Use of Natural Deep Eutectic Solvents (NADES) in Food Science and Food Processing
Sustainability
Abstract and Figures
Natural deep eutectic solvents (NADESs) are a new class of solvent systems with applications in the food industry. Due to their reduced toxicity and their enhanced biodegradability over traditional fossil-fuel based solvents, NADESs are seen as environmentally friendly, “green” solvents. The review covers their use in the extraction of nutritionally valuable molecules, including biopolymers from plants and from agricultural and food wastes. NADESs are used in the preservation of fruits and vegetables, in active packaging or direct produce coating. They also play a role in flavor and food enhancement applications and can be used in food analysis. Current limitations as to recovery methods of the target compounds from the extracts, the scale-up of operations, costs and regulations are discussed in the review. Some of the start-up companies are introduced that develop DES/NADES solvents for the market, thereby accelerating the shift from petroleum-based solvents to green solvents.
![Natural product-derived hydrogen bond acceptor (HBA) used in NADESs [Choline chloride (1), (2-hydroxyethyl) ethyldimethylammonium chloride (2), choline chloride chloroformate (3), O-benzyl choline chloride (4), betaine (5), betaine hydrochloride (6), glycine (7), tetrabutylammonium chloride (8), tetramethylammonium chloride (9), menthol (10), proline hydrochloride (11), decanoic acid (12), nicotinic acid (13)].](https://www.researchgate.net/profile/Thies-Thiemann/publication/389601624/figure/fig1/AS:11431281318651021@1742557695540/Natural-product-derived-hydrogen-bond-acceptor-HBA-used-in-NADESs-Choline-chloride_Q320.jpg)
![Natural product-derived hydrogen bond donor (HBD) used in NADES [Urea (14), thiourea (15), 4-hydroxybenzoic acid (16), caffeic acid (17), glycerin (glycerol, 18), acetamide (19), oxalic acid (20), lactic acid (21), propane-1,2,3-tricarboxylic acid (22), thymol (23), citric acid (24), phenol (25), α-naphthol (26), ethylene glycol (27), malonic acid (28), β-D glucose (29), fructose (30), adipic acid (31)].](https://www.researchgate.net/profile/Thies-Thiemann/publication/389601624/figure/fig2/AS:11431281318600641@1742557695760/Natural-product-derived-hydrogen-bond-donor-HBD-used-in-NADES-Urea-14-thiourea_Q320.jpg)
![Typical compounds of interest in the extraction of biomass with DES/NADES [catechin 32, epicatechin 33, procyanidin 34, favonol 35, dihydrochalcone [aspalathin, 36], and anthocyanin [pelargonidin, 37]].](https://www.researchgate.net/profile/Thies-Thiemann/publication/389601624/figure/fig3/AS:11431281318641475@1742557695993/Typical-compounds-of-interest-in-the-extraction-of-biomass-with-DES-NADES-catechin-32_Q320.jpg)
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Orange and coffee grounds by-products, rich in phenolic bioactive compounds, can be used in the food industry as antioxidants, colorants, flavorings and additives, mainly because they are solvents that are easy to prepare, have a lower cost, are thermally stable, biodegradable, renewable, and are considered GRAS (Generally Recognized as Safe). Deep eutectic solvents, which are sustainable and have lower melting points, are effective for extracting these compounds. This study aimed to evaluate the use of deep eutectic solvents (DES) in extracting Total Phenolic Compounds (TPC), from orange by-products and spent coffee grounds. DES formed by citric acid: mannitol (CM-DES), and lactic acid: glucose (LG-DES), were evaluated by varying the following parameters: water content (10–50%), solid–liquid ratio (1:5–1:50 w/w) and temperature (40–50 °C). DES citric acid: mannitol presented the best efficiency in the extraction of TPC under the conditions of 10% water, 80 °C, and solid–liquid ratio 1:10 (w/w) for the orange by-products (1782.92 ± 4.50 mg GAE/L) and 1:15 (w/w) for spent coffee grounds (1620.71 ± 3.72 mg GAE/L). The highest antioxidant activity was observed in the extraction with CM-DES for both by-products in the three methods evaluated: Ferric Reducing Antioxidant Power (FRAP) (1.087 ± 0.004 and 1.071 ± 0.006 mol ascorbic acid/L), DPPH radical scavenging activity (2,2-difenil-1-picrilhidrazil—DPPH) (0.233 ± 0.003 and 0.234 ± 0.001 mol Trolox equivalent/L), and radical cation scavenging activity ABTS (2,2-azino-bis (3-ethyl-benzothiazoline-6-sulfonic acid—ABTS) (0.284 ± 7.16 and 0.319 ± 0.002 mol Trolox equivalent/L). Therefore, DES with citric acid: mannitol is a promising alternative to conventional solvents to recover phenolic compounds in agro-industrial by-products, such as orange by-products and SCG.
Deep Eutectic Solvents (DESs) emerge as innovative 21st-century solvents, supplanting traditional ones like ethanol and n-hexane. Renowned for their non-toxic, biodegradable, and water-miscible nature with reduced volatility, DESs are mostly synthesized through heating and stirring method. Physicochemical properties such as polarity, viscosity, density and surface tension of DESs influenced their application. This review paper gives the overview of application of eco-benign DESs in fruits, vegetables, cereals, pulses, spices, herbs, plantation crops, oil seed crops, medicinal and aromatic plants, seaweed, and milk for the extraction of bioactive compounds. Also, it gives insight of determination of pesticides, insecticides, hazardous and toxic compounds, removal of heavy metals, detection of illegal milk additive, purification of antibiotics and preparation of packaging film. Methodologies for separating bioactive compounds from DESs extracts are systematically examined. Further, safety regulations of DESs are briefly discussed and reviewed literature reveals prevalent utilization of DES-based bioactive compound rich extracts in cosmetics, indicating untapped potential of their application in the food industry.
