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•Natural antioxidants as phenolic compounds are present in food by-products.•Extraction of phenolic compounds promotes food processing waste valorization.•Neoteric solvents can ...replace conventional organic solvents for extraction.•Ionic liquids, eutectic solvents and bio-solvents are promising extractants.
The loss and waste of food is a matter of great concern, leading to a multifaceted problem with negative economic, social, and environmental impacts as addressed in the UN Sustainable Development Goals number 2: zero hunger. The wine, fruit juice and vegetable oil processing industries generate significant amounts of wastes and side streams containing potentially valuable bioactive compounds. Some of them are plant secondary phenolic metabolites that offer remarkable health benefits (as antioxidants and anti-inflammatory compounds). One of the current challenges is the recovery of such bioactive compounds from residual matrices for further applications in food, pharmaceutical and cosmetic industries. Within this framework and in the scope of the Green Chemistry concept, one of the current challenges is to find eco-efficient techniques for the recovery of bioactive compounds. In this context, neoteric solvents are considered a greener alternative to traditional solvents, as the latter are more harmful to human and animal health, and environment. This overview focuses on recent advances in the use of hydrophobic neoteric solvents, i.e. ionic liquids, eutectic solvents, and bio-based solvents, for liquid–liquid extraction of phenolic compounds from liquid agri-food matrices.
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•Hydrophobic eutectic solvents with ammonium salts and natural compounds were formed.•Liquid-liquid extraction of wine-derived phenolic antioxidants was optimized.•Extraction ...efficiencies were determined by spectrophotometric methods and HPLC.•N8881Cl-based HESs can efficiently recover wine-derived phenolic antioxidants.•Hydrophobic eutectic solvents are promising for winery wastewater treatment.
Global food waste is a far-reaching problem, where the recovery of high-value compounds from agri-food effluents using green solvents is an attractive valorisation strategy. Wine industry is an important business sector which generates significant volumes of wastewater, with negative economic and environmental implications. However, winery wastewater can be exploited as a rich source of phenolic antioxidants for food and fine chemical applications. For that purpose, the main goal of this work is the recovery of wine-derived phenolic compounds from liquid effluents using hydrophobic eutectic solvents (HESs). In particular, HESs composed of ammonium salts, DL-menthol and fatty acids, were prepared and evaluated for liquid–liquid extraction of phenolic compounds from synthetic winery wastewater. To achieve optimum extraction performance, the experimental conditions were optimized, including extraction time, solvent to feed volume ratio, dilution factor and type of HESs. The extraction method developed was used for the efficient extraction of natural antioxidants from wine-derived samples and gallic acid from aqueous solutions. The extracted phenolic compounds were quantified and determined by spectrophotometric methods and high-performance liquid chromatography (HPLC). The experimental results showed satisfactory recoveries of the target compounds within the range of 64.14–84.10% from winery wastewater and recoveries between 74.86 and 92.31% from gallic acid solutions. Chloride ammonium salts-based HESs, especially N8881Cl-DL-Menthol and N8881Cl-Octanoic acid, proved the highest potential for phenolic compounds recovery from winery wastewater matrices and aqueous solutions. Finally, the antioxidant capacity of the extracts was confirmed.
A novel strategy for pre-treated biomass detoxification combining emerging green solvents and low environmental impact extraction technologies was evaluated. Steam-exploded biomass was subjected to ...microwave-assisted or orbital shaking extraction using bio-based or eutectic solvents. The extracted biomass was enzymatically hydrolysed. The potential of this detoxification methodology was studied in terms of phenolic inhibitors extraction and sugar production improvement. The effect of adding a post-extraction water washing step before hydrolysis was also evaluated. Excellent results were achieved when steam-exploded biomass was subjected to the microwave-assisted extraction combined with the washing step. The highest sugar production was achieved when ethyl lactate was used as extraction agent (49.80 ± 3.10 g total sugar/L) over the control (30.43 ± 0.34 g total sugar/L). Results suggested that a detoxification step based on green solvents would be a promising option to extract phenolic inhibitors, which can be revalorized as antioxidants, and improve the sugar production from the extracted pre-treated biomass.
