Lignocellulose nanocrystals from pineapple peel: Preparation, characterization and application as efficient Pickering emulsion stabilizers

Fabrication of sustainable and multifunctional gelatin/dialdehyde pectin composite film incorporating lignin-containing nanocellulose stabilized Pickering emulsion for active food packaging

In response to growing concerns over plastic pollution and food safety, this study aims to develop functional and biodegradable packaging materials from food processing by-products. We prepared eco-friendly active packaging films by integrating pomelo peel essential oils (PEOs)-loaded lignin-containing nanocellulose-stabilized Pickering emulsion (PEOs-PE) into a matrix of fish scale gelatin (FSG) and pomelo peel dialdehyde pectin (DAP). The addition of 30 wt% PEOs-PE significantly improved the mechanical performance of the FSG/DAP composite film, evidenced by a 55.61 % increase in tensile strength (TS) and a 4.09-fold increase in elongation at break (EB). Concurrently, it reduced water solubility, water vapor, and oxygen permeability, while improving thermal stability. At a PEOs-PE content of 40 wt%, the antibacterial activities of the FSG/DAP/PEOs-PE film against S. aureus and E. coli reached 96.59 % and 90.18 %, respectively, while the scavenging rates against DPPH and ABTS radicals were 84.11 % and 94.45 %, respectively. Moreover, the composite film exhibited sustained release of PEOs into food simulants, along with biodegradability and biosafety. Additionally, the FSG/DAP/PEOs-PE composite film effectively safeguarded strawberries against microbial contamination, prolonging their shelf-life to 7 days at ambient temperature. This study offers a promising and sustainable strategy for the development of active food packaging materials.

Chitosan-assisted dilute acid pretreatment with enhanced prehydrolysate fermentability and enzyme digestibility of pretreated substrates

Primary challenges in enhancing the dilute acid pretreatment of biomass include improving enzyme digestibility of pretreated substrates and efficiently utilizing sugars in the prehydrolysate. This study provides novel evidence indicating that incorporating chitosan as an in situ modifier in the dilute acid pretreatment of poplar notably enhances the fermentability of initially unfermentable prehydrolysate and increases the enzymatic hydrolysis yield of pretreated substrates by 26.83 %. Eliminating 54 % of major carbonyl inhibitors from the prehydrolysate through the application of chitosan enabled S. cerevisiae to produce 8.62 g/L of ethanol from 18.93 g/L of glucose within 24 h. Furthermore, increased cellulose accessibility, coupled with reduced lignin condensation facilitated by chitosan during pretreatment, likely contributed to the enhanced digestibility of the substrates. This innovative enhancement of dilute acid pretreatment, involving the direct incorporation of 4 % (w/w) chitosan, offers a cost-effective strategy to simultaneously address the challenges posed by fermentation inhibitors and the limited enzyme digestibility associated with dilute acid pretreatment across various pretreatment severities.

Influence of different pulping processes, cold caustic extraction, and bleaching as common post-treatments on properties of produced lignocellulose nanocrystals (LCNCs) from bagasse

The influence of different pulping processes-soda, monoethanolamine, and Formacell-along with cold caustic extraction (CCE) and a bleaching sequence (DEpD) as post-treatments on the properties of lignocellulosic nanocrystals (LCNCs) was evaluated. LCNCs were produced through acid hydrolysis from the pulps. SEM and AFM analyses confirmed the successful production of LCNCs with dimensions under 100 nm. FT-IR analysis indicated the presence of lignin in the nanocrystals. X-ray diffraction demonstrated that acid hydrolysis and CCE significantly impacted the crystallinity of the LCNCs; however, the bleaching effect was minimal. Thermal analysis revealed that LCNCs derived from post-treated pulps exhibited greater thermal stability than those from untreated pulps. LCNCs were utilized to create films using the solution-casting method. The produced films from various pulps and post-treatments displayed excellent and diverse mechanical and aesthetic properties. The results indicated that the pulping processes, post-treatments, and chemical composition of the pulps influenced the characteristics of both LCNCs and LCNC films. The findings suggest that CCE can be a cost-effective and eco-friendly alternative to bleaching in the production of LCNCs. Furthermore, an increase in lignin content within the pulps was found to reduce the efficiency of acid hydrolysis and crystallinity while increasing the dimensions of the LCNCs.

