Identification of aroma active compounds in orange essence oil using gas chromatography-olfactometry and gas chromatography-mass spectrometry

Chemical and Enantioselective Analyses of an Unprecedented Essential Oil from Ecuadorian Aiouea montana: A Natural Source of S-Methyl-O-2-phenylethyl Carbonothioate

Fresh and dry leaves of Aiouea montana (Sw.) R. Rohde (Lauraceae) produced, in a quite high yield (0.88% and 1.60%, respectively), an unpleasantly smelling essential oil. The chemical composition was described in this study for the first time, detecting and quantifying 48 compounds. Major components of fresh and dry leaf essential oils were α-pinene (6.7-10.3%), β-pinene (2.8-3.8%), α-phellandrene (12.6-14.5%), α-copaene (3.1-15.7%), δ-cadinene (0.9-3.3%), and S-methyl-O-2-phenylethyl carbonothioate (58.5-33.3%). The dominant compound was already known in the literature by synthesis; however, it was unprecedented so far in nature. The carbonothioate was identified after purification and structure elucidation, by means of mass spectrometry, NMR spectroscopy, and FTIR spectrophotometry. The spectral results were identical to all data reported in the literature for the same molecule. Furthermore, the enantioselective analysis of the essential oil was conducted on a β-cyclodextrin-based stationary phase. Two chiral constituents, (+)-β-phellandrene and (1R,2S,6S,7S,8S)-(-)-α-copaene, were enantiomerically pure, whereas α-thujene, camphene, β-pinene, α-phellandrene, limonene, linalool, and germacrene D were scalemic mixtures. The different chemical and enantiomeric compositions suggested that enzymatic transformations could occur while drying.

Enhancing Odor Analysis with Gas Chromatography-Olfactometry (GC-O): Recent Breakthroughs and Challenges

Gas chromatography-olfactometry (GC-O) has made significant advancements in recent years, with breakthroughs in its applications and the identification of its limitations. This technology is widely used for analyzing complex odor patterns. The review begins by explaining the principles of GC-O, including sample preparation, separation methods, and olfactory evaluation techniques. It then explores the diverse range of applications where GC-O has found success, such as food and beverage industries, environmental monitoring, perfume and aroma development, and forensic analysis. One of the major breakthroughs in GC-O analysis is the improvement in separation power and resolution of odorants. Techniques like rapid GC, comprehensive two-dimensional GC, and multidimensional GC have enhanced the identification and quantification of odor-active chemicals. However, GC-O also has limitations. These include the challenges in detecting and quantifying trace odorants, dealing with matrix effects, and ensuring the repeatability and consistency of results across laboratories. The review examines these limitations closely and discusses potential solutions and future directions for improvement in GC-O analysis. Overall, this review presents a comprehensive overview of the recent advances in GC-O, covering breakthroughs, applications, and limitations. It aims to promote the wider usage of GC-O analysis in odor analysis and related industries. Researchers, practitioners, and anyone interested in leveraging the capabilities of GC-O in analyzing complex odor patterns will find this review a valuable resource. The article highlights the potential of GC-O and encourages further research and development in the field.

Inheritance and Quantitative Trait Loci Mapping of Aromatic Compounds from Clementine (Citrus × clementina Hort. ex Tan.) and Sweet Orange (C. × sinensis (L.) Osb.) Fruit Essential Oils

Despite their importance in food processing, perfumery and cosmetics, the inheritance of sweet orange aromatic compounds, as well as their yield in the fruit peel, has been little analyzed. In the present study, the segregation of aromatic compounds was studied in an F1 population of 77 hybrids resulting from crosses between clementine and blood sweet orange. Fruit-peel essential oils (PEOs) extracted by hydrodistillation were analyzed by gas chromatography coupled with flame ionization detection. Genotyping by sequencing was performed on the parents and the hybrids. The resulting "clementine × sweet blood orange" genetic map consists of 710 SNP markers distributed in nine linkage groups (LGs), representing the nine citrus chromosomes, and spanning 1054 centimorgans. Twenty quantitative trait loci (QTLs) were identified, explaining between 20.5 and 55.0% of the variance of the major aromatic compounds and PEO yield. The QTLs for monoterpenes and aliphatic aldehydes predominantly colocalized on LGs 5 and 8, as did the two QTLs for PEO yield. The sesquiterpene QTLs were located on LGs 1, 3, 6 and 8. The detection of major QTLs associated with the synthesis of aliphatic aldehydes, known for their strong aromatic properties, open the way for marker-assisted selection.

The role of oak wood in the mint and floral notes of whisky: identification of common terpenoids by aromatic fractionation

Understanding the development of the whisky aroma during maturation in oak casks provides a rational basis for improvements in product quality. While oak wood is an important contributor to the spicy, toasted, and smoky aromatic notes, limited studies have focused on its role in floral and mint notes of matured whiskies.  However, achieving consistent flavour profiles remains difficult since the odorant molecules are mostly present in low concentration. A semi-preparative ultra-high-performance liquid chromatography (UHPLC) method was applied to whisky and oak wood extracts and used to isolate fractions characterised by floral and mint aromas. To investigate the contribution of terpenoids in these floral and fresh fragrances, a similar analytical process was applied on solutions of targeted reference compounds. This approach, coupled to gas-chromatography/mass-spectrometry analyses, indicated the presence of terpenoids in the fractions of interest as well as selective separation according to chemical structure (i.e., monoterpenes, monoterpenols, ketone monoterpenes, and C13-norisoprenoids). This approach resulted in the detection of respectively, ten and seven new terpenoids in whisky and oak wood. To the best of our knowledge, piperitone, mintlactones, and

Correspondence between the Compositional and Aromatic Diversity of Leaf and Fruit Essential Oils and the Pomological Diversity of 43 Sweet Oranges (Citrus x aurantium var sinensis L.)

