Deep eutectic solvents for sustainable extraction of polyphenols and saponins from plant sources: assessment of the impact of influencing factors

With the requirement to increase the safety and sustainability of the separation processes, there has been a shift toward the utilization of green solvents in the extraction processes. Deep eutectic solvents (DESs) are neoteric solvents with several advantages over conventional organic solvents or ionic liquids (ILs). They are nontoxic, nonflammable, biodegradable, and less costly. Moreover, they can be regenerated and reused in the extraction process in repeated cycles. The extraction yield using DESs can be improved through the employment of ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), ultrahigh pressure extraction (UHPE), or negative pressure cavitation extraction (NPCE). These techniques not only shorten the processing time but also intensify the mass transfer and facilitate the diffusion and extraction of bioactive ingredients. With the raised interest in the separation and purification of polyphenol and saponin compounds with several therapeutic properties, DESs have found their applications as alternative solvents. This review aims to highlight recent applications of DESs for the extraction of flavonoids, curcuminoids, and saponins from plant sources and discuss and compare the factors that should be considered for enhancing the extraction efficiency of these bioactive ingredients. The discussed works lay the foundations for further development of the extraction processes using these solvents.</p

Column chromatography for separation and fractionation of flavor-active esters on hydrophobic resins and simulation of breakthrough behavior

For simulating an adsorption/elution step for separation and recovery of flavor-active esters in beer in the presence of ethanol at various temperatures, and validating the predicted breakthrough behavior, equilibrium data on concentration of each ester is required. This work evaluates the application of frontal analysis method (FA) for prediction of breakthrough behavior for adsorption of ethyl acetate, and determination of equilibrium concentrations and binding capacity for competitive adsorption of four major flavor-active esters in beer (i.e. ethyl acetate, isopentyl acetate, ethyl 4-methylpentanoate, and ethyl hexanoate), together with improvement of the obtained results, through fraction collection, and offline analysis, on columns packed with hydrophobic resins, Amberlite XAD16N and Sepabeads SP20SS. Single-component adsorption of ethyl acetate reveals a shorter breakthrough time, and higher slope of breakthrough curve for adsorption on SP20SS, due to smaller particle size, (50–100 μm), and enhanced mass transfer characteristics of this resin. Competitive frontal analysis tests, neatly demonstrate that increase in temperature is not favorable for adsorption but aids the elution step, 63–100% recovery of flavors at 333.15 K in comparison to 40–80% recovery at 298.15 K. Lower binding capacity of esters and shorter adsorption/elution cycle time is achieved at higher ethanol concentration and cyclic operation simulated under non-isothermal condition, exhibit higher accuracy between predicted and experimental breakthrough curves for XAD16N. A cyclic operation is simulated, for a larger scale column, for two scenarios, separation of ethyl acetate and complete separation of all flavor-active esters in the mixture. For more detailed prediction of breakthrough behavior, the influence of other components present in process streams needs to be investigated on competitive adsorption of esters

Influence of ethanol and temperature on adsorption of flavor-active esters on hydrophobic resins

Flavor-active esters, produced during fermentation, are vital components and important contributors to the aroma of beer. In order to separate trace amounts of esters, their adsorption behavior in the presence of high concentrations of ethanol and their thermodynamic behavior under the influence of temperature needs to be understood. This study reports the influence of temperature on single component adsorption isotherms of four esters (i.e. ethyl acetate, isopentyl acetate, ethyl 4-methylpentanoate, and ethyl hexanoate) on two hydrophobic resins (i.e. Amberlite XAD16N, and Sepabeads SP20SS) and the estimation of heat, entropy, and Gibbs energy of adsorption. Higher heat and entropy of adsorption are obtained for ethyl hexanoate and ethyl 4-methylpentanoate in comparison, due to their higher hydrophobicity, stronger binding, and the exothermic nature of their adsorption. A higher concentration of ethanol (tested from 1 to 30% (v/v)), lowers the activity coefficient of esters in the aqueous phase, and subsequently lowers adsorption and Langmuir affinity parameters. Increase of temperature from 284.15 to 325.15 K shows a reverse influence on maximum adsorption capacity and Langmuir affinity parameters. Langmuir affinity parameters are obtained at various ethanol concentrations and temperatures. The reported parameters and thermodynamic properties in this paper, are essential for designing an industrial scale adsorption step for separation of flavor-active esters under non-isothermal conditions