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Biosynthesis of plant-derived flavor compounds

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Abstract

Plants have the capacity to synthesize, accumulate and emit volatiles that may act as aroma and flavor molecules due to interactions with human receptors. These low-molecular-weight substances derived from the fatty acid, amino acid and carbohydrate pools constitute a heterogenous group of molecules with saturated and unsaturated, straight-chain, branched-chain and cyclic structures bearing various functional groups (e.g. alcohols, aldehydes, ketones, esters and ethers) and also nitrogen and sulfur. They are commercially important for the food, pharmaceutical, agricultural and chemical industries as flavorants, drugs, pesticides and industrial feedstocks. Due to the low abundance of the volatiles in their plant sources, many of the natural products had been replaced by their synthetic analogues by the end of the last century. However, the foreseeable shortage of the crude oil that is the source for many of the artificial flavors and fragrances has prompted recent interest in understanding the formation of these compounds and engineering their biosynthesis. Although many of the volatile constituents of flavors and aromas have been identified, many of the enzymes and genes involved in their biosynthesis are still not known. However, modification of flavor by genetic engineering is dependent on the knowledge and availability of genes that encode enzymes of key reactions that influence or divert the biosynthetic pathways of plant-derived volatiles. Major progress has resulted from the use of molecular and biochemical techniques, and a large number of genes encoding enzymes of volatile biosynthesis have recently been reported.

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... As mentioned above, plant secondary metabolites have enormous economic importance in food, pharmaceutical, chemical, and agricultural industries due to their biological activities and characteristics. These flavored and fragranced compounds are used in food and beverages, in personal care and household products as well as in pesticides and industrial feedstocks [32,38,40]. However, research about natural products synthesis, started several decades ago and led to the emergence of nature-identical compounds (NICs) [40,41], which are chemically synthesized compounds but identical to their counterparts present in plant essential oils (EO) and oleoresins (OR) [18]. ...
... These flavored and fragranced compounds are used in food and beverages, in personal care and household products as well as in pesticides and industrial feedstocks [32,38,40]. However, research about natural products synthesis, started several decades ago and led to the emergence of nature-identical compounds (NICs) [40,41], which are chemically synthesized compounds but identical to their counterparts present in plant essential oils (EO) and oleoresins (OR) [18]. These NICs present many advantages compared to the use of plant compounds. ...
... These NICs present many advantages compared to the use of plant compounds. Firstly, NICs are more available than natural compounds [40] due to the fact that it is possible to obtain chemical of plants that are not present in a specific country or region or even outside of the harvesting period. Secondly, NICs are cheaper than natural compounds [18,40,[42][43][44]. ...
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Aquaculture sustainable development is necessary since it is categorized as the most important source of aquatic products for human consumption and it is expected to keep growing shortly. For this reason, the addition of natural immunostimulants to fish diet to improve fish health and to preserve the environment have great importance in aquaculture. In this sense, new biotechnological tools as nature-identical compounds are now being used as feed additives to strengthen and stimulate the fish immune system to prevent and/or control diseases due to their lesser cost and higher availability than plant compounds. This review aims to present the most recent studies in which nature-identical compounds have been used in the fish diet to establish their possible use in aquaculture. Nature-identical compounds can be considered a promising alternative to be added to fish diets to promote growth performance, manipulate the gut microbiota, and improve the immune and oxidative status of fish as wells as control bacterial infections in this important aquatic industry.
... Norisoprenoids are volatile compounds of 9, 10, 11, or 13 carbon cyclic chemical structures derived from carotenoids [4,38,39]. Carotenoids are pigments produced in the chloroplast and decline during grape ripening due to the unavailability of the chloroplast [40][41][42]. Hence, decreasing the norisoprenoids synthesized. ...
... Fatty acid-derived volatiles, including alcohols, aldehydes, ketones, lactones, esters, and acids, constitute the majority of volatile compounds in grapes [38,42]. These compounds are synthesized through the α-oxidation, β-oxidation, or lipoxygenase pathways [42]. ...
... Fatty acid-derived volatiles, including alcohols, aldehydes, ketones, lactones, esters, and acids, constitute the majority of volatile compounds in grapes [38,42]. These compounds are synthesized through the α-oxidation, β-oxidation, or lipoxygenase pathways [42]. C 6 aldehydes and alcohols are the most abundant compounds among these derivatives. ...
Article
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Elicitors as alternatives to agrochemicals are widely used as a sustainable farming practice. The use of elicitors in viticulture to control disease and improve phenolic compounds is widely recognized in this field. Concurrently, they also affect other secondary metabolites, such as aroma compounds. Grape and wine aroma compounds are an important quality factor that reflects nutritional information and influences consumer preference. However, the effects of elicitors on aroma compounds are diverse, as different grape varieties respond differently to treatments. Among the numerous commercialized elicitors, some have proven very effective in improving the quality of grapes and the resulting wines. This review summarizes some of the elicitors commonly used in grapevines for protection against biotic and abiotic stresses and their impact on the quality of volatile compounds. The work is intended to serve as a reference for growers for the sustainable development of high-quality grapes.
... Branched-chain volatiles have been recognized as being crucially responsible for the distinctive flavor and aroma properties of many commercially important fruits such as apple, banana, melon, and pineapple, among others (Wyllie et al., 1995;Plotto, 1998;Dixon and Hewett, 2000;Boudhrioua et al., 2003;Tokitomo et al., 2005;Wendakoon et al., 2006). In terms of effect on human sensory perception it has been widely reported that branched-chain volatile esters tend to impart characteristic "fruity" aroma notes, while non-ester branched-chain volatiles induce a broader range of olfactory sensations (Schwab et al., 2008;Sugimoto, 2011;El Hadi et al., 2013;Lytra et al., 2014). Fruity aroma is a characteristic shared with several other nonbranched-chain volatile compounds, particularly short-and medium-length straight-chain esters (Schwab et al., 2008;El Hadi et al., 2013). ...
... In terms of effect on human sensory perception it has been widely reported that branched-chain volatile esters tend to impart characteristic "fruity" aroma notes, while non-ester branched-chain volatiles induce a broader range of olfactory sensations (Schwab et al., 2008;Sugimoto, 2011;El Hadi et al., 2013;Lytra et al., 2014). Fruity aroma is a characteristic shared with several other nonbranched-chain volatile compounds, particularly short-and medium-length straight-chain esters (Schwab et al., 2008;El Hadi et al., 2013). However, it has been observed that ester compounds containing the branched-chain moiety have significantly lower odor thresholds than the corresponding straight-chain counterparts (Takeoka et al., 1995), indicating that BCVs may be more potent stimulators of the "fruity" olfactory sensation. ...
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Branched-chain volatiles (BCVs) constitute an important family of fruit volatile metabolites essential to the characteristic flavor and aroma profiles of many edible fruits. Yet in contrast to other groups of volatile organic compounds important to fruit flavor such as terpenoids, phenylpropanoids, and oxylipins, the molecular biology underlying BCV biosynthesis remains poorly understood. This lack of knowledge is a barrier to efforts aimed at obtaining a more comprehensive understanding of fruit flavor and aroma and the biology underlying these complex phenomena. In this review, we discuss the current state of knowledge regarding fruit BCV biosynthesis from the perspective of molecular biology. We survey the diversity of BCV compounds identified in edible fruits as well as explore various hypotheses concerning their biosynthesis. Insights from branched-chain precursor compound metabolism obtained from non-plant organisms and how they may apply to fruit BCV production are also considered, along with potential avenues for future research that might clarify unresolved questions regarding BCV metabolism in fruits.
... In order to reveal the molecular mechanisms underlying the synthesis of volatile compounds, transcriptome sequencing of the Granny Smith and Jonagold apples was performed using the Illumina Novaseq 6000. It has been reported that at least four pathways are responsible for the production of volatile compounds in apples [6]: Straight-chain aldehydes, alcohols and esters are synthesized from fatty acid metabolism pathway [13]; Branched-chain aldehydes, alcohols and esters are derived from isoleucine pathway [34]; Sesquiterpenes are synthesized via the mevalonate pathway and phenylpropenes are synthesized from the phenylpropanoid pathway [12,35]. In this study, a total of 94 DEGs were detected in these four pathways, indicating the dramatical differences in volatile synthesis between the Granny Smith and Jonagold apples. ...
... Combined with the measurement results of volatile profiles, the upregulated expression pattern of MdLOX genes in the Jonagold apple may play a key role in the volatile compounds accumulation. Products of the LOX reaction can be converted to aldehydes by the hydroperoxide lyase (HPL) enzyme and aldehydes are subsequently reduced to the corresponding alcohol by the alcohol dehydrogenase (ADH) [12]. The alcohols resulting from ADH enzymatic activity are natural substrates for the alcohol acyltransferase (AAT), which transfers an acyl group through an oxygen-dependent reaction from acyl-CoA to the OH group of an alcohol forming an ester [39]. ...
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Aroma is a key quality attribute of apples, making major contributions to commercial value and consumer choice. However, the mechanism underlying molecular regulation of aroma formation genes and transcription factors remains poorly understood in apples. Here, we investigated the aroma volatile profiles of two apple varieties with distinctive flavors using headspace solid-phase microextraction (HS-SPME) combined with gas chromatography–mass spectrometry (GC-MS). A total of 35 volatile compounds were identified in Granny Smith and Jonagold apples. Aldehydes were the most abundant volatiles contributing to the aroma in Granny Smith apple while esters were the dominant volatile compounds in Jonagold apple. In order to know more about the expression levels of aroma-related genes involved in the metabolic pathways, transcriptome sequencing of these two different apple varieties was conducted utilizing the Illumina platform. In total, 94 differentially expressed genes (DEGs) were found in the fatty acid metabolism, amino acid metabolism, the mevalonate pathway and phenylpropanoid pathway. Furthermore, compared to the Granny Smith apple, the expression of multiple genes and transcription factors were upregulated in the Jonagold apple, which might play important roles in the synthesis of aroma volatile compounds. Our study contributes toward better understanding on the molecular mechanism of aroma synthesis in apples and provides a valuable reference for metabolic engineering and flavor improvement in the future.
... Only five of them were found during the analysis with an electronic nose: 2-phenylacetaldehyde, 2-phenylethyl acetate, 2-phenylethanol, acetophenone, and linalool. However, other volatile compounds could be responsible for floral aroma (Schwab et al., 2008). ...
Thesis
Theobroma cacao est un arbre originaire des régions tropicales humides d’Amérique latine. Il est cultivé pour ses fèves qui permettent la production de chocolat. Le Nacional, originaire d’Equateur, est une variété de cacao fin connue pour ses arômes floraux et épicées, appelée saveur « Arriba ». Les mécanismes de la synthèse de ses arômes restent peu connus. Les travaux de cette thèse ont porté sur l’étude des déterminants génétiques et biochimiques des arômes des cacaos fins équatoriens afin d’initier de contribuer aux connaissances dans ce domaine.Une première partie de l’étude a été réalisée à partir d’une population de cacaoyer de type Nacional moderne, qui est la variété de Nacional actuellement cultivée. Des études d’associations ont été réalisées sur l’ensemble du génome (GWAS) et ont porté sur l’analyse des composés volatils relatifs aux arôme floraux et fruités (fruits frais et fruits secs) contenus dans les fèves, avant et après torréfaction, ainsi que, sur des résultats d’analyses sensorielles de liqueurs. Cette première étude a pu montrer que les arômes floraux du Nacional étaient principalement synthétisés grâce à deux voies de biosynthèse: celle des monoterpènes et la voie de dégradation du L-phénylalanine. Les résultats relatifs aux arômes fruités ont permis de mettre en lumière cinq voies métaboliques majeures: la voie de biosynthèse des monoterpènes, les voies de dégradations du L-phénylalanine, des sucres, des acides gras et des protéines. Des gènes candidats codant pour des enzymes impliqués dans ces voies métaboliques ont été identifiés dans les zones d’associations correspondantes.La variété Nacional moderne est issue de diverses générations de croisements entre des Trinitario (hybrides Amelonado/Criollo) et le Nacional ancestral, mettant ainsi en jeu 3 ancêtres contrastés. L’effet de cette étape de domestication récente sur les arômes de la variété Nacional moderne a été étudié. Grâce aux données de génotypage des trois ancêtres de référence et aux résultats des GWAS portant sur l’ensemble des caractères de qualité (composés volatils et non-volatils, analyses sensorielles), il a été possible de déterminer l’origine des allèles ayant un effet positif sur les arômes dans les différentes zones d’associations. Cette étude a montré que l’ensemble des ancêtres fondateurs ont apporté des allèles favorables à la synthèse d’arômes de qualité (floraux, fruités, …) mais aussi à la synthèse de défauts (amertume, astringence, …). Nous avons pu montrer que les zones d’associations en lien avec les arômes de qualité et celles avec les défauts n’étaient pas liées génétiquement. Il est donc possible de sélectionner les zones d’intérêts pour les arômes tout en contre-sélectionnant les zones apportant des défauts.La deuxième partie de cette étude a porté sur l’analyse des arômes d’une population de cacaoyers natifs d’Amazonie et issus de la zone d’origine de la variété Nacional ancestral. Dans cette étude, des analyses GWAS ont également été effectuées sur l’ensemble des caractères de qualité analysés précédemment. Quatre vingt dix sept gènes candidats sont communs aux deux populations analysées. De nouveaux composés volatils ainsi que de nouvelles zones d’associations ont également été détectées montrant ainsi une plus grande diversité et richesse aromatique de ces nouvelles ressources génétiques et leur intérêt pour la création de nouvelles variétés aromatiques adaptées à l’Amazonie.Enfin, une étude GWAS sur les composés non-volatils, les caractères sensoriels liés à l’amertume et à l’astringence, ainsi que la teneur en matière grasse et en protéines, a également été réalisée sur les deux populations. Des gènes candidats en lien avec la voie de biosynthèse de la caféine et celle des polyphénols, ou en lien avec la voie de biosynthèse des acides gras ont pu être observés dans les zones d’associations.