Orange (Citrus x aurantium var sinensis) is the most widely consumed citrus fruit, and its essential oil, which is made from the peel, is the most widely used in the food, perfume, and cosmetics industries. This citrus fruit is an interspecific hybrid that would have appeared long before our era and would result from two natural crosses between mandarin and pummelo hybrids. This single initial genotype was multiplied by apomictic reproduction and diversified by mutations to produce hundreds of cultivars selected by men essentially based on phenotypic characteristics of appearance, spread of maturity, and taste. Our study aimed to assess the diversity of essential oil composition and variability in the aroma profile of 43 orange cultivars representing all morphotypes. In agreement with the mutation-based evolution of orange trees, the genetic variability tested with 10 SSR genetic markers was null. The oils from peels and leaves extracted by hydrodistillation were analyzed for composition by GC (FID) and GC/MS and for aroma profile by the CATA (Check All That Apply) method by panelists. Oil yield varied between varieties by a factor of 3 for PEO and a factor of 14 for LEO between maximum and minimum. The composition of the oils was very similar between cultivars and was mainly dominated by limonene (>90%). However, small variations were observed as well as in the aromatic profile, with some varieties clearly distinguishing themselves from the others. This low chemical diversity contrasts with the pomological diversity, suggesting that aromatic variability has never been a selection criterion in orange trees.

Effects of Fermentation on the Physicochemical Properties and Aroma of Lamb Liver Paste

The probiotic fermentation of lamb liver paste is a new method with which to utilize sheep by-products and address the issue of waste. In this study, a pH meter, chromaticity meter, texture analyzer, and gas chromatograph–mass spectrometer (GC–MS) were used to determine various indicators. The objective was to investigate the effect of fermentation on the physical properties and aroma of lamb liver paste. The results showed that the L* (brightness), a* (redness), and b* (yellowness) of the samples were significantly higher in the starter fermentation group than in the other two groups after storage for 0, 1, 7, 14, 21, and 28 days (p < 0.05). In addition, cohesiveness, adhesion, and chewiness were lower in the starter fermentation group after 7 days (p < 0.05). TVB-N and fat were lower in the starter fermentation group compared to the sterilization group at 28 days. pH was significantly lower in the starter fermentation group at the beginning of storage, and lactic acid bacteria numbers were significantly higher than in the sterilization groups (p < 0.05). Important aroma compounds, such as 2-undecenal, 1-octen-3-ol, and anethole, were significantly higher in the starter fermentation group than in the sterilization group (p < 0.05). Fermented lamb liver paste is a new by-product that exhibits a high degree of freshness and a low degree of fat oxidation during storage. This study provides a theoretical basis for future industrial production.

Investigations of the Chemical Composition and Aromatic Properties of Peel Essential Oils throughout the Complete Phase of Fruit Development for Two Cultivars of Sweet Orange (Citrus sinensis (L.) Osb.)

The peel essential oil (PEO) of sweet orange is used for flavoring liquors or foods and in the perfumery and cosmetics industry. The fruit maturity stage can modify the essential oil composition and aromatic properties, but little information is available on the evolution of PEO during the entire time set of fruit development. In this study, the yield, chemical composition and aromatic profile over the three phases of orange development were monitored. Four fruit traits (peel color, weight, acidity and sweetness) were recorded to characterize fruit development. Fruits of two sweet orange cultivars were sampled every two weeks from June to May of the next year. PEO was obtained by hydrodistillation and analyzed by gas chromatography coupled with a flame ionization detector (GC-FID). Compounds were identified with GC coupled with mass spectrometry (GC/MS). Ten expert panelists using the descriptor intensity method described the aromatic profile of PEO samples. The PEO composition was richer in oxygenated compounds at early fruit development stages, with an aromatic profile presenting greener notes. During fruit growth (Phases I and II), limonene's proportion increased considerably as a few aliphatic aldehydes brought the characteristic of orange aroma. During fruit maturation (from November to March), the PEO composition and aromatic profile were relatively stable. Later, some modifications were observed. Regardless of the fruit development stage, the two sweet oranges presented distinct PEO compositions and aromatic profiles. These results constitute a temporal reference for the chemical and aromatic evolution of sweet orange PEO in the fruit development process under Mediterranean conditions. During the first two phases of fruit development, many changes occur in the PEO composition and aroma, suggesting that their exploitation could create new products.

Bacterial Communities Related to Aroma Formation during Spontaneous Fermentation of ‘Cabernet Sauvignon’ Wine in Ningxia, China

Bacteria are an important part of wine ‘microbial terroir’ and contribute to the formation of wine flavor. Based on high-throughput sequencing and non-targeted metabonomic technology, this study first explored the bacterial composition and its effect on the aroma formation of spontaneously fermented ‘Cabernet Sauvignon’ (CS) wine in the Eastern Foot of Helan Mountain (EFHM), Ningxia. The results showed that there were significant differences in bacterial communities during fermentation of CS grapes harvested from different sub-regions of EFHM, with the earlier-established vineyard obtaining more species. The level of bacterial diversity initially decreased and then increased as the fermentation proceeded. Malolactic fermentation (MLF) was spontaneously initiated during alcohol fermentation (AF). Pantoea, Lactobacillus, Rhodococcus, Fructobacillus, and Komagataeibacter were the core bacterial genera in the fermentation mixture. Lactobacillus contributed to the synthesis of methyl and isobutyl esters and the formation of red and black fruity fragrances of wine. Fructobacillus was closely related to the synthesis of aromatic alcohols and the generation of floral flavors.

