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Browsing by Author "Vale, Mariana Ribeiro de Paula"

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  • Solubility of olive oil phenolic compounds in green solvents
    Publication . Vale, Mariana Ribeiro de Paula; Ferreira, Olga; Peres, António M.; Martins, Mónia
    The extraction of olive oil generates different phenolic-rich by-products, containing hydroxytyrosol (HTy), tyrosol (Ty), and their derivatives. These phenolic compounds exhibit remarkable pharmacological bioactivity, including anti-atherogenic, cardioprotective, anticancer, neuroprotective, and endocrine-modulating effects. Consequently, the recovery of these compounds is of high significance for their potential application as functional additives in various industrial formulations. A review of extraction and purification methodologies for phenolic compounds from olive oil by-products highlights that water and water-ethanol mixtures are the most used solvents in conventional extraction processes, or when coupled with diverse extraction techniques. Recent research has also explored the use of deep eutectic solvents and supercritical carbon dioxide in these processes. To optimize these extraction processes, it is essential to know the solubility of target phenolic molecules (Ty and HTy) in green solvents and their partition behavior across different aqueous biphasic systems. Initially, the solubility of Ty was experimentally determined in water and nine individual organic solvents. Solubility data for 1,3- butanediol, 1,3-propanediol, 1-propanol, acetone, and methanol were reported here for the first time. Subsequently, solubility measurements were conducted for mixtures comprising water and a co-solvent (acetone, ethanol, 2-propanol, 1,3-butanediol, and 1,3-propanediol). These measurements were carried out at 298 K using the analytical isothermal shake-flask method, with analysis by UV-spectrophotometry and gravimetry. Further, the solubility of Ty and HTy in various organic solvents was modeled using the COSMO-RS method with BP_TZVP parametrization. This model was employed to predict solubility in the pure and mixed solvents tested experimentally, as well as in additional green solvents, including 2-methyltetrahydrofuran, cyclopentyl methyl ether, dimethyl carbonate, dimethyl isosorbide (DMI), glycerol, gamma-valerolactone, lactic acid, limonene, and triolein. Water-miscible co-solvent systems, involving DMI, lactic acid, urea, and citric acid, were also assessed. Results showed that ethanol, methanol, and acetone were the most effective pure solvents for the solubilization of Ty and HTy, with strong correlations observed between experimental and predicted data. The study demonstrated that Ty exhibits higher solubility than HTy in water/organic solvent systems with lower co-solvent concentrations. Protic alcohols, particularly ethanol and methanol, facilitated superior solubility for Ty, whereas acetone (an aprotic solvent) yielded the highest solubility in select conditions. Overall, COSMO-RS effectively predicted solubility trends across different solvents, supporting its utility in solvent selection for Ty and HTy extraction. These findings underscore the value of COSMO-RS in accurately modeling complex solute-solvent interactions for process optimization namely in phenolic compound recovery.
    2024Master thesis Restricted access Show more