Determination of Volatile Flavour Profiles of Citrus spp. Fruits by SDE-GC-MS and Enantiomeric Composition of Chiral Compounds by MDGC-MS

Recent progress in the extraction of terpenoids from essential oils and separation of the enantiomers by GC-MS

Terpenoids possess significant physiological activities and are rich in essential oils. Some terpenoids have chiral centers and could form enantiomers with distinct physiological activities. Therefore, the extraction and separation of terpenoids enantiomers are very important and have attracted extensive attention in recent years. Meanwhile, the specific distribution and enantiomer excess results (the excess of one enantiomer over the other in a mixture of enantiomers) could be used as quality markers for illegitimate adulteration, origin identification, and exploring component variations and functional interrelations across different plant tissues. In this study, an overview of the progress in the extraction of terpenoids from essential oils and the separation of their enantiomers over the past two decades has been made. Extraction methods were retrieved by the resultant network visualization findings. The results showed that the predominant methods are hydrodistillation, solvent-free microwave extraction, headspace solid-phase microextraction and supercritical fluid extraction methods. GC-MS combined with chiral chromatography columns is commonly used for the separation of enantiomers, while 2D GC is found to have stronger resolution ability. Finally, some prospects for future research directions in the extraction and separation identification of essential oils are proposed.

Chiral isotopic fractionation in lemon essential oil: A tool for authenticity assessment?

The present research aimed to retrieve key information about the genuineness of Sicilian lemon essential oils by evaluating simultaneously the chiral and isotopic data of target terpene components. With respect to previous literature references, where chiral recognition and isotope discrimination were performed by distinct gas chromatographic methods, this study aimed to develop a single analytical approach. To overcome limitations associated to monodimensional gas chromatographic approaches, an enantio‑selective multidimensional gas chromatographic approach coupled to isotopic ratio mass spectrometry and to parallel single quadrupole detection (Es-MDGC-C-IRMS/qMS) was developed. Thanks to the features of this system, enantiomeric excesses and target δ13C of the chiral and achiral components were evaluated in a single gas chromatographic run, allowing to reduce total time analysis, as well the consumption of electricity, solvents and samples. Moreover, due to the capability to baseline separate the enantiomeric couples, further considerations were done about the specific δ13C value of the target separated enantiomers. Dealing with the genuine lemon oils analysed, a different δ13C value was found between the enantiomers of the same chiral component, namely (-) and (+) of α and β-pinene, suggesting a different isotopic fractionation related to a specific biosynthetic pathway. This research aimed to evaluate the reasons behind this behaviour, paving the way to newer considerations in the field of authenticity assessment.

Advances in detecting fruit aroma compounds by combining chromatography and spectrometry

Fruit aroma is produced by volatile compounds, which can significantly enhance fruit flavor. These compounds are highly complex and have remarkable pharmacological effects. The synthesis, concentration, type, and quantity of fruit aroma substances are affected by various factors, both abiotic and biotic. To fully understand the aroma substances of various fruits and their influencing factors, detection technology can be used. Many methods exist for detecting aroma compounds, and approaches combining multiple instruments are widely used. This review describes and compares each detection technology and discusses the potential use of combined technologies to provide a comprehensive understanding of fruit aroma compounds and the factors influencing their synthesis. These results can inform the development and utilization of fruit aroma substances. © 2023 Society of Chemical Industry.

Enantiomeric separation and precise quantification of chiral volatiles in Wuyi rock teas using an efficient enantioselective GC × GC-TOFMS approach

Chiral volatiles play important roles in the formation of aroma quality of foods. To date, enantiomeric characteristics of chiral volatiles in Wuyi rock tea (WRT) and their aroma contributions are still unclear. In this study, an efficient enantioselective comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (Es-GC × GC-TOFMS) approach to separate and precisely quantitate 24 pairs of chiral volatiles in WRTs was established, and the enantiomeric distribution and aroma contribution of chiral volatiles among WRTs from four representative cultivars were investigated. Enantiomeric ratio (ER) of R-α-ionone (80%) in Dahongpao (DHP), ER of S-α-terpineol (57%) in Jinfo (JF), ERs of R-γ-heptanolactone (69%), S-γ-nonanolactone (55%), (2R, 5S)-theaspirane B (91%), concentration of S-(E)-nerolidol (313.37 ng/mL) in Rougui (RG) and concentration of R-α-ionone (33.01 ng/mL) in Shuixian (SX) were unique from other types of WRTs, which were considered as the potential chemical markers to distinguish WRT cultivars. The OAV assessment determined 7 volatile enantiomers as the aroma-active compounds, especially R-α-ionone and R-δ-octanolactone in SX, as well as S-(E)-nerolidol and (1R, 2R)-methyl jasmonate in RG contribute much to aroma formation of the corresponding WRTs. The above results provide scientific references for discrimination of tea cultivars and directed improvement of the aroma quality of WRT.

