Citrus Essential Oils Research Articles

Revealing the off-flavors in hydro-distilled essential oils of sweet orange (Citrus sinensis) by flavoromics strategy and computational simulation

Citrus essential oils (EOs) are renowned for their aroma, but thermal extraction methods can introduce undesirable cooking and pungent odors. The specific compounds responsible for these off-flavors and their perception mechanisms remain unclear. This study investigated the flavor differences between cold pressing (CP) and hydro-distilled (HD) extracted essential oils from sweet oranges (SEOs) using flavoromics strategy. The results indicated that increased levels of alcohol compounds, particularly terpinen-4-ol, β-citronellol, geraniol, trans-carveol, and α-terpineol, were primarily responsible for the off-flavors in HD-extracted SEOs. Furthermore, molecular docking and dynamics simulations revealed that off-flavor compounds bind to olfactory receptors through hydrogen bonding and hydrophobic interactions, inducing slight structural and conformational changes that facilitate odor recognition and activate downstream signaling events. This study offers crucial insights into the mechanisms underlying off-flavor development in citrus EOs, providing valuable knowledge for optimizing extraction methods, controlling SEOs quality, and advancing flavor science.

Antifungal Activity of Citrus Essential Oil in Controlling Sour Rot in Tahiti Acid Lime Fruits.

Sour rot, caused by Geotrichum citri-aurantii, is a significant post-harvest disease in citrus, resulting in economic losses due to the lack of effective fungicides. This study investigates the antifungal activity of citrus essential oils in controlling sour rot in Tahiti acid lime fruits. Essential oils were extracted via hydrodistillation with chemical composition analyzed by CG-MS and tested in vitro and in vivo. In vitro assays evaluated mycelial growth inhibition at 2 to 32 µL mL-1 concentrations. In vivo trials involved preventive and curative treatments on artificially inoculated fruits stored at 25 °C ± 2, and the results showed that Pera IAC sweet orange oil, at 32 µL mL-1, reduced disease severity by 96% in curative treatments. In contrast, Late IAC 585 willowleaf mandarin oil demonstrated moderate inhibition (44%) at the highest concentration in vitro. The oils did not affect key fruit quality parameters such as juice yield and total soluble solids. These findings suggest that citrus essential oils could be natural alternatives to synthetic fungicides for post-harvest sour rot management, combining effectiveness with maintaining fruit quality.

Nanoencapsulation of citrus essential oils in systematic modified chitosan‐based nanofibers

AbstractIn this study, chitosan (CH)/polyvinyl alcohol (PVA) hybrid nanofibers incorporating three distinct essential oils lemon, lime, and grapefruit were successfully obtained via the innovative electrospinning technique. Characteristics of the electrospinning polymeric mixture loaded with essential oils using variable ratios of CH/PVA were evaluated. The nanoencapsulation process of citrus essential oils was achieved with 47.67%–88.16% encapsulation efficiency. Notably, the thermal stability of the encapsulated essential oils experienced a significant enhancement after encapsulation. Scanning electron microscopy analysis revealed valuable insights, revealing that an increased amount of incorporated essential oil within the polymeric mixture solutions led to a reduction in the average fiber diameters. The resulting nanofibers demonstrated notable attributes such as antioxidant, tyrosinase inhibitory, and antibacterial activities. The present research demonstrates the ability of CH/PVA hybrid nanofibers obtained through an electrospinning process to preserve citrus essential oils properties quality and reveals a high potential application of nonencapsulated citrus essential oils in biomaterials, food packaging, and advanced cosmetic application.

Antifungal activities of some citrus essential oils against Pyricularia oryzae

Rice is a staple food worldwide because many families depend on it as an everyday source of food. However, there are some agents posing as threat to the availability of rice worldwide thereby threatening food security. Pyricularia oryzae is a fungal agent notable for causing rice blast disease thereby causing shortage in the production of rice. Essential oils (EOs) from peels (fresh and dried) of three species of citrus fruit (lime, grapefruit and tangerine) were investigated for their antifungal activity against P. oryzae. The EOs were extracted and analysed for their composition using standard analytical techniques. Their antifungal activities were also tested on potato dextrose agar (PDA) medium using disc diffusion method and the results obtained were compared with standard antifungal agents. Dried tangerine EO had the highest fungal mycelial growth inhibition (90%) which was followed by fresh tangerine EO (76.2%). The compounds detected in the essential oils composed majorly hydrocarbons and oxygenated hydrocarbons with limonene, beta myrcene and alpha terpineol detected in fairly high amount in all the investigated essential oils. This study, shows that the peels of these citrus fruits could be of great importance in combating the scourge of P. oryzae, reducing the occurrence of rice blast disease, enhancing rice availability as a staple food and by extension, ensuring food security. These attributes highlight the potential benefits of citrus fruit peels instead of regarding them as mere waste materials.