... In general, terpenoids are important in pollinator attraction, reproduction, plant seed dispersal for pollination success [38,46,53], and defense against herbivorous and pathogenic attacks [54,55]. In addition, terpenoids are widely used in the perfume and cosmetics industries and used as additives and flavors in food due to their distinctive scents and taste [56,57]. Terpenoid metabolites also frequently have high medicinal value [58][59][60]. ...
Article
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Hoya’s R.Br. attractive flower shapes and unique scents make it suitable to be exploited as a new source of tropical fragrance. Therefore, this study aims to elucidate the biosynthesis of secondary metabolites using phytochemical and transcriptomic approaches to understand the mechanisms of scents biosynthesis, especially terpenoid in Hoya. Three Hoya flower species were selected in this study: Hoya cagayanensis, Hoya lacunosa, and Hoya coriacea. The secondary metabolite profiles characterizing scents on flowers were performed using head space solid phase microextraction (HS-SPME). Gas chromatography-mass spectrometry (GC-MS) revealed 23 compounds from H. cagayanensis, 14 from H. lacunose, and 36 from H. coriacea. Volatiles from the three species had different fragrance profiles, with β-ocimene and methyl salicylate compounds dominating the odor in H. cagayanensis. The 1-octane-3-ol was found highest in H. lacunosa, and (Z)-acid butyric, 3-hexenyl ester was found highest in H. coriacea. Subsequent studies were conducted to identify the biosynthesis pathway of secondary metabolites responsible for the aroma profile released by Hoya flowers through transcriptome sequencing using the Illumina Hiseq 4000 platform. A total of 109,240 (75.84%) unigenes in H. cagayanensis, 42,479 (69.00%) in H. lacunosa and 72,610 (70.55%) in H. coriacea of the total unigenes were successfully annotated using public databases such as NCBI-Nr, KEGG, InterPro, and Gene Ontology (GO). In conclusion, this study successfully identified the complete outline of terpenoid biosynthesis pathways for the first time in Hoya. This discovery could lead to the exploitation of new knowledge in producing high-value compounds using the synthetic biology approach.
... Vanillic, p-coumaric, and ferulic acids were detected with two characteristic peaks; the left peak indicated the unoxidized species (a) while the right peak indicated the more polar oxidized species (b). All three compounds contain a double bond in the carboxylic acid hydrocarbon chain, which is likely to be susceptible to oxidation [41]. Although the retention times of a particular phenolic acid differed slightly depending on whether it was in a UAE or an MAE extract (Figure 3), this did not prevent the identification of the acids. ...
Article
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This study investigated the effect of ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) conditions (extraction time, acetone concentration, solid-to-solvent ratio) on the efficiency of polyphenol recovery from distillery stillage and antioxidant activity of the extracts. The highest total polyphenol content, flavonoid content, and phenolic acid content were obtained with 10-min UAE and 5-min MAE at a solid-to-acetone ratio of 1:15 (w:v). Recovery yield was the highest with an aqueous solution of 60% acetone, confirming the results of Hansen Solubility Parameter analysis. Although UAE resulted in approximately 1.2 times higher extraction yield, MAE showed a better balance between extraction yield and energy consumption exhibited by its 3-fold higher extraction rate than that of UAE. Content of total polyphenols and phenolic acids strongly correlated with antioxidant activity, indicating that these compounds provide a substantial contribution to the bioactive properties of the extracts. Six phenolic acids were extracted, predominately ferulic and p-coumaric acids, and free forms of these acids constituted 91% of their total content, which opens various possibilities for their application in the food, cosmetics, and pharmaceutical industries.
... The jujube ID was mainly correlated with the amino acids (THR, GLU, GLY, ALA, VAL, LEU, TYR, PHE, LYS, HIS, and ARG). This finding could be correlated with the phenomenon that free amino acids may transaminate or dehydrogenate into aldehydes or acids [32]; for example, phenylacetaldehyde and isobutanoic acid could be issued from the oxidation of PHE and VAL, separately [33]. Thus, phenylacetaldehyde and isobutanoic acid may be contributors to the jujube ID. ...
Article
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The aroma characteristics of six red jujube cultivars (Jinchang—‘JC’, Junzao—‘JZ’, Huizao—‘HZ’, Qiyuexian—‘QYX’, Hetiandazao—‘HTDZ’, and Yuanzao—‘YZ’), cultivated in Xinjiang Province, China, were studied by E-nose and GC-IMS. The presence of acetoin, E-2-hexanol, hexanal, acetic acid, and ethyl acetate played an important role in the classification results. JC, JZ, HZ, and YZ were different from others, while QYX and HTDZ were similar to each other. HZ had the most abundant specific VOCs, including linalool, nonanoic acid, methyl myristoleate, 2-acetylfuran, 1-octen-3-one, E-2-heptenal, 2-heptenone, 7-octenoic acid, and 2-pentanone. HZ had higher intensity in jujube ID, floral, sweet, and fruity attributes. Correlation analysis showed that jujube ID (identity) might be related to phenylacetaldehyde and isobutanoic acid that formed by the transamination or dehydrogenation of amino acids; meanwhile, the sweet attribute was correlated with amino acids, including threonine, glutamic acid, glycine, alanine, valine, leucine, tyrosine, phenylalanine, lysine, histidine, and arginine.
... The linoleic acid and linolenic acid are applied to aroma synthesis as precursors in the LOX pathway and catalyzed by a series of key enzymes, such as lipoxygenase (LOX), hydroperoxidase lyase (HPL), and alcoholyl transferase (AAT) to produce ester aroma compounds (Dudareva et al., 2013;Schiller et al., 2015;Schwab et al., 2008). ...
Article
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Our previous study on differential proteome and transcriptome of refrigerated “Nanguo” pears found that the PuLOX2S gene was very active in the LOX pathway of aroma synthesis, but the regulation of expression behavior of the gene and how to mediate the aroma synthesis were still unknown. Partial genome sequences of PuLOX2S were cloned, and its promoter was analyzed by Tail‐PCR. The PuLOX2S promoter sequences of 610 bp were isolated and identified using Plant CARE, which were composed of cis‐acting elements, such as ABRE, AE‐box, ARE, CAAT‐box, Box 4, TCCC‐motif, CAT‐box, CGTCA‐motif, G‐Box, TATA‐box, TCA‐element, TGA‐element, and TGACG‐motif. The Y1H technology was used to determine whether proteins interacted with PuLOX2S based on the pGADT7‐Chinese white pear cDNA library. The Y1H results were shown that 52 proteins could interact with the PuLOX2S promoter, which was compared with sequences in the GenBank database. The three genes PuERF12, PuMYB44, and PuRF2a were the candidate transcription factors of PuLOX2S and PuCDPK10 played an important role in the gene expression in Nanguo pears. Therefore, the results of this study supply important information for revealing new function of PuLOX2S and the regulation mechanism of expression behavior of the gene. It provides new ideas for the regulation of aroma synthesis in Nanguo pears. Practical applications The gene PuLOX2S was very active in the LOX pathway of aroma synthesis, but the regulation of expression behavior of the gene and how to mediate the aroma synthesis were still unknown. We have successfully cloned the partial sequence of the gene and the 610 bp promoter sequence upstream of PuLOX2S and analyzed the structure of cis‐acting elements. There are 52 proteins that interact with the PuLOX2S promoter revealed by the Y1H technique. Three transcription factors among the proteins can regulate the level of PuLOX2S expression, which provides new ideas for the regulation of aroma synthesis in “Nanguo” pears. Moreover, the study results could supply scientific information for the quality improvement and genetic modification of Nanguo pears.
... The highly abundant volatiles in fresh bananas are aldehydes, ketones, alcohols, carboxylic acids, and esters. It has been recognized that the production of straight chain alcohols, aldehydes, ketones, and acids in fruit is largely derived from α-oxidation, β-oxidation, or the lipoxygenase pathway [2,3]. Branched chain volatiles are derived from branched chain amino acids [4,5]. ...
Article
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Butanol vapor feeding to ripe banana pulp slices produced abundant butyl butanoate, indicating that a portion of butanol molecules was converted to butanoate/butanoyl-CoA via butanal, and further biosynthesized to ester. A similar phenomenon was observed when feeding propanol and pentanol, but was less pronounced when feeding hexanol, 2-methylpropanol and 3-methylbutanol. Enzymes which catalyze the cascade reactions, such as alcohol dehydrogenase (ADH), acetyl-CoA synthetase, and alcohol acetyl transferase, have been well documented. Aldehyde dehydrogenase (ALDH), which is presumed to play a key role in the pathway to convert aldehydes to carboxylic acids, has not been reported yet. The conversion is an oxygen-independent metabolic pathway and is enzyme-catalyzed with nicotinamide adenine dinucleotide (NAD+) as the cofactor. Crude ALDH was extracted from ripe banana pulps, and the interference from ADH was removed by two procedures: (1) washing off elutable proteins which contain 95% of ADH, but only about 40% of ALDH activity, with the remaining ALDH extracted from the pellet residues at the crude ALDH extraction stage; (2) adding an ADH inhibitor in the reaction mixture. The optimum pH of the ALDH was 8.8, and optimum phosphate buffer concentration was higher than 100 mM. High affinity of the enzyme was a straight chain of lower aldehydes except ethanal, while poor affinity was branched chain aldehydes.
... These observations suggest that the biosynthesis of fatty acids and their derivatives during fruit ripening is highly regulated. Fatty acid-derived short-chain VOCs are synthesized through the lipoxygenase (LOX) pathway [4], which includes LOX, hydroperoxide lyase (HPL), and alcohol dehydrogenase (ADH). These C6 alcohols can be further converted into esters through the action of alcohol acetyltransferases (AATs). ...
Article
Volatile organic compounds (VOCs) derived from fatty acids are major contributors to fruit flavor and affect human preferences. The omega-3 fatty acid linolenic acid 3, (18:3) serves as an important precursor for synthesis of (E)-2-hexenal and (Z)-3-hexenol. These short chain C6 VOCs provide unique fresh notes in multiple fruit species. Metabolic engineering to improve fruit aroma requires knowledge of regulation of fatty acid derived VOCs. Here, we determined that ripe fruit-specific expression of PpFAD3–1 contributes to 18:3 synthesis in peach fruit. However, no significant increases in (E)-2-hexenal and (Z)-3-hexenol were detected after overexpressing PpFAD3–1. Interestingly, overexpressing the PpNAC1 transcription factor increased the content of 18:3 and enhanced the production of its derived volatiles. Moreover, induced expression of genes responsible for downstream VOC synthesis was observed for transgenic tomato fruit overexpressing PpNAC1, but not for transgenic fruit overexpressing PpFAD3–1. EMSA and ChIP-Seq assays showed that PpNAC1 activated PpFAD3–1 expression via binding to its promoter. Therefore, PpNAC1 plays an important role in modulating fatty acid flux to produce fruit flavor-related VOCs. In addition to PpNAC1, PpFAD3–1 expression was also associated with epigenetic modifications during peach fruit ripening. Taken together, our results provide new insights into the molecular mechanisms regulating biosynthesis of fatty acid and short-chain VOCs in fruit.
... The major water content of tomato fruits is negatively related to most of the parameters studied, except with the concentration of lycopene, total carotenoids, vitamin C content, total antioxidant capacity, and the volatile components 6-methyl-5-hepten-2-one and methyl salicylate. It has been shown that carbohydrates, fatty acids present in fat, and amino acids in proteins, represent the natural carbon reserves for the generation of volatile compounds (55). In general with Malacara tomato fruits, the volatile components detected increase when the concentration of the proximate fraction of the tomato is higher. ...
