Effect of drying pretreatment methods on structural features and antioxidant activities of Brauns native lignin extracted from Chinese quince fruit

Preparation of high antioxidant nanolignin and its application in cosmetics

Lignin, as a natural polyphenol, displays anti-oxidant activity by trapping and binding free radicals through its free phenolic hydroxyl groups. However, the most accessible form, industrial lignins, generally has low phenolic hydroxyl content, which severely limits their application value and scenarios. Herein, we showed that potassium-glycerate deep eutectic solvent (PG-DES) treatment can be combined with laccase oxidation to afford prepared high antioxidant lignin nanoparticles (HA-LNPs) with notably improved anti-oxidant activities benefiting from both the enhanced phenolic hydroxyl content 170.8 % and reduced average particle size (59.0 nm). At concentrations as low as 60 μg/mL, HA-LNPs showed favorable effects in promoting collagen formation. When HA-LNPs were used as an active ingredient in the anti-aging mask formulation, the reactive oxygen species (ROS) scavenging activity of mask samples containing 0.4 % HA-LNPs reached 37.2 %. The data suggest great promise of HA-LNPs as a natural antioxidant for formulating in anti-aging skin care products.

Synergism of jet milling and deep eutectic solvent pretreatment on grapevine lignin fractionation and enhancing enzymatic hydrolysis

Herein, we investigated the synergistic effects of jet milling (JM) and deep eutectic solvent (DES) pretreatment on the fractionation of grapevine lignin and the consequent enhancement of enzymatic hydrolysis. Grapevine, a substantial byproduct of the wine industry, was subjected to JM pretreatment to produce finely powdered particles (median diameter D50 = 98.90), which were then further treated with acidic ChCl-LA and alkaline K2CO3-EG DESs. The results revealed that the combined JM + ChCl-LA pretreatment significantly increased the cellulose preservation under optimal conditions (110 °C, 4 h, and 20 % water content), achieving removal rates of 74.18 % xylan and 66.05 % lignin, respectively. The pretreatment temperature and inhibitor production were reduced, resulting in a remarkable threefold increase in glucose yield compared to untreated samples. Moreover, the structural analysis of the pretreated lignin indicated an enrichment of phenolic units, leading to enhanced antioxidant and antibacterial activities, particularly in the JM pretreated samples. These findings underscore the promising potential of the synergistic JM and DES pretreatment in facilitating the efficient utilization of grapevine lignocellulosic biomass for sustainable biorefinery technologies.

Effect of the Pulsed Electric Field Treatment on Physical, Chemical and Structural Changes of Vacuum Impregnated Apple Tissue in Aloe Vera Juices

Vacuum impregnation (VI) stands as a diffusion-driven food processing method that has found recent application within the food industry, particularly for the cold formulation of fortified food products. Pulsed electric field (PEF) treatment can affect the food structure, influencing therefore the mass transfer phenomena during the further processing. Thus, the study aimed at investigating the effect of PEF treatment on selected physicochemical properties of vacuum-impregnated apples. Apple slices were vacuum impregnated with aloe vera juice solution with or PEF treatment at different intensities (125, 212.5 or 300 V/cm). The PEF was applied as a pretreatment-applied before the VI process as well as posttreatment-applied after the VI process. The VI process with aloe vera juice resulted in a sample weight increase of over 24% as well as structural changes, partial cell viability loss and color alteration. In addition, the decrease of bioactive compounds was observed, while antioxidant activity remained at a similar level as in raw material. PEF treatment adversely affected vacuum impregnation efficiency, causing microstructural changes and cell viability loss. Additionally, chemical composition modifications were evident through thermogravimetric analysis (TGA) and Fourier Infrared Spectroscopy (FTIR) analyses. Tissue hardness decreased significantly due to structural damage and caused high leakage from plant tissue, which resulted in hindering saturation with aloe vera juice during the VI process. Additionally, reduced bioactive substance content after PEF treatment was observed and the VI process did not restore apple samples of the bioactive compounds from aloe vera juice.

Nanogreen is the new future: the conversion of lignin and lignocellulosic wastes into nanomaterials

The lignocellulose biorefinery industry has assumed an important role within the current scenario. Lignin is an abundant and available biopolymer and one of the compounds present in the lignocellulosic waste. Therefore, processing lignin into new materials and nanomaterials, such as nanolignin, has attracted the attention of the scientific community. Lignin nanoparticles are materials that have excellent properties, such as biodegradability and non-toxicity, and have great potential as chelating agents, antimicrobials agents, UV protectors, nanofillers, adsorbents, catalysts, supercapacitors, emulsion stabilizers, delivered systems, drugs, and gene carriers. This review article covers the emergent scenario of nanolignin and the main aspects of scientific interest, such as the conversion and functionalization of lignin, the valorization of lignocellulose waste, and nanoparticle synthesis. A techno-economic evaluation of the biorefinery model of the nanolignin synthesis is presented based on the simulation of the process on the experimental and commercial databases available and reported by some authors. Finally, the techno-economic assessment is complemented by the life cycle assessment of various nanolignin synthesis pathways reported to evaluate the environmental implications and support this emergent technology development.