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•Green (bio-based and eutectic) solvents extraction-based detoxification was evaluated.•Phenolic inhibitors were solvent-extracted from steam-exploded lignocellulosic biomass.•Microwaves enhance the efficiency of green solvents extraction.•Enzymatic convertibility and sugar production improved with solvent detoxification.•A washing step after solvents extraction and prior to hydrolysis was favourable.
The presence of bioactive compounds in winery waste streams represents a great opportunity to revalue these effluents that constitute a challenging environmental and economic problem. The main ...objective of this research is to develop an efficient and environmentally friendly liquid-liquid extraction process for the recovery of phenolic antioxidants from winery wastewater. Two bio-based solvents, 2-methyltetrahydrofuran (2-MeTHF) and cyclopentyl methyl ether (CPME), were evaluated as potential extractants along with ethyl acetate (EA) as benchmark organic solvent. Extraction efficiencies were maximized by testing several operation factors such as stirring time, solvent to feed ratio, concentration and alcohol effect. Subsequently, the extracted phenolic compounds were quantified by spectrophotometric (using the Folin-Ciocalteu assay, the flavonoid-aluminum chloride complexation assay and the DPPH free radical assay) and chromatographic (HPLC-DAD) methods. Overall, 2-MeTHF showed the highest extraction efficiency of target antioxidants, yielding up to 96.46% for gallic acid, 87.44% for protocatechuic acid, 80.82% for 4-hydroxybenzoic acid, 92.24% for caffeic acid, 75.18% for vanillic acid and 38.19% for syringic acid. In the interest of full sustainability, the isolation of the phenolic compounds as a solid fraction from the extraction solvent was efficiently accomplished, while the recyclability of 2-MeTHF was successfully demonstrated.
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•Sustainable recovery of antioxidants was proposed for winery wastewater valorization.•Bio-based solvents extracted target phenolic antioxidants from winery effluents.•2-MeTHF showed the highest extraction yield over the conventional solvent.•LLE optimization was performed using spectrophotometric/chromatographic methods.•2-MeTHF was efficiently recycled and reused in the extraction process.
The evaluation of sustainable solvents as alternatives to more harmful conventional solvents combined with intensification techniques to recover phenolic compounds from agri-food waste is in the ...spotlight. The wine industry generates large amounts of waste as a consequence of grape processing operations, which can be revalued by solvent extraction of valuable antioxidants for food and fine chemical applications. Therefore, the present study focuses on the use of natural eutectic solvents (NAESs) with benign environmental, health, and safety profiles, for valorization of grape waste in the context of a circular economy. Herein, up to 15 NAESs consisting of combinations of three hydrogen bond acceptors (choline chloride, L-proline, and betaine) and four hydrogen bond donors (1,2-propanediol, glycerol, and 1,2- and 1,3-butanediol) were evaluated for antioxidant recovery. After an initial screening of the performance of NAESs by conventional extraction, the process was intensified by microwave-assisted extraction (MAE). The extracts were analyzed by UV/VIS spectrophotometric and HPLC methods. Promising results were obtained with the solvent betaine, 1,2-butanediol 1:4, using MAE at 100 °C for 3 min. Overall, the proposed NAESs-based MAE method was successfully applied to recover target compounds from grape waste, with great prospects for the antioxidants market and sustainable development for the winery sector.
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•Removal of phenolic acids in solution using bio-based solvents was assessed.•Effect of key parameters on liquid–liquid extraction efficiency was studied.•Molecular structures played ...a significant role in the extraction process.•2-MeTFH provided the highest extraction and was successfully recycled.•Bio-based solvents are promising for phenolic acids recovery from aqueous matrices.
