Since solvents of petroleum origin are now strictly regulated worldwide, there is a growing demand for using greener, bio-based and renewable solvents for extraction, purification and formulation of natural and food products. The ideal alternative solvents are non-volatile organic compounds (VOCs) that have high dissolving power and flash point, together with low toxicity and less environmental impact. They should be obtained from renewable resources at a reasonable price and be easy to recycle. Based on the principles of Green Chemistry and Green Engineering, vegetable oils could become an ideal alternative solvent to extract compounds for purification, enrichment, or even pollution remediation. This review presents an overview of vegetable oils as solvents enriched with various bioactive compounds from natural resources, as well as the relationship between dissolving power of non-polar and polar bioactive components with the function of fatty acids and/or lipid classes in vegetable oils, and other minor components. A focus on simulation of solvent-solute interactions and a discussion of polar paradox theory propose a mechanism explaining the phenomena of dissolving polar and non-polar bioactive components in vegetable oils as green solvents with variable polarity.

The present study was designed to evaluate five green solvents, i.e. 2-methyltetrahydrofuran (2-MeTHF), dimethyl carbonate (DMC), cyclopentyl methyl ether (CPME), isopropyl alcohol (IPA) and ethyl acetate, for the substitution of n-hexane in the extraction of carotenoids from carrots. Initially, solvent selection was made through the theoretical physicochemical solvent properties and solubility results obtained using two simulation programs, Hansen Solubility Parameters (HSPs) and Conductor-like Screening Model for Realistic Solvation (COSMO-RS) which use a statistical thermodynamics approach based on the result of quantum chemical calculation, for comprehension of the dissolving mechanism. On the basis of the HSPs analysis, non-polar or slightly polar solvents were the most suitable solvents for extraction of carotenoids. COSMO-RS analysis showed a higher probability of solubility for all the carotenoids from carrot in CPME, 2-MeTHF and ethyl acetate compared with n-hexane. The experimental results using a conventional solid–liquid extraction by maceration showed that the best green solvents were CPME, 2-MeTHF and ethyl acetate in accordance with the predictive results from COSMO-RS. The highest carotenoid content (78.4 mg 100 g⁻¹ DM) was observed in CPME where 66% was represented by β-carotene and 34% was α-carotene. These results support the potential of CPME and 2-MeTHF as alternative green solvents for extraction of carotenoids.

A set of compounds from non-edible fat waste was prepared and their thermal behavior was studied. The fat was hydrolyzed and crystallized in a simple and robust process to yield palmitic acid–stearic acid (PA–SA) mixtures. The PA–SA mass ratios determined by GC-FID (gas chromatography-flame ionization detection) were similar to those reported for eutectic mixtures of PCMs (phase change materials). DSC (differential scanning calorimetry) results indicated that the melting and solidification temperatures were around 55 °C and 52 °C and the latent heat of the crystallized fractions measured was around 180 kJ kg⁻¹. The thermal cycling reliability of the eutectic mixtures was also tested during 1000 melting/freezing cycles. The loss in melting and solidification enthalpies was below 14% in all mixtures showing a promising behavior for PCM applications. Additionally, the unsaturated fatty acids were recovered and transformed to threo-9,10-dihydroxystearic acid (DHSA) and some of their inorganic salts, which were analyzed by FT-IR (Fourier transform-infrared spectroscopy) and tested for the first time using the DSC technique.