Article
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The loss of genetic diversity due to the replacement of local tomato ( Solanum lycopersicum L.) varieties by improved cultivars has been mitigated in many cases by the good work of organic farmers in maintaining local agricultural biodiversity. In parallel to these initiatives, in recent years, consumers have developed an increasing awareness of both food-related health, environmental issues, and food demand to recover the flavors of the past. In the case of tomatoes, these attributes (nutritional, organoleptic, social, and environmental) are closely related to organic production using local varieties. “Malacara” tomato is an example of a local variety. Coming from Sierra de Cádiz, it is a varietal type called “Cuelga” (“for hanging,” because the tomato trusses are hung from beams in the farmhouses). Cultivated and harvested in the open air during the summer months, these tomatoes are commercialized and consumed in the winter. Historically, this variety has enabled the fresh consumption of tomatoes during the winter, without the need to force cultivation. It is highly appreciated in the local cuisine and is the basis for sauces figuring in typical dishes. Its characteristic traits are small, pallid fruits, and long shelf life. The main objective of this work has been to typify two Malacara tomato cultivars (red and yellow color) grown under organic farming conditions, through the characterization of morphological, nutritional, and volatile parameters. The main differences are due to morphological parameters (fruit weight and color of the exocarp and endocarp). Other characteristics such as the content of ash, fiber, moisture, the concentration of iron, magnesium, and calcium, and content of lycopene are different between both cultivars. This study provides information on the nutritional and aromatic composition of two Malacara tomato cultivars, differentiated by their color and grown under organic farming conditions. The results add value to the native horticultural heritage and can aid in the selection of tomato varieties suitable for a sustainable production system and to produce tomatoes with high nutritional value and rich in aroma.
... For example, they attract pollinators such as insects, which play an important role in the reproduction of plants and enable the development and growth of fruits and seeds [3,4]. VOCs contribute to protection against herbivores, microbial growth, and abiotic stress [5,6]. In some plants, VOCs have allelopathic effects on surrounding plants, protecting the plant and reducing damage from the outside world when they are injured [7,8]. ...
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Nymphaea hybrid, a precious water lily, is a widely-cultivated aquatic flower with high ornamental, economic, medicinal, and ecological value; it blooms recurrently and emits a strong fragrance. In the present study, in order to understand the volatile components of N. hybrid and its relationship with petals structure characteristics, the morphologies and anatomical structures of the flower petals of N. hybrid were investigated, and volatile compounds emitted from the petals were identified. Scanning and transmission electron microscopy were used to describe petal structures, and the volatile constituents were collected using headspace solid-phase microextraction (HS-SPME) fibers and analyzed using gas chromatography coupled with mass spectrometry (GC-MS). The results indicated that the density and degree of protrusion and the number of plastids and osmiophilic matrix granules in the petals play key roles in emitting the fragrance. There were distinct differences in the components and relative contents of volatile compounds among the different strains of N. hybrid. In total, 29, 34, 39, and 43 volatile compounds were detected in the cut flower petals of the blue-purple type (Nh-1), pink type (Nh-2), yellow type (Nh-3) and white type (Nh-4) of N. hybrid at the flowering stage, with total relative contents of 96.78%, 97.64%, 98.56%, and 96.15%, respectively. Analyses of these volatile components indicated that alkenes, alcohols, and alkanes were the three major types of volatile components in the flower petals of N. hybrid. The predominant volatile compounds were benzyl alcohol, pentadecane, trans-α-bergamotene, (E)-β-farnesene, and (6E,9E)-6,9-heptadecadiene, and some of these volatile compounds were terpenes, which varied among the different strains. Moreover, on the basis of hierarchical cluster analysis (HCA) and principal component analysis (PCA), the N. hybrid samples were divided into four groups: alcohols were the most important volatile compounds for Nh-4 samples; esters and aldehydes were the predominant volatiles in Nh-3 samples; and ketones and alkenes were important for Nh-2 samples. These compounds contribute to the unique flavors and aromas of the four strains of N. hybrid.
... Plants have the capacity to synthesize, accumulate and spread aroma and scent molecules. These are commercially important in food, pharmacy, agriculture, chemical industries in terms of flavorings, drugs, pesticides, industrial feed stocks (Schwab, 2008). These aroma and scent molecules are also found in pepper. ...
... Despite the significance, headway in this field is not simple and has experienced slow progress in recent decades due to the complexity of measuring the "flavor phenotype" (Klee, 2010). Human perception of flavor is subjective and depends on the integration of multiple sensory systems, specifically taste and olfaction, which can create a myriad of flavor experiences (Klee and Tieman, 2018;Goff and Klee, 2006;Schwab et al., 2008). In this scenario, the challenge faced by modern breeding programs is to disentangle the chemical compounds that effectively contribute to human liking and, more importantly, use this information to select and release cultivars with improved sensory perception by consumers. ...
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Among the main features treasured by blueberry consumers, flavor is the most important. Human perception of food flavors can primarily be divided into two main sensory inputs, taste and aroma. Through retronasal olfaction, a group of metabolites called volatile organic compounds (VOCs) emitted from the fruit are able to produce the sensation of aroma, creating the myriad of flavors experienced during our life. In blueberry, breeders have noticed some genotypes with unique floral and sweet flavor notes that, ultimately, enhance human aroma perception. Despite the importance, both the understanding of which chemicals are mediating this variation across phenotypes and the potential impact on consumer acceptability remains largely unknown. In this study we dissected the main components underlying blueberry aroma and associated it with consumer predilections by paring metabolomics with sensory analysis. Our contribution in this study is four-fold: (i) first, based on a representative blueberry germplasm cultivated at the University of Florida, we differentiated genotypes with floral and sweet aromatic notes and confirmed that such unique characteristics are preferred by consumers; (ii) at the chemical level, we showed that a group of eight terpene volatiles constitute the primary metabolic group associated with aroma sensation; (iii) we demonstrated that aromatic genotypes can be classified using information from a group of a few key volatiles; and finally, (iv) we combined pedigree and metabolomic information in a single predictive framework and showed the importance of metabolomic data for flavor-assisted selection. For the blueberry community, our findings open new venues to explore flavor. Broadly, we present an emerging view about flavor and provide a detailed blueprint of how this target could be addressed in fruits and vegetables.
... Plants provide multiple ranges of aromas and flavors well notice by the most sensitive human senses, taste, and odor [180]. Over www.videleaf.com ...
Chapter
Aroma and flavor compounds play a critical role in the quality of vegetables, medicinal and aromatic plants (MAPs), being two of the most important sensory attributes for consumer‘s preferences. Throughout the last decades, many studies have correlated the presence of bioactive compounds with consumer‘s choices or with their beneficial health properties. The purpose of this review is to provide an updated overview regarding the presence of volatile and non-volatile compounds in some of the most economically relevant vegetables and MAPs. Particular emphasis is placed on bioactive polyphenols, polyphenols as prebiotics, and discuss the most important factors that affect the content and profile of the volatile and non-volatile compounds responsible for the aromatic features of vegetables and MAPs. The new challenges and future perspectives for science will also be reported in improving and intensifying the aroma and flavors of vegetables and MAPs.
... Many surveys have summarized the consumers' lesser keenness in purchasing products containing artificial additives, in contradiction to natural food additions (Drew, 1994). Also, many research types have proved that a good number of flavoring agents and their precursors exert health-benefiting properties (Ayseli & Ipek Ayseli, 2016;Schwab, Davidovich-Rikanati, & Lewinsohn, 2008). Many flavors have been detected and developed since 1960. ...
Chapter
Plant extracts contain a varied range of chemicals such as terpenoids, phenolic compounds, alkaloids, glucosinolates, and various organic acids. These chemicals are responsible for their unique nature and perceived biological activity of plant extracts. Owing to the wide acclaimed biological activities of plant extracts, they have been used as natural ingredients and have received significant renewed interest recently. Several plant extracts have been used as commercial preservatives in food because of their green image. The current chapter discusses various chemicals present in plant extracts and emphasizes the structure activity relationship of these chemicals.
... Fatty acid derivatives in ornamental plants are mainly synthesized by C18 fatty acids, including linolenic and linoleic acid. The biosynthesis of fatty acid derivatives begins with stereospecific oxygenation catalyzed by the lipoxygenase (LOX) pathway [215] . At present, the studies on fatty acid derivatives are mainly focused on genes involved in the lipoxygenase pathway [216] , but there are few studies on expression in flower organs. ...
... Hydroxy fatty acids and their derivatives are compounds of growing interest in many scientific areas. In industry, they are widely used as lubricants [1][2][3], surfactants [4,5], plasticizers [6], additives in coatings and paintings [7,8], components of detergents, cosmetics [9,10], flavors [11], and foods [12][13][14]. They are ubiquitous in the biological world and are mainly found in triacylglycerols, membrane phospholipids, waxes, cerebrosides, and other lipids [15][16][17]. ...
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A series of regioisomers of the hydroxystearic acid (HSA) was prepared, and the effect of the position of the hydroxyl group along the chain on a panel of human cancer cell lines was investigated. Among the various regioisomers, those carrying the hydroxyl at positions 5, 7, and 9 had growth inhibitor activity against various human tumor cell lines, including CaCo-2, HT29, HeLa, MCF7, PC3, and NLF cells. 10-HSA and 11-HSA showed a very weak effect. 8-HSA did not show inhibitory activity in all cell lines. The biological role of 7-HSA and 9-HSA is widely recognized, while little is known about the effects of 5-HSA. Therefore, the biological effects of 5-HSA in HeLa, HT29, MCF7, and NLF cell lines were investigated using the Livecyte’s ptychography technology, which allows correlating changes in proliferation, motility, and morphology as a function of treatment at the same time. 5-HSA not only reduces cell proliferation but also induces changes in cell displacement, directionality, and speed. It is important to characterize the biological effects of 5-HSA, this molecule being an important component of fatty acyl esters of hydroxy fatty acids (FAHFA), a class of endogenous mammalian lipids with noticeable anti-diabetic and anti-inflammatory effects.
... The various aroma-types, such as chestnut-like, cooker corn-like, orchid-like and clean aroma, might be resulted from the differences of the OAVs for volatile compounds in the green teas [18][19][20]48]. Table 4 also showed that the key odorants in the XYMJ green teas and other green teas almost belong to endogenous biosynthesis volatiles, including fatty acid derived volatiles (FADVs), amino acid derived volatiles (AADVs), volatile terpenes (VTs) and carotenoid derived volatiles (CDVs) [49,50]. It is reported that most FADVs presented a fresh or green odor. ...
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Xinyang Maojian (XYMJ) green tea is one of the top ten teas in China, and the consumers prefer spring tea due to its umami taste and pleasurable aroma. However, the knowledge about temporal variation of the volatile compounds in XYMJ green teas harvested during different seasons is very limited. In the present work, the main non-volatile compounds that endowed the taste and volatile compounds responsible for the aroma in XYMJ green teas harvested during the spring and autumn seasons were determined. The average contents of free amino acids (FAA) were significantly higher and gradually declined in the spring teas, whereas the caffeine was significantly lower and gradually increased in the spring teas. A total of 39 volatile compounds of six chemical classes were detected in XYMJ green teas, and they displayed various change trends during the spring and autumn seasons, among which 15 volatile compounds were identified as the key odorants based on odor activity value (OAV). The highest OAV of 2195.05 was calculated for the violet-like smelling trans-β-ionone followed by decanal, nonanal, dimethyl sulfide, linalool, geraniol and naphthalene. The OAVs of geraniol, (Z)-3-hexenyl hexanoate, heptanal, benzaldehyde and hexanal in XYMJ spring teas were higher than XYMJ autumn teas. The hierarchical clustering analysis indicated that XYMJ green teas were divided into three clusters and the quality of XYMJ green teas changed greatly within spring season. Harvest season is a crucial factor affecting the flavor quality of XYMJ green teas.
... Terpenoids affect the flavour profiles of most fruits and are synthesized either from acetyl-CoA and pyruvate in the berry cytoplasm (mevalonate pathway) or can be formed in the plastids (DOXP pathway) [20]. Another important source of volatiles are amino acids, from which a large number of different compounds is formed by degradation [21]. ...
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The production of high-quality wines requires the use of high-quality grapes. Tasting represents a widespread method for the determination of grape maturity and quality aspects such as the corresponding aroma profile. However, sensory analysis always remains subjective and it is not possible to judge only aroma compounds because the overall impression is also influenced by main components (e.g. sugars and acids). In contrast, the use of near-infrared (NIR) spectroscopy allows the simultaneous determination of various compounds without being affected by personal preferences. In this study, grape mash samples were examined under comparable conditions to those in the mouth. Differences between grape mashes with varying phytosanitary status of the corresponding grapes as well as for different grape varieties were detected. The quantified concentrations of the detected aroma compounds were used to develop calibration models for determination by NIR spectroscopy. Using global calibration models, the single aroma compounds could be determined by NIR spectroscopy with accuracies reaching from R ² C = 0.365 to R ² C = 0.976. Separate calibration models for cultivation region and grape colour improved the prediction accuracy. Instrumental analysis cannot totally replace sensory evaluation, however, NIR spectroscopy has the potential to be used as an objective, additional method for the evaluation of grape aroma quality.