In the current context of a growing demand for environmentally friendly technologies, this study aims to evaluate and develop an efficient liquid–liquid extraction procedure of phenolic acid antioxidants from aqueous environments using bio-based solvents. Due to their abundance in industrial effluents and their importance for human health, a better understanding of how the molecular structures of phenolic antioxidants impact their recovery for pharmaceutical and fine chemical applications is required. Following the principles established by Green Chemistry, the use of eco-friendly solvents including 2-methyltetrahydrofuran (2-MeTHF), cyclopentyl methyl ether (CPME) and D-limonene (LIM) was evaluated in comparison with the conventional organic solvent, ethyl acetate (EA), for liquid–liquid extraction of nine representative phenolic acids: five hydroxybenzoic acids and four hydroxycinnamic acids. The distribution of the target compounds in each phase after the extraction process was obtained by UV–Visible spectrophotometry. The highest extraction yields, up to 100%, were obtained with 2-MeTHF, followed by the conventional solvent EA and CPME. On the contrary, LIM showed the lowest extraction efficiencies. The effect of the molecular structures of the compounds involved in the extraction process was analysed. In addition, the recyclability of 2-MeTHF in consecutive extraction cycles was demonstrated. Overall, a simple and more environmentally friendly liquid–liquid extraction process was developed for the recovery of hydroxybenzoic and hydroxycinnamic acids, while providing insights into the behaviour of the extraction process of phenolic acids using more sustainable solvents.
•Sustainable valorization of white grape waste by recovering antioxidants was proposed.•A series of promising bio-renewable green solvents were evaluated as extractive agents.•EtOH and 2-MeTHF showed ...the highest selective extraction yields of phenolic compounds.•Recycling of solvents and recovery of antioxidants as a solid fraction was achieved.•The process was efficiently enhanced by ultrasound-assisted extraction.
Winemaking industry generates significant waste rich in bioactive compounds, particularly phenolic compounds with strong antioxidant properties. Bio-renewable green solvents are promising candidates for the sustainable recovery of such antioxidants. For these reasons, the aim of this study was to evaluate green solvents (alcohols, ethers, esters, and terpenes) for extracting phenolic compounds from white grape waste (WGW). The solid-liquid extraction process was optimized by adjusting parameters like extraction time, temperature, and solid:liquid ratio. Under most favourable conditions, ethanol yielded the highest total phenolic content at 9.43 ± 0.16 mg GAE/g WGW, followed by 2-methyltetrahydrofuran at 7.23 ± 0.08 mg. The total phenolic content of the different WGW fractions (skin and seeds) was also evaluated. The solvent extracts were analyzed by UV–Visible spectrophotometry and chromatographic (HPLC-DAD) methods to characterize the phenolic profile, and the antioxidant capacity was also measured. Alcohols and ethers emerged as the most selective solvents, particularly for catechin and gallic acid. Additionally, successful solvent recycling and antioxidant recovery as a solid fraction were accomplished. Lastly, ultrasound-assisted extraction intensified the process, reducing time and energy consumption. Overall, this work exemplifies the "Circular Bioeconomy" concept, promoting sustainable waste biomass valorization to produce high-value bioproducts in demand by industry and society.
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•Extraction efficiency of phenols and sugar from water using eutectic solvents was analyzed.•Phenol, guaiacol and syringol have shown high percentage of extraction.•Extraction of ...glucose from water is not possible using the studied eutectic mixtures.•The highest extraction efficiencies were obtained using HES 12.
Biomass can be transformed into energy, high value chemicals or bioethanol. Nevertheless, the production of the latter is limited by the presence of inhibitory compounds that hinder the sugar fermentation process. This paper proposes menthol-based Hydrophobic Eutectic Solvents (HESs) as green solvents in the liquid extraction of phenolic compounds from diluted aqueous solutions. In particular, the main goal of the work is to analyse the capacity of the HESs to extract phenolic compounds (phenol, guaiacol and syringol) and glucose (as model sugar), since both types of compounds are present in the aqueous phase generated after washing with water the oil obtained in the fast pyrolysis of the biomass. As this is a preliminary study, two model mixtures constituted by solute (phenolic compound or glucose) and deionized water were used. Once HESs were prepared using menthol and three organic acids (octanoic acid, decanoic acid and dodecanoic acid), liquid–liquid extractions were performed in order to test the ability of these solvents to extract the abovementioned compounds from water. Firstly, stirring and centrifuging times were optimized and the effect of varying the solvent/feed ratio and the initial concentration of the solution {phenolic compound + water} were studied. Afterwards, since the goal of this work is to remove phenols from water to enhance sugars fermentability, the liquid extraction of glucose from water using the same HESs were also experimentally carried out at the optimized conditions. The obtained results are very promising, as HESs can easily extract phenols but not glucose, which would improve the subsequent sugar fermentation process.