Essential oil release from zein particles as modulated by inorganic coating and biopolymeric networking

Zein particles (ZPs) have emerged as a popular delivery carrier for hydrophobic bioactive substances. However, some lipophilic compounds are easily released from ZPs because of the low polarity compatibility between zein and the compounds. The loss of encapsulated substances is particularly evident for citrus essential oil (CEO), an extremely hydrophobic ingredient. The premature release of CEO from ZPs was mitigated by developing a modification approach using ZPs coated with calcium phosphate (CaP) and networked with Ca2+-alginate gel (CaAlg). The approach involved the preparation of ZPs (through the antisolvent addition procedure) in phosphate buffer, and supplementation of the particles consecutively with sodium alginate and Ca2+ ions (as CaCl2). This procedure resulted in retention of up to 28% of CEO within ZPs after the accelerated storage experiment. Under in vitro gastric and intestinal digestion condition, the CaP-coated and CaAlg-networked ZPs had a significantly lower release of CEO compared to their non-coated and non-networked counterparts. The morphology of the particles was investigated by scanning (SEM) and transmission (TEM) electron microscopies, as well as confocal laser scanning microscopy. SEM imaging showed that sodium alginate could facilitate the formation of CaP coating through preventing CaP crystallization. CaP coating also decreased the ZPs fusion/aggregation as evidenced by comparing the ζ-potential and microscopic morphology of the particles. Examination of the infrared spectra of the particles revealed that the formation of CaP coating occurred at Ca2+ ion concentrations ≥ 10 mM.

Exploring the chemotaxonomic significance of selected Citrus essential oils through GC-MS/FID and multivariate correlation analyses

The volatile chemical composition and qualitative as well as quantitative variation of the leaf and peel essential oils of five species belonging to Citrus genus were studied. The investigated Citrus species were Citrus aurantifolia (Christm.) Swingle, Citrus limon L. (Osbeck), Citrus maxima (Burm.f.) Merr. R, Citrus medica L. and Citrus medica *Citrus limon. Essential oils were isolated by hydrodistillation and analysed using GC-MS/FID. In total 49 compounds comprising of 83.1-99.0% of the volatile compositions were identified in five leaf essential oils whereas 45 compounds comprising of 97-99.4% of the volatile compositions were identified in peel essential oils. Oxygenated monoterpenes were the predominant composition present in the leaf oils of all Citrus species whereas sesquiterpene hydrocarbons were the main composition found in C. maxima leaf oil (39.9%). Monoterpene hydrocarbons were predominating in the isolated peel oils. Principal component analysis of Citrus species was employed to provide a comprehensive evaluation of essential oil components. Both PCA and cluster analysis of both leaf and peel essential oils were classified into two clusters and then subsequent subclusters, characterized according to the major essential oil components. Monoterpene hydrocarbons, oxygenated hydrocarbons and diterpenes were identified as the significant category of compounds characterised for Citrus essential oils.

Toxicity and enzymatic mechanism of Citrus spp. essential oils and major constituents on Haemaphysalis longicornis (Acari: Ixodidae) and non-target Harmonia axyridis (Coleoptera: Coccinellidae)

