Maria Jose Cocero

Triglyceride hydrolysis in subcritical and supercritical water was investigated at 25 MPa over 300–400 °C with residence times of 0.4–41 s using coconut oil as feedstock. Two modelling frameworks were compared: a pseudo-homogeneous (PH) consecutive first-order kinetic model and a mass-transfer (MT) model in which water is the sole transferring species, migrating from the aqueous bulk into the oil-rich droplets where hydrolysis occurs. GCA-EOS phase-equilibrium calculations at 25 MPa confirm that the aqueous phase remains essentially pure water while water dissolves progressively into the oil phase with increasing temperature, reaching full miscibility under supercritical conditions. Both formulations reproduced the experimental concentration–time profiles of TG, DG, MG, glycerol and FFA within ±0.004 mol L⁻¹. Effective rate constants ranged from 3.6 × 10⁻⁴ s⁻¹ at 300 °C to ~0.4 s⁻¹ at 400 °C, with Arrhenius activation energies of 190–240 kJ mol⁻¹ for the TG → DG and DG → MG steps and 280–290 kJ mol⁻¹ for MG → G. The volumetric mass-transfer coefficient KLa increased by nearly four orders of magnitude (5.7 × 10⁻⁴ to 9.7 s⁻¹) and the water partition coefficient Kw rose from 0.043 to unity between 300 and 400 °C. At 300 °C the process is mass-transfer-limited; at 350 °C a mixed-control regime emerges; at 380 °C hydrolysis transitions to reaction-controlled behavior. At 400 °C, where the GCA-EOS confirms a single-phase system, the MT model reduces to the PH model, confirming that mass transfer plays no role under supercritical conditions. High-pressure visual-cell observations independently corroborate this regime transition.

Cutin is a structural biopolyesters that forms the scaffold of the plant cuticle, an insoluble and chemically resilient barrier at the plant–environment interface. Cuticle plays a crucial role in preventing water loss, regulating gas (CO₂, O₂) permeability, protecting against microbial invasion, shielding against ultraviolet radiation, and mitigating other environmental stressors. Tomato native cutin conventional valorization strategies rely on harsh chemistries that destroy its native polyester architecture, limiting mechanistic insight and material exploitation. Here we report an ultrafast depolymerization strategy based on supercritical water hydrolysis that enables complete conversion of native tomato cutin into soluble branched polyesters within 10.5 seconds. Precise control of residence time reveals a hierarchical cleavage mechanism in which secondary esters at branching points hydrolyze preferentially over primary backbone esters. Spectroscopic and chromatographic analyses (FTIR, NMR, GPC, GC–MS) confirm selective bond scission, progressive molecular weight reduction, and identify 10,16-dihydroxyhexadecanoic acid as the dominant monomeric unit and revealed 16-hydroxy-9Z-hexadecenoic acid as a novel SCW-specific product, formed via a carbocation-driven intramolecular dehydration pathway inaccessible under alkaline conditions. A structurally constrained network model derived from reactive group analysis depicts cutin as a heterogeneous crosslinked polyester dominated by 10,16-dihydroxyhexadecanoic acid, with glycerol acting as a branching node, multifunctional C18 hydroxy acids and α,ω-diacids as linkers, and fatty acids as chain terminators. Green metrics confirm the process achieves an E-factor of 0.8 kg waste kg product⁻¹ with water recovery, outperforming alkaline hydrolysis (E-factor 4.1) in mass efficiency. This process-intensified approach enables structural resolution of native cutin and establishes a scalable platform for plant polyester valorization.

A continuous and efficient method to extract and enrich cutin from tomato waste preserved the native three-dimensional polyester network.

Natural biopolyesters in the form of suberin could be a promising resource for the synthesis of a wide array of chemicals, fuels and materials. However, access to this molecule is limited by a chemical-intensive and laborious work-up procedure based on alkaline hydrolysis or methanolysis. Herein, we propose the ultrafast supercritical hydrolysis as a novel and scalable approach for the facile access to suberin from cork. Supercritical water (SCW) with high or low ionic properties (pK_w of 13 and 15) would allow the liquefaction of lignocellulosic materials while avoiding the hydrolysis of ester linkages. Therefore, extractives and carbohydrates partition in aqueous products while suberin and lignin are enriched in the solid products. Suberin yield reached as high as 66.6% of the dry cork at 386 °C and 1.27 s (pK_w = 13), owing to the removal of up to 94.7% of polysaccharides content of the original cork biomass. The occurrence of repolymerization reaction, however, was observed under this condition, including an increase in Klason lignin presumably due to pseudo-lignin formation. Meanwhile, lower repolymerization products accompanied by a 77.1% polysaccharides and 14% lignin removal was achieved when working at 395 °C and 0.25 s (pK_w = 15), at the expense of lower suberin yield of 59.8%. It appears that even a longer reaction time of 1.27 s would not lead to hydrolysis of ester linkages in suberin but influences the extent of liquefaction of the lignocellulosic matrix and the formation of repolymerization products. A lower ion product and a reaction time of less than 1 s would be preferable to strike a balance between maximum polysaccharides removal and minimum repolymerization products generation. This study has contributed towards the development of a new sustainable process to access valuable molecules from cork and has highlighted the importance of obtaining high quality and highly functionalized biopolymers as a source of new building blocks.

