of lignin-enzyme interaction remains elusive. In this review, optimization strategies for enzymatic hydrolysis based on the lignin structural modification, enzyme engineering, and different additives are critically reviewed. Lignin-enzyme interaction mechanism is also discussed (lignin and various cellulases). In addition, the mathematical models and simulation of lignin, cellulose and enzyme aims for promoting an integrated biomass-conversion process for sustainable production of value-added biofuels.

Ultrasound-assisted alkaline proteinase extraction enhances the yield of pecan protein and modifies its functional properties.

To enhance the extraction yield of pecan protein and modify its functional properties, this study investigated whether both ultrasound and enzyme have a synergistic impact on the extraction of pecan (Carya illinoinensis (Wangenh.) K. Koch) protein. The highest protein extraction rate (25.51%) was obtained under the conditions of 1415.43 W.cm-2, 15 min, pH 10.0, 50 °C, and 1% (w/w) alkaline proteinase. Owing to its high shear, mechanical energy and cavitation, the ultrasound process increased the solubility of the substrate making it readily accessible to the enzyme, thereby accelerating the chemical reaction and improving the yield of the protein. The optimized ultrasound-assisted enzymatic method (400 W, 20 kHz, 5 s/3s) effectively changed the secondary and tertiary structure of the pecan protein. The results of surface hydrophobicity, intrinsic fluorescence spectra, sulfhydryl content and scanning electron microscopy all indicated the unfolding of protein and exposure of hydrophobic groups and sulfhydryl groups. Moreover, the protein obtained by this method showed higher solubility (70.77%), higher emulsifying activity (120.56 m2/g), smaller particle size (326.7 nm), and better dispersion (0.305) than single ultrasound and non-ultrasound methods (p < 0.05). To conclude, ultrasound-assisted enzymatic method could be an appropriate technique to improve the yield and quality of the pecan protein. The study also provides a theoretical basis for the application of pecan protein in food processing.

Fabrication of pickering high internal phase emulsions stabilized by pecan protein/xanthan gum for enhanced stability and bioaccessibility of quercetin.

The stabilizing effect of pecan protein (PP)/xanthan gum (XG) complex on the Pickering high internal phase emulsion (HIPE) has been examined in this study. Shear viscosity of HIPEs increased with respect to XG concentration due to the formation of hydrogen bonds between PP and XG. Confocal laser scanning microscopy (CLSM) imaging showed fairly even distribution and polygonal shapes of oil droplets (30-70 µm). When used to encapsulate quercetin, this Pickering HIPE exhibited high retention rate and improved gel strength. Furthermore, the interface film of PP/XG on oil-water interface contributed to the high retention of quercetin in Pickering HIPEs when exposure to heat, iron ions, and hydrogen peroxide in aqueous phase. The bioaccessibility of quercetin after in vitro simulated digestion were also improved by HIPE encapsulation than that in oil. To conclude, PP/XG complex stabilized HIPEs may be suitable delivery systems for improving colloidal stability and bioaccessibility of hydrophobic bioactives.

Chemical physics of whey protein isolate in the presence of mucin: From macromolecular interactions to functionality.

Oral processing, textural perception and functionality of colloidal foods are strongly influenced by the interactions between the salivary mucins and the food proteins. This work studies the physico-chemical aspects of mixtures of a typical food protein, whey protein isolate (WPI) and mucin. Phase separations result from aggregation between the two components at pH 7 and at pH 3. ζ-potential and fluorimetry data show that electrostatics contribute to entropically-driven interactions at pH 3, while at pH 7, two different non-electrostatic interactions, an entropically-driven and an enthalpically-driven one lead to aggregation and phase separation. Substitution of WPI with increasing mucin concentrations at pH 7 results in a marked increase of the shear viscosity in comparison with pH 3. Mucin enhances the extensional viscosity in a similar fashion, e.g. the incorporation of mucin into a WPI system at 6:4 ratio increases the extensional viscosity ≥ 3-fold (0.27-0.85 Pa s) and ≥2-fold (0.38-0.89 Pa s) at pH 3 and pH 7, respectively. These results indicate a notable increase of the extensional over shear viscosity ratio (Trouton's ratio). The above highlight the effect of the molecular-level interactions between food and salivary macromolecules on phase behavior and flow during oral processing.

Shear and extensional rheological characterisation of mucin solutions.

The objective of this work is to obtain a concise image of mucin's assembly, structure and mechanics in saliva imitating buffer, in comparison to low ionic strength solutions. The systems show shear and extensional thinning, coupled with very high Trouton ratios, that is an extensional viscosity dominated mucin flow. Low-shear oscillation shows weak gels forming at low ionic strengths, while viscous systems form at high ionic strength saliva imitating buffer. Nanoparticle tracking results suggest that ionic environment affects the self-assembly of mucin. Extensional elasticities are within the size order of the shear ones; while extensional elastic moduli are smaller to the shear ones. Relaxation times and surface tensions are concentration-dependent, suggesting the build-up of aggregated structures with the addition of new material. The above conclude to the existence of finely-tuned, weak structure-spanning mucin networks in saliva imitating buffer, reminiscent to the ones proposed for the bulk self-assembly of mucus.

Fabrication and characterization of novel semolina-based antimicrobial films derived from the combination of ZnO nanorods and nanokaolin.

This study aimed to provide novel biopolymer-based antimicrobial films as food packaging that may assist in reducing environmental pollution caused by the accumulation of synthetic food packaging. The blend of ZnO nanorods (ZnO-nr) and nanokaolin in different ratios (1:4, 2:3, 3:2 and 4:1) was incorporated into semolina, and nanocomposite films were prepared using solvent casting. The resulting films were characterized through field-emission scanning electron microscopy and X-ray diffraction. The mechanical, optical, physical, and antimicrobial properties of the films were also analyzed. The water vapor permeability of the films decreased with increasing ZnO-nr percentage, but their tensile strength and modulus of elasticity increased with increasing nanokaolin percentage. The UV transmittance of the semolina films were greatly influenced by an increase in the amount of ZnO-nr. The addition of ZnO-nr: nanokaolin at all ratios (except 1:4) into semolina reduced UV transmission to almost 0%. Furthermore, the ZnO-nr/nanokaolin/semolina films exhibited a strong antimicrobial activity against Staphylococcus aureus. These properties suggest that the combination of ZnO-nr and nanokaolin are potential fillers in semolina-based films to be used as active packaging for food and pharmaceuticals.