... It is conceivable that the unique features of the volatile profile of natural processed green coffee beans arise from their prolonged contact with the coffee fruit during the drying process, as dried fruits of both C. arabica and C. robusta emit increased quantities of several alcohols compared to fresh fruits 56 . Alcohols, like many other classes of plant volatiles, can be derived from fatty acids through either α-oxidation, β-oxidation, or the lipoxygenase pathway 57 . In grapes, it has been demonstrated that lipoxygenase activity increases during the early stages of the post-harvest drying process, presumably being liberated due to structural damage to the fruit 58 . ...
Article
Background: After the harvest, green coffee beans are dried on the farm using several methods: the wet process, natural process, pulped natural process, or mechanical demucilaging. This study evaluated how the choice of a specific processing method influenced the volatile organic compounds of the coffee beans, before and after roasting, and the sensory characteristics of the beverage. Coffea arabica beans of two varieties (Mundo Novo and Catuai Vermelho) were subjected to these four processing methods on a single farm in the cerrado area of Brazil. Results: Analysis by GC-MS HS-SPME identified 40 volatile organic compounds in green coffee beans and 37 in roasted beans. The main difference between post-harvest treatments was that natural processed green beans of both varieties contained a different profile of alcohols, acids, and lactones. In medium-roasted beans, those differences were not observed. The coffee beverages had similar taste attributes but distinct flavor profiles. Some of the treatments resulted in specialty-grade coffee, while others did not. Conclusion: The choice of a specific post-harvest processing method influences the volatile compounds found in green beans, the final beverage's flavor profile, and the cupping score, which can have a significant impact on the profitability of coffee farms operations. This article is protected by copyright. All rights reserved.
... These results suggest that FA treatment improved the aroma quality of coldstored fresh-cut taros. LOX is also involved in the formation of some aromatic components (72). In this study, LOX activity was enhanced in FA treatment within the first 3 days (Figure 6B), implying that the enhanced LOX activity at the initial phase of cold storage might be involved in the formation of aroma components in fresh-cut taros. ...
Article
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Taro (Colocasia esculenta) is a major root crop or vegetable in the world, and the corm is a good source of many nutrients including starch, vitamins, and minerals. Taro corms are processed into various forms before consumption, which makes them perishable, reduces the shelf life, and increases postharvest losses. The surface browning of fresh-cut taros is one of the major factors that limits storage life and affects consumer acceptance. In this study, the effects of ferulic acid (FA) as an effective agent in the prevention of quality deterioration were investigated. Fresh-cut taros were immersed in distilled water and different concentrations of FA (1, 2, 5, 10, and 20 mM) solutions for 30 min, air-dried at 25°C for 30 min, and then stored at 5°C for 12 days to investigate the effects of FA on browning. Among the FA concentrations tested, 10 mM resulted in significantly higher L* values, lower a* and b*, and browning index values. FA treatment (10 mM) also induced de novo biosynthesis of two volatile compounds, including non-anal and octanoic acid ethyl ester in fresh-cut taros following extended cold storage. The results suggest that FA treatment maintains the quality of fresh-cut taros under cold conditions. FA treatment enhanced PAL activity and gene expression but reduced total phenolic content and the expression of six C4H, 4CL, and CHS genes, suggesting that FA treatment reduced phenolic biosynthesis. FA treatment reduced PPO activity and gene expression and decreased soluble quinone content, suggesting that FA treatment suppressed the phenolic oxidation. FA treatment enhanced the activity and gene expression of CAT and POD, reduced those of LOX, and decreased MDA and H2O2 levels, suggesting that FA treatment activated the antioxidant defense system and thereby reduced oxidative damage. These findings demonstrated that FA treatment could serve as an effective approach to retard the browning of fresh-cut taros and provided a basis for the feasible application of FA in the preservation of fresh-cut foods.
... The health benefits of strawberries are due to high vitamin C, phenolic compounds and folates. Strawberries are low in kilojules and high in dietary fibres (Proteggente et al., 2002;Schwab et al., 2008). Consumers enjoy strawberries in different forms such as fresh, frozen and processed forms (jams, juices and confections). ...
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Strawberry varieties grown in Australia are mostly introduced, and are predominantly sourced from the USA. Consequently, these varieties are well suited to the USA climate. The Australian Strawberry Breeding Program focuses on locally bred varieties and the environmental and genotypic factors that influence berry quality and flavour profile. As such, enhancing the flavour of strawberries (Fragaria x annanasa) is one of the industry highest priorities. The breeding program supports this initiative and has resulted in increasing industry acceptance of Australian varieties. Most Australian-grown strawberries are produced in open fields and are heavily impacted by environmental factors. This research aims to understand the environmental effects on strawberry quality attributes [volatile compounds, total soluble solids (sugars) and titratable acidity and the consumer preference of the cultivars]. Australian-grown cultivars and advanced-breeding lines were analysed for their quality attributes and the influence of growing environment on these compounds. These quality attributes were then assessed to identify the compounds that were responsible for consumer preference. Levels of some esters, lactones and sugars were found to be responsible for the consumer preference of certain genotypes compared with others. Sampling were carried out in two seasons (2013-2014 and 2014-2015) for 15 non-consecutive weeks. The sampled commercial cultivars were Albion, Melba, San Andreas, Palomar and Camino Real. Apart from these, few advanced-breeding lines were sampled. The advanced breeding lines are Australian plant breeding materials selected by the breeders. These lines included; 10-004-168, 10-004-165, 10-057-27, 08-029-80, 06-050-202 and 07-048-190. The cultivars and Australian advanced-breeding lines contained esters, terpenoids, lactones, aldehydes, furans, alcohols and acids. These findings provided sufficient information that Australian advanced-breeding lines contain favourable compounds which are stable in the Australian growing condition. The effect of environmental parameters was analysed. The variation of the volatile compounds, sugars and acids were explained using the genotype, environment and GxE interaction. This study intended to understand the genotypes that perform well in the Australian growing conditions. Furthermore, the current study revealed 39 important strawberry flavour compounds with high broad-sense heritability. Analysis of the most and least consumer preferred strawberries showed -dodecalactone, ethyl hexanoate, (E)-Hex-2-enyl butanoate, TSS, 1-methylethyl hexanoate, mesifurane, methyl octanoate, ethyl butanoate, S-methyl thiobutanoate were important for consumer desirability. This study demonstrated that a combination of chemical compounds and sugars create better strawberries.
... 6 Carbohydrates, fatty acids and amino acids are known to be the main precursors of most aroma related volatiles, which include straight-chain aldehydes, lactones, ketones, alcohols and esters. 7 The main contributors to fruity aroma are esters such as methyl butanoate, ethyl butanoate, butyl butanoate, methyl hexanoate, ethyl hexanoate, butyl acetate and hexyl acetate. 8 Furans (specifically, furaneol and mesifurane) add caramel notes, while the terpenoids linalool and nerolidol impart flowery notes. ...
Article
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Volatile compounds produced during ripening of strawberry are key determinants of fruit quality and consumer preference. Strawberry volatiles are largely esters which are synthesized by alcohol acyltransferases (AATs) and degraded by carboxylesterases (CXEs). Although CXEactivity can have a marked influence on volatile contents in ripe strawberry fruits, CXE function and regulation in them are poorly known. Here, we report the biochemical and functional characterization of the fruit receptacle-specific and ripening-related carboxylesterase FanCXE1. The expression of the corresponding gene was found to be antagonistically regulated by auxins and abscisic acid, key hormones that regulate fruit growth and ripening in strawberry. In vitro, FanCXE1 was able to hydrolyze artificial ester substrates similar to those produced by ripe strawberry fruits. Transient suppression of the FanCXE1 gene by RNAi resulted in an increase of important volatile esters such as methyl hexanoate, methyl butanoate and ethyl hexanoate as well as a decrease of the alcohols hexenol and linanool. The results of this work enhance our understanding of the molecular basis for volatile syntheses and facilitate production of better flavored strawberry fruits by introduction of the relevant alleles into common cultivars.
... In the process of fruit growth and ripening, alcohols are produced partly by glucose through glycolysis and decarboxylation, and dehydrogenation, and partly by the degradation of amino acids generated by protein hydrolysis through deamination by anaerobic metabolism of yeast (Wilfried et al., 2008). Esters are mainly produced in the second stage of alcoholic fermentation and are generated by alcohols and acids through esterification (Amores et al., 2020). ...
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In this experiment, Guangxi passion fruit was used as the raw material for natural aroma extraction using the spinning cone column (Spinning Cone Column, SCC) technique. In combination with the semi‐quantitative method, the aroma characteristics of the raw pulp (raw whole‐fruit puree, PU) before SCC processing, residue (Residue, RS) and extract (Extract, EX) after SCC processing, and passion fruit juice (Juice, JU) were evaluated for their aroma characteristics using headspace gas chromatography‐mass spectrometry (HS‐SPME‐GC‐MS), gas chromatography‐ion mobility spectrometry (GC‐IMS), electronic nose, and sensory evaluation. As a result, a total of 110 aroma substances were detected in four samples, and 33, 38, 73, and 28 aroma components were detected from PU, RS, EX, and JU, respectively. There are 50 compounds in EX with concentrations greater than 10 μg/kg, and 19 of them had OAV values greater than 1, including β‐Ionone and linalool, which contributed significantly to the aroma. The aroma profiles and characteristics were further analyzed for JU and EX using the e‐nose sensor, and it was found that both showed similar aroma profiles. The sensory evaluation results were also in general agreement with the results obtained from the electronic nose, with EX having mainly “floral”, “fruity,” and “sweet” aromas. The results demonstrated that the spinning cone column technique can increase the fresh and natural fruity aroma of passion fruit in the extract, which has the effect of enriching the aroma and improving the aftertaste. This study will make a foundation for passion fruit SCC extract application in drinks. Practical applications Compared with traditional extraction technology, spinning cone column technology has the advantages of high mass transfer efficiency, short extraction time, a wide range of temperature control, and the most complete extracted flavor substances, which greatly reduces the damage degree of heat‐sensitive flavor substances and condense aroma. It is widely used in beverages, wine, dairy products, fruit and vegetable, spice essential oil, and other industries. Passion fruit flavor prepared by SCC technology has the advantages of high purity and high concentration, which can be used in solid drinks, baked food, convenience food, tobacco, perfume, and other products. Besides, GC‐IMS is an efficient and rapid new analytical technique, which has been widely used in the flavor analysis of volatile organic compounds in food and traditional Chinese medicine samples.
... The content of (Z)-2-hexen-1-ol in the fresh-scented type was significantly higher than that in other types. Previous studies have shown that C 6 , C 9 aldehydes, and alcohols have fresh and green aromas [40,41], and these aldol compounds were formed by the gradual oxidation, cleavage, and reduction in precursor fatty acids by lipoxygenase (LOX) [42]. Therefore, it is further speculated that they may contribute greatly to the formation of this aroma type. ...
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Prunus mume is a traditional ornamental plant, which owed a unique floral scent. However, the diversity of the floral scent in P. mume cultivars with different aroma types was not identified. In this study, the floral scent of eight P. mume cultivars was studied using headspace solid-phase microextraction (HS-SPME) and organic solvent extraction (OSE), combined with gas chromatography-mass spectrometry (GC-MS). In total, 66 headspace volatiles and 74 endogenous extracts were putatively identified, of which phenylpropanoids/benzenoids were the main volatile organic compounds categories. As a result of GC-MS analysis, benzyl acetate (1.55–61.26%), eugenol (0.87–6.03%), benzaldehyde (5.34–46.46%), benzyl alcohol (5.13–57.13%), chavicol (0–5.46%), and cinnamyl alcohol (0–6.49%) were considered to be the main components in most varieties. However, the volatilization rate of these main components was different. Based on the variable importance in projection (VIP) values in the orthogonal partial least-squares discriminate analysis (OPLS-DA), differential components of four aroma types were identified as biomarkers, and 10 volatile and 12 endogenous biomarkers were screened out, respectively. The odor activity value (OAV) revealed that several biomarkers, including (Z)-2-hexen-1-ol, pentyl acetate, (E)-cinnamaldehyde, methyl salicylate, cinnamyl alcohol, and benzoyl cyanide, contributed greatly to the strong-scented, fresh-scented, sweet-scented, and light-scented types of P. mume cultivars. This study provided a theoretical basis for the floral scent evaluation and breeding of P. mume cultivars.
... Plants and plant-based products are well known for having distinctive flavors because they can synthesize, accumulate, and release a wide array of flavor-active compounds (Schwab et al., 2008). Plant-derived flavor molecules are synthesized as such by plants as a defense response mechanism or generated from flavor precursors in plants (e.g., amino acids, fatty acids, and carbohydrates) during harvesting, processing, and storage (Roland et al., 2017). ...
