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Orange peel wastes, with an estimated global annual production of 25 million tonnes, are problematic to dispose of but can be used to obtain a range of valuable products, among them the main constituent of orange essential oil, d-limonene (DL). This review aims to layout recent advances in the field of DL extraction and purification. Besides substitution of the conventional solvent hexane with certain bio-based solvents, a range of techniques are presented. These include enhanced solvent extraction processes through temperature and pressure intensification or ultrasound, improved distillation most commonly using different microwave-based techniques but also enzymes, and supercritical CO2 extraction. Even though purification has been found to be the most energy-intensive and environmentally impacting step, most studies did not improve on existing centrifugation, decantation, or fractional distillation methods. Chromatography has been proven effective at obtaining high DL purities; however, it still has to be improved because of its high costs and low productivity.
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... The use of limonene as solvent offers the benefit of lower toxicity, flammability, and environmental risk as compared to conventional solvents, such as n-hexane (Bertouche et al., 2013;. The high hydrophobicity makes it very suitable to be used as a solvent in lipids extraction (Siddiqui et al., 2022) and, its use can provide higher vegetable oil yields in extraction processes over hexane, due to its slightly polar nature and greater ability to dissolve triacylglycerols, since it is necessary to use higher extraction temperature to boil it, giving the extract a lower viscosity and providing a higher rate of oil diffusion in the matrix (Liu and Mamidipally, 2005;Mamidipally and Liu, 2004). ...
This work aimed to investigate the replacement of hexane by limonene in the extraction of wax from sugarcane peel, comparing the use of both solvents in terms of waxes yields, physicochemical properties, and composition, and presenting the difficulties faced in this replacement. The use of limonene produced extracts with similar melting points and higher content of fatty acids than the extracts obtained using hexane. Regarding the fatty alcohol percentage, while it decreased along the extraction time for the hexane extracts, due to the extraction of other chemical species, the opposite behavior occurred for limonene extracts. Although the purified limonene and hexane waxes showed similar physical properties, the use of limonene presented some drawbacks associated with the sample's residual limonene and the higher temperature required to boil it, which hinder its complete recovery and reuse. Thus, this work exemplifies the processing difficulties faced in replacing fossil solvents with renewables.
Agricultural waste material even if free from toxic compounds or pathogens can cause environmental problems and their unsustainable use can lead to health and environmental risks. Orange and olive food processing wastes are rich in chemical compounds and could offer many opportunities of use, especially for the high level of nutritional components. This paper proposes to validate anaerobic digestion, aerobic digestion, and raw agricultural waste management as possible ecofriendly methods to turn these wastes into fertilizers. The byproducts obtained by these three different processes, have been chemically analyzed and assessed on soil, growth and antioxidant properties of garlic (Allium sativum). Results evidenced that the chemical properties of the soil treated with all the byproducts were positively influenced, even if the effects were different and depended on the type of the byproduct used and on the organic wastes from which the byproducts came from. The byproducts coming from orange wastes (pastazzo) were a bit more effective than those coming from olive pomace and among the byproducts the compost was the best one. Results evidenced that garlic increased its growth and antioxidant capacity when cultivated with all byproducts. The results of this study evidenced that all the byproducts obtained can be used in agriculture with success and the transformation methods used even if differently, are environmentally, economically and/or agriculturally valid.
Culled whole grapefruit (WG) and grapefruit juice processing residues (GP) are currently incorporated into low-cost animal feed. If individual chemical components found within these side streams could be recovered as high-value coproducts, this would improve the overall value of the grapefruit crop. In this study, pectic hydrocolloids, sugars, volatiles, phenolics, and flavonoids were extracted from Star Ruby, Rio Red, and Ruby Red GP and WG using a continuous pilot scale steam explosion system. Up to 97% of grapefruit juice oils and peel oils could be volatilized and contained 87–94% d -limonene. The recovery of pectin, as determined by galacturonic acid content, was between 2.06 and 2.72 g 100 g ⁻¹ . Of the phenolics and flavonoids analyzed in this study, narirutin and naringin were extracted in the amounts of up to 10,000 and 67,000 μg g ⁻¹ , respectively.
Background: Orange peel essential oils were obtained using supercritical fluid extraction. This method is an important high scaling extraction method used for the extraction of plant and animal extracts.
Objectives: The aim of this study was the optimization of the extraction of the orange peel essential oil.
Methods: The experimental parameters of Supercritical Fluid Extraction (SFE) such as temperature, pressure, and extraction time, and modifier volume were optimized using a central composite design after a 24-1 fractional factorial design. Orange peels were collected from ripe orange and were washed, air dried, and milled. Then, a Suprex MPS/225 system in the SFE mode with a maximal operating pressure of 395 bars was used for essential oil extraction. Moreover, GC-MS and GC-FID were used for the identification and determination of oil compounds, respectively.
Results: Eight compounds have been identified based on their retention indices and mass spectra. According to the results, α-pinene, β-pinene, myrcene, d-limonene, terpinolene, C8-aldehyde, citronellol, and linalool were identified in orange peel essential oil. The optimum SFE conditions were obtained at a pressure of 347.07 atm, temperature of 55° C, extraction time of 30.16 min, and ethanol volume of 147.05 µL. Moreover, extraction yields based on SFE varied in the range of 0.04% to 1.18% (w/w).