Effect of Drying Methods on Volatile Compounds of Citrus reticulata Ponkan and Chachi Peels as Characterized by GC-MS and GC-IMS

To reflect the volatile differences of dried citrus peel as affected by cultivars and drying methods, the volatile compounds of dried citrus peel of two cultivars (Citrus reticulata "Chachi" and Citrus reticulata "Ponkan"), prepared under three drying methods (sun-drying (SD), hot-air-drying (AD), and freeze-drying (FD)), were analyzed by GC-MS, odor activity values (OAVs), and GC-IMS. GC-MS data indicated that SD was favorable to preserve terpenic alcohols (linalool, α-terpineol and terpinene-4-ol), β-cymene, methyl methanthranilate, and monoterpenes; while AD was favorable to preserve aliphatic aldehydes and sesquiterpenes; and SD was more similar with AD in GC-MS analysis of volatile profile (of higher MW) for both cultivars from the PCA outcome. Furthermore, significant difference in volatile isomeric composition of different samples was also clearly demonstrated through extracted ion chromatogram (EIC) by GC-MS analysis. GC-IMS analysis showed the favorability of FD to preserve ketones, phenols, esters, and aromatic aldehydes; and SD was more similar with FD in GC-IMS analysis of volatile profile (of smaller MW) for both cultivars from the PCA outcome. Moreover, the OAVs indicate that 2-methoxy-4-vinylphenol contributed much to the flavor of dried Ponkan peel, while 2-methoxy-4-vinylphenol, methyl methanthranilate, and methyl anthranilate played an important role in the flavor of dried Chachi peel; and the highest OAVs for monoterpenes were observed at SD for both cultivars. Thus, the combination of GC-MS and GC-IMS analyses with PCA in this paper suggested the superiority of SD to preserve volatiles and characteristic aroma in dried citrus peel, and that SD contributed much to the quality of dried Chachi peel.

Analysis of Streptomyces Volatilomes Using Global Molecular Networking Reveals the Presence of Metabolites with Diverse Biological Activities

Streptomyces species produce a wide variety of specialized metabolites, some of which are used for communication or competition for resources in their natural environments. In addition, many natural products used in medicine and industry are derived from Streptomyces, and there has been interest in their capacity to produce volatile organic compounds (VOCs) for different industrial and agricultural applications. Recently, a machine-learning workflow called MSHub/GNPS was developed, which enables auto-deconvolution of gas chromatography-mass spectrometry (GC-MS) data, molecular networking, and library search capabilities, but it has not been applied to Streptomyces volatilomes. In this study, 131 Streptomyces isolates from the island of Newfoundland were phylogenetically typed, and 37 were selected based on their phylogeny and growth characteristics for VOC analysis using both a user-guided (conventional) and an MSHub/GNPS-based approach. More VOCs were annotated by MSHub/GNPS than by the conventional method. The number of unknown VOCs detected by the two methods was higher than those annotated, suggesting that many novel compounds remain to be identified. The molecular network generated by GNPS can be used to guide the annotation of such unknown VOCs in future studies. However, the number of overlapping VOCs annotated by the two methods is relatively small, suggesting that a combination of analysis methods might be required for robust volatilome analysis. More than half of the VOCs annotated with high confidence by the two approaches are plant-associated, many with reported bioactivities such as insect behavior modulation. Details regarding the properties and reported functions of such VOCs are described. IMPORTANCE This study represents the first detailed analysis of Streptomyces volatilomes using MSHub/GNPS, which in combination with a routinely used conventional method led to many annotations. More VOCs could be annotated using MSHub/GNPS as compared to the conventional method, many of which have known antimicrobial, anticancer, and insect behavior-modulating activities. The identification of numerous plant-associated VOCs by both approaches in the current study suggests that their production could be a more widespread phenomenon by members of the genus, highlighting opportunities for their large-scale production using Streptomyces. Plant-associated VOCs with antimicrobial activities, such as 1-octen-3-ol, octanol, and phenylethyl alcohol, have potential applications as fumigants. Furthermore, many of the annotated VOCs are reported to influence insect behavior, alluding to a possible explanation for their production based on the functions of other recently described Streptomyces VOCs in dispersal and nutrient acquisition.

Volatile composition changes in lemon during fruit maturation by HS-SPME-GC-MS

BACKGROUND

Volatiles are determinants of fruit aroma and flavor characteristics and also provide valuable information for lemon as ingredient for the food and drinks industry. Volatiles in 'Eureka' lemon and 'Xiangshui' lemon pulps from 130 to 186 days after flowering were enriched by headspace-solid-phase microextraction (HS-SPME), and analyzed by gas chromatography-mass spectrometry (GC-MS).

RESULTS

Seventy-seven volatiles of two lemon cultivars at the different ripening stages were identified and divided into six categories. Varieties and ripening stages had significant effects on individual volatiles in each category. The proportion of monoterpenes was found to be higher in 'Eureka' lemon, while 'Xiangshui' lemon had a higher proportion of sesquiterpenes, aldehydes and alcohols. The proportion of monoterpene fluctuation decreased during fruit ripening, while fluctuation of sesquiterpenes, alcohols, aldehydes and esters increased. Among the hydrocarbons, monoterpenes decreased their relative abundance from 91.67% to 81.04% in 'Eureka' lemon, and from 83.01% to 60.04% in 'Xiangshui' lemon; conversely, sesquiterpenes increased from 0.73% to 2.89% in 'Eureka' lemon, and from 3.21% to 8.48% in 'Xiangshui' lemon. Among the oxygenated volatiles, the proportions of alcohols, aldehydes and esters were higher at 186 days after flowering in both two cultivars.

CONCLUSION

The volatile organic compounds during fruit ripening of lemon varieties with different resistance were elucidated. The proportion of oxygenated volatiles increased during fruit ripening, and disease-resistant varieties had a higher proportion. These results provided important theoretical support for the utilization of lemon fruits and the innovation of disease-resistant germplasm resources. © 2021 Society of Chemical Industry.

Screening of orange peel waste on valuable compounds by gradient multiple development diode-array high-performance thin-layer chromatography

High-performance thin-layer chromatography (HPTLC), as the modern form of TLC (thin-layer chromatography), is suitable for detecting pharmaceutically active compounds over a wide polarity range using the gradient multiple development (GMD) technique. Diode-array detection (DAD) in conjunction with HPTLC can simultaneously acquire ultraviolet‒visible (UV‒VIS) and fluorescence spectra directly from the plate. Visualization as a contour plot helps to identify separated zones. An orange peel extract is used as an example to show how GMD‒DAD‒HPTLC in seven different developments with seven different solvents can provide an overview of the entire sample. More than 50 compounds in the extract can be separated on a 6-cm HPTLC plate. Such separations take place in the biologically inert stationary phase of HPTLC, making it a suitable method for effect-directed analysis (EDA). HPTLC‒EDA can even be performed with living organism, as confirmed by the use of Aliivibrio fischeri bacteria to detect bioluminescence as a measure of toxicity. The combining of gradient multiple development planar chromatography with diode-array detection and effect-directed analysis (GMD‒DAD‒HPTLC‒EDA) in conjunction with specific staining methods and time-of-flight mass spectrometry (TOF‒MS) will be the method of choice to find new chemical structures from plant extracts that can serve as the basic structure for new pharmaceutically active compounds.