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•Carboxylic acid-based hydrophobic eutectic solvents were formed and characterized.•Extraction efficiency of hydrophobic eutectic solvents and bio-based solvents were obtained by ...HPLC-DAD/RI.•Selective extraction of phenols from sugar-rich aqueous streams could enhance fermentation processes.•Best selectivity and efficiency results were obtained with cyclopentyl methyl ether.•The experimental results were analyzed by means of COSMO-RS methodology.
Integrated biorefineries are the current trend to produce energy, biochemicals and biofuels. A variety of sugar-rich biorefinery streams can be further valorized by fermentation but the presence of inhibitory compounds hinders the fermentation yields. This paper proposes a detoxification method by selective liquid extraction of phenolic compounds using sustainable solvents to improve the fermentation of sugar-rich aqueous streams. Specifically, three hydrophobic eutectic solvents constituted by binary mixtures of octanoic, decanoic or dodecanoic acid (octanoic: decanoic acid 1:1, octanoic: dodecanoic acid 3:1, decanoic: dodecanoic acid 2:1) and three bio-based solvents (2-methyltetrahydrofuran, cyclopentyl methyl ether and limonene) were selected to analyze their capacity to extract representative phenolic compounds (phenol, o-cresol, guaiacol, syringol and vanillin) from aqueous solutions. Extraction efficiencies of individual compounds and mixtures of them were evaluated at different concentrations and temperatures using the proposed solvents. Finally, the liquid extraction of a solution containing 500 mg/L of phenolic compounds and 50 g/L of glucose, as a representative concentration in biorefinery streams, was performed. The distribution of the target compounds in each phase after the extraction process was analyzed by HPLC-DAD in the case of phenolic compounds and HPLC-RI for glucose, and discussed in terms of selectivity. The results obtained are very promising, as the studied solvents can easily extract phenolic compounds but not glucose, which could improve the subsequent sugar fermentation process. In particular, the bio-based solvent cyclopentyl methyl ether provided extraction efficiencies of phenolic compounds above 93%, while that of glucose remained lower than 4%. Finally, all the experimental results were analyzed by means of COSMO-RS methodology, obtaining reliable trends and concluding that the ability of the solvents to form hydrogen bonds with phenolic compounds determines the extraction efficiencies.
The growing demand for high added-value products, such as vanilla-derived compounds, and increasing environmental regulations make evident the need to find new sustainable solvents for extraction ...processes, which meet both legislative requirements and expected yields. Vanilla-derived compounds are known for their antioxidant and beneficial properties for human health. These compounds can be recovered from effluent streams, promoting decontamination and revaluation of wastewater. The potential of using neoteric solvents, i.e., biobased solvents and hydrophobic eutectic solvents, as an alternative to conventional volatile organic solvents, such as ethyl acetate, for sustainable recovery of vanilla-derived compounds through liquid–liquid extraction from aqueous environments was investigated. Three biobased solvents (2-methyltetrahydrofuran, cyclopentyl methyl ether, and d-limonene) and three hydrophobic eutectic solvents constituted by menthol and organic acids (1:1 dl-menthol:octanoic acid, 1:1 dl-menthol:decanoic acid, and 2:1 dl-menthol:dodecanoic acid) were evaluated. The extraction process was optimized in terms of the stirring time and solvent:feed volume ratio. The effect of the initial solute concentration was also analyzed. The extraction efficiency of solvents was determined by UV–visible spectrophotometry and high-performance liquid chromatography with diode-array detection. The experimental results indicated that 2-methyltetrahydrofuran yielded the highest extraction efficiency from a vanilla bean extract solution for both vanillin (95.37%) and vanillic acid (91.96%) with good repeatability (RSD < 0.40%). Regarding the rest of the neoteric solvents, cyclopentyl methyl ether and hydrophobic eutectic solvents provided extraction values between 31.6 and 95.4% for both vanilla-derived compounds, while d-limonene was significantly less effective. Finally, a solvent recycling and reuse study was successfully carried out, showing that 2-methyltetrahydrofuran stands out as a promising biobased extraction solvent for sustainable recovery of valuable vanilla constituents.