Conclusion: The Results showed supercritical fluid technology as the best alternative technique for the extraction of pure and high-quality essential oil from orange peel. It is a green method and does not have any environmental impact.
Byproducts such as orange peel have potential uses because of their bioactive compounds, which are important for their potential to reduce the risk factors of diseases caused by aging. The lack of effective techniques and the high levels of pollution produced by the conventional extraction of bioactive compounds using organic solvents have highlighted the need to enhance the ‘green chemistry’ trend. This study evaluates the use of ultrasound to extract bioactive compounds from orange peel. The antioxidant capacity, phenolic content, ascorbic acid, total carotenoids, and HPLC profile of phenolic compounds from orange peel extracts were obtained by a physicochemical evaluation. The results demonstrate that the optimal conditions for the ultrasound-assisted extraction of bioactive orange peel compounds were a power of 400 W, a time of 30 min, and 50% ethanol in water. These conditions were used to obtain a total carotenoid concentration of 0.63 mg ß-carotene/100 g, vitamin C concentration of 53.78 mg AA/100 g, phenolic concentration of 105.96 mg GAE/100 g, and antioxidant capacity of ORAC = 27.08 mM TE and TEAC = 3.97 mM TE. The major phenolic compound identified in all orange peel extracts was hesperidin, with a maximum concentration of 113.03 ± 0.08 mg/100 g.
A new research approach has been applied to the extraction of lemon essential oils to increase the extraction efficiency and improve the quality of isolated essential oils. In this study, the combination of microwave extraction method and response surface method is employed to investigate factors influencing lemon peel essential oil extraction process; including size of the raw material particles, raw material to water ratio, extraction time, and microwave power. The results showed that lemon peel of sizes 1 to 2 mm, material: solvent ratio 1:3 g/mL, extraction time of 60 min and microwave power of 450 W gave the highest yield of essential oil (2.4 %). The GC-MS results showed the domination of D-Limonene, the main ingredient of citrus essential oils, in higher concentrations than those reported by previous studies.
Citrus peel waste is a valuable lignocellulosic feedstock for bioethanol production due to its richness in fermentable sugars and low lignin content. Citrus peel contains two major value-added products: d-limonene and pectin. d-Limonene is widely used in food, cosmetics, and pharmaceutical industries. However, it acts as a microbial growth inhibitor for yeast during the fermentation process and hence it has to be removed prior to fermentation. Pectin is used as thickening agent, gelling agent, and stabilizer in the food industry. Since pectin increases the viscosity of the fermentation medium and makes fermentation a troublesome, it has to be either extracted or degraded into galacturonic acid using pectinase enzyme. Thus, the removal and recovery of both D-limonene and pectin from citrus peel are essential for better fermentation. For bioethanol production, pretreatment plays a crucial role in the utilization of citrus peels since the reduction of d-limonene concentration to less than 0.05% is necessary. This review solely describes the potential of citrus waste for value added products such as d-limonene and pectin and the production of bioethanol from citrus peel waste is discussed in detail.
D-limonene and geranial are, respectively, the most abundant terpenic and oxygenated compounds found in lemon essential oil. The main objective of this research work is to study the technical feasibility of molecular distillation, in order to separate and concentrate those thermal labile compounds of lemon essential oil and to determine the best evaporation temperature and feed flow rate values which will lead to high separation efficiency. The highest temperature analyzed allowed to obtain a residue poor in d-limonene and enriched in geranial, with low geranial yield (between 35-50%). Regarding d-limonene, the highest temperature (30 degrees C) used, led to higher yields of d-limonene. Lower feed flow rate (0.6 ml min(-1)) led to low concentrations of d-limonene (320 g kg(-1)) and geranial (70 g kg(-1)) in the residue, with low yield for geranial (23.5%). A high yield of geranial in the residue (76.4%) can be obtained by using a feed flow rate of 1.3 ml min(-1), which leads to the highest geranial concentration (113 g kg(-1)).
Limonene is present in orange peel wastes and is known as an antimicrobial agent, which impedes biogas production when digesting the peels. In this work, pretreatment of the peels to remove limonene under mild condition was proposed by leaching of limonene using hexane as solvent. The pretreatments were carried out with homogenized or chopped orange peel at 20-40°C with orange peel waste and hexane ratio (w/v) ranging from 1 : 2 to 1 : 12 for 10 to 300 min. The pretreated peels were then digested in batch reactors for 33 days. The highest biogas production was achieved by treating chopped orange peel waste and hexane ratio of 12 : 1 at 20°C for 10 min corresponding to more than threefold increase of biogas production from 0.061 to 0.217 m(3) methane/kg VS. The solvent recovery was 90% using vacuum filtration and needs further separation using evaporation. The hexane residue in the peel had a negative impact on biogas production as shown by 28.6% reduction of methane and lower methane production of pretreated orange peel waste in semicontinuous digestion system compared to that of untreated peel.
Microwave assisted extraction has been demonstrated as an efficient green technology for the recovery of D-limonene from orange waste. Microwave irradiation was shown to be a more efficient method when compared to conventional heating due to its high selectivity for D-limonene, significantly shortened extraction durations and D-limonene yields twice that of conventional heating. Kinetic analysis of the extraction process indicated a typical two-step diffusion process, an initial stage of extraction from the exterior of the cells (1st stage) and diffusion of solute across the membrane (2nd stage). Diffusion coefficients for the initial stage of extraction from the exterior of cells (1st stage) for both conventional and microwave extraction demonstrated similar trends and activation energies. Interestingly, trans-membrane diffusion coefficient for the microwave assisted extraction at 110 °C was significantly high. Crucially, this was not observed with conventional heating suggesting that microwave radiation favourably interacts with the sample during extraction, causing simultaneous cell rupture and diffusion, resulting in greater yield. This provides an important insight into the development of extraction processes for orange peel.