Corn Stover-derived nanocellulose and lignin-modified particles: Pickering emulsion stabilizers and potential quercetin sustained-release carriers

Pickering emulsions (PEs) have wide applications in delivering nutraceuticals. However, the impact of extracting nanocellulose from corn stover on stabilizing PEs and delivering nutraceuticals remains unclear. In this study, four types of nanocellulose, cellulose nanocrystals (CNC), cellulose nanofibers (CNF), lignin-containing cellulose nanocrystals (LCNC), and lignin-containing cellulose nanofibers (LCNF) were successfully prepared from corn stover, an agricultural waste. Among them, LCNC and LCNF exhibited stable reticulated microstructures, lower crystallinity, and excellent thermal stability. Besides, lignin enhanced the nanoparticles' hydrophobicity, promoting the formation of more ideally amphiphilic particles, resulting in denser emulsions at the oil-water interface. Furthermore, emulsions stabilized by LCNC and LCNF demonstrated remarkable resistance to quercetin degradation under UV light exposure (with residual level exceeding 90 %) and improved quercetin's bioaccessibility during the in vitro digestion tests, achieving the highest bioaccessibility of 48.3 %. This study provided an innovative perspective on utilizing stover-derived materials for stabilizing PEs and delivering lipophilic nutrients.

Sulfonated cellulose nanocrystalline- and pea protein isolate-mixture stabilizes the citral nanoemulsion to maintain its functional activity for effectively preserving fruits

The instability of citral greatly limits its application in food field. This study aimed to develop a safe and green emulsifier-stabilized nanoemulsion (NE) to encapsulate citral for exerting its activities. A series of NEs were prepared using varying proportions (1:2 and 1:3) of sulfonated cellulose nanocrystalline- (CNC-C) and pea protein isolate- (PPI) mixture as emulsifier to encapsulate citral with different content (1 %, 2 %, and 3 %), and their stability, antioxidant and antibacterial activities were evaluated to identify the optimal system. When CNC-C and PPI proportion was 1:3 and citral content was 2 % (CC1-P3-C2), the obtained CC1-P3-C2 incorporated into pectin achieved the excellent preservation effect on kiwifruits and blueberries. It was attributed to the stability and functional activities of CC1-P3-C2. On the one hand, after storage (25 d) or at pH 11 or 100 mM NaCl, its size and polydispersity index were still within acceptance level (<300 nm and 0.3). On the other hand, it showed good antioxidant and antibacterial activities against Escherichia coli, Staphylococcus aureus, Botrytis cinerea, and Botryosphaeria dothidea, which was due to its high encapsulation efficiency (96.78 %). Therefore, CC1-P3-C2 showed a great application potential in fruit preservation, which also provided a feasible strategy to design stable citral NEs.

Lignin-containing cellulose nanocrystals from maple leaves: A natural Pickering emulsion stabilizer for food preservation

Cellulose nanocrystals have been obtained from maple leaves for stabilizing Pickering emulsions, but a chemical modification is required to improve hydrophobicity and the yield is relatively low due to the removal of non-cellulose components. Herein, lignin was retained while isolating cellulose from maple leaves, and the prepared lignin-containing cellulose nanocrystals (LCNCs) were applied as natural Pickering emulsion stabilizers. Rod-like shaped LCNCs with tunable lignin contents had suitable hydrophobicity and high aspect ratios, resulting in long-term stability of LCNC-stabilized Pickering emulsions. The obtained emulsions provided good encapsulation and protection of cinnamaldehyde, and the controlled release of cinnamaldehyde promoted sustained antibacterial efficacy. Both direct-contact and non-contact preservation modes were investigated for shrimp preservation, where headspace release of cinnamaldehyde from emulsions at non-contact mode was more effective in inhibiting bacterial proliferation compared to direct-contact (spray-coating) mode. This work demonstrates the feasibility of developing value-added LCNCs from maple leaves as sustainable Pickering emulsion stabilizers.