Co-cultures of Propionibacterium freudenreichii and Bacillus amyloliquefaciens cooperatively upgrade sunflower seed milk to high levels of vitamin B12 and multiple co-benefits

Background

Sunflower seeds (Helianthus annuus) display an attractive source for the rapidly increasing market of plant-based human nutrition. Of particular interest are press cakes of the seeds, cheap residuals from sunflower oil manufacturing that offer attractive sustainability and economic benefits. Admittedly, sunflower seed milk, derived therefrom, suffers from limited nutritional value, undesired flavor, and the presence of indigestible sugars. Of specific relevance is the absence of vitamin B₁₂. This vitamin is required for development and function of the central nervous system, healthy red blood cell formation, and DNA synthesis, and displays the most important micronutrient for vegans to be aware of. Here we evaluated the power of microbes to enrich sunflower seed milk nutritionally as well as in flavor.

Results

Propionibacterium freudenreichii NCC 1177 showed highest vitamin B₁₂ production in sunflower seed milk out of a range of food-grade propionibacteria. Its growth and B₁₂ production capacity, however, were limited by a lack of accessible carbon sources and stimulants of B₁₂ biosynthesis in the plant milk. This was overcome by co-cultivation with Bacillus amyloliquefaciens NCC 156, which supplied lactate, amino acids, and vitamin B₇ for growth of NCC 1177 plus vitamins B₂ and B₃, potentially supporting vitamin B₁₂ production by the Propionibacterium. After several rounds of optimization, co-fermentation of ultra-high-temperature pre-treated sunflower seed milk by the two microbes, enabled the production of 17 µg (100 g)⁻¹ vitamin B₁₂ within four days without any further supplementation. The fermented milk further revealed significantly enriched levels of l-lysine, the most limiting essential amino acid, vitamin B₃, vitamin B₆, improved protein quality and flavor, and largely eliminated indigestible sugars.

Conclusion

The fermented sunflower seed milk, obtained by using two food-grade microbes without further supplementation, displays an attractive, clean-label product with a high level of vitamin B₁₂ and multiple co-benefits. The secret of the successfully upgraded plant milk lies in the multifunctional cooperation of the two microbes, which were combined, based on their genetic potential and metabolic signatures found in mono-culture fermentations. This design by knowledge approach appears valuable for future development of plant-based milk products.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-022-01773-w.

Floral Scents and Fruit Aromas: Functions, Compositions, Biosynthesis, and Regulation

Floral scents and fruit aromas are crucial volatile organic compounds (VOCs) in plants. They are used in defense mechanisms, along with mechanisms to attract pollinators and seed dispersers. In addition, they are economically important for the quality of crops, as well as quality in the perfume, cosmetics, food, drink, and pharmaceutical industries. Floral scents and fruit aromas share many volatile organic compounds in flowers and fruits. Volatile compounds are classified as terpenoids, phenylpropanoids/benzenoids, fatty acid derivatives, and amino acid derivatives. Many genes and transcription factors regulating the synthesis of volatiles have been discovered. In this review, we summarize recent progress in volatile function, composition, biosynthetic pathway, and metabolism regulation. We also discuss unresolved issues and research perspectives, providing insight into improvements and applications of plant VOCs.

α-Amyrin and β-Amyrin Isolated from Celastrus hindsii Leaves and Their Antioxidant, Anti-Xanthine Oxidase, and Anti-Tyrosinase Potentials

Celastrus hindsii is a popular medicinal plant in Vietnam and Southeast Asian countries as well as in South America. In this study, an amount of 12.05 g of an α-amyrin and β-amyrin mixture was isolated from C. hindsii (10.75 g/kg dry weight) by column chromatography applying different solvent systems to obtain maximum efficiency. α-Amyrin and β-amyrin were then confirmed by gas chromatography-mass spectrometry (GC-MS), electrospray ionization-mass spectrometry (ESI-MS), and nuclear magnetic resonance (NMR). The antioxidant activities of the α-amyrin and β-amyrin mixture were determined via 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,20-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays with IC₅₀ of 125.55 and 155.28 µg/mL, respectively. The mixture exhibited a high potential for preventing gout by inhibiting a relevant key enzyme, xanthine oxidase (XO) (IC₅₀ = 258.22 µg/mL). Additionally, an important enzyme in skin hyperpigmentation, tyrosinase, was suppressed by the α-amyrin and β-amyrin mixture (IC₅₀ = 178.85 µg/mL). This study showed that C. hindsii is an abundant source for the isolation of α-amyrin and β-amyrin. Furthermore, this was the first study indicating that α-amyrin and β-amyrin mixture are promising in future therapies for gout and skin hyperpigmentation.

Utilization and evaluation of Citrus natsudaidai peel waste as a source of natural food additives

This study aims to obtain beneficial ingredients from Citrus natsudaidai (CN) peel waste. The yields of ingredients were 26.2-31.6 mg/g dried material (DM) in pectin, 466-581 mg/g DM in insoluble dietary fiber, 5.56-7.15 g/kg fresh material (FM) in the hexane extracts obtained from CN peels, 23.8-27.0 mg/g DM in naringin, and 8.30-10.2 mg/g DM in neohesperidin. A sensory evaluation and instrumental assays using an Electronic nose and Electronic tongue were performed to evaluate aqueous solutions flavored with 0.02% hexane extracts obtained from CN peels. CN-flavored solutions had a preferred smell over commercial citrus-flavored drinks and were classified into the same group as commercial citrus juices in the Electronic nose assay. In addition, CN-flavored solutions showed sourness, bitterness, and orange-like taste, and the overall acceptance of CN-flavored solutions did not significantly differ from commercial citrus-flavored drinks. CN peel waste can be industrially utilized as a source of natural food additives.