In this work lime essential oils were extracted by hydrodistillation and supercritical carbon dioxide. In the case of hydrodistillation, the parameters evaluated were e xtraction time and characteristics of t he plant material. In supercritical extraction, the parameters evaluated were temperature, pressure, CO2 flow, extraction time and material characteristics. Considering citral content, the best results for hydrodistillation were obtained with a distillation time of 3 hours using whole peels. The best results for supercritical extraction were found using 60ºC, 90 bar, at a CO2 flow rate of 1 mL/ min for 30 minutes using milled peels. The best yields of lime oil were obtained by hydrodistillation (5.45% w/w) and supercritical extraction (7.93% w/w) for milled peels.
A microwave steam distillation (MSD) of essential oils from fresh citrus by-products (orange peels) was studied. The effectiveness of this innovative method in extraction of citrus essential oils have been evaluated and compared to conventional steam distillation. MSD offers important advantages like shorter extraction time (6 min), cleaner features and provides an essential oil with better sensory properties (better reproduction of natural fresh fruit aroma of the citrus essential oil) at optimized power (500 W). Results from chemical and cytological approaches confirm the effectiveness of this new technique, that allows substantial savings in terms of time and energy.Industrial relevanceThe treatment of by-products represents a strong demand for industrial fruits processing, which produces tonnages of waste material such as peels, seeds and fibers. The disposal of these materials usually represents an industrial legal restriction problem. Moreover, the waste treatment represents significant costs and is often misjudged by companies. Transformation of waste products with high value-added allows companies to reduce the global treatment costs, sometimes even to take some profits and thus improve their competitiveness. Moreover, the recovery process of by-products is part of the current existing sustainable development and environmental protection.Research Highlights► Development of new separation technique for extraction of essential oil. ► An improved microwave steam distillation (MSD). ► Valorization of by-products : part of development and environmental protection. ► Extraction of essential oil from orange peels. ► Comparison with conventional steam distillation (SD).
The object of the present work is to evaluate the possibility of carrying out the deterpenation of the citrus essential oil by using a mixture of ethanol and water as a solvent for liquid-liquid extraction. Liquid-liquid equilibrium has been determined for limonene + linalool + ethanol + water quaternary system at 298.15 K. Partitioning and selectivity of extraction were analyzed. Experimental data were correlated using the UNIQUAC and NRTL equations and the energetic parameters of these models at this temperature are determined.
L'objet du présent travail est d'évaluer la possibilité de réaliser la déterpénation de l'huile essentielle du citron en utilisant un mélange d'éthanol et d'eau comme solvant en extraction liquide-liquide. On a déterminé l'équilibre liquide-liquide pour le système quaternaire Limonène + Linalool + Éthanol + Eau à 298,15 K. On a analysé le partitionnement et la sélectivité de l'extraction. Les données expérimentales ont été corrélées à l'aide d'équations UNIQUAC et NRTL, et les paramètres énergétiques de ces modèles à cette température sont déterminés.
A useful and green method for the extraction of fats and oils with a new procedure combining Soxhlet extraction and Clevenger
distillation using d-limonene (bio-solvent) as a substitute for n-hexane (petroleum solvent) is reported. This method using green solvent is a laboratory exercise which easily teaches fundamental
green analytical chemical lessons and successfully incorporates green “analytical chemistry” into the teaching and the research
laboratory to both developed and developing nations.
This research investigates the use of seven natural deep eutectic solvents (NADESs) for valorisation of orange peel waste, with the final goal to propose a unique NADES for integrated biorefinery. Initial screening of NADESs revealed the excellent ability of cholinium-based NADES with ethylene glycol as hydrogen bond donor (ChEg50) to serve as a medium for orange peel-catalysed kinetic resolution (hydrolysis) of (R,S)-1-phenylethyl acetate with high enantioselectivity (ee = 83.2%, X = 35%), as well as it’s stabilizing effect on the hydrolytic enzymes (hydrolytic enzymes within ChEg50 peel extract were stabile during 20 days at 4 °C). The ChEg50 also showed a satisfactory capacity to extract D-limonene (0.5 mg gFW⁻¹), and excellent capacity to extract polyphenols (45.7 mg gFW⁻¹), and proteins (7.7 mg gFW⁻¹) from the peel. Based on the obtained results, the integrated biorefinery of orange peel waste using ChEg50 in a multistep process was performed. Firstly, enantioselective kinetic resolution was performed (step I; ee = 83.2%, X = 35%), followed by isolation of the product 1-phenylethanol (step II; h = 82.2%) and extraction of polyphenols (step III; h = 86.8%) from impoverished medium. Finally, the residual orange peel was analysed for sugar and lignin content, and results revealed the potential of waste peel for the anaerobic co-digestion process. The main bottlenecks and futures perspective of NADES-assisted integrated biorefinery of orange peel waste were outlined through SWOT analysis.