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Demand for plant‐based meat alternatives has increased in recent years due to concerns about health, ethics, the environment, and animal welfare. Nevertheless, the market share of plant‐based meat alternatives must increase significantly if they are to support sustainable food production and consumption. Flavor is an important limiting factor of the acceptability and marketability of plant‐based meat alternatives. Undesirable chemosensory perceptions, such as a beany flavor, bitter taste, and astringency, are often associated with plant proteins and products that use them. This study reviewed 276 articles to answer the following five research questions: (1) What are the volatile and nonvolatile compounds responsible for off‐flavors? (2) What are the mechanisms by which these flavor compounds are generated? (3) What is the influence of thermal extrusion cooking (the primary structuring technique to transform plant proteins into fibrous products that resemble meat in texture) on the flavor characteristics of plant proteins? (4) What techniques are used in measuring the flavor properties of plant‐based proteins and products? (5) What strategies can be used to reduce off‐flavors and improve the sensory appeal of plant‐based meat alternatives? This article comprehensively discusses, for the first time, the flavor issues of plant‐based meat alternatives and the technologies available to improve flavor and, ultimately, acceptability.
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With the aim of gaining insights into the evolution of quality characteristics of banana (Musa ABB Pisang Awak) during postharvest ripening, the cultivar 'Guangefen 1' was used to investigate the changes in physiological quality, the changes in volatile aroma components with maturity and the changes in the expression patterns of the gene related to aroma synthesis during postharvest storage at room temperature (25 ℃). The results showed that fruit firmness decreased sharply within 2 days after harvest, and the contents of total soluble solids (TSS) and soluble sugar increased significantly. Full ripening was reached on the 6 th day of storage. On the 8 th day, fruit firmness was reduced to a very low level, and the contents of TSS, and total aroma substances were maximized while the maximum contents of TSS and amino acid occurred on the 6 th day. A smaller number of volatile compounds were detected in immature bananas at lower levels, consisting mainly of C6-C9 aldehydes and alcohols along with a lesser amount of esters. The content of volatile compounds increased significantly with fruit ripening, including isoamyl isobutyrate, hexyl acetate, isoamyl acetate as esters, contributing to the unique aroma of Pisang Awak bananas. Expression analysis of the key genes involved in fruit aroma synthesis revealed that the expression of LOX (lipoxygenase), AAT (alcohol acyltransferase), ADH (alcohol dehydrogenase), BCAT (branched chain
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The volatile compounds of eight peach varieties (Prunus persica L.)—“Filina”, “Gergana”, “Ufo-4”, “July lady”, “Laskava”, “Flat Queen”, “Evmolpiya”, and “Morsiani 90”—growing in Bulgaria were analyzed for the first time. Gas chromatography–mass spectrometry (GC–MS) analysis and the HS-SPME technique revealed the presence of 65 volatile compounds; the main identified components were aldehydes, esters, and fatty acids. According to the provided principal component analysis (PCA) and hierarchical cluster analysis (HCA), the relative quantities of the identified volatile compounds depended on the studied peach variety. The results obtained could be successfully applied for the metabolic chemotaxonomy of peaches.
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Flavor is among the most important traits valued by consumers of fresh fruits. Human perception of flavor occurs primarily through two main sensory inputs, taste and aroma. Through retronasal olfaction, volatile organic compounds (VOCs) emitted by the fruit are able to produce the sensation of aroma which when combined with gustatory inputs from the tongue together underly our perception of the thousands of flavors we experience throughout our lives. In blueberry, breeders have observed that some genotypes possess berries with unique ‘floral’ and ‘sweet’ flavor and aroma notes. The potential impact these characteristics might have on consumer acceptability is largely unknown and represents an opportunity to better understand how aroma attributes affect the perception of blueberry flavor. In this study, we dissected the main components of blueberry aroma and associated it with consumer predilections by pairing metabolomics with sensory analysis. Our contribution in this study is four-fold: (i) first, we differentiated genotypes with floral and sweet aroma notes and confirmed that such characteristics are preferred by consumers; (ii) at the chemical level, we showed that a group of eight terpenoid volatiles (p-cymene, myrtenal, linalool, L-carvenol, geranyl acetone, geranyl acetate, D-limonene and β-myrcene) constitute the primary metabolic group associated with these aroma sensations; (iii) we demonstrated that aromatic genotypes can be classified using metabolomics; and finally, (iv) we combined pedigree and metabolomic information and showed the importance of metabolomic data for flavor-assisted selection. Our findings open new avenues to explore the phenomenon of flavor in blueberries and also allow us to present an emerging view about flavor and provide a detailed blueprint of how this targeted trait could be addressed in fruit and vegetable breeding.
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Aroma is a crucial quality attribute of apple fruit, mainly determined by volatile compounds. However, to our knowledge, the physiological and molecular roles of brassinosteroids (BRs) in volatile compound biosynthesis had not been elucidated. In this study, 24-epibrassinolide (EBR) inhibited fruit firmness and ethylene production and delayed fruit ripening. Total soluble solids, fructose content, glucose, and sucrose content were inhibited by EBR treatment. Most importantly, enzyme activity, volatile compound production, and genes involved in volatiles biosynthesis were suppressed compared with those in the control after EBR treatment. Furthermore, volatile compounds production and biosynthesis gene expressions was decreased by the overexpression of MdBZR1, whereas opposite results were observed when MdBZR1 was silenced. Notably, OE-MdBZR1 calli showed lower volatile compound content than that of the control calli by EBR treatment. Collectively, these results indicate that BR activate MdBZR1 expression, which in turn inhibited volatile compound production.
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As a famous table fruit in Xinjiang, apricot has gained an increasing number of consumers because of its rich nutritional value and seductive flavor. The aim of this study was to assess the sensory qualities, the nutritional value, antioxidant properties, and flavor of Xinjiang apricots, which were investigated using high-performance liquid chromatography (HPLC) and headspace-solid phase micro-extraction with gas chromatography-mass spectrometry (HS-SPME/GC-MS). The results revealed that while there were similarities in the components contributing to nutrition and flavor, the Xinjiang apricots had distinct features. The "Luopuhongdaike" cultivar was superior in taste based on the comprehensive evaluation of the sugar, and acid contents and the sugar-acid ratio. The "Suogejianali" and "Luopuhongdaike" cultivars were the best in terms of nutrients and antioxidant activity. All Xinjiang apricots possessed similar volatile compounds, including linalool, nonanal, decanal, (E)-2-nonenal, and octanal, which provided fatty, green, lemon, floral, and orange aromatic notes. In conclusion, Xinjiang apricots have high nutritional and aromatic value. These results will provide a complete chemical characterization of the taste, nutritional ingredients, and aroma of Xinjiang apricots, and help breeders better develop polyphenol-rich varieties with superior antioxidant activity. PRACTICAL APPLICATION: This study investigated the sensory characteristics, nutritional value, antioxidant activity, and flavor of fresh apricots in Xinjiang. The research results will provide a theoretical basis for the development of the sensory characteristics, aroma, nutritional value, and medicinal value of fresh apricots in Xinjiang.
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The improvement of fruit flavor is a challenge for producers and breeders. This study investigated the effects and mechanisms of preharvest hydrogen nanobubble water (HNW) application on the flavor of cultivated strawberry (Fragaria × ananassa ‘Benihoppe’). Compared with surface water, HNW enhanced the volatile profiles, sugar-acid ratio, and sensory attributes (e.g., aroma, flavor, and overall liking) with/without fertilizer application. Meanwhile, flavor components such as esters (e.g. ethyl hexanoate), acids (e.g., hexanoic acid), and soluble sugars (including glucose, fructose, and sucrose) significantly contributed to increased strawberry flavor achieved with HNW. Importantly, HNW may alleviate the negative effects of fertilizers on strawberry fruit aroma. Further study elucidated that the aroma-related genes (including FaLOX, FaADH, FaAAT, FaQR, FaOMT, and FaNES1) were involved in the accumulation of specific volatiles after HNW treatment. This study provided evidence that the practical application of H2 can improve horticultural product quality at a lower carbon cost.
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Fruit aroma makes an initial flavor impression and largely determines the consumer preference and acceptance of fruit products. Free volatile organic compounds (FVOCs) directly make up the characteristic aromas of fruits. While glycosidically bound volatile compounds (GBVs) can be hydrolyzed during fruit ripening, postharvest storage, and processing, releasing the attached aglycones as free volatiles that could alter the overall aroma attributes of fruits. GBVs typically exhibit significantly higher concentrations than their free counterparts in fruits such as grapes, cherries, kiwifruits, tomatoes, and tamarillos. This review highlights the biosynthesis of FVOCs and GBVs in fruit and illustrates their biological transformations for various functional purposes such as detoxification, aroma enhancement, plant defense, and pollinator attraction. Practical applications for regulating the levels of aroma compounds emitted or accumulated in fruit are also reviewed, emphasizing the metabolic engineering of free volatile metabolites and hydrolytic technologies on aroma glycosides. Generally, enzymatic hydrolysis using AR2000 is a common strategy to enhance the sensory attributes of fruit juices/wines, while acidic hydrolysis induces the oxidation and rearrangement of aglycones, generating artifacts with off-aromas. This review associates the occurrence of free and glycosidic bound volatiles in fruit and addresses their importance in fruit flavor enhancement and industrial applications.
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Dianhong tea (DHT) is popular for its pleasant caramel-like aroma. In this study, the aroma profile of high-grade DHT have been studied using gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O) combined with headspace solid phase microextraction (HS-SPME). A total of 52 aroma-active compounds were identified by GC-O coupled with aroma extract dilution analysis (AEDA) and odor specific magnitude estimation (Osme). Among them, quantification of 21 aroma-active compounds indicated that the content of linalool (5928 µg/kg) was the highest in high-grade DHT, followed by phenylethanol (3923 µg/kg) and phenylacetaldehyde (1801 µg/kg). Sensory-directed aroma recombination and omission tests further verified that phenylacetaldehyde, linalool, geraniol and 3-ethyl-2,5-dimethylpyrazine were important contributors to the overall sensory characteristics of high-grade DHT which dominated mainly by floral, sweet and caramel-like odors. This work will provide a theoretical reference for comprehensively understanding the aroma characteristic of DHT.
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Honey peach (Prunus persica (L.) Batsch) is a climacteric fruit with short storage period. Generally, the low temperature storage (LTS) technology is implemented to lessen aroma loss and keep the quality. However, the LTS procedure brings about cold stress issues and affects the aroma metabolism. It is essential to unravel the primary aroma and the corresponding metabolism mechanism through key proteins under abiotic stress. In this study, the primary components were characterized under LTS at 1 °C during 0 to 40 days. Furthermore, the proteomics analysis was performed to acquire differentially expressed proteins to clarify the underlying metabolism mechanisms of the primary aroma and potential proteins. As a result, four proteins were considered as potential key proteins that associated with fatty acid and amino acid metabolism under cold stress. Additionally, this study provides theoretical cornerstones for regulating and improving the quality of honey peach.
Article
Rosa roxburghii Tratt (Chestnut rose) is native to China where it is cultivated for its strongly aromatic hips (pseudo fruits); locally known as cili. Increasing interest in cili for food and beverage products prompted an evaluation of its aroma compounds and the influence of geographic source. Accordingly, the volatile compounds in cili from five locations in Guizhou province were analysed by headspace‐solid‐phase microextraction coupled with gas chromatography‐mass spectrometry. Sixty‐seven volatile compounds were identified. Principal component analysis distinguished three sample groups by geographic source. The aroma of cili juice from each location was characterized by quantitative descriptive analysis using six odour descriptors. Cili aroma was predominantly sweet/fruity, floral and green, but geographic source significantly influenced the intensity of the sweet/fruity and floral notes. Odour activity analyses indicated that 40 volatile compounds contribute appreciably to the aroma of cili. Of those compounds, only ten esters, two aldehydes, one alcohol and one aromatic compound were common to all regional samples. Those findings extend the range of volatiles detected in cili. These results identify those that are present in odour active amounts and provide the first evidence of the impact of geographic source on the aroma and flavour of cili. Chestnut rose (Rosa roxburghii) hips (cili) have 67 identified volatile compounds Cili from five Chinese geographic regions can be typified by volatile compounds. Over 40 volatile compounds contribute substantially to the aroma of cili. Sweet/fruity and floral cili rosehip aromas differ between regional samples. A benchmark for future elucidation and regional discrimination of cili quality.