Understanding of formation and change of chiral aroma compounds from tea leaf to tea cup provides essential information for tea quality improvement

Abundant secondary metabolites endow tea with unique quality characteristics, among which aroma is the core component of tea quality. The ratio of chiral isomers of aroma compounds greatly affects the flavor of tea leaves. In this paper, we review the progress of research on chiral aroma compounds in tea. With the well-established GC-MS methods, the formation of, and changes in, the chiral configuration of tea aroma compounds during the whole cycle of tea leaves from the plant to the tea cup has been studied in detail. The ratio of aroma chiral isomers varies among different tea varieties and finished teas. Enzymatic reactions involving tea aroma synthases and glycoside hydrolases participate the formation of aroma compound chiral isomers during tea tree growth and tea processing. Non-enzymatic reactions including environmental factors such as high temperature and microbial fermentation involve in the change of aroma compound chiral isomers during tea processing and storage. In the future, it will be interesting to determine how changes in the proportions of chiral isomers of aroma compounds affect the environmental adaptability of tea trees; and to determine how to improve tea flavor by modifying processing methods or targeting specific genes to alter the ratio of chiral isomers of aroma compounds.

Citrus Essential Oils in Aromatherapy: Therapeutic Effects and Mechanisms

Citrus is one of the main fruit crops cultivated in tropical and subtropical regions worldwide. Approximately half (40-47%) of the fruit mass is inedible and discarded as waste after processing, which causes pollution to the environment. Essential oils (EOs) are aromatic compounds found in significant quantities in oil sacs or oil glands present in the leaves, flowers, and fruit peels (mainly the flavedo part). Citrus EO is a complex mixture of ~400 compounds and has been found to be useful in aromatic infusions for personal health care, perfumes, pharmaceuticals, color enhancers in foods and beverages, and aromatherapy. The citrus EOs possess a pleasant scent, and impart relaxing, calming, mood-uplifting, and cheer-enhancing effects. In aromatherapy, it is applied either in message oils or in diffusion sprays for homes and vehicle sittings. The diffusion creates a fresh feeling and enhances relaxation from stress and anxiety and helps uplifting mood and boosting emotional and physical energy. This review presents a comprehensive outlook on the composition, properties, characterization, and mechanism of action of the citrus EOs in various health-related issues, with a focus on its antioxidant properties.

Comparative Analysis of Flavor, Taste, and Volatile Organic Compounds in Opossum Shrimp Paste during Long-Term Natural Fermentation Using E-Nose, E-Tongue, and HS-SPME-GC-MS

The present study focused on the determination of color, flavor, taste, and volatile organic compounds (VOCs) changes of shrimp paste fermented for 1, 2, 3, and 8 years by E-nose, E-tongue, and headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS). During fermentation, the color of shrimp paste turned dark brown with decreases in L*, a*, and b* values. Inorganic sulfide odor was dominant in all fermented samples. The umami, richness, and aftertaste-B reached a maximum in year 3 of fermentation. A total of 182 volatiles, including long-chain alkanes, esters, aldehydes, olefins, ketones, acids, furans, and pyrazines, were detected. Sixteen VOCs including dimethyl disulfide, methional, trimethyl-pyrazine, (E,E)-2,4-heptadienal, benzeneacetaldehyde were selected as flavor markers. Correlation analysis showed that 94 VOCs were related to saltiness while 40, 17, 21, 22, and 24 VOCs contributed to richness, umami, aftertase-B, sourness, and bitterness, respectively. These novel data may help in optimizing fermentation duration to achieve target flavor indicators in opossum shrimp paste production.

Oviposition Responses of Female Mediterranean Fruit Flies (Diptera: Tephritidae) to Fruit Volatile Compounds

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is one of the most important pests of fruits worldwide. In the present study, we investigated the ovipositional response of C. capitata females to 37 compounds of fruit volatiles from various chemical groups and the dose response to five of them. Red plastic hollow hemispheres (domes) were used as oviposition substrates in all tests. Twenty of the compounds tested increased female egg laying compared to control substrates that contain no chemicals. With 16 compounds, similar number of eggs was deposited in treated and in control oviposition substrates. One terpene ((±)-linalool) reduced egg laying indicating a deterrent ovipositional effect. Both the esters and aldehydes tested increased the ovipositional responses in C. capitata. Most of the monoterpene hydrocarbons increased oviposition, while oxygenated monoterpenes, sesquiterpenes hydrocarbons, and oxygenated sesquiterpenes had mostly neutral effect. Ethyl hexanoate and R-(+)-limonene increased oviposition in the majority of doses tested. Different doses of (-)-linalool elicited differential female ovipositional responses. In contrast, valencene and citral, regardless of dose did not affect female oviposition. Practical implications of these findings are discussed.