Extra virgin olive oil (EVOO) is recognized for its numerous health benefits, attributed to its rich phenolic components. NMR has emerged as a prevalent technique for precisely identifying these compounds. Among Mediterranean countries, Greece stands as the third-largest producer of olives, with the Epirus region notably advancing in olive cultivation, contributing significantly to the dynamic growth of the region. In this study, an NMR method was employed based on the acquisition of a 1H NMR spectrum along with multiple resonant suppression in order to increase the sensitivity. Using the above method, 198 samples of extra virgin olive oil, primarily sourced from the Epirus region, were analyzed, and both the qualitative and quantitative aspects of the phenolic compounds were obtained. In addition, we examined the effects of various factors such as variety, harvest month, and region origin on the phenolic compounds’ concentration. The results revealed an average total phenolic content of 246 mg/kg, closely approaching the EU health claim limit of 250 mg/kg. Approximately 15% of the samples were confidently characterized as high-phenolic olive oil. The highest concentrations were observed in the Thesprotia samples, with several Lianolia varieties exceeding the total phenolic content of 400 mg/kg. Statistical tests demonstrated a significant influence of the olive variety and the month of fruit harvest on phenolic component concentration, followed by the region of origin. A very strong correlation was noted between the total phenolics content and the levels of oleocanthal and oleacein, with a correlation coefficient (r) of 0.924. Upon optimization of all factors affecting olive oil quality, the majority of the EVOOs from the Epirus region have the potential to be characterized as high in phenolic content.
The present study aimed to evaluate the efficacy of natural deep eutectic solvents (NADESs) on the extraction of phytochemicals from eight Algerian date fruit cultivars (Phoenix dactylifera L.). In this study, lactic acid/sucrose-based NADESs were used as an alternative to conventional chemical solvents using the ultrasound-assisted extraction (UAE) method. The obtained extracts were assessed for the determination of bioactive compound contents, phenolic composition, antioxidant activity, and enzyme inhibitory potential. The results showed a considerable variation in phytochemical compositions and related activities between cultivars, where the greatest contents of total phenolics (1288.7 mg GAE/100 g), total flavonoids (53.8 mg QE/100 g), proanthocyanidins (179.5 mg CE/g), and total triterpenoids (12.88 mg OAE/100 g) were detected in the fruits of the Ourous cultivar. The same cultivar displayed the highest antioxidant capacity against DPPH• free radical (595 mg AAE/100 g), ABTS•+ cation radical (839 mg TE/100 g), and ferric reducing antioxidant potential (704 mg AAE/100 g). All extracts manifested moderate antioxidant activities tested by phosphomolybdenum, NO•, and linoleic acid lipid peroxidation assays. These extracts also exhibited interesting levels of in vitro enzyme inhibition; the Ourous cultivar gave the best inhibitory activity against α-amylase and acetylcholinesterase with 45 and 37%, respectively. HPLC-DAD-MS detected a total of five compounds, with phenolic acids and flavonoids being the main phenolics identified in the extract. The phenolic composition exhibited significant variability among cultivars. Notably, the highest amounts were revealed in the Tazizaout cultivar, with the predominance of gallic acid. The results confirmed that the combination of UAE and NADESs provides a novel and important alternative to chemical solvents for sustainable and environmentally friendly extraction and can represent a good alternative in food and pharmaceutical industry applications.
The capacity of four formulations of natural deep eutectic solvents (NDESs) for extraction of canola protein was compared to alkaline extractions at pH 12 and pH 9. NDESs were prepared with a 1:2:1 ratio of choline chloride/d-sorbitol, glycerol, d-glucose or urea/water. The urea formulation showed the lowest viscosity and density and highest polarity; and extracted a bright-yellow isolate with extraction efficiency of 52.89% and protein content of 84.03%. The rest of NDESs extracted light-green isolates with efficiencies of approximately 44%. Furthermore, All NDESs offered lower extraction efficiencies than pH 12 (68.34%, dark-green isolate) but higher than pH 9 (39.14%, yellow isolate). Molecular analysis via SE-HPLC and SDS-PAGE showed the presence of cruciferins and napins in all isolates, but higher napin contents for NDES isolates with cruciferin-to-napin ratios of around 60:40. NDESs also altered the secondary and tertiary structure of the protein to a lesser extent. The functionality analyses at pH range of 3–7 revealed better solubility for pH 9 (72.09%–39.35%) and glycerol formulation (68.61%–39.05%) isolates; and better foaming properties for all NDES isolates, possibly due to their higher napin contents. NDES isolates also showed better emulsifying properties at pH 5 and 7, while alkaline isolates produced more stable emulsions at pH 3, possibly due to the better solubility of their cruciferins at pH 3. Overall, NDES isolates offered higher extraction efficiencies and a close functionality compared to pH 9 isolate, better color and functionality than pH 12 isolate, and better preservation of native protein structure compared to both alkaline treatments.
Deep Eutectic Solvents (DESs) offer a promising, sustainable alternative for extracting polyphenols from food plants, known for their health benefits. Traditional extraction methods are often costly and involve toxic solvents. This review discusses the basic concepts, preparation techniques, and factors influencing the effective and safe use of DESs in polyphenol extraction. DESs' adaptability allows integration with other green extraction technologies, such as microwave- and ultrasound-assisted extractions, enhancing their efficiency. This adaptability demonstrates the potential of DESs in the sustainable extraction of bioactive compounds. Current research indicates that DESs could play a significant role in the sustainable procurement of these compounds, marking an important advancement in food science research and development. The review underscores DESs as a realistic, eco-friendly alternative in the realm of natural extraction technologies, offering a significant contribution to sustainable practices in food science.