Article
Lipoxygenase (LOX) pathway is the key and the most important pathway for the metabolism of fruit volatile. However, the transcription mechanism of the LOX pathway is still obscure in non-climacteric fruit. In order to identify the transcription factor involved in LOX-derived volatile metabolism, RNA sequencing and metabolome were used to profile strawberry (Fragaria × ananassa Duch.). Correlation analysis shows that the expression of FaLOX2 was negatively correlated with the hexanal content (r = −0.985). The RY element that specifically bound by the B3 domain transcription factors, are found in FaLOX2 promoter. B3 domain-containing transcription factors including LEAFY COTYLEDON2 (LEC2)–ABI3–VAL (LAV, 3), RELATED TO ABI3 and VP1 (RAV, 18), AUXIN RESPONSE FACTOR (ARF, 13), and REPRODUCTIVE MERISTEM (REM, 9) are identified. It is noticed that FaLEC2 expression is negatively correlated with (E,Z)-2,6-nonadienal content (r = −1.000). Yeast one-hybrid analysis and dual-luciferase analysis suggest that FaLEC2 transcriptionally represses the activity of FaLOX2 promoter. Moreover, FaLEC2 expression level is negatively correlated with FaLOX2 expression (r = −0.956). Here, our demonstration that FaLEC2 trans-represses the activity of the FaLOX2 promoter provides evidence that FaLEC2 directly controls a transcriptional program for LOX-derived volatile metabolism in strawberries.
Chapter
Flavor is an important concept in the sensory acceptance and consumer decision process. The specific sensation of flavor from each food is because of the characteristic chemical compounds in that particular food product. Though the flavor is a combination of aroma and tastes sensory perceptions, it has been established that the flavor and aroma of food substrates are correlated, autonomous of the taste perception. The chemical compounds in food substances act as chemical triggers to stimulate the aroma and flavor receptors in buccal cavity. Plant extracts are rich carriers of the aromatic and phenolic compounds that impart the characteristic flavor to specific foods. Along with being the carriers of flavor-rich compounds, plant extracts also serve as antioxidant, antimicrobial, and can exert therapeutic properties. The plant extracts serving as flavor components in food systems have gained much importance in recent days due to increased consumer demand.
Article
Ester loss due to chilling injury adversely affects the quality of ‘Nanguo’ pears. Salicylic acid (SA) is a well-known regulator of many physiological processes. Nevertheless, the regulatory mechanism underlying SA-mediated biosynthesis of esters remains largely unknown. Herein, we reported that SA treatment increased the kinds of esters and content of main and total esters in cold-stored ‘Nanguo’ pears. Yeast-hybridization, subcellular localization assay, transient transfection and β-glucuronidase analysis showed that the nuclear-localized PuMYB308-like and PuMYB6-like directly bound and activated PuAAT, moreover, overexpression of PuMYB308-like and PuMYB6-like promoted the expression of PuAAT as well as the main volatile content, and these functions were further enhanced by SA treatment. Furthermore, PuNAC68-like was found to be a negative regulator that inhibited the transcription of PuAAT. However, this effect was suppressed by SA treatment. Collectively, this study uncovered the transcriptional mechanism underlying SA promoted the transcription of PuAAT thus mediating ester formation.
Article
'Nanguo' pear (Pyrus ussuriensis Maxim.) is a typical climacteric fruit with an attractive aroma after postharvest ripening. Esters are the key volatile compounds determining the typical aroma formation. However, the mechanism of aroma-related ester formation remains largely unknown. In this study, we performed transcriptome and metabolome analyses to reveal the changes of aroma-related compounds during pear ripening in the optimal taste period (OTP). During the pear ripening process, typical fatty acid-derived volatile organic compounds (VOCs) are transformed from aldehydes, alcohols, and ketones to esters, where ethyl hexanoate, hexyl acetate, and ethyl butanoate are the dominant esters in the OTP. Rich aroma-related esters in the OTP are associated with the accumulation of important precursors of aroma volatiles, including linoleic acid, α-linolenic acid, γ-linolenic acid, and oleic acid. Genes encoding key biosynthetic enzymes are associated with the altered levels of aroma-related esters. The candidate genes associated with the high levels of aroma-related esters in 'Nanguo' pears are PuFAD2, PuLOX2, PuLOX5, and PuAAT. Additionally, transcription factor (TF) genes such as PuWRKY24, PuIAA29, and PuTINY may play crucial roles in aroma formation during fruit ripening. Hence, we summarized the TFs that regulate VOC metabolism in different fruit species. The results provided a foundation for further research on aroma-related esters in 'Nanguo' pears and could help to elucidate the mechanisms regulating fruit quality improvement.
Article
Dancong is a Chinese oolong tea famous for its aroma diversity. However, this diversity in characteristic is challenging to be clarified in either sensory or chemical aspects. In this study, the aromas from Dancong teas were characterized based on the typical odors of “floral” and “honey”. The volatile compounds underlying the odors were investigated through chemometrics. Seventy Dancong teas of various categories were collected to approximate the diversity in aroma. According to the sensory evaluation, the floral or honey odor was detected at every sample. For volatile characterization, 57 compounds were identified by gas chromatography-mass spectrometry (GC-MS) coupled with headspace-solid phase microextraction (HS-SPME) across samples. The difference in floral and honey odors was related to volatile variation among the teas, as both the odor-based classification and the volatile-based unsupervised learning analyses yielded consistent sample clustering patterns. Nine volatiles were identified as putative markers for the odor difference, where indole, (E)-nerolidol, 2-phenylacetonitrile and γ-caprolactone were accounted for the floral odor predominance, while hexyl 2-methylbutanoate, (Z)-3-hexenyl pentanoate, (Z)-linalool oxide (pyranoid), (E)-linalool oxide (furanoid), and (Z)-linalool oxide (furanoid) were contributed to the honey odor perception. These results point to a volatile-endorsed categorization framework based on the floral and honey odors that can assist Dancong aroma quality control.
Article
Jerusalem artichoke (Helianthus tuberosus L.) bears flowers with bright colors and diverse fragrances. It can be used for greening, and brewing flower tea, and has great ornamental and edible values. However, little is known about the floral components and genetic differences in their biosynthetic processes. In this study, we detected the floral components of two Jerusalem artichoke flowers having different fragrances by headspace solid-phase microextraction gas chromatography/mass spectrometry (HS-SPME-GC/MS), along with the analysis of related pathways of differential metabolites, differential expression genes (DEGs) and terpenoid biosynthesis. The results showed that 201 metabolites, primarily monoterpenoids and sesquiterpenoids, were detected in JA192 and JA399. Among them, most terpenoids were found in metabolites and their relative contents of JA399 were significantly higher than those of JA192. Safranal and rimuene were unique components of JA399. The combined transcriptomic and metabolomic analyses showed that among the JA192 and JA399, gcpE1, gcpE2, IDI1, and IDI2 genes were the key genes in the biosynthetic pathway of (+)-α-pinene, (-)-β-pinene and safranal. DXS1 gene played an important role in the biosynthetic pathway of rimuene. IDI1, IDI2, HMGR3, and HMGS1 genes played positive roles in the biosynthetic pathway of β-copaene and (+)-δ-cadinene. In summary, differences in terpenoids and their contents were the major factors responsible for the differences in floral components between the two genotypes of Jerusalem artichoke. These were associated with DEGs related to terpenoid synthesis.
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Aroma is one of the major inherent quality characteristics in fruits. Understanding the composition of aroma volatiles and their biosynthesis mechanism is crucial to improving fruit quality. However, the biosynthesis mechanism of aroma volatiles has not been characterized yet in white-fleshed pitaya (Hylocereus undatus). This study was performed to investigate aroma volatiles and related gene expression patterns in the pulp of "mild grassy" and "strong grassy" aroma cultivars. Analysis of volatile composition and concentration showed that aldehydes, alcohols, esters, and alkenes were predominant in both cultivars. However, comparative analysis revealed a significant difference in the concentration of several metabolites, particularly hexanal and 1-hexanol. The results of the comparative transcriptome identified a large number of aroma-related differentially expressed genes. The majority of these genes were enriched in fatty acid and isoleucine degradation pathways. According to integrative analyses, changes in the expression of lipoxygenase pathway genes, specifically FAD, LOXs, HPLs, and ADHs, probably lead to the difference in strength of "grassy" aroma between both cultivars. The qRT-PCR of 18 aroma-related genes was performed to validate the transcriptome analysis. Our results identified key genes and pathways connected with the biosynthesis of aroma volatiles in white-fleshed pitaya. These results will be useful to dissect the genetic mechanism of fruit aroma in white-fleshed pitaya.
Article
In this study, the volatile changes of noni fruit in various ripening stages were analysed using gas chromatography–mass spectrometry. Eleven of the 35 identified volatiles were found odour‐active through gas chromatography–olfactometry. Based on the aroma extract dilution analysis, hexanoic acid, octanoic acid and their methyl esters were considered as the key odorants for the smell of noni fruit. Results also indicated that the sensory perception of the rancid smell was resulted from the antagonistic effects of the key acid and methyl ester odorants. This study may facilitate the improvement of the acceptability of noni processed foods in the future. The pleasantness of noni fruit smell is primarily determined by the overall contribution of two fatty acids and their methyl esters.
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The fragrance of Clarkia breweri (Onagraceae), a California annual plant, includes three benzenoid esters: benzylacetate, benzylbenzoate, and methylsalicylate. Here we report that petal tissue was responsible for the benzylacetate and methylsalicylate emission, whereas the pistil was the main source of benzylbenzoate. The activities of two novel enzymes, acetyl-coenzyme A:benzylalcohol acetyltransferase (BEAT), which catalyzes the acetyl esterification of benzylalcohol, andS-adenosyl-l-methionine:salicylic acid carboxyl methyltransferase, which catalyzes the methyl esterification of salicylic acid, were also highest in petal tissue and absent in leaves. In addition, the activity of both enzymes in the various floral organs was developmentally and differentially regulated.S-Adenosyl-l-methionine:salicylic acid carboxyl methyltransferase activity in petals peaked in mature buds and declined during the next few days after anthesis, and it showed a strong, positive correlation with the emission of methylsalicylate. The levels of BEAT activity and benzylacetate emission in petals also increased in parallel as the buds matured and the flowers opened, but as emission began to decline on the 2nd d after anthesis, BEAT activity continued to increase and remained high until the end of the lifespan of the flower.
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Recently, a novel family of methyltransferases was identified in plants. Some members of this newly discovered and recently characterized methyltransferase family catalyze the formation of small-molecule methyl esters using S-adenosyl-l-Met (SAM) as a methyl donor and carboxylic acid–bearing substrates as methyl acceptors. These enzymes include SAMT (SAM:salicylic acid carboxyl methyltransferase), BAMT (SAM:benzoic acid carboxyl methyltransferase), and JMT (SAM:jasmonic acid carboxyl methyltransferase). Moreover, other members of this family of plant methyltransferases have been found to catalyze the N-methylation of caffeine precursors. The 3.0-Å crystal structure of Clarkia breweri SAMT in complex with the substrate salicylic acid and the demethylated product S-adenosyl-l-homocysteine reveals a protein structure that possesses a helical active site capping domain and a unique dimerization interface. In addition, the chemical determinants responsible for the selection of salicylic acid demonstrate the structural basis for facile variations of substrate selectivity among functionally characterized plant carboxyl-directed and nitrogen-directed methyltransferases and a growing set of related proteins that have yet to be examined biochemically. Using the three-dimensional structure of SAMT as a guide, we examined the substrate specificity of SAMT by site-directed mutagenesis and activity assays against 12 carboxyl-containing small molecules. Moreover, the utility of structural information for the functional characterization of this large family of plant methyltransferases was demonstrated by the discovery of an Arabidopsis methyltransferase that is specific for the carboxyl-bearing phytohormone indole-3-acetic acid.
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In snapdragon flowers, the volatile ester methyl benzoate is the most abundant scent compound. It is synthesized by and emitted from only the upper and lower lobes of petals, where pollinators (bumblebees) come in contact with the flower. Emission of methyl benzoate occurs in a rhythmic manner, with maximum emission during the day, which correlates with pollinator activity. A novel S-adenosyl-l-methionine:benzoic acid carboxyl methyl transferase (BAMT), the final enzyme in the biosynthesis of methyl benzoate, and its corresponding cDNA have been isolated and characterized. The complete amino acid sequence of the BAMT protein has only low levels of sequence similarity to other previously characterized proteins, including plant O-methyl transferases. During the life span of the flower, the levels of methyl benzoate emission, BAMT activity, BAMT gene expression, and the amounts of BAMT protein and benzoic acid are developmentally and differentially regulated. Linear regression analysis revealed that production of methyl benzoate is regulated by the amount of benzoic acid and the amount of BAMT protein, which in turn is regulated at the transcriptional level.