In this work, the ionic liquid [Aliquat][Cl] was supported into alginate and silica aerogel matrices and applied as a catalyst in the cycloaddition reaction between CO₂ and a bio-based epoxide (limonene oxide). The efficiency of the alginate aerogel system is much higher than that of the silica one. The method of wet impregnation was used for the impregnation of the aerogel with [Aliquat][Cl] and a zinc complex. The procedure originated a well-defined thin solvent film on the surface of support materials. Final materials were characterised by Fourier Transform Infrared Spectroscopy, N₂ Adsorption–Desorption Analysis, X-ray diffraction, atomic absorption and Field Emission Scanning Microscopy. Several catalytic tests were performed in a high-pressure apparatus at 353.2 K and 4 MPa of CO₂.

The potential of saffron flowers as a source of polyphenols, and in particular anthocyanins, for the extraction of bioactive compounds and the production of a cyanic colorant was analyzed. A microwave pretreatment, prior to the conventional solid–liquid extraction process, was proposed as a feasible intensification step. The effectiveness of microwave pretreatment was assessed in terms of increased yield and improved quality of the final product. The operational variables studied were the pretreatment temperature (60–120 °C) and the solid–liquid ratio (0.30–0.50 g/mL). It was found that the addition of the microwave pretreatment to the conventional process allowed one to reduce extraction time by up to 12 times and to greatly improve the characteristics of the final product, using microwave energy densities as low as 0.16–0.54 kJ/mL. The extract quality was evaluated in terms of polyphenol richness (25% increase), product composition (80% of the anthocyanins was delphinidin), antioxidant capacity (boosted by the pretreatment) and color (variations in red and blue hue depending on conditions). To conclude, a microwave pretreatment in which the material is heated to a temperature of 65 °C with a solvent ratio of 0.30 g/mL was selected as the optimum to maximize process efficiency and product quality.

Arbutus unedo L., commonly known as the strawberry-tree fruit, is an endemic species of the Mediterranean flora. Microwave extraction technology has been considered as a fast and “green” method for the production of extracts rich in bioactive compounds, although the energy consumption is high. To overcome this bottleneck, microwave was used as a pretreatment procedure in short time periods. This technique promotes the burst of intracellular vacuoles leading to an increase in the lixiviation of phenolic compounds. Different approaches were tested, namely a solvent-free irradiation (SFI), a solvent-assisted irradiation (SAI) and a pressurized solvent-assisted irradiation (PSAI). After irradiation, a solid–liquid extraction procedure was performed using a mixture of water and ethanol. A kinetic evaluation of the total phenolic content (TPC) was performed using the Folin–Ciocalteu method. For the total anthocyanin content, a UV-spectrophotometric method was used. HPLC-UV and LC-MS were used for TPC and identification of present compounds. Microwave irradiation led to an increase in TPC of extracts after SAI (52%) and PSAI (66%) along with a reduction in time of extraction from 30 min to less than 2 min. The anthocyanin content also increased by 66% for the SAI and PSAI extractions.

Phenolics present in grapes have been explored as cosmeceutical principles, due to their antioxidant activity and ability to inhibit enzymes relevant for skin ageing. The winemaking process generates large amounts of waste, and the recovery of bioactive compounds from residues and their further incorporation in cosmetics represents a promising market opportunity for wine producers and may contribute to a sustainable development of the sector. The extracts obtained from grape marc and wine lees, using solid–liquid (SL) extraction with and without microwave (MW) pretreatment of the raw material, were characterized in terms of antioxidant activity through chemical (ORAC/HOSC/HORAC) and cell-based (keratinocytes—HaCaT; fibroblasts—HFF) assays. Furthermore, their inhibitory capacity towards specific enzymes involved in skin ageing (elastase; MMP-1; tyrosinase) was evaluated. The total phenolic and anthocyanin contents were determined by colorimetric assays, and HPLC–DAD–MS/MS was performed to identify the main compounds. The MW pretreatment prior to conventional SL extraction led to overall better outcomes. The red wine lees extracts presented the highest phenolic content (3 to 6-fold higher than grape marc extracts) and exhibited the highest antioxidant capacity, being also the most effective inhibitors of elastase, MMP-1 and tyrosinase. The results support that winemaking waste streams are valuable sources of natural ingredients with the potential for cosmeceutical applications.