Agro-industrial waste valorization is an attractive approach that offers new alternatives to deal with shrinkage and residue problems. One of these approaches is the synthesis of advanced carbon materials. Current research has shown that citrus waste, mainly orange peel, can be a precursor for the synthesis of high-quality carbon materials for chemical adsorption and energy storage applications. A recent approach to the utilization of advanced carbon materials based on lignocellulosic biomass is their use in solar absorber coatings for solar-thermal applications. This study focused on the production of biochar from Citrus aurantium orange peel by a pyrolysis process at different temperatures. Biochars were characterized by SEM, elemental analysis, TGA-DSC, FTIR, DRX, Raman, and XPS spectroscopies. Optical properties such as diffuse reflectance in the UV−VIS−NIR region was also determined. Physical-chemical characterization revealed that the pyrolysis temperature had a negative effect in yield of biochars, whereas biochars with a higher carbon content, aromaticity, thermal stability, and structural order were produced as the temperature increased. Diffuse reflectance measurements revealed that it is possible to reduce the reflectance of the material by controlling its pyrolysis temperature, producing a material with physicochemical and optical properties that could be attractive for use as a pigment in solar absorber coatings.

The properties of biological-chemical chitosan (BCh) films from marine-industrial waste and a non-conventional Ramon starch (RS) (Brosimum alicastrum) were investigated. Blended films of BCh/RS were prepared to a volume ratio of 4:1 and 1:4, named (BChRS-80+q, biological-chemical chitosan 80% v/v and Ramon starch, BChRS-20+q, biological-chemical chitosan 20% v/v and Ramon starch, both with quercetin), Films from commercial chitosan (CCh) and corn starch (CS), alone or blended (CChCS-80+q, commercial chitosan 80% v/v and corn starch, CChCS-20+q commercial chitosan 20% v/v and corn starch, both with quercetin) were also prepared for comparison purposes. Films were investigated for their physicochemical characteristics such as thickness, moisture, swelling, water-vapor permeability, and water solubility. In addition, their mechanical and structural properties were studied using Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric analysis (TGA) and Scanning Electron Microscopy (SEM) techniques. Antioxidant activity was evaluated as radical scavenging, and antimicrobial effect was also determined. The BCh and RS films presented similar tensile strength values compared with commercial biopolymers. Only films with chitosan presented antioxidant and antimicrobial activity. The FTIR spectra confirmed the interactions between functional groups of the biopolymers. Although, BChRS-80+q and BChRS-20+q films exhibited poor mechanical performance compared to their commercial counterparts, they showed good thermal stability, and improved antioxidant and antimicrobial activity in the presence of quercetin. BChRS-80+q and BChRS-20+q films have promising applications due to their biological activity and mechanical properties, based on a novel material that has been underutilized (Ramon starch) that does not compete with materials for human feeding and may be used as a coating for food products.

The objective of this work was the recovery of chitosan by ultrasound-assisted extraction (UAE) from white shrimp (Litopenaeus vannamei) chitin, and the physicochemical and structural characterization of the obtained biopolymer, as well as its antimicrobial effect on Pythium ultimum growth. A 2³ factorial design was used to evaluate chitosan extraction conditions. Instrumental analysis techniques for chitosan characterization and radial growth inhibition, as an antifungal activity test, were performed. The ultrasonically extracted chitosan (UC) reached a yield of 86.96% with 100% solubility, a degree of deacetylation (DDA) >78%, molecular weight (M_W) of 3.928 × 10⁵ g mol⁻¹, and a crystallinity index (Icr) of 87%, calculated through nuclear magnetic resonance (¹H NMR) and Fourier transform infrared spectroscopy (FTIR), size exclusion chromatography (SEC), and X-ray diffraction (XRD), respectively. The inhibitory activity of the chitosan was evaluated against the oomycete Pythium ultimum, observing a 93% radial inhibition over 24 h. UAE proved to be an excellent alternative to the conventional deacetylation, reducing reaction time and obtaining a UC with higher M_W and (Icr) than the commercial one, which could potentiate its applications.

The production and surface modification of cellulose nanocrystals (CNC) fromAgave tequilanaWeber waste (ATW) and their effect on the melt rheology of PLA were investigated. For that, CNC were obtained from ATW residues by acid hydrolysis and grafted with 2-ethyl hexyl acrylate (2-EHA) to promote compatibility with nonpolar polymers, such as PLA. The morphology of CNC occurred as rods, spheres, and the so-called porous network observed by scanning electron microscopy (SEM) and electron transmission microscopy (TEM), and the crystallinity of the cellulose fibers was ~73% and increased up to ~94% for CNC followed by X-ray diffraction (XRD). The acid hydrolysis and alkali extraction process produce changes on the native cellulose type I from ATW bagasse resulting in a mixture of cellulose type I and II and was preserved after CNC isolation and surface grafting. Polymer grafting was assessed using Fourier-transform infrared spectroscopy (FTIR) and X-ray electron spectroscopy (XPS). Upon surface modification, the grafted CNC presented better thermal stability than CNC pristine evaluated by thermogravimetric analysis (TGA), and the surface energy of the CNC was decreased which could promote CNC dispersion within polymers. Both pristine and surface modified CNC were melt mixed with PLA to produce nanocomposites at different concentrations of CNC. Dynamic time sweep tests showed that the introduction of CNC and CNC/2-EHA decreased the complex viscosity of PLA due to polymer degradation during compounding.

Avocado landraces have gained great interest due to their importance in maintaining biodiversity and the presence of bioactive compounds in their fruit, depending on fruit tissues or ripening stages. This study aimed to evaluate the morpho-physicochemical and nutritional components of the peel, pulp, and seed tissues from Lagunero (LA) and Criollo (CA) avocado landraces at different ripening stages. Additionally, phenolic profiles were analyzed by using UPLC-DAD/ESI-MS, and a principal component analysis (PCA) was constructed to determine variations among the determined contents from avocado landraces, fruit tissues, and ripening stages. The CA showed a 30% higher fruit weight and higher percentages of seed (0.52%) and peel (3.62%) weight yields as compared to the LA. Ripening significantly affected the physical characteristics of LA and CA, and a substantial decrease in hardness (83%) after 4 days of storage. In LA, ripening resulted in an increase in fat content in both the peel and pulp. In contrast, CA showed an increase in protein content in the peel and pulp but a decrease in seeds; fat content increased significantly in the pulp of CA and carbohydrates remained the predominant component in all tissues, though they decreased slightly in CA peels during ripening. The ripe LA peel presented approximately 50% more total phenolic compounds than other tissues. The unripe CA peel showed a higher antioxidant capacity according to DPPH (3831.97 µMol Eq Trolox/g dw) and ABTS+ (3674.70 µMol Eq Trolox/g dw) assays. The main phenolic compounds identified in the avocado peel were chlorogenic acid, catechin, quercetin-3-O-hexoside, quercetin-3-O-pentoside, coumaric acid, caffeic acid, neochlorogenic acid, ferulic acid, kaempferol-3-O rhamnoside, and quercetin-3-O-rhamnoside. The PCA analysis revealed a strong correlation between chlorogenic acid and caffeic acid with TPC, while catechin was more closely related to antioxidant activity. These findings suggest that peel and seed tissues of avocado landraces, often considered byproducts, are valuable sources of bioactive compounds with high antioxidant potential.