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Some basil varieties are able to convert the phenylpropenes chavicol and eugenol to methylchavicol and methyleugenol, respectively. Chavicol O-methyltransferase (CVOMT) and eugenol O-methyltransferase (EOMT) cDNAs were isolated from the sweet basil variety EMX-1 using a biochemical genomics approach. These cDNAs encode proteins that are 90% identical to each other and very similar to several isoflavone O-methyltransferases such as IOMT, which catalyzes the 4′-O-methylation of 2,7,4′-trihydroxyisoflavanone. On the other hand, CVOMT1 and EOMT1 are related only distantly to (iso)eugenol OMT from Clarkia breweri, indicating that the eugenol O-methylating enzymes in basil and C. breweri evolved independently. Transcripts for CVOMT1 and EOMT1 were highly expressed in the peltate glandular trichomes on the surface of the young basil leaves. The CVOMT1 and EOMT1 cDNAs were expressed in Escherichia coli, and active proteins were produced. CVOMT1 catalyzed the O-methylation of chavicol, and EOMT1 also catalyzed the O-methylation of chavicol with equal efficiency to that of CVOMT1, but it was much more efficient in O-methylating eugenol. Molecular modeling, based on the crystal structure of IOMT, suggested that a single amino acid difference was responsible for the difference in substrate discrimination between CVOMT1 and EOMT1. This prediction was confirmed by site-directed mutagenesis, in which the appropriate mutants of CVOMT1 (F260S) and EOMT1 (S261F) were produced that exhibited the opposite substrate preference relative to the respective native enzyme.
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SABATH MTs are found only in the plant kingdom, and they also do not display significant sequence similarity to other known plant MTs. However, they share several physical characteristics with some other families of plant MTs, such as forming homodimers and sharing similar SAM binding residues. The SABATH protein family appears to be unique among plant MT families in containing enzymes that transfer the methyl group to an oxygen while other members of the family transfer the methyl group to a nitrogen; previously described plant MT families contain members that appear to modify only one type of functionality.
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Petunia hybrida W115 was transformed with a Clarkia breweri S-linalool synthase cDNA (lis). Lis was expressed in all tissues analysed, and linalool was detected in leaves, sepals, corolla, stem and ovary, but not in nectaries, roots, pollen and style. However, the S-linalool produced by the plant in the various tissues is not present as free linalool, but was efficiently converted to non-volatile S-linalyl-β-d-glucopyranoside by the action of endogenous glucosyltransferase. The results presented demonstrate that monoterpene production can be altered by genetic modification, and that the compounds produced can be converted by endogenous enzymatic activity.
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A pathogen-inducible oxygenase in tobacco leaves and a homologous enzyme from Arabidopsiswere recently characterized (Sanz, A., Moreno, J. I., and Castresana, C. (1998) Plant Cell 10, 1523–1537). Linolenic acid incubated at 23 °C with preparations containing the recombinant enzymes underwent α-oxidation with the formation of a chain-shortened aldehyde, i.e., 8(Z),11(Z),14(Z)-heptadecatrienal (83%), an α-hydroxy acid, 2(R)-hydroxy-9(Z),12(Z),15(Z)-octadecatrienoic acid (15%), and a chain-shortened fatty acid, 8(Z),11(Z),14(Z)-heptadecatrienoic acid (2%). When incubations were performed at 0 °C, 2(R)-hydroperoxy-9(Z),12(Z),15(Z)-octadecatrienoic acid was obtained as the main product. An intermediary role of 2(R)-hydroperoxy-9(Z),12(Z),15(Z)-octadecatrienoic acid in α-oxidation was demonstrated by re-incubation experiments, in which the hydroperoxide was converted into the same α-oxidation products as those formed from linolenic acid. 2(R)-Hydroperoxy-9(Z),12(Z),15(Z)-octadecatrienoic acid was chemically unstable and had a half-life time in buffer of about 30 min at 23 °C. Extracts of cells expressing the recombinant oxygenases accelerated breakdown of the hydroperoxide (half-life time, about 3 min at 23 °C), however, this was not attributable to the recombinant enzymes since the same rate of hydroperoxide degradation was observed in the presence of control cells not expressing the enzymes. No significant discrimination between enantiomers was observed in the degradation of 2(R,S)-hydroperoxy-9(Z)-octadecenoic acid in the presence of recombinant oxygenases. A previously studied system for α-oxidation in cucumber was re-examined using the newly developed techniques and was found to catalyze the same conversions as those observed with the recombinant enzymes, i.e. enzymatic α-dioxygenation of fatty acids into 2(R)-hydroperoxides and a first order, non-stereoselective degradation of hydroperoxides into α-oxidation products. It was concluded that the recombinant enzymes from tobacco and Arabidopsis were both α-dioxygenases, and that members of this new class of enzymes catalyze the first step of α-oxidation in plant tissue.
Chapter
Fragrant flowers emit aroma bouquets containing anywhere from a few to more than one hundred different compounds present in varying amounts. The number and diversity of these constituents make floral scent one of the most variable aspects of plant phenotype. Yet, floral scent compounds have a common function in promoting cross pollination, a vital process in the life cycle of most plants. Accompanied by visual and tactile cues, these substances mediate plant-pollinator interactions, which usually benefit both partners. In return for being pollinated, pollinators are rewarded with pollen, nectar, and oils. However, deceptive pollination systems that involve floral scent as an attractant are also well known. Because of its commercial importance in the perfume and flavor industries, the chemistry of floral scents has been studied for a long time. Among the most striking recent examples is a series of papers published during the last 15 years by Roman Kaiser and collaborators at Givaudan Roure. These authors have contributed significantly to our knowledge of floral scents in the orchid family,1-2 and Kaiser and his collaborators have presented many astonishing new scent molecules from various other plant families.3-14 Apart from many studies of medicinal plants,15-17 e.g., most investigators have focused on species from one or a few plant families, either from the perspective of pollination biology and/or chemotaxonomy.
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Floral scents are a diverse blend of low molecular weight, mostly lypophilic compounds (Chapter 2). Although there are more than 1000 known volatiles, most of them are produced by only a few major biochemical pathways (isoprenoid, lipoxygenase, and phenylpropanoid/benzenoid pathways). Their diversity is mainly derived from specific enzymatic derivatizations, which increase the volatility of compounds at the final step of their formation.1 In the past decade or so, significant progress has been made in understanding the biochemical routes to floral volatiles and the molecular mechanisms that regulate their formation. Several model plant species with powerful floral scents, such as Clarkia breweri, snapdragon (Antirrhinum majus), Petunia hybrida, rose (Rosa spp.), Stephanotis floribunda, and Nicotiana suaveolens have been used to isolate and characterize enzymes and genes involved in the biosynthesis of floral volatiles. Moreover, investigations of volatile production in vegetative tissues and fruits, as well as genes expressed in Arabidopsis flowers, have also significantly contributed to our understanding of the formation of floral volatiles.
Article
Get a good start in flavor and fragrance chemistry!. This book presents a survey of those natural and synthetic fragrance and flavor materials which are commercially available, produced and used on a relatively large scale and which are important ingredients for the creation of fragrance and flavor compositions because of their specific sensory characteristics, e.g., smell, taste. It provides information on their properties, methods employed in their manufacture, and their areas of application. This is the 5th edition of the classic "Bauer-Garbe". '...The excellent and concise introduction to this unique industry is followed by extensive information on nearly 500 of the most used fragrance and flavor compounds. Names, molecular formula, physical data, odor and flavor descriptions, uses, and a number of processes for the larger scale production of chemicals are all included. Successive chapters deal with essential oils, animal secretions, quality control, toxicology and literature. The formula, name and CAS registry number index are an invaluable and timely addition.' - Parfumer and Flavorist. '...Data that would normally have to be selected from many different books are available in one source with this book...with over 800 citations throughout the text, this is a nearly inexhaustible source of information.' - Euromaterials.
Article
For thousands of years microbial processes have accompanied mankind playing the decisive but unrecognised role of producing more flavourful foods and beverages such as bread, cheese, beer, wine and soy sauce. It was in 1923 that the first scientific review on microbial flavours appeared [1]. With the dynamic development of modern analytical techniques in the middle of the twentieth century when isolation, chromatographic separation and structural identification of volatiles became routine, the basis for a more systematic elucidation of microbial flavour generation was given.Research in the last decades has led to a tremendous increase in knowledge of microbial and enzymatic flavour generation which has been frequently reviewed [2-8] and was reviewed in several multiauthor works dealing with this topic [9], [10] and one comprehensive book exclusively dedicated to aroma biotechnology published in 1995 [11].
Chapter
The origin of using odorous substances simply for enjoyment or medicinal reasons is as old as mankind. People have used perfume oils, and unguents on their bodies for thousands of years in lesser or greater amounts dependent on fashion whims. The early Egyptians used perfumed balms as part of religious ceremonies and later as part of pre-love-making preparations. Myrrh and frankincense were exuded gums from trees used to scent the atmosphere in rituals. Other plants such as rose and peppermint were steeped in oils until a perfumed unguent formed. The unguent was then rubbed into the skin. It is interesting to note that perfume has come full circle today as more and more of us seek out high-quality aroma therapy perfumed oils to use in exactly the same way as our ancestors did. Perfume fell out of use during early Christianity, but was revived in the medieval period.By the 1600s scents were applied to objects such as furniture, gloves, and fans. In the Georgian era non-greasy eau de Cologne was developed and it had many uses from bath essence to mouthwash [1].
Chapter
This chapter gives an introduction to the field of carotenoid-derived aroma compounds and illustrates the importance of short-chain carotenoid metabolites as flavor and fragrance substances. Although carotenoid-derived aroma compounds (so-called norterpenoids or norisoprenoids) are ubiquitous constituents in plant derived aromas, very little is known about their biogeneration. Hence, possibilities for an efficient biotechnological production are still limited. After a brief summary of the historical development of norisoprenoid chemistry, this introductory chapter reviews the present knowledge about the occurrence and formation of carotenoid-derived aroma compounds in natural tissues and discusses possibilities for a biotechnological production.
Article
An enzyme with fatty acid α-oxidation activity (49 nkat mg−1; substrate: lauric acid) was purified from germinating pea (Pisum sativum) by a five-step procedure to apparent homogeneity. The purified protein was found to be a 230-kD oligomer with two dominant subunits, i.e. a 50-kD subunit with NAD+ oxidoreductase activity and a 70-kD subunit, homolog to a pathogen-induced oxygenase, which in turn shows significant homology to animal cyclooxygenase. On-line liquid chromatography-electrospray ionization-tandem mass spectrometry revealed rapid α-oxidation of palmitic acid incubated at 0°C with the purified α-oxidation enzyme, leading to (R)-2-hydroperoxypalmitic acid as the major product together with (R)-2-hydroxypalmitic acid, 1-pentadecanal, and pentadecanoic acid. Inherent peroxidase activity of the 70-kD fraction decreased the amount of the (R)-2-hydroperoxy product rapidly and increased the level of (R)-2-hydroxypalmitic acid. Incubations at room temperature accelerated the decline toward the chain-shortened aldehyde. With the identification of the dual functionα-dioxygenase-peroxidase (70-kD unit) and the related NAD+ oxidoreductase (50-kD unit) we provided novel data to rationalize all steps of the classical scheme ofα-oxidation in plants.
Chapter
The present work is based on the comparative headspace analysis of twenty-seven varieties of living roses. A classification of the volatile constituents into six functional groups including the most abundant and characteristic chemicals is proposed: hydrocarbons, alcohols, aldehydes and ketones, esters, aromatic ethers and other miscellaneous functions. A presentation of the analytical results is given in the form of a stylized flower (exogram): this graphical illustration allows at one glance a symbolization and recognition of odoriferous flowers or any other scenting living plant material.
Chapter
Vanilla extract is widely used in the food and the confectionery industry. Vanillin is the most abundant component of vanilla extract. An understanding of the biosynthetic pathway of vanillin may be important for regulating the production of the compound in plants. It is agreed that vanillin (C6-C1) is a product of phenylpropanoid (C6-C3) compounds. One school of thought suggests that vanillin is formed from ferulic acid that undergoes chain shortening. It was shown that inVanilla planifoliatissue cultures the benzoate derivative pathway operates using phenylpropanoid substrates, leading from trans-cinnamic acid to flavor compounds. The branch point between the C6-C3and C6-C1pathways most likely occurs at the level of p-coumaric acid. The tissue possesses constitutive 3-0-methyltransferase, capable of methylation of externally added 3,4-dihydroxybenzaldehyde. Aromatic C6-C1aldehydes are reduced to the corresponding alcohols by a specific alcohol dehydrogenase and stored.
Chapter
Only substances that have a molecular weight below about 400 and an appreciable vapor pressure at room temperature can be perceived as having odor. The spectrum of odorants is thus limited to relatively small, neutral organic compounds, including undissociated acids and nitrogenous bases.1 Relatively few organic acids are sufficiently volatile to contribute to natural aromas. Acetic (vinegary), propionic (goaty), butyric (spoiled butter), and lactic (sauerkraut) acids are odorous at relatively high concentration.
Chapter
Essential oil, also defined as essence, volatile oil, etheric oil or aetheroleum, is a complex mixture of volatile constituents biosynthesised by living organisms. Essential oils can be liberated from their matrix by water, steam and dry distillation, or expression in the case of citrus fruits [1-5]. Their occurrence and function in nature is still a question and the subject of ongoing research. However, there is evidence that organisms produce essential oils for defence, signalling or as part of their secondary metabolism.As a consequence essential oils comprise an important bioresource for renewable natural products [1-25].