Untargeted Metabolomics of Rind Essential Oils Allowed to Differentiate Two Closely Related Clementine Varieties

Chemical characterization of clementine varieties (Citrus clementina Hort. ex Tan.) essential oils (EO) can lead to variety identification and valorization of their potential use in food and aroma industries. The goal of this study was the chemometric discrimination between two very closely related and morphologically identical clementine varieties, Clemenules (NL) and Clemenpons (PO), based on their rind EO, to identify the differential volatile organic compounds (VOCs) and to determine their antioxidant capacity. EO rind volatile profile was determined by gas chromatography coupled to mass spectrometry in Citrus fruit at different ripening stages grown two independent years in two different locations. Untargeted metabolomics and multivariate data analysis showed an evolution of EO volatile profiles markedly parallel in both varieties. Although EO qualitative composition was identical in both varieties, PLS-DA allowed the identification of characteristic VOCs, quantitatively discriminating them along all the ripening process. PO showed higher accumulation of several mono- and sesquiterpene compounds such as trans-carveol, while NL showed higher levels of aldehyde and alcohol non-terpenoids like dodecanal. Both varieties evinced identical EO antioxidant activities, indicating a similar value for food preservation. Hence, untargeted metabolomics approach based on rind EO volatiles was revealed as a powerful technique able to differentiate between morphologically undistinguishable Citrus varieties.

Evaluation of Postharvest Drying, Key Odorants, and Phytotoxins in Plai (Zingiber montanum) Essential Oil

Plai or cassumunar ginger (Zingiber montanum), mainly distributed in tropical Asia, is an essential oil-bearing rhizomatous crop belonging to the Zingiberaceae family. Rhizomes and essential oil of this herb are used in culinary as flavoring agents, traditional medicines, and aromatherapy. In this study, the effect of different postharvest drying methods (air-, oven-drying at 40 and 60 °C, sun-, microwave-, and freeze-drying) of its sliced rhizome on the essential oil yield, composition, and sensory quality was investigated. The major key odorants and phytotoxins in its essential oil were identified for the first time through sensory- or bioassay-guided fractionation. Although the drying methods did not alter the oil composition significantly, oven-drying at 40 °C and freeze-drying produced the highest oil yield (81.0% of fresh rhizome) while maintaining the sensory quality. 4-Terpineol was found to be the majorly abundant key odorant in its oil through detailed sensory analysis. This oxygenated monoterpene was also demonstrated to be the major phytotoxin negatively affecting seed germination and shoot and root growth of wheatgrass seeds with IC₅₀ values of 0.67, 0.10, and 0.17 mM, respectively. The current study is beneficial for further value addition of this crop in food industries and the agricultural sector.

Sensory active substances causing off-odour in liquid whey during storage

Liquid whey is a nutritious product with high water activity and neutral pH. Therefore, it is very susceptible to microbiological spoilage that results in undesirable off-odors. Additionally, minimally processed foods are the recent trend so setting an appropriate shelf life is essential. The commonly used microbiological methods are lengthy and time-demanding, so a quick and early identification of microbial degradation would be a significant benefit. Here we tested a solid-phase microextraction, gas chromatography with mass spectrometry coupled with olfactometry analysis (SPME-GC-MS/O) on samples of sweet unpasteurized liquid whey stored at 6 °C, 12 °C and 25 °C for a week. We compared the common methods – plate methods, measurement of pH, and dry matter determination with our proposed SPME-GC-MS/O. We have identified seven sensory active compounds while octanoic acid and a compound not reliably identified by the MS detector (with main m/z observed 133 (100), 151 (65), and 135 (26)) being the most prominent. Microbiological methods proved irreplaceable for proper setting of storage conditions (with the growth of coliforms being significant (p <0.001) at 25 °C). However, SPME-GC-MS/O was able to identify volatile substances responsible for off-odors and can be used as a powerful tool to detect the cause of undesirable chemical and microbial changes in whey beverages.

Volatile compounds of a pumpkin (Cucurbita moschata) purée processed by high pressure thermal processing

BACKGROUND

The changes in the volatile profile of a pumpkin (Cucurbita moschata, Duch.) purée processed by high pressure thermal (HPT) processing at different pressure and initial temperature intensities (300, 600, 900 MPa and 60, 80 °C, respectively) was evaluated. Headspace solid-phase microextraction (HS-SPME) technique was used for the extraction and concentration of volatile compounds and the analysis was performed by gas chromatography-mass spectrometry (GC-MS).

RESULTS

Alcohols were the volatile compounds most abundantly isolated in the headspace of pumpkin purée (control and processed purées had ranges between 43 and 56%), followed by aldehydes (14-28%), hydrocarbons (8-13%) and terpenes (7-10%). Lipid oxidation, Maillard reaction and carotenoids degradation were the main chemical routes of formation of volatile compounds after HPT processing. Initial temperature or pressure intensity of HPT processing, within the ranges tested in this study, did not affect the initial levels of volatile compounds of pumpkin purée.

CONCLUSION

HPT processing is an effective technology for the preservation of the original aroma of low acid vegetables such as pumpkin. © 2020 Society of Chemical Industry.

Effect of roasting temperature and time on volatile compounds, total polyphenols, total flavonoids, and lignan of omija (Schisandra chinensis Baillon) fruit extract

In this study, roasting was applied to enhance the volatile compound content and antioxidant activity of hot-air dried omija (Schisandra chinensis Baillon) fruit. The major volatile compounds were furfural, 1,8-cineole and terpinen-4-ol. Total volatile compound concentration in omija roasted at 150 ℃ for 15 min was approximately 4 times higher than that in hot-air dried omija. Contents of monoterpenes and sesquiterpenes in roasted omija were significantly increased, compared to that of the hot-air dried omija (P < 0.05). The contents of schizandrin in extracts of hot-air dried omija and omija roasted at 150 ℃ for 10 min were determined to be 28.9 and 106.5 mg/100 g extract, respectively. The content of gomisin A from roasted omija was about 5 times higher than that of hot-air dried omija. Through this study, it is believed that the usability of omija will be expanded.