Citrus limetta is a widely-processed fruit that generates 40 % peel waste involving considerable constraints for waste management. Citrus limetta peel is a rich source of essential oil, especially d-limonene, commonly used as a fragrance and flavor ingredient. This study investigated the application of ultrasonication as a process intensification tool with improved extraction-efficiency. Peleg’s mathematical model was used to study the kinetics of ultrasound-assisted extraction (UAE) of d-limonene. The use of UAE reduces the total extraction time to 20 min compared to 185 min in a conventional process. In UAE, the highest extraction yield of d-limonene (32.9 mg/g, 97 %) was obtained using hexane as food-grade solvent, biomass:solvent ratio of 1:10, 2 mm particle size, agitation speed 300 rpm, temperature 60°C with ultrasonic power 80 W, 50 % duty cycle and frequency 25 kHz. Analysis and characterization of the extract were carried out using HPLC, GC-MS, and FTIR. Also, the surface morphology of raw material after extraction was studied using SEM analysis. The acceptable agreement was seen in the calculated values of Ceq from Peleg’s mathematical model and actual experimental results of extracted d-limonene. UAE stands as a fast, efficient, and economical method for the extraction of d-limonene from the fresh sweet lime peel.
Citrus waste (CW) consists mainly of peels and pressed pulp (seeds and segment membranes), which represent approximately 50% of the fruit weight. In the framework of bioeconomy, this type of waste could serve as a valuable raw material for the manufacture of biofuels and other commodities. Specifically, CW comprises high levels of pectin, cellulose, hemicellulose and soluble sugars, and to lesser extent essential oils. D-limonene is a terpenic compound and main component of essential oils in CW. In the present study, alternative and low environmental impact technologies for the valorization of CW are evaluated in the framework of a biorefinery strategy. Although D-limonene is the target product, a "closing the loop" strategy has been incorporated obtaining biogas and digestate as co-products from the residual side-streams. Plant-wide simulations are performed according to four different scenarios (Scenario I to Scenario IV) comprising four sections: pre-treatment, extraction, purification and anaerobic digestion. The main differences between the scenarios correspond to the extraction (hydrodistillation, cold pressing and solvent extraction) and purification stages. Scenarios III and IV use ethanol and hexane, respectively, as extractive agents. The results show that Scenario I has the worst environmental profile, while Scenario II has the best profile of all the scenarios analysed. In addition, purification stage is the main responsible for the highest environmental burdens in scenarios I, II and IV due to the energy required. In Scenario II, pre-treatment and extraction steps are identified as hotspots, due to the high electricity requirements. There is therefore still room for improvement, and future research should focus on optimising the purification stages to reduce the impacts of those scenarios with poorer environmental profiles.
Evaporation from a surface under atmospheric conditions can be difficult to characterize as the process involves both thermodynamics and kinetics. Thermogravimetric analysis was used to study the evaporation of d-limonene under several nitrogen flow rates above the surface. Instead of the common thermodynamic analysis, a kinetic treatment resulted in an activation energy of evaporation that is comprised mostly of the enthalpy of vaporization with a smaller, additional energy due to the diffusion of molecules through the laminar boundary layer above the evaporating surface. As the flow rate over the sample increased from 60 mL/min to 200 mL/min, the activation energy decreased from 57.3 kJ/mol to 49.7 kJ/mol and approached reported enthalpy of vaporization values. Thus, thermogravimetric analysis can be used to quantitatively characterize both the kinetic and thermodynamic aspects of non-equilibrium evaporation processes.
The present research has been planned to evaluate the effect of enzymatic maceration on the recovery of essential oil during hydrodistillation of orange (Citrus sinensis L.) peel. In the execution phase, the orange peel was hydrolysed under different conditions regarding enzyme concentration, liquid‐to‐solid ratio, temperature and incubation time, which established that hydrolysis of orange peel with 3.9% (mL/100 g) Viscozyme L® at liquid/solid ratio of 4.0 (mL/g) and 55°C for 3.8 hours can produce essential oil fourfold higher as compared to untreated orange peel. The kinetic modelling of the data further established that the incorporation of enzymatic pretreatment can reduce the extraction time up to 4 hours without any loss of aroma compounds. The GC‐MS analysis of orange peel essential oil obtained under optimum conditions of enzyme‐assisted hydrodistillation (EAHD) revealed the presence of D‐limonene as a major constituent (66%) followed by β‐caryophyllene (23%) and isopropyl myristate (11%). Moreover, the orange peel essential oil expressed via EAHD showed a good tendency to neutralize free radicals and protect linoleic acid under ambient conditions. Henceforth, it might be brought forward that enzyme‐assisted hydrodistillation worked more efficiently and economically than the conventional counterpart. Effect of Enzymatic maceration on Hydro‐distillation of d‐limonene from citrus peel.
Supercritical fluid extraction (SFE) is an innovative, clean, sustainable, and efficient technology to obtain essential oils and bioactive substances from plants and herbs. This work focused on the SFE of lemon essential oil using dehydrated and ground waste peels from a Protected Geographical Indication Italian cultivar. After the characterization of peels, both traditional hydro-distillation and SFE were applied to extract lemon essential oil. The most abundant compound in extract was d-limonene, equal to 82% in fruits harvested in November, 88% in December, and 80% in January. The effect of operating conditions on total extract and d-limonene yield was analyzed in a series of experiments at 35–50 °C and 12.5–20 MPa. The optimum conditions for limonene extraction were 15 MPa and 40 °C. The effect of ripening stage, particle size, and CO2 flow rate was also investigated and discussed. Moreover, theoretical and experimental pressure drop and bed void fraction during SFE were analyzed, showing a packing phenomenon. Sovová’s approximate model was applied to analyze the experimental results and it successfully fitted the extraction kinetics of essential oil. SFE can successfully be integrated in an intensified green process of citrus peel valorization to produce high-value and quality essential oil, with no use of chemical solvents, downstream treatments, and long-time extractions for a greener environment.