Recent advance on lignin-containing nanocelluloses: The key role of lignin

Nanocelluloses (NCs) isolated from lignocellulosic resources usually require harsh chemical pretreatments to remove lignin, which face constraints such as high energy consumption and inefficient resource utilization. An alternative strategy involving the partial retention of lignin can be adopted to endow NCs with better versatility and functionality. The resulting lignin-containing nanocelluloses (LNCs) generally possess better mechanical property, thermal stability, barrier property, antioxidant activity, and surface hydrophobicity than lignin-free NCs, which have attracted extensive interest as a promising green nanomaterial for numerous applications. This review provides a comprehensive overview of the recent advances in the preparation, properties, and food application of LNCs. The effect of residual lignin on the preparation and properties of LNCs is discussed. Furthermore, the key roles of lignin in the properties of LNCs, including particle size, crystalline structure, dispersibility, thermal, mechanical, antibacterial, rheological and adhesion properties, are summarized comprehensively. Furthermore, capitalizing on their dietary fiber and nanostructure properties, the food applications of LNCs in the forms of films, gels and emulsions are also discussed. Finally, the challenges and opportunities regarding the development of LNCs are provided.

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.

In Vitro Gastrointestinal Digestion of Corn-Oil-in-Water Pickering Emulsions: Influence of Lignin-Containing Cellulose Nanofibrils Loading

There is a growing trend in incorporating biomass-based engineered nanomaterials into food products to enhance their quality and functionality. The zeta potential, droplet size, microstructure, and content of free fatty acid (FFA) release were determined to investigate the influence of a plant-derived particle stabilizer, i.e., lignin-containing cellulose nanofibrils (LCNFs). Remarkable differences were observed during digestion stages, which were found to be correlated with the concentrations of LCNFs. The gradual FFA release in the small intestine stage from LCNF-coated lipid droplets was monitored over time, with a final lowest release of FFAs amounting to 26.3% in the emulsion containing 20.0% (v/v) of the dispersed phase stabilized by 3 mg/mL of LCNFs. This release can be attributed to the physical barrier at lipid droplet surfaces and the network effect created by the free LCNFs in the continuous phase. This work provides a foundation for the potential application of nature-derived LCNF materials in reducing fat absorbance.

Capsicum leaf protein-based bionanocomposite films for packaging application: Effect of corn starch content on film properties

The addition of corn starch (CS) enhances the interfacial adhesion of the film-forming liquids (FFLs), weakening the internal relative molecular motion. As a result, the rheological properties and zeta potential values of the FFLs were affected. A tight spatial network structure between capsicum leaf protein (CLP), lignocellulose nanocrystals (LNCs) and CS can be formed through intermolecular entanglement and hydrogen bonding interactions. The crystallinity, thermal degradation temperature, tensile strength and water contact angle of the protein-based bionanocomposite films (PBBFs) increased with increasing CS addition. This is due to the transformation of the secondary space structure of the CLP inside the PBBFs and the increase in cohesion. However, the excessive addition of CS forms aggregated clusters on the surface of PBBFs, which increases the surface roughness of PBBFs and causes more light scattering. Therefore, the brightness and yellowness values of the PBBFs increase, and the transmittance decreases.

Recent progress on Pickering emulsion stabilized essential oil added biopolymer-based film for food packaging applications: A review

Nowadays food safety and protection are a growing concern for food producers and food industry. The stability of food-grade materials is key in food processing and shelf life. Pickering emulsions (PEs) have gained significant attention in food regimes owing to their stability enhancement of food specimens. PE can be developed by high and low-energy methods. The use of PE in the food sector is completely safe as it uses solid biodegradable particles to stabilize the oil in water and it also acts as an excellent carrier of essential oils (EOs). EOs are useful functional ingredients, the inclusion of EOs in the packaging film or coating formulation significantly helps in the improvement of the shelf life of the packed food item. The highly volatile nature, limited solubility and ease of oxidation in light of EOs restricts their direct use in packaging. In this context, the use of PEs of EOs is suitable to overcome most of the challenges, Therefore, recently there have been many papers published on PEs of EOs including active packaging film and coatings and the obtained results are promising. The current review amalgamates these studies to inform about the chemistry of PEs followed by types of stabilizers, factors affecting the stability and different high and low-energy manufacturing methods. Finally, the review summarizes the recent advancement in PEs-added packaging film and their application in the enhancement of shelf life of food.