Biosynthetic pathways and metabolic engineering of spice flavors

Historically, spices have played an important economic role, due to their large applications and unique flavor. The supply and cost of spice materials and their corresponding natural products are often affected by environmental, geopolitical and climatic conditions. Secondary metabolite composition, including certain flavor compounds in spice plants, is recognized and considered closely related to plant classification. Both genes and enzymes involved in the biosynthesis of spice flavors are constantly identified, which provides insight into metabolic engineering of flavor compounds (i.e. aroma and pungent compounds) from spice plants. In this review, a systematic meta-analysis was carried out based on a comprehensive literature survey of the flavor profiles of 36 spice plants from nine families. We also reviewed typical biosynthetic pathways and metabolic engineering of most representative aroma and pungent compounds that may assist in the future study of spice plants as biosynthetic factories facing a new challenge in creating spice products.

Chemical composition and evaluation of antileishmanial and cytotoxic activities of the essential oil from leaves of Cryptocarya aschersoniana Mez. (Lauraceae Juss.)

Leishmaniasis is an endemic disease caused by protozoa of the genus Leishmania, which affects around two million people worldwide. One major drawback in the treatment of leishmaniasis is the emergence of resistance to current chemotherapeutics. Medicinal and aromatic plants constitute a major source of natural organic compounds. In this study, the leaf essential oil of Cryptocarya aschersoniana was obtained by hydrodistillation in a Clevenger-type apparatus, and the chemical composition was analyzed by GC-MS and GC-FID. The essential oil of these species was predominantly constituted by monoterpene hydrocarbons (48.8%). Limonene (42.3%), linalool (9.7%) and nerolidol (8.6%) were the main constituents in the oil of C. aschersoniana. The in vitro activity of the oil was evaluated against the promastigote forms of Leishmania amazonensis, the causative agent of cutaneous leishmaniasis in humans. The essential oil of C. aschersoniana showed high activity against L. amazonensis promastigote forms (IC50 = 4.46 µg/mL), however, it also demonstrated a relatively high cytotoxicity on mouse peritoneal macrophages (CC50 = 7.71 µg/mL). This is the first report of the chemical composition and the leishmanicidal and cytotoxic activities of the leaf essential oil of C. aschersoniana.

Chemical and sensory characterization of corn oil flavoured by citrus

Abstract A commercial and refined corn oil was added with fresh lemon and orange fruits to produce corn oil flavoured (COF), which were characterized for their quality parameters, fatty acid profile and concentrations of minor components. The sensory analysis was performed by a panel using the quantitative descriptive analysis and the hedonic score. Results showed that the addition of citrus fruits did not affect the oil quality indices, accomplishing the requirements for commercialization. The biophenols and pigments, initially absent in the refined oil, were detected in COF. The addition of orange or lemon fruits to the corn oil had no effects on oil stability, while the volatile profile in the headspace of flavoured oils showed the presence of several terpenes that were originally absent, among them: limonene; γ-terpinene; α-pinene and β-pinene. The sensory results confirmed that positive attributes and the acceptability of the unflavored corn oil can be improved by increasing amounts of both fruits.

Evolution of temporal dynamic of volatile organic compounds (VOCs) and odors of hemp stem during field retting

New non-destructive approach to evaluate the retting process was investigated. Increase of retting duration led to a decrease of VOCs emitted by plants and change of color and plant odor. The variation of VOCs and odor could be used as indicators for the degree of retting. In the hemp industry, retting is an upstream bioprocessing applied to the plants to facilitate the decortication of fibres from the central woody part of the stem. This treatment is currently carried out in an empirical way on the ground which leads to variability in the hemp stems quality, and thus to the hemp fibres quality. Therefore, controlling retting treatment is a crucial step for high-performance hemp fibre. In this study, a new approach is used to assess the retting degree by following the evolution of VOCs emitted by plants during different retting durations. Either harvest time or retting induces a change in VOCs released by plants. During plant maturity, volatile compounds emitted decreased with a factor of about 2, in relation to VOCs released at the end of flowering. Regardless of the harvest period, the majority of VOCs and odor concentrations, monitored by olfactometric analysis, decrease gradually until some of them disappear at the end of retting. Likewise, the green plant odor disappears during retting with an increase of dry plants odor and an appearance of fermented odor at the end of retting. Following the evolution of VOCs emitted by plants during retting could be a tool for farmers to improve the retting management.

Mapping metabolome changes in Luffa aegyptiaca Mill fruits at different maturation stages via MS-based metabolomics and chemometrics

Introduction

Luffa aegyptiaca Mill, sponge gourd or Egyptian cucumber, is grown worldwide for its edible fruit consumed as a vegetable like cucumber. Unlike young fruit (YF), the fully mature ripened fruit (MF) is strongly fibrous and is used as a cleanser to make scrubbing bath sponges. YF undergoes a complex series of physiological and biochemical changes during fruit ripening. However, the chemical compositional differences between YF and MF in Luffa aegyptiaca have not been distinguished to date.

Objectives

Comprehensively compare the metabolites profile of YF and MF to give insight on how maturation stage affects chemical composition.

Methods

Mass-based metabolomics comprising GC/MS and UHPLC/MS were adopted in this study targeting its volatile and non-volatile metabolites coupled with chemometrics to rationalize for the differences.

Results

A total of 53 volatile metabolites were identified via headspace solid phase microextraction (SPME) comprising 66.2% aldehydes/furans, 51.6% alcohols, 38.2% ketones, 15.1% acids and 10.1% aromatics of which aldehydes/ furans were dominant at both fruit stages. Young fruit was in general more erniched in metabolites as revealed from UHPLC/MS and GC/MS analyses. The YF group encompassed higher levels of short chain alcohols (1-octen-3-ol) and aldehydes ((E)-2-hexenal and cucumber aldehyde) in addition to terpenoids (linalool). In contrast, fatty acids (octanoic acid) predominated MF specimens. UHPLC/MS analysis revealed for several oleanene triterpene glycosides as major secondary bioactive compounds, dihydroxy-oxo-oleanenoic acid glycoside found more abundant in YF versus MF as revealed from multivariate data analyses.