Characterization of Aroma-Active Compounds in Northern Highbush Blueberries "Bluecrop" (Vaccinium corymbosum "Bluecrop") and "Elliott" (Vaccinium corymbosum "Elliott") by Gas Chromatography-Olfactometry Dilution Analysis and Odor Activity Value

Aroma-active compounds in northern highbush blueberries "Bluecrop" (Vaccinium corymbosum "Bluecrop") and "Elliott" (Vaccinium corymbosum "Elliott") were isolated using solvent extraction followed by solvent-assisted flavor evaporation. The aroma-active compounds were compared by aroma extract dilution analysis (AEDA) on a polar and a chiral column and odor activity values (OAVs). The results showed that both cultivars had similar aroma-active compounds, but the flavor dilution (FD) factors and OAV values varied, responsible for the subtle aroma differences. AEDA (FD ≥ 64) suggested that the important aroma-active compounds in both cultivars could be ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, (Z)-3-hexenal, 1-octen-3-one, (Z)-3-hexen-1-ol, methional, linalool, (E,Z)-2,6-nonadienal, 2-methylbutanoic acid, α-terpineol, (E,E)-2,4-nonadienal, β-damascenone, geraniol, geranyl acetone, o-cresol, eugenol, and vanillin. Different isomers can have different sensory thresholds and attributes. Enantiomer analysis revealed that although S-(+)-linalool was dominant in blueberry, R-(-)-linalool had a higher FD value and OAVs than that of the (S)-isomer. The S-(-)-α-terpineol was slightly elevated than R-(+)-α-terpineol in both cultivars.

Citrus species: A Review of Traditional Uses, Phytochemistry and Pharmacology

The Citrus species from family Rutaceae has worldwide applications such as cardiovascular and gastrointestinal problems. Phytochemical investigations have shown that these plants have constituents including flavonoids, limonoids and carotenoids. There are many reports on a wide range of activities such as antiinflammatory, anti-oxidant, immunomodulatory, metabolic, cardiovascular and neuroprotective effects. In the current review, we discuss information regarding botany, phytochemistry, ethnobotany uses, traditional knowledge and pharmacological aspects of the Citrus species.

The Blossoming of Technology for the Analysis of Complex Aroma Bouquets-A Review on Flavour and Odorant Multidimensional and Comprehensive Gas Chromatography Applications

Multidimensional approaches in gas chromatography have been established as potent tools to (almost) attain fully resolved analyses. Flavours and odours are important application fields for these techniques since they include complex matrices, and are of interest for both scientific study and to consumers. This article is a review of the main research studies in the above theme, discussing the achievements and challenges that demonstrate a maturing of analytical separation technology.

Rapid assessment of the authenticity of limequat fruit using the electronic nose and gas chromatography coupled with mass spectrometry

Abstract

Citrus fruits are very popular food products. There are many species and varieties of them. There are also documented cases of some citrus fruits causing a severe allergic reaction. Some species of the citrus fruits, especially hybrid ones show a reduced allergenic effect due to the lack of seeds. There is a need for rapid methods for evaluation of citrus’ botanical origin. During research, the headspace of three citrus fruits Citrus Aurantifolia, Citrus japonica, and Citrus × floridana was analysed using electronic nose based on ultrafast gas chromatography and gas chromatography with mass spectrometry. In the paper, two approaches were compared. The usefulness of an electronic nose to control the quality of hybrids was demonstrated. The results obtained during ultrafast gas chromatography analyses were subjected to statistical analysis. Four chemometric methods namely: principal component analysis (PCA), discriminant function analysis (DFA), soft independent modeling of class analogies (SIMCA), statistical quality control (SQC) were used to distinguish between limequat and its parent fruits. Electronic nose combined with chemometrics is a novel analytical tool for hybrid fruits’ classification due to their botanical origin. It can supplement established techniques by providing results in a short time and at a low cost.

Graphical abstract

Citrus essential oils: Extraction, authentication and application in food preservation

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.