Preparation and properties of films loaded with cellulose nanocrystals stabilized Thymus vulgaris essential oil Pickering emulsion based on modified tapioca starch/polyvinyl alcohol

Pickering emulsions were prepared by stabilizing thymus vulgaris essential oil (TEVO) with cellulose nanocrystals (CNCs), which formed composite films by loading the emulsions into modified tapioca/polyvinyl alcohol (PVA)-based films. The results showed that the 1.0 % CNCs-15 % TEVO emulsion had optimal stability and smaller particle size. The emulsion increased the thickness of the composite film in the form of solid material additions (thickness, 0.062-0.099 mm), which opacity given the laminating film's superior UV-blocking ability compared to blank film. The emulsion plasticizing effect enhanced the film's elongation at break (EAB, 123-159 %). In addition, due to the hydrophobicity and influencing the diffusion path of water molecules in the emulsion, the denser microstructure composite film had a lower water vapor transmission coefficient (WVP, 6.22 × 10-11-5.35 × 10-11g∙cm/cm2∙s∙Pa) to impede moisture penetration. Meanwhile, the composite film can effectively maintain the color and inhibit the growth of microorganisms to extend the storage time of fish fillets.

Insight into the effect of different nanocellulose types on protein-based bionanocomposite film properties

This paper investigates the effect of five different types of nanocellulose on the properties of protein-based bionanocomposite films (PBBFs) and the mechanism of action. The results show that TEMPO-oxidized nanocellulose (TNC) PBBFs have the smoothest surface structure. This is because some hydroxyl groups in TNC are converted to carboxyl groups, increasing hydrogen bonding and cross-linking with proteins. Bacterial nanocellulose (BNC) PBBFs have the highest crystallinity. Filamentous BNC can form an interlocking network with protein, promoting effective stress transfer in the PBBFs with maximum tensile strength. The PBBFs of lignin nanocellulose (LNC) have superior elasticity due to the presence of lignin, which gives them the greatest creep properties. The PBBFs of cellulose nanocrystals (CNCs) have the largest water contact angle. This is because the small particle size of CNC can be uniformly distributed in the protein matrix. The different types of nanocellulose differ in their microscopic morphology and the number of hydroxyl groups and hydrogen bonding sites on their surfaces. Therefore, there are differences in the spatial distribution and the degree of intermolecular cross-linking of different types of nanocellulose in the protein matrix. This is the main reason for the differences in the material properties of PBBFs.

Sustainable Pickering Emulsions with Nanocellulose: Innovations and Challenges

The proper mix of nanocellulose to a dispersion of polar and nonpolar liquids creates emulsions stabilized by finely divided solids (instead of tensoactive chemicals) named Pickering emulsions. These mixtures can be engineered to develop new food products with innovative functions, potentially more eco-friendly characteristics, and reduced risks to consumers. Although cellulose-based Pickering emulsion preparation is an exciting approach to creating new food products, there are many legal, technical, environmental, and economic gaps to be filled through research. The diversity of different types of nanocellulose makes it difficult to perform long-term studies on workers' occupational health, cytotoxicity for consumers, and environmental impacts. This review aims to identify some of these gaps and outline potential topics for future research and cooperation. Pickering emulsion research is still concentrated in a few countries, especially developed and emerging countries, with low levels of participation from Asian and African nations. There is a need for the development of scaling-up technologies to allow for the production of kilograms or liters per hour of products. More research is needed on the sustainability and eco-design of products. Finally, countries must approve a regulatory framework that allows for food products with Pickering emulsions to be put on the market.

Stabilization of ginger essential oil Pickering emulsions by pineapple cellulose nanocrystals

Pickering emulsions (PE) are systems made up of two incompatible fluids, these are stabilized by solid organic or inorganic particles located on their interface. Cellulose nanocrystals (CNCs) are sustainable and biocompatible value-added naturally occurring biomolecules which are being investigated as PE stabilizers in the cosmetic, food, and pharmaceutical industries. The objective of this research was to investigate the efficacy of pineapple cellulose nanocrystals as stabilizers for a ginger essential oil-in-water Pickering emulsion. Anionic pineapple cellulose nanocrystals were prepared by acid hydrolysis. Ginger essential oil-in-water emulsions were prepared by ultrasonication. Pineapple CNC produced stable Pickering emulsions with surface average droplet size of 4.3 μm-6.2 μm, high negative zeta potential, high viscosity, and high adsorption at the interface. Pickering emulsions by ultrasonication were stable against droplet coalescence, phase separation, and droplet flocculation for at least 8 weeks at 25 °C or 40 °C at various droplet sizes. The emulsion droplet size and volume density (droplet size distribution) were evaluated by varying the particle concentration (CNC 0.25 g/100 ml or 0.50 g/100 ml) and/or oil fraction (10-20 g/100 ml). At constant oil fraction, the emulsion viscosity increased as the nanocrystal concentration increased. The cellulose nanocrystal-stabilized ginger oil-Pickering emulsions exhibited shear-thinning characteristics of a pseudo-plastic fluid. Pineapple nanocellulose crystal -stabilized ginger oil-Pickering emulsions exhibited high stability with a creaming index of zero. CNC was found to be an effective Pickering stabilizer for oil-in-water emulsions in various food applications.