A review on lignin antioxidants: Their sources, isolations, antioxidant activities and various applications

Lignin, a biopolymer obtained from agricultural/forestry residues or paper pulping wastewater, is rich in aromatic structure, which is central to its adoption as a candidate to natural antioxidants. Through insight into its structural features from biomass, different functional groups would influence lignin antioxidant activity, wherein phenolic content is the most important factor, hence massive studies have focused on its improvement via different pretreatments and post-processing methods. Besides, lignin nanoparticles and chemical modifications are also efficient methods to improve antioxidant activity via increasing free content and decreasing bond dissociation enthalpy of phenolic hydroxyl. Lignin samples exhibit comparable radicals scavenging ability to commercial ones, showing their potential as renewable alternatives of synthesized antioxidants. Besides, their applications have also been discussed, which demonstrates lignin potential as an inexpensive antioxidant additive and consequent improvements on multiple functionalities. This review is dedicated to summarize lignin antioxidants extracted from biomass resources, methods to improve their antioxidant activity and their applications, which is beneficial for realizing lignin valorization.

Effect of Thermal and Non-Thermal Technologies on Kinetics and the Main Quality Parameters of Red Bell Pepper Dried with Convective and Microwave-Convective Methods

The drying process preserves the surplus of perishable food. However, to obtain a good-quality final product, different pretreatments are conducted before drying. Thus, the aim of the study was the evaluation of the effect of thermal (blanching treatments with hot water) and non-thermal technologies (pulsed electric field (PEF) and ultrasound (US)) on the kinetics of the drying process of red bell pepper. The convective and microwave-convective drying were compared based on quality parameters, such as physical (water activity, porosity, rehydration rate, and color) and chemical properties (total phenolic content, total carotenoids content, antioxidant activity, and total sugars content). The results showed that all of the investigated methods reduced drying time. However, the most effective was blanching, followed by PEF and US treatment, regardless of the drying technique. Non-thermal methods allowed for better preservation of bioactive compounds, such as vitamin C in the range of 8.2% to 22.5% or total carotenoid content in the range of 0.4% to 48%, in comparison to untreated dried material. Moreover, PEF-treated red bell peppers exhibited superior antioxidant activity (higher of about 15.2-30.8%) when compared to untreated dried samples, whereas sonication decreased the free radical scavenging potential by ca. 10%. In most cases, the pretreatment influenced the physical properties, such as porosity, color, or rehydration properties. Samples subjected to PEF and US treatment and dried by using a microwave-assisted method exhibited a significantly higher porosity of 2-4 folds in comparison to untreated material; this result was also confirmed by visual inspection of microtomography scans. Among tested methods, blanched samples had the most similar optical properties to untreated materials; however non-thermally treated bell peppers exhibited the highest saturation of the color.

Sequential aqueous acetone fractionation and characterization of Brauns native lignin separated from Chinese quince fruit

Lignin, especially Brauns native lignin (BNL), from Chinese quince (Chaenomeles sinensis) fruit represents a potential source of natural antioxidants. However, the highly inhomogeneous structure and the carbohydrate impurity reduce the antioxidant properties of BNL. Accordingly, a sequential aqueous acetone fractionation was used to prepare pure lignin fractions with homogeneous molecular structures; these fractions showed strong antioxidant properties. Analytical results showed that the yields of F_50% and F_60% exceeded 20% (i.e., 20.6% and 24.1%, respectively). The sugar impurities in BNL were mainly retained in the F_30% and F_40% fractions. For all fractions, molecular weight increased as the acetone concentration increased. The results from 2D HSQC NMR and ³¹P NMR indicated that the number of lignin linkages (β-O-4', β-β' and β-5') and functional groups (S-OH, G-OH, H-OH, and COOH) of these fractions varied with their molecular weights. Antioxidant assays showed that F_40%, F_50% and F_60% had higher antioxidant properties than BNL. Overall, the study provides a simple, environmentally friendly fractionation method to prepare lignin with various structural features and strong antioxidant properties from Chinese quince fruit. These lignin fractions have promising application in some fields with high value, such as antioxidants production, biomaterials, packaging materials, and drug delivery and so on.