Plant essential oils (EOs)-based acaricides have been recognized as environmentally-friendly alternatives to synthetic acaricides because of their low toxicity against non-target species. Despite this, there are knowledge gaps regarding the toxicity mechanisms of plant EOs against non-target species. Here, the toxicology and enzymatic mechanism of Citrus reticulata and Citrus lemon EOs were evaluated against the vector pest, Haemaphysalis longicornis, and non-target ladybird beetle, Harmonia axyridis. Both EOs were mainly composed of d-Limonene, followed by β-Myrcene and γ-Terpinene in C. reticulata, and (−)-β-Pinene and γ-Terpinene in C. lemon. Citrus reticulata and C. lemon EOs were toxic to Hae. longicornis, with 50 % lethal concentration (LC50) values estimated at 0.43 and 0.98 μL/mL via nymphal immersion test, and 42.52 and 46.38 μL/mL via spray application, respectively. Among the constituents tested, β-Myrcene was the most effective, with LC50 values of 0.17 and 47.87 μL/mL via immersion and spray treatment, respectively. A significant mortality of non-target Har. axyridis was found when treated by the EOs at concentrations two times greater than LC50 estimated against H. longicornis. The biochemical assay revealed that the EOs induced changes in the antioxidant enzyme activity of superoxide dismutases, catalase, and glutathione peroxidase in Hae. longicornis and Har. axyridis. The results demonstrated the acaricidal potential of citrus EOs and their major constituents for tick control, revealed the risk of the EOs to non-target species, and provided relevant insights into the mechanisms underlying their toxicity.

Sustained-release mechanism of β-Cyclodextrin/cationic cellulose-stabilized Pickering emulsions loaded with citrus essential oil

Citrus oil (CO) is a commonly used natural flavor with high volatility, which is not conducive to sustained release under food environmental stress. This study constructed novel β-cyclodextrin/cationic cellulose nanocrystal (β-CD/C-CNC) complexes via noncovalent interaction, which were used to stabilize CO-loaded Pickering emulsions (PEβ-CD/C-CNC). The C-CNC greatly improved the physical stability, droplet dispersion and viscoelasticity of PEβ-CD/C-CNC by forming a tight network structure, as verified by rheological behavior. Moreover, C-CNC improved the wettability of β-CD/C-CNC complexes and enhanced the interaction between adjacent β-CD/C-CNC complexes. C-CNC also contributed to the interfacial viscoelasticity, hydrated mass, and layer thickness via the interfacial dilational modulus and QCM-D. β-CD/C-CNC complexes adsorbed on the oil–water interface gave rise to a dense filling layer as a physical barrier, enhancing the sustained-release performance of PEβ-CD/C-CNC by limiting diffusion of citrus essential oil into the headspace. This study provides new technical approaches for aroma retention in the food industry.

The Effect of Electrical Stimulation & Citrus Essential Oils Therapies “ESCO’s” Model for Diabetic Foot Ulcer: A Systematic Review

The Effect of Electrical Stimulation & Citrus Essential Oils Therapies “ESCO’s” Model for Diabetic Foot Ulcer: A Systematic Review

A cleaner and eco-friendly approach to simultaneous extraction and characterization of essential oil and pectin from Assam lemon peel and its application for energy generation through TENG devices

Scientists have been working on developing a green bio-TENG for portable remote devices, including wearables in the biomedical sector. The process involves obtaining pectin, a green material with anti-microbial properties, as a Triboelectric material. This study focuses on the extraction of essential oil (EO) and pectin from Assam lemon peel simultaneously. A single-step strategy was optimized using a central composite design-based response surface approach. The extracted pectin yielded 4.19 ± 0.31 % and 11.53 ± 0.11 %, respectively. GC-MS analysis revealed 52 volatile components in the Assam lemon EOs, with limonin being 94.47 % and β-Bisabolene being 1.26 %. Only khusilal was found in the EOs, a rare discovery in the scientific domain. The extracted pectin showed good purity and antimicrobial properties. The in vitro activities of the citrus EO against microbial cultures revealed its activity in controlling and eradicating bacterial and fungal growth. Hydro distillation followed by enzyme treatment is a promising approach that combines two separate extraction procedures. The produced biopolymer showed the generation of electrical signals under minimal pressure and stretching and prevented microbial degeneration when applied to a nanogenerator.