Conclusions

Our results reveal for the distinct metabolite changes in L. aegyptiaca fruit in its different stages and to rationalize for its different usage.

Analysis of Volatile Constituents in Platostoma palustre (Blume) Using Headspace Solid-Phase Microextraction and Simultaneous Distillation-Extraction

Hsian-tsao (Platostoma palustre Blume) is a traditional Taiwanese food. It is admired by many consumers, especially in summer, because of its aroma and taste. This study reports the analysis of the volatile components present in eight varieties of Hsian-tsao using headspace solid-phase microextraction (HS-SPME) and simultaneous distillation-extraction (SDE) coupled with gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS). HS-SPME is a non-heating method, and the results show relatively true values of the samples during flavor isolation. However, it is a kind of headspace analysis that has the disadvantage of a lower detection ability to relatively higher molecular weight compounds; also, the data are not quantitative, but instead are used for comparison. The SDE method uses distillation 2 h for flavor isolation; therefore, it quantitatively identifies more volatile compounds in the samples while the samples withstand heating. Both methods were used in this study to investigate information about the samples. The results showed that Nongshi No. 1 had the highest total quantity of volatile components using HS-SPME, whereas SDE indicated that Taoyuan Mesona 1301 (TYM1301) had the highest volatile concentration. Using the two extraction methods, 120 volatile components were identified. Fifty-six volatile components were identified using HS-SPME, and the main volatile compounds were α-pinene, β-pinene, and limonene. A total of 108 volatile components were identified using SDE, and the main volatile compounds were α-bisabolol, β-caryophyllene, and caryophyllene oxide. Compared with SDE, HS-SPME sampling extracted a significantly higher amount of monoterpenes and had a poorer detection of less volatile compounds, such as sesquiterpenes, terpene alcohols, and terpene oxide.

Comprehensive Fractionation of Antioxidants and GC-MS and ESI-MS Fingerprints of Celastrus hindsii Leaves

Background: In this study, column chromatography was applied to separate active fractions from the ethyl acetate extract of Celastrus hindsii, a medicinal plant widely used in Southern China, Northern Vietnam, Myanmar, and Malaysia. Methods: Fourteen fractions from different dilutions of chloroform and methanol were separated by column chromatography and examined for biological activities. Results: It was found that a dilution of 50–70% methanol in chloroform yielded the highest total phenolics, flavonoids, and antioxidant activities (1,1-dipheny1-2-picrylhydrazyl (DPPH), 2,2-azinobis (3-ehtylbenzothiazoline-6-sulfonic acid), diammonium salt (ABTS) radical scavenging activity, and β-carotene bleaching method measured by lipid peroxidation inhibition). In addition, by gas chromatography-mass spectrometry (GC-MS) and electrospray ionization-mass spectrometry (ESI-MS) analyses, fifteen principal compounds from bioactive fractions belonging to fatty acids, amides, flavonoids, sterols, terpenes, and phenols were identified. Of these compounds, α-amyrin, β-amyrin, hydrazine carboxamide, hexadecanoic acid, fucosterol, (3β)-D:C-friedours-7-en-3-ol, rutin, and 2-hydroxy-1-ethyl ester accounted for maximal quantities, whilst concentrations of other constituents were <5%. Conclusions: It is suggested that these identified compounds may greatly contribute to the antioxidant capacity of C. hindsii as well as its potential pharmaceutical properties.

Feature Extraction and Classification of Citrus Juice by Using an Enhanced L-KSVD on Data Obtained from Electronic Nose

Aroma plays a significant role in the quality of citrus fruits and processed products. The detection and analysis of citrus volatiles can be measured by an electronic nose (E-nose); in this paper, an E-nose is employed to classify the juice which is stored for different days. Feature extraction and classification are two important requirements for an E-nose. During the training process, a classifier can optimize its own parameters to achieve a better classification accuracy but cannot decide its input data which is treated by feature extraction methods, so the classification result is not always ideal. Label consistent KSVD (L-KSVD) is a novel technique which can extract the feature and classify the data at the same time, and such an operation can improve the classification accuracy. We propose an enhanced L-KSVD called E-LCKSVD for E-nose in this paper. During E-LCKSVD, we introduce a kernel function to the traditional L-KSVD and present a new initialization technique of its dictionary; finally, the weighted coefficients of different parts of its object function is studied, and enhanced quantum-behaved particle swarm optimization (EQPSO) is employed to optimize these coefficients. During the experimental section, we firstly find the classification accuracy of KSVD, and L-KSVD is improved with the help of the kernel function; this can prove that their ability of dealing nonlinear data is improved. Then, we compare the results of different dictionary initialization techniques and prove our proposed method is better. Finally, we find the optimal value of the weighted coefficients of the object function of E-LCKSVD that can make E-nose reach a better performance.

Volatile Compounds in Citrus Essential Oils: A Comprehensive Review

The essential oil fraction obtained from the rind of Citrus spp. is rich in chemical compounds of interest for the food and perfume industries, and therefore has been extensively studied during the last decades. In this manuscript, we provide a comprehensive review of the volatile composition of this oil fraction and rind extracts for the 10 most studied Citrus species: C. sinensis (sweet orange), C. reticulata (mandarin), C. paradisi (grapefruit), C. grandis (pummelo), C. limon (lemon), C. medica (citron), C. aurantifolia (lime), C. aurantium (bitter orange), C. bergamia (bergamot orange), and C. junos (yuzu). Forty-nine volatile organic compounds have been reported in all 10 species, most of them terpenoid (90%), although about half of the volatile compounds identified in Citrus peel are non-terpenoid. Over 400 volatiles of different chemical nature have been exclusively described in only one of these species and some of them could be useful as species biomarkers. A hierarchical cluster analysis based on volatile composition arranges these Citrus species in three clusters which essentially mirrors those obtained with genetic information. The first cluster is comprised by C. reticulata, C. grandis, C. sinensis, C. paradisi and C. aurantium, and is mainly characterized by the presence of a larger abundance of non-terpenoid ester and aldehyde compounds than in the other species reviewed. The second cluster is comprised by C. junos, C. medica, C. aurantifolia, and C. bergamia, and is characterized by the prevalence of mono- and sesquiterpene hydrocarbons. Finally, C. limon shows a particular volatile profile with some sulfur monoterpenoids and non-terpenoid esters and aldehydes as part of its main differential peculiarities. A systematic description of the rind volatile composition in each of the species is provided together with a general comparison with those in leaves and blossoms. Additionally, the most widely used techniques for the extraction and analysis of volatile Citrus compounds are also described.