Chitosan particles modulate the properties of cellulose nanocrystals through interparticle interactions: Effect of concentration

The physical and chemical properties of cellulose nanocrystals (CNC) were regulated by physical crosslinking with chitosan particles (CSp). At a fixed concentration (0.5 wt%) of CNC, varying CSp concentration (0.02-0.5 wt%) influenced the morphologies and chemical properties of the obtained complex particles (CNC-CSp). The results of Fourier transform infrared spectroscopy (FTIR) and zeta potential confirmed the electrostatic and hydrogen bonding interactions between CSp and CNC. At a low CSp concentration (0.02-0.05 wt%), the charge shielding effect induced the formation of particle aggregation networks, thus showing increased viscosity, turbidity and size (153.4-2605.7 nm). At a higher CSp concentration (0.1-0.5 wt%), the hydrogen bonding interaction promoted CSp adsorption onto the surface of CNC, thus facilitating the dispersion of CNC-CSp due to electrostatic repulsion caused by surface-adsorbed CSp. In addition, CSp improved the thermal stability, hydrophobicity (41.87-60.02°) and rheological properties of CNC. Compared with CNC, CNC-CSp displayed a better emulsifying ability and emulsion stability, in which CSp could play a dual role (i.e., charge regulator and stabilizer). This study suggests that introducing CSp can improve the properties and application potentials of CNC as food colloids.

Preparation and Characterization of Porous Materials from Pineapple Peel at Elevated Pyrolysis Temperatures

In this work, pineapple peel (PP) was reused as a precursor in biochar (BC) production at elevated temperatures (i.e., 500−900 °C) for residence times of 0−60 min. The findings showed that pyrolysis temperature and residence time played a vital role in pore development. As pyrolysis temperature increased from 800 to 900 °C for residence times of 20 and 60 min, the data on the Brunauer−Emmett−Teller (BET) surface area of the resulting biochar products significantly jumped from 11.98−32.34 to 119.43−133.40 m2/g. In addition, there was a significant increase in the BET surface area from 1.02 to 133.40 m2/g with the residence time of 0 to 20 min at 900 °C. From the data of the nitrogen adsorption−desorption isotherms and the pore size distribution, both micropores (pore diameters of <2.0 nm) and mesopores (pore diameters of 2.0−50.0 nm) are present in the PP-based biochar products. Due to its good fittings in the pseudo-second-order model and its hydrophilic nature, as seen in the Fourier transform infrared spectroscopy (FTIR), the resulting biochar could be a porous material to be used for the effective removal of cationic compounds (i.e., methylene blue (MB)) from liquid phases.

Lignocellulose Extraction from Sisal Fiber and Its Use in Green Emulsions: A Novel Method

Regenerated lignocellulose nanofibrils (RLCNFs) have recently piqued the interest of researchers due to their widespread availability and ease of extraction. After dewaxing, we treated sisal fiber with alkali, followed by heating and agitation, to obtain RLCNFs, which were then vacuum oven-dried. We used a variety of characterization techniques, including XRD, SEM, and FT-IR, to assess the effects of the alkali treatment on the sisal fiber. Various characterizations demonstrate that lignocellulose fibrils have been successfully regenerated and contaminants have been removed. In addition, employing the RLCNFs as a stabilizer, stable Pickering emulsions were created. The effects of RLCNF concentration in the aqueous phase and water-to-oil volume ratio on stability were studied. The RLCNFs that have been produced show promise as a stabilizer in Pickering emulsions.