Orange peel waste (OPW) can be an effective feedstock for extraction of natural bioactive components such as limonene, a high value-added chemical broadly exploited for food, pharmaceutical, and cosmetic industrial applications. Extraction of limonene from OPW has been conventionally performed via solvent extraction using hexane, a hazardous petrochemical solvent currently restricted under international regulations. In this work, we have conducted a comparative assessment of the performance of a variety of green solvents for sustainable valorisation of OPW through limonene extraction. In particular, cyclopentyl methyl ether (CPME), ethyl lactate (EL), isopropyl alcohol (IPA), polyethylene glycol 300 (PEG 300), isopropyl acetate (IAc), dimethyl carbonate (DMC), methyl ethyl ketone (MEK), 2-methyl-tetrahydrofuran (2-MeTHF) and ethyl acetate (EAc) have been evaluated as hexane replacement for the recovery of limonene from OPW. Initially, a preliminary solvent screening was carried out using the COnductor-like Screening MOdel for Real Solvents (COSMO-RS) to estimate the solubility of limonene in the proposed solvents and rank their theoretical extraction performance. Afterwards, experimental studies were performed to determine the limonene extraction yields and optimize the operating conditions (temperature, time and solvent load) for limonene recovery from OPW using the various solvents, as confirmed by gas chromatography mass spectrometry (GC–MS) analysis. Overall, results support that CPME and 2-MeTHF bio-based solvents significantly outperform the benchmark petrochemical solvent hexane by increasing limonene extraction yields up to 80% and 40% respectively at optimum operating conditions. Moreover, recovery and reuse of these solvents in consecutive extraction cycles was successfully accomplished, while scanning electron microscopy analysis (SEM) suggests that solvent effects on biomass structure disruption could be beneficial for further bioprocessing.
Bioactive compounds should be extracted using alternative solvents and enabling technologies, in accordance with green extraction principles. The aim of this study is to develop an eco-friendly extraction method for grape-pomace anthocyanins on a larger scale. From a preliminary screening of 8 different natural deep eutectic solvents (NADES), a combination of choline chloride:citric acid was selected because of its price, physicochemical properties, and anthocyanin recovery and stability. The effects of multimode-microwave (MW), and low-frequency-ultrasound (US) irradiation (used alone or simultaneously), as well as that of process parameters on extraction efficiency have been investigated in order to maximise anthocyanin extraction yield. The best conditions were found to be: simultaneous ultrasound/microwave-assisted extraction (UMAE) (MW power at 300 W, US power 50 W), for 10 min with 30% (v/v) of water. This gave 1.77 mg gdw-1 of anthocyanins. Anthocyanins were efficiently recovered from NADES, which were recycled. The optimised procedure was scaled up to a half-litre batch.
The usage of the citrus wastes for strategic valorization is a concept for the production of various commercial products. Wastes from citrus fruits have a considerate amount of sugar and limonene. In the present work, partially removed limonene from hydrolysed orange peel was used for supplementation as carbon source in minimal media for the production of ethanol. A novel yeast strain, Saccharomyces cerevisiae strain BT1 (MK373758) was isolated from Toddy, obtained from Borassus flabellifer (toddy palm), Bhatan, Mumbai. This strain was used in the formulated fermentation media for the production of bioethanol. Optimization of critical parameters was done for pH, temperature and time of fermentation vs production of bioethanol. The Brix, pH, sugar content and ethanol content were measured during the fermentation process. The ethanol content was estimated by dichromate method and high performance liquid chromatography (HPLC) and the yield obtained was 0.95%. In addition, limonene was also extracted from hydrolysed orange peel and estimated by gas chromatography-flame ionization detection (GC-FID) and was found to be 0.4% (v/v). The two valuable products, bioethanol, and d-limonene, obtained from orange peel waste, promises its valorisation at a larger scale.
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Distillation is a process of heating a substance until the most volatile constituents change into the vapor phase, and then cooling the vapors to recover the constituents in liquid form by condensation. The main purpose of distillation is to separate a mixture into individual components by taking advantage of their different level of volatilities. Distillation is one of the main methods of extracting essential oils from plants. The percentage of each constituent in the vapor phase usually depends on its vapor pressure at a certain temperature. The principle of vacuum distillation may be applied to substances such as oils that would be damaged by overheating by the conventional method . There are different methods of distillation, depending on the desired product; some of these processes are described below.