Citrus essential oils nano-emulsions: formulation and characterization

The use of citrus essential oils nano-emulsions (CEO-NE) plays a crucial role in enhancing food safety. This is achieved through various mechanisms such as the enhancement of organoleptic properties, increased bioavailability of bioactive components from essential oils, controlled release of key compounds for long-term efficacy, and extension of the shelf life of food and beverages (antioxidant and antimicrobial activity). In this work, CEO-NEs, formulated with different types of citrus essential oils, Tween 80, and alcohol, were obtained by magnetic stirring combined with ultrasound method. The main component of CEO-NEs was D-limonene (31.37 % bergamot-loaded nano-emulsions, 48.81 % tangerine-loaded nano-emulsions, 87.82 % orange-loaded nano-emulsions, 87.09 % grapefruit-loaded nano-emulsions, 48.53 % lemon-loaded nano-emulsions). The selected formulations demonstrated a mean droplet diameter of 47.285 nm. The nano-emulsions were stable even after 30 days of storage (except tangerine nano-emulsions). The bergamot-loaded nano-emulsion had the highest antibacterial activity against Escherichia coli, while Staphylococcus aureus and Listeria monocytogenes seemed to be more resistant to citrus nano-emulsions.

Metabolic profiling and enzyme inhibitory activity of the essential oil of citrus aurantium fruit peel

BackgroundBitter orange (Citrus aurantium) is a fruiting shrub native to tropical and subtropical countries around the world and cultivated in many regions due to its nutraceutical value. The current study investigated the metabolic profiling and enzyme inhibitory activities of volatile constituents derived from the C. aurantium peel cultivated in Egypt by three different extraction methods.MethodsThe volatile chemical constituents of the peel of C. aurantium were isolated using three methods; steam distillation (SD), hydrodistillation (HD), and microwave-assisted hydrodistillation (MAHD), and then were investigated by GC-MS. The antioxidant potential was evaluated by different assays such as DPPH, ABTS, FRAP, CUPRAC, and phosphomolybdenum and metal chelating potential. Moreover, the effect of enzyme inhibition of the three essential oils was tested using BChE, AChE, tyrosinase, glucosidase, as well as amylase assays.ResultsA total of six compounds were detected by GC/MS analysis. The major constituent obtained by all three extraction methods was limonene (98.86% by SD, 98.68% by HD, and 99.23% by MAHD). Differences in the composition of the compounds of the three oils were observed. The hydrodistillation technique has yielded the highest number of compounds, notably two oxygenated monoterpenes: linalool (0.12%) and α-terpineol acetate (0.1%).ConclusionIn our study differences in the extraction methods of C. aurantium peel oils resulted in differences in the oils’ chemical composition. Citrus essential oils and their components showed potential antioxidant, anticholinesterase, antimelanogenesis, and antidiabetic activities. The presence of linalool and α-terpineol acetate may explain the superior activity observed for the oil isolated by HD in both radical scavenging and AChE inhibition assays, as well as in the enzyme inhibition assays.

Enhancing fractionation of terpenoids and terpenes in citrus essential oils by a biphasic extraction system

Efficient deterpenation of essential oils is crucial for obtaining high value-added products. In this work, a biphasic extraction system integrated with associative extraction was utilized to enhance fractionation of terpenoids and terpenes, where organic salt and organic solvent were employed as extractants in each phase. Ten different organic solvents were evaluated in terms of their phase behavior, extraction performance, and EHS-related properties. The positive or negative effect of organic solvents on biphasic extraction performance was elucidated through molecular dynamics simulations and FT-IR spectra analysis. The results indicate that an organic solvent lacking hydrogen bonding ability can reduce its interaction with organic salt or terpenoids, thereby exerting a positive contribution to biphasic extraction. For crude orange sweet essential oil, the biphasic system containing tetrabutylammonium chloride and n-hexane achieves a 6.2-fold concentration of terpenoids, demonstrating its effectiveness in enhancing extractive deterpenation of essential oil.

Essential oils loaded biodegradable PBAT/PBS films as young coconut packaging after harvest

The polybutyrate adipate terephthalate/polybutylene succinate (PBAT/PBS) films were produced by the single screw blown-film extrusion method for the young coconut packaging application. The antifungal performance of the film was enhanced by the addition of essential oils, including cinnamon essential (CIN) and citrus essential (CT) oils. The mechanical properties, physical properties, thermal properties, oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) of the film with essential oils were evaluated. The results found that 10 wt% of PBAT content in the PBS matrix was suitable for biodegradable film creation. In the film packaging, essential oils at 5 phr might be a plasticizer by increasing the tensile strength, elongation at break and toughness, while the tensile modulus decreased. The oxygen and water vapor transmission rates (OTR, WVTR) trended to increase, especially of the 10CT_10PBAT/PBS film. The essential oils could show antifungal performance by inhibiting the A. Niger growth. In the case of film packaging application, the film with essential oils could enhance the storage time of young coconut to 21 days without yeast growth on the surface, while the quality of coconut water did not change.