Date palm wood as a new source of phenolic antioxidants and in preparation of smoked salmon

The potential of date palm wood (DPW) as a new source of phenolic antioxidants was investigated in this contribution. The total phenolic content and antiradical activity of soluble and insoluble-bound fractions of DPW was compared to those of maple wood (MW). Furthermore, salmon was smoked with DPW and MW. Irrespective of the wood type, volatile phenolic compounds were mainly methoxyphenols, with the highest contribution from eugenol followed by guaiacol and their corresponding derivatives, as evaluated by solid-phase microextraction and gas chromatography-mass spectrometry. Salmon smoked with DPW showed a higher oxidative stability than that of MW during 21 days of storage at 4°C, which was explained by the higher content of volatile phenolic compounds in the smoke generated from DPW. Minor differences were detected for the instrumental color between both samples of smoked salmon. Therefore, smoking with DPW may be used for industrial meat and fish smoking purposes. PRACTICAL APPLICATIONS: Smoking has long been used to preserve fish and meat products. The process changes the appearance and gives a desirable flavor to the product. However, high temperatures applied during smoking may also induce lipid oxidation, the extent of which is counterbalanced by the antioxidant action of phenolics in woodsmoke. In this sense, the desired interactions of the smoke volatiles in the food matrix dictates the quality of the final product. Volatile phenolics released upon smoking are dependent on the type of wood. Thus, use of a specific wood might provide unique products, hence date palm wood (DPW) used in this work may not only provide special smoked fish products but its use could be extended to other smoked products. Hence, this contribution extends the possible feedstocks for the preparation of smoked products.

Carbonyl compounds in different stages of vinification and exposure risk assessment through Merlot wine consumption

The objective of this research was to estimate for the first time the transformations that the free form of some target carbonyl compounds may undergo during winemaking and assess the exposure risk to these compounds through the consumption of the Merlot commercial wines under study. Acrolein and furfural were found in grapes and the respective wines, although levels were observed to decline throughout the winemaking process. Formaldehyde was found in all stages of wine production in levels lower than the limit of quantification of the method and ethyl carbamate was not found in samples. Acetaldehyde seems to be a precursor of acetoin and 2,3-butanediol, since the levels of this aldehyde decreased along winemaking and the formation of the ester and alcohol was verified. Furfural levels decreased, while the occurrence of furan-containing compounds increased during winemaking. The formation of acetaldehyde during alcoholic fermentation and the potential environmental contamination of grapes with acrolein and furfural are considered as the critical points related to the presence of toxic carbonyl compounds in the wine. Acrolein was found in the samples under study in sufficient quantities to present risk to human health, while other potentially toxic carbonyl compounds did not result in risk. This study indicated for the first time the presence of acrolein in grapes suggesting that environmental pollution can play an important role in the levels of this aldehyde detected in wines. Reduction of the emission of this aldehyde to the environment may be achieved by replacing wood burning by another heat source in fireplaces or wood stones, and abandoning the practice of burning garbage and vegetation.

Use of Orange Oil Loaded Pectin Films as Antibacterial Material for Food Packaging

This study aims to develop orange oil loaded in thin mango peel pectin films and evaluate their antibacterial activity against Staphylococcus aureus. The mango peel pectin was obtained from the extraction of ripe Nam Dokmai mango peel by the microwave-assisted method. The thin films were formulated using commercial low methoxy pectin (P) and mango pectin (M) at a ratio of 1:2 with and without glycerol as a plasticizer. Orange oil was loaded into the films at 3% w/w. The orange oil film containing P and M at ratio of 1:2 with 40% w/w of glycerol (P₁M₂GO) showed the highest percent elongation (12.93 ± 0.89%) and the lowest Young's modulus values (35.24 ± 3.43 MPa). For limonene loading content, it was found that the amount of limonene after the film drying step was directly related to the final physical structure of the film. Among the various tested films, P₁M₂GO film had the lowest limonene loading content (59.25 ± 2.09%), which may be because of the presence of numerous micropores in the P₁M₂GO film's matrix. The inhibitory effect against the growth of S. aureus was compared in normalized value of clear zone diameter using the normalization value of limonene content in each film. The P₁M₂GO film showed the highest inhibitory effect against S. aureus with the normalized clear zone of 11.75 mm but no statistically significant difference. This study indicated that the orange oil loaded in mango peel pectin film can be a valuable candidate as antibacterial material for food packaging.

Environmental conditions influence the biochemical properties of the fruiting bodies of Tuber magnatum Pico

The influences of various factors, including the symbiosis established with the roots of specific tree species, on the production of volatiles in the fruiting bodies of Tuber magnatum have not been investigated yet. Volatiles in T. magnatum fruiting bodies were quantitatively and qualitatively determined by both PTR-MS and GC-MS in order to compare the accuracy of the two methods. An electronic nose was also used to characterize truffle samples. The influence of environmental changes on the antioxidant capabilities of fruiting bodies was also determined. Statistically significant differences were found between fruiting bodies with different origins. The relationship between the quality of white truffle fruiting bodies and their specific host plant is described along with an analysis of metabolites other than VOCs that have ecological roles. Our results indicate that the geographical origin (Italy and Istria) of the fruiting bodies is correlated with the quantity and quality of volatiles and various antioxidant metabolites. This is the first report characterizing antioxidant compounds other than VOCs in white truffles. The correlation between geographical origin and antioxidant contents suggests that these compounds may be useful for certifying the geographical origin of truffles.