This study analyses the quantitative and qualitative characteristics of citrus peel waste and discusses the systems for its valorisation. Citrus peel waste (CPW) is the main residue of the citrus processing industries and is characterised by a seasonal production (which often requires biomass storage) as well as high water content and concentration of essential oils. The disposal of CPW has considerable constraints due to both economic and environmental factors. Currently this residue is mainly used as food for animals, thanks to its nutritional capacity. If enough agricultural land is available close to the processing industries , the use of CPW as organic soil conditioner or as substrate for compost production is also possible, thus improving the organic matter content of the soil. Recently, the possibility of its valorisation for bio-methane or bioethanol production has been evaluated by several studies, but currently more research is needed to overcome the toxic effects of the essential oils on the microbial community. Considering the high added value of the compounds that can be recovered from CPW, it has promising potential uses: in the food industry (for production of pectin, dietary fibres, etc.), and in the cosmetic and pharmaceutic industries (extraction of flavonoids, flavouring agents and citric acid). However, in many cases, these uses are still not economically sustainable.
Attention is presently drawn to the development of a new and green alternative technique for the extraction of essential oil from citrus plant materials. This study was aimed at the extracting essential oil from orange and lemon peels using solvent-free microwave method. This process uses microwave-assisted hydro-diffusion technique to extract essential oil from citrus peels. Response surface methodology was used to investigate the effect of microwave power (200–1,000 W) and extraction time (10–40 min) on the essential oil yield. The oil extracted was characterized using Fourier transform infrared radiation (FTIR) and Gas chromatography–mass spectrometry analysis to determine the functional groups and chemical components present, respectively. The optimum yield of extract from orange and lemon peels were 3.7 and 2.0%, respectively at corresponding power of 1,000 W and time of 10 min. The analysis of variance results showed that the resulting models for both orange and lemon peels were significant and microwave power had greater influence on the extraction processes at both linear and quadratic levels. The FTIR analysis revealed prominent functional groups of alkenes that majorly constitute limonene compound at 1,642 and 1,643 cm⁻¹ for orange and lemon peels, respectively. The present process permits fast and efficient extraction, avoids water and solvent consumption, and allows substantial energy savings.
The recent advances and future perspectives in the complete valorization of citrus processing waste (CPW), a by-product of citrus processing industries, are presented in this review paper. First, the importance of valorization of CPW to develop a bio-economy and to reduce its negative environmental impacts is assessed. A brief survey of applications of native/modified CPW for nanoparticle, bio-sorbent, and biofertilizer production is presented. As the core part of the valorization scheme and regarding the environmental aspects, the perspectives for the application of CPW are via green extraction techniques, e.g., microwave- and ultrasound-assisted extractions, and biochemical processes. Furthermore, green extraction and biochemical techniques result in processes’ intensification toward integrated biorefinery models. The superiority of green extraction techniques over traditional techniques, challenges for implementation, and the valuable extracts obtained by these methods as well as a summary of their analytical techniques are discussed. The challenges of bioconversion of CPW to biofuels and fermentative products and strategies to overcome them are later presented. Finally, a literature review on using the concept of green chemistry for the integrated biorefinery of CPW and its engineering challenges is presented and a biorefinery scheme is proposed accordingly.
Citrus EOs is an economic, eco-friendly and natural alternatives to chemical preservatives and other synthetic antioxidants, such as sodium nitrites, nitrates or benzoates, commonly utilized in food preservation. Citrus based EOs is obtained mainly from the peels of citrus fruits which are largely discarded as wastes and cause environmental problems. The extraction of citrus oils from the waste peels not only saves environment but can be used in various applications including food preservation. The present article presents elaborated viewpoints on the nature and chemical composition of different EOs present in main citrus varieties widely grown across the globe; extraction, characterization and authentication techniques/methods of the citrus EOs; and reviews the recent advances in the application of citrus EOs for the preservation of fruits, vegetables, meat, fish and processed food stuffs. The probable reaction mechanism of the EOs based thin films formation with biodegradable polymers is presented. Other formulation, viz., EOs microencapsulation incorporating biodegradable polymers, nanoemulsion coatings, spray applications and antibacterial action mechanism of the active compounds present in the EOs have been elaborated. Extensive research is required on overcoming the challenges regarding allergies and obtaining safer dosage limits. Shift towards greener technologies indicate optimistic future towards safer utilization of citrus based EOs in food preservation.
The citrus peels and residue of fruit juices production are rich in d-limonene, a cyclic terpene characterized by antimicrobial activity, which could hamper energy valorization bioprocess. Considering that limonene is used in nutritional, pharmaceutical and cosmetic fields, citrus by-products processing appear to be a suitable feedstock either for high value product recovery or energy bio-processes. This waste stream, more than 10MTon at 2013 in European Union (AIJN, 2014), can be considered appealing, from the view point of conducting a key study on limonene recovery, as its content of about 1%w/w of high value-added molecule. Different processes are currently being studied to recover or remove limonene from citrus peel to both prevent pollution and energy resources recovery. The present review is aimed to highlight pros and contras of different approaches suggesting an energy sustainability criterion to select the most effective one for materials and energy valorization.
The objective of this study was to analyze the anaerobic digestion process inhibition by limonene, the main component of citrus essential oils (CEO) present in citrus peel. The biochemical methane potential (BMP) values of the citrus waste tested (orange peel, mandarin peel, mandarin pulp and rotten fruit) were 354-398LCH4kgVS-1. Grinding the orange peel (2.5glimoneneL-1) did not influence the BMP values, but slowed the kinetics, due to the increased availability of CEO caused by the grinding. The effect of (R)-limonene (0-3000mgL-1) on the batch anaerobic digestion of microcrystalline cellulose was also assessed. The half maximal inhibitory concentration, IC50, was 423mgkg-1 in an initial run and 669mgkg-1 in a second run of batch experiments. The methane course and IC50 values indicate that there are reversible inhibition and biomass activity recovery during the anaerobic digestion process, despite the non-reversible antimicrobial mechanism described in the literature for limonene to date.