Chemical composition of stored smoked clupeids, Ethmalosa fimbriata and Sardinella maderensis after preservative treatment with citrus essential oil

Chemical composition of stored smoked clupeids, Ethmalosa fimbriata and Sardinella maderensis after preservative treatment with citrus essential oil

Chemical Variability, Antioxidant and Larvicidal Efficacy of EOs from Citrus sinensis (L.) Osbeck Peel, Leaf, and Flower

Essential oils (EOs) from Citrus sinensis (Rutaceae) possess diverse biological activities. However, a comprehensive comparison of their chemical composition and bioactivity across different plant parts has not been studied yet. The current research comparatively assesses the yield, chemical composition, chiral distribution, antioxidant properties, and larvicidal activity of EOs extracted from the peels, leaves, and flowers of C. sinensis. EOs extracted via hydro-distillation (HD) and steam distillation (SD) were analyzed by gas chromatography–mass spectrometry (GC-MS) and chiral GC-MS to explore their chemical composition and enantiomeric distribution. In addition, their larvicidal and antioxidant potentials were evaluated following standard protocols. Peels of C. sinensis exhibited significantly higher oil content (1.75–2.25%) compared to its leaves (0.75–0.78%) and flowers (0.20–0.25%). The GC-MS analysis identified around 60 compounds, including terpenoids, sesquiterpenoids, and oxygenated terpenoids in the HD and SD extractions. Higher concentrations of sabinene were found in flower extract (38.05–39.89%) and leaf extract (32.30–36.91%), while peel extract contained more than 90% limonene. The larvicidal activity of peel oil was primarily attributed to limonene, with an LC50 value of 0.0031 µL/mL. The current study reports the first chiral (GC-MS) analysis in the essential oil of the leaves and flowers of C. sinensis, paving the way for authenticity and purity. Furthermore, the chemical profiling of citrus EOs, particularly from the peel, demonstrates a safe and promising candidate for diverse biological applications.

Preparation and characterization of chitosan-based corn protein composites constructed with TG enzyme and their preservation performance on strawberries

This study describes the synthesis of Chitosan - corn protein (CSZ-TG) composites using TG enzyme (TG) as a cross-linking agent and the preparation of chitosan-based composite membrane material (CSZEO-TG) by blending citrus essential oil (EO) with the synthesized CSZ-TG. The prepared composite membrane material was used for fresh strawberry preservation and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-spectral diffraction, tensile properties, and water vapor and CO2 permeability. Scanning electron microscopy results showed a smooth surface of the composite membrane material after the addition of TG enzyme, while Fourier transforms infrared spectroscopy results showed a structural change of the composite membrane material after the addition of corn protein (Z). The tensile results showed an increase in the tensile strength of the composite membrane material after the addition of TG enzyme, while the flexibility of the composite membrane material was enhanced after the addition of EO. Compared with the pure chitosan membrane (CS), the water vapor and CO2 barrier properties of the composite membrane material after the addition of Z, TG, and EO did not change much, and they all showed better water vapor barrier properties. The results of the antioxidant analysis of the solution of the CSZEO-TG composite membrane material showed that the composite membrane material had efficient antioxidant properties. The effects of the composite film material on the storage period and quality of strawberries were evaluated by the indicators of weight loss, hardness, decay rate, soluble solids, titratable acid content, MDA content, and the content of four enzymes, SOD, POD, PPO and CAT. Comprehensive freshness data analysis showed that CSZEO-TG had the best freshness preservation performance and effectively extended the shelf life of strawberries.

Quantitative analysis of oxygen heterocyclic compounds using liquid chromatography coupled to tandem mass spectrometry, method development and environmental assessment

The latest trends in the field of laboratory method development concern the validation of fast procedures, and the safety of the operator and environment. The present research is focused on the development of fast and environmentally-friendly analytical method of liquid chromatography-triple quadrupole mass spectrometry for the determination of oxygen heterocyclic compounds in Citrus-flavored products. To the best of the authors’ knowledge, this is the first approach for the characterization of thirty-six oxygen heterocyclic compounds in less than four minutes using water/ethanol as mobile phase. Molecules were characterized in Citrus essential oils and beverages. Figures of merit determined were linearity, precision, limits of detection and quantification. The method was compared in terms of greenness with our two methodologies previously published for analysis of oxygen heterocyclic compounds. The analytical greenness metric approach and the “RGB model” were used. According to these approaches, the method proposed here is faster, safer and more eco-friendly.