Citrus fruit peels and leaves have always been the imperative attention of different researchers in pharmaceutical and cosmeceutical field. Moreover, the aroma of essential oil gains good reputation in aromatherapy. The volatile oil from leaves and rind of the citrus fruit has been reported by Hydrodistillation and expression methods several times. At this time, in present study, extraction of volatile oil forms the leaves and peels of fruit from citrus plants were obtained by hydrodistillation. Total seven Citrus plants Citrus lemon, Citrus medica, Citrus aurantium, Citrus pseudolemon, Citrus sinensis, Citrus reticulate and Citrus maxima were selected here for extraction. The percentage yield so obtained was compared.
This chapter presents a complete picture of current knowledge on a useful and green biosolvent “d-limonene” obtained from citrus peels through a steam distillation procedure followed by a deterpenation process. Limonene is a substitute for petroleum solvents such as dichloromethane, toluene, or hexane for the extraction of natural products. This chapter provides the necessary theoretical background and some details about extraction using limonene, the techniques, the mechanism, some applications, and environmental impacts. The main benefits are decreases in extraction times, the amount of energy used, solvents recycled, and CO2 emissions.
In this study, non-polar and polar compounds from coriander (Coriandrum sativum L.) seeds (CS) were fractionated using modern extraction techniques. CS were fractionated on non-polar fraction using supercritical fluid extraction (SFE) and influence of mean particle size on yield and chemical profile was investigated. Results were compared with conventional techniques used in essential oil isolation. It has been shown that SFE has certain advantages comparing to traditional techniques in terms of extraction yield and selectivity, since it provided highest linalool content (877.07 mg/100 g CS). Raffinate exhausted by SFE could be suitable for further processing, and it was subjected to ultrasound-assisted extraction (UAE) of moderately polar and polar fraction of polyphenolic compounds. Results showed that ethanolic extracts had higher antioxidant activity than water extracts for all CS mean particle sizes. The highest content of hydroxicinammic acids was observed in ethanolic extracts obtained from exhausted CS with lowest mean particle size. Therefore, coriander seeds, which have been known for its rich essential oil content, could be used for sequential production of polyphenolic-rich extracts with high antioxidant activity.
(+)-Limonene is a renewable chemical with numerous and growing applications. Traditional uses such as flavor, fragrance and green solvent are rapidly expanding to include its utilization as a platform chemical, extraction solvent for natural products and active agent for functionalized products. Said constant demand expansion will feed back into rising production and use of this relevant natural product, especially for advanced applications.
Second cooling was added to the oil collectors of an improved Clevenger type apparatus (ICT) to investigate the thermal reaction of essential oils from orange peel comparing to traditional Clevenger type apparatus (CT). The results demonstrated the yield rate of essential oil from ICT was significantly higher (p < 0.05) than that from CT. The major components of the essential oils consisted of monoterpenes, such as d-limonene, β-myrcene, β-pinene，γ-terpinene, α-pinene, and etc. Interestingly, we found that ICT prevented the thermal reaction-the transformation of β-myrcene to β-thujene and, reduced the oxidation on α-pinene and β-pinene of the essential oil in comparison to CT. In addition, the yield rate of γ-terpinene can also be improved via ICT comparing to CT. Thus, ICT is an effective improvement to traditional CT.
A certain combination of natural products in the solid state becomes liquid, so called natural deep eutectic solvents (NADES). Recently, they have been considered promising new green solvents for foods, cosmetics and pharmaceuticals due to their unique solvent power which can dissolve many non-water-soluble compounds and their low toxicity. However, in addition to the features as solvents, the stabilisation ability of NADES for compounds is important for their further applications. In the study, the stability analysis demonstrates that natural pigments from safflower are more stable in sugar-based NADES than in water or 40% ethanol solution. Notably, the stabilisation capacity of NADES can be adjusted by reducing water content with increasing viscosity. The strong stabilisation ability is due to the formation of strong hydrogen bonding interactions between solutes and NADES molecules. The stabilising ability of NADES for phenolic compounds shows great promise for their applications in food, cosmetic and pharmaceutical industries.
Citrus by-products are the processing wastes generated after citrus juice extraction and constitute about 50 % of fresh fruit weight. This solid residue comprised of peel (flavedo and albedo), pulp (juice sac residue), rag (membranes and cores) and seeds. The disposal of the fresh peels is becoming a major problem to many factories. Usually, citrus juice industries dry the residue and it is either sold as raw material for pectin extraction or pelletized for animal feeding, though none of these processes is very profitable. This residual material is a poor animal feed supplement because of its extremely low protein content and high amount of sugar. The application of agroindustrial by-products in bioprocesses offers a wide range of alternative substrates, thus helping solve pollution problems related to their disposal. This article reviews attempts that have been made to use citrus by-products to generate several value-added products, such as essential oils, pectin, enzymes, single cell protein, natural antioxidants, ethanol, organic acids, and prebiotics.