Characterization of volatile compounds from healthy and citrus black spot-infected Valencia orange juice and essential oil by using gas chromatography–mass spectrometry

Citrus black spot (Phyllosticta citricarpa, CBS) is an important fungal disease that causes rind blemishes and affects quality of citrus fruits. The response of citrus to CBS in terms of volatiles was evaluated using molecular sensory science approaches. Fifty and twenty-one volatiles were identified in the orange juice and essential oil samples, respectively, via gas chromatography–mass spectrometry (GC–MS). The total volatile content in the samples increased after CBS infection, especially in the severe-infection group (SEG) juice and moderate-infection group (MOG) essential oil, which reached the highest levels. CBS enhanced floral, fruity, and off-flavor aromas and decreased the green aroma in citrus juice. Citrusy, floral, and green aromas increased in the CBS-infected essential oil. Six/five potential markers were screened in citrus juice/essential oil, respectively using the orthogonal partial least-square discriminant analysis (OPLS-DA) model. The changes in aroma profile and the difference in infection levels in citrus were attributed to these odorants.

Process kinetics optimization for extraction of essential oil from the peel of Citrus sinensis for the development of food packaging film

AbstractThe goals of the present work were to achieve maximum extraction efficiency from Citrus sinensis peel and effective utilization of its bioactive compounds. This work focused on studying the physicochemical characteristics and yield percentage of citrus essential oil (CEO) extracted from citrus peels at different extraction times, extraction temperatures, solid–liquid ratios, and solvent combinations, and the data of yield percentage was subjected to find the best kinetic model for better yield. C. sinensis peel powder was subjected to Soxhlet extraction of essential oil at varied solid:liquid ratios (1/2, 1/4, 1/6, 1/8, and 1/10), time intervals in minutes (120, 150, 180, 210, 240, 270, and 280), temperatures (50, 60, 70, 80, 90, and 100°C), and solvents (n‐hexane, petroleum ether, chloroform, methanol, and water) to characterize their impact on yield percentage. The essential oil extraction kinetics were assessed using the experimental data and two different kinetic models (zero‐order and first‐order kinetic model). The bioactive compounds were assessed using GC–MS, as well. Amongst the other solvents, maximum extraction yield was observed at 90°C for 270 min using n‐hexane. GC–MS results showed that d‐limonene was the predominant compound constituting 41.41%. A good agreement between applied kinetic models and experimental data was demonstrated by the first‐order model (R2 = .9830) and the zero‐order kinetic model (R2 = .9719). Thus, the effective conditions for maximum extraction yield of CEO peels were optimized and the extracted CEO can be used in food packaging applications for shelf‐life extension.Practical applicationsEffective food waste management is vital for promoting sustainable resource usage, reducing environmental impact, saving money and energy, addressing global hunger, and upholding ethical and social responsibilities. It is important to minimize food waste throughout the entire food supply chain. Citrus peels are the by‐products of the citrus fruit processing industry and households which contribute to organic waste and its management is an important consideration for environmental sustainability. Thus, this study aims to manage these wastes by extracting essential oil from them and optimizing their process. The role of Citrus sinensis essential oil in the food industry includes natural flavoring with a consistent flavor profile, versatility in culinary applications, provides a natural and clean label, and are cost‐effective. Also, the universally recognized and enjoyed flavor of C. sinensis makes its essential oil a popular choice for products with broad consumer appeal. However, it is essential to follow regulatory guidelines for food‐grade essential oils and adhere to recommended usage levels. The results of this study have practical implications for improving yield, quality, efficiency, and sustainability of the extracted essential oil in the food industry. The optimized data can positively impact various aspects of food production, by enhancing flavor profiles, reducing the processing time and costs, and thus facilitating scale‐up potential. In addition, proper storage conditions should be maintained to ensure the stability and quality of the extracted essential oil over time.