The application of steam explosion and enzymatic hydrolysis pretreatments on lemon (Citrus limon L.) citrus peel wastes was studied to obtain bioethanol, galacturonic acid and other co-products, such as d-limonene and citrus pulp pellets. Steam explosion pretreatment and recovery of lemon citrus essential oils was carried out at pilot plant scale. The effect of steam explosion on lignocellulosic composition of lemon peel wastes was studied by thermogravimetric analysis. The antimicrobial activity of lemon essential oil on Saccharomyces cerevisiae and its influence on ethanol production during fermentation were also studied. The steam-exploded lemon peel wastes were processed by sequential and simultaneous hydrolysis and fermentation. Concentrations of sugars, galacturonic acid and ethanol were analyzed to measure the efficiency of these processes. Significant antimicrobial activity of lemon essential oils has been observed on S. cerevisiae at concentrations above 0.025%. The steam explosion pretreatment has shown an interesting effect on lemon peel wastes processing for obtaining ethanol and galacturonic acid. This pretreatment reduces the residual content of essential oils below 0.025% and significantly decreases the hydrolytic enzyme requirements. Ethanol production in excess of 60 L/1000 kg fresh lemon peel biomass can be obtained.
Perfume Engineering is a must-have reference for engineers who design any products that require fragrances, such as perfumes, cosmetics, healthcare and cleaning products.
This book provides the reader with practical guidance on perfume design, performance and classification, from its beginnings as a liquid mixture to the vapour phase, by way of odorant dispersion and olfactory perception. It does this through the application of development and validation models to account for fragrance evaporation, propagation and perception.
d-Limonene, a major constituent of citrus oils, is a monoterpene widely used as a flavor/fragrance additive in cosmetics, foods, and industrial solvents as it possesses a pleasant lemon-like odor. d-Limonene has been designated as a chemical with low toxicity based upon lethal dose (LD50) and repeated-dose toxicity studies when administered orally to animals. However, skin irritation or sensitizing potential was reported following widespread use of this agent in various consumer products. In experimental animals and humans, oxidation products or metabolites of d-limonene were shown to act as skin irritants. Carcinogenic effects have also been observed in male rats, but the mode of action (MOA) is considered irrelevant for humans as the protein α2u-globulin responsible for this effect in rodents is absent in humans. Thus, the liver was identified as a critical target organ following oral administration of d-limonene. Other than the adverse dermal effects noted in humans, other notable toxic effects of d-limonene have not been reported. The reference dose (RfD), the no-observed-adverse-effect level (NOAEL), and the systemic exposure dose (SED) were determined and found to be 2.5 mg/kg/d, 250 mg/kg//d, and 1.48 mg/kg/d, respectively. Consequently, the margin of exposure (MOE = NOAEL/SED) of 169 was derived based upon the data, and the hazard index (HI = SED/RfD) for d-limonene is 0.592. Taking into consideration conservative estimation, d-limonene appears to exert no serious risk for human exposure. Based on adverse effects and risk assessments, d-limonene may be regarded as a safe ingredient. However, the potential occurrence of skin irritation necessitates regulation of this chemical as an ingredient in cosmetics. In conclusion, the use of d-limonene in cosmetics is safe under the current regulatory guidelines for cosmetics.
The physicochemical indices and the qualitative and quantitative composition of the volatile fraction and the oxygenated heterocyclic fraction of cold-pressed Key lime oil (types A and B) and Persian lime oil are reported. The volatile fraction of Persian lime oil is characterized by a higher content of limonene, γ-terpinene, esters, and monoterpene aldehydes and a lower content of β-pinene + sabinene, sesquiterpenes, and aliphatic aldehydes than Key lime oils. Oxypeucedanin was not detected in Key lime oil type A, while it is present in Key lime oil type B and Persian lime oil. This is probably due to the extraction technology used for Key lime oil type A, which allows the essential oil to come into contact with the juice. Under these conditions, the epoxy ring of oxypeucedanin is opened by hydrolysis to form oxypeucedanin hydrate. Keywords: Citrus aurantifolia Swingle; cold-pressed Key lime oil; type A; type B; Citrus latifolia Tanaka; cold-pressed Persian lime oil; volatile fraction; limonene; γ-terpinene; β-pinene + sabinene; coumarins; psoralens; oxypeucedanin
Production of ethanol, biogas, pectin and limonene from citrus wastes (CWs) by an integrated process was investigated. CWs were hydrolyzed by dilute-acid process in a pilot plant reactor equipped with an explosive drainage. Hydrolysis variables including temperature and residence time were optimized by applying a central composite rotatable experimental design (CCRD). The best sugar yield (0.41 g/g of the total dry CWs) was obtained by dilute-acid hydrolysis at 150 °C and 6 min residence time. At this condition, high solubilization of pectin present in the CWs was obtained, and 77.6% of total pectin content of CWs could be recovered by solvent recovery. Degree of esterification and ash content of produced pectin were 63.7% and 4.23%, respectively. In addition, the limonene of the CWs was effectively removed through flashing of the hydrolyzates into an expansion tank. The sugars present in the hydrolyzates were converted to ethanol using baker’s yeast, while an ethanol yield of 0.43 g/g of the fermentable sugars was obtained. Then, the stillage and the remaining solid materials of the hydrolyzed CWs were anaerobically digested to obtain biogas. In summary, one ton of CWs with 20% dry weight resulted in 39.64 l ethanol, 45 m3 methane, 8.9 l limonene, and 38.8 kg pectin.