Article
Salicylic acid (SA) is an important component of systemic-acquired resistance in plants. It is synthesized from benzoic acid (BA) as part of the phenylpropanoid pathway. Benzaldehyde (BD), a potential intermediate of this pathway, was found in healthy and tobacco mosaic virus (TMV)-inoculated tobacco (Nicotiana tabacum L. cv Xanthi-nc) leaf tissue at 100 ng/g fresh weight concentrations as measured by gas chromatography-mass spectrometry. BD was also emitted as a volatile organic compound from tobacco tissues. Application of gaseous BD to plants enclosed in jars caused a 13-fold increase in SA concentration, induced the accumulation of the pathogenesis-related transcript PR-1, and increased the resistance of tobacco to TMV inoculation. [¹³C6]BD and [²H5]benzyl alcohol were converted to BA and SA. Labeling experiments using [¹³C1]Phe in temperature-shifted plants inoculated with the TMV showed high enrichment of cinnamic acids (72%), BA (34%), and SA (55%). The endogenous BD, however, contained nondetectable enrichment, suggesting that BD was not the intermediate between cinnamic acid and BA. These results show that BD and benzyl alcohol promote SA accumulation and expression of defense responses in tobacco, and provide insight into the early steps of SA biosynthesis.
Article
Tomato (Lycopersicon esculentum) plants were transformed with gene constructs containing a tomato alcohol dehydrogenase (ADH) cDNA (ADH 2) coupled in a sense orientation with either the constitutive cauliflower mosaic virus 35S promoter or the fruit-specific tomato polygalacturonase promoter. Ripening fruit from plants transformed with the constitutively expressed transgene(s) had a range of ADH activities; some plants had no detectable activity, whereas others had significantly higher ADH activity, up to twice that of controls. Transformed plants with fruit-specific expression of the transgene(s) also displayed a range of enhanced ADH activities in the ripening fruit, but no suppression was observed. Modified ADH levels in the ripening fruit influenced the balance between some of the aldehydes and the corresponding alcohols associated with flavor production. Hexanol and Z-3-hexenol levels were increased in fruit with increased ADH activity and reduced in fruit with low ADH activity. Concentrations of the respective aldehydes were generally unaltered. The phenotypes of modified fruit ADH activity and volatile abundance were transmitted to second-generation plants in accordance with the patterns of inheritance of the transgenes. In a preliminary taste trial, fruit with elevated ADH activity and higher levels of alcohols were identified as having a more intense "ripe fruit" flavor.
Article
We have previously shown (R.A. Raguso, E. Pichersky [1995] Plant Syst Evol 194: 55–67) that the strong, sweet fragrance of Clarkia breweri (Onagraceae), an annual plant native to California, consists of 8 to 12 volatile compounds, including 4 phenylpropanoids. Although some C. breweri plants emit all 4 phenylpropanoids (eugenol, isoeugenol, methyleugenol, and isomethyleugenol), other C. breweri plants do not emit the latter 2 compounds. Here we report that petal tissue was responsible for the bulk of the phenylpropanoid emission. The activity of S-adenosyl-L-methionine: (iso)eugenol O-methyltransferase (IEMT), a novel enzyme that catalyzes the methylation of the para-4[prime]-hydroxyl of both eugenol and (iso)eugenol to methyleugenol and isomethyleugenol, respectively, was also highest in petal tissue. IEMT activity was absent from floral tissues of plants not emitting (iso)methyleugenol. A C. breweri cDNA clone encoding IEMT was isolated, and its sequence was shown to have 70% identity to S-adenosyl-L-methionine:caffeic acid O-methyltransferase. The protein encoded by this cDNA can use eugenol and isoeugenol as substrates, but not caffeic acid. Steady-state IEMT mRNA levels were positively correlated with levels of IEMT activity in the tissues, and no IEMT mRNA was observed in flowers that do not emit (iso)methyleugenol. Overall, the data show that the floral emission of (iso)methyleugenol is controlled at the site of emission, that a positive correlation exists between volatile emission and IEMT activity, and that control of the level of IEMT activity is exerted at a pretranslational step.
Article
THIS MONTH, BAYER EXPECTS TO begin receiving binding bids for its flavors and fragrances subsidiary Haarmann & Reimer. Bayer put H&R on the block at the end of November 2001 and has said it hopes to raise roughly $1.3 billion from the sale. The sale in a sense marks the end of an era: Bayer follows Roche, which spun off its Givaudan division in 2000, in ending a decades-long involvement with the flavors and fragrances, or F&F, industry. The industry itself has global sales that will probably top $16 billion this year. The only remaining major F&F business held by a chemical company is Quest International, owned by ICI. Quest—cobbled together from a number of smaller suppliers-became part of ICI when ICI purchased Unilever's specialty chemicals business in the mid-1990s; unlike its peers, ICI considers the sector one of its core interests. So now, industry gossip is turning on who is to buy ...
Article
Typical apple (Malus domestica Borkh.) flavour develops during ripening. Maximum endogenous volatile concentration occurs at the climacteric peak but it is not known whether the volatile biosynthetic enzymes are constitutive or induced during the climacteric. Exposing apples to hypoxic conditions induces accumulation of high concentrations of acetaldehyde and ethanol; after return to air ethyl esters are enhanced and non‐ethyl esters decrease. There are differences in degree of ethyl ester enhancement among cultivars. These may be because of: differential activity or synthesis of alcohol acyl CoA transferase (AAT) or alcohol dehydrogenase (ADH); separate iso‐forms of AAT and ADH each with their own substrate specificity; variation in alcohol precursors in different cultivars; or a combination of all three. Volatile production is greater at higher temperatures in the range from 0 to 30°C but exposure to low temperatures (
Article
Fruit flavor is a result of a complex mixture of numerous compounds. The formation of these compounds is closely correlated with the metabolic changes occurring during fruit maturation. Here, we describe the use of DNA microarrays and appropriate statistical analyses to dissect a complex developmental process. In doing so, we have identified a novel strawberry alcohol acyltransferase (SAAT) gene that plays a crucial role in flavor biogenesis in ripening fruit. Volatile esters are quantitatively and qualitatively the most important compounds providing fruity odors. Biochemical evidence for involvement of the SAAT gene in formation of fruity esters is provided by characterizing the recombinant protein expressed in Escherichia coli. The SAAT enzyme showed maximum activity with aliphatic medium-chain alcohols, whose corresponding esters are major components of strawberry volatiles. The enzyme was capable of utilizing short- and medium-chain, branched, and aromatic acyl-CoA molecules as cosubstrates. The results suggest that the formation of volatile esters in fruit is subject to the availability of acyl-CoA molecules and alcohol substrates and is dictated by the temporal expression pattern of the SAAT gene(s) and substrate specificity of the SAAT enzyme(s).
Chapter
The present review demonstrates that EOs and their components have many functional properties and exert their action in mammals as well as in other organisms (insects, fungi, bacteria and viruses). The synergistic effect of EO components is a promising field that could lead to the optimisation of a given bioactivity. This phenomenon has been observed in many activities, such as those of antimicrobials, antioxidants, analgesics and semiochemicals. EOs are complex mixtures of components that show higher activities than their isolated components; their final activities are due to the combine effects of several minor components. Thus, EOs contain multifunctional components that exert their activities through different mechanisms. EOs and their components may have new applications against various diseases of different origins (cancer, fungal, bacterial or viral), because some of these complex diseases require multiple components and multifunctional therapies. The natural product industry is actively seeking natural therapeutics, preservatives, repellents and other agents that can replace synthetic compounds. The scientific literature has identified new applications and uses of both traditional and exotic EOs. These applications can ultimately assist growers and rural communities in the developing world to increase interest in their products.
Article
InEurycotis floridana, the male calling behavior is associated with the exposition of epidermal glands located under tergites 2, 7, and 8. 4-Hydroxy-5-methyl-3(2H)-furanone and 4-hydroxy-2,5-dimethyl-3(2H)-furanone were recently identified as the specific components of tergite 7 secretion. Methylene chloride extracts of tergite 7 and its major compound 4-hydroxy-5-methyl-3(2H)-furanone attract the conspecific females at a distance. Methylene chloride extracts of tergite 8 are also attractive at a distance to the females, whereas extracts of tergite 2 had no effect on males and females. Our GC investigations showed the absence of specific compounds in tergite 2 secretions. The GC-MS analyses revealed that the male secretion of the gland under tergite 8 is mainly a mixture of (2R*, 3R*)-butanediol, 1-dodecanol and benzyl 2-hydroxybenzoate. These compounds were tested at different concentrations on their own, or as a mixture. Only (2R*, 3R*)-butanediol and 1-dodecanol were attractive for the females. Their functions, as components of the male sex pheromone, in addition with the two derivatives of the furanone are discussed.
Article
Geraniol and nerol were reduced to citronellol by a solubilized enzyme preparation from rose petals. The terpene reductase was specific for primary terpene alcohols with a cis or trans allylic double bond. The cofactor requirement was fulfilled only by NADPH.
Plants produce over 100,000 small molecules, derived from phenylpropanoid, isoprenoid, and alkaloid biosynthetic pathways. This rich chemical diversity is the result of a rapidly diversifying and ongoing evolutionary process. Recent advances in the molecular biology of plants, particularly in the area of large-scale genomics, have revealed the way by which the enzymes of secondary metabolism arise through processes of mutation and gene duplication, leading to continued elaboration of new chemical structures that are selected for as they impart an adaptive advantage for the plant. Structural biology provides an important tool for the detailed characterization of proteins at the atomic level. This level of functional understanding can lead to a more complete appreciation of complex biosynthetic pathways by the elucidation of the mechanisms of individual biosynthetic reactions. Plant small molecule methyltransferases (MTs) constitute a large and important class of enzymes critical to many metabolic pathways. Most MTs methylate hydroxyl and carboxyl moieties, referred to as “O-methyltransferases” (OMTs) and target nitrogen and sulfur atoms of small molecules occasionally.
Article
Bitter fennel (Foeniculum vulgare Mill. var. vulgare, Apiaceae) is a common perennial hemicryptophyte, used since antiquity as a medicinal and aromatic herb in the Mediterranean basin. We describe the anatomical specialization and some of the factors that affect phenylpropene accumulation in the fruits of a t-anethole-rich chemotype during development. Histological examination of fruits by longitudinal sections indicated that each oil duct is an elongated cavity with a series of internal septa at 200-400 μm intervals. Oleoresin accumulation is accompanied by an increase in the oil duct area, as observed in transversal cross sections in early stages of development (from the yellow bud stage to the open flower stage). Upon maturation, oleoresin is further accumulated due to increased duct volume as a result of duct elongation. The main component of the oleoresin, t-anethole, is synthesized during flowering and in the early stages of fruit development, as monitored by the levels of S-adenosine methionine: t-anol O-methyltransferase activity. Upon transition from the waxy fruit stage (28 days after the yellow bud stage) to fully ripe fruit (42 days after the yellow bud stage) O-methyltransferase activity apparently ceases, indicating the cessation of de novo biosynthesis, while oleoresin levels remain constant, likely due to a lack of further metabolism and minimal volatilization, as indicated by apparent high lignification of the cells lining the oil ducts.
Article
A comparative study between the aromatic profile of muskmelon aqueous essence and the puree of fresh fruit was carried out using gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O). Results obtained show a total of 53 components quantified in the essence and 38 in the fresh fruit. In addition, four new components are described for the first time as contributors to the aromatic profile of muskmelon including 2-methyl-3-buten-2-ol, 2,3-butanediol, methyl 3-phenylpropionate, and ethyl 3-phenylpropionate (found only in the puree of the fruit). The olfactometric analysis revealed the presence of 25 components with aromatic activity. Esters, alcohols, and one sulfur component [ethyl 3-(methylthio)propionate] appear to be the most important contributors to the essence aroma. The aromagram of fresh fruit is richer in high molecular weight components, which have not yet been positively identified and do not present detectable peaks in the flame ionization detector.
Article
The volatiles of fresh mountain papaya (Carica candamarcensis, syn. C. pubescens Lenne et Koch) were separated from the fruit pulp by high-vacuum distillation and subsequent solvent extraction (pentane-dichloromethane, 2:1). In three fractions obtained by preseparation of the concentrated extract with adsorption chromatography on silica gel (pentane-diethyl ether gradient) the volatiles were analyzed by capillary gas chromatography and combined capillary gas chromatography-mass spectrometry. From 199 volatiles identified by these methods 103 compounds showed structures of esters, among them some uncommon substances such as, e.g., ethyl 3-mercaptopropanoate, ethyl 4-hydroxy- and 4-acetoxybutanoate, methyl (E)-2- and (E)-3-octenoate, butyl and hexyl (E)-2-butenoate, and butyl 2-furoate and butyl nicotinoate were found.
Article
Peaches (Prunus persica L., Batsch; cv. Glohaven) and nectarines (P. persica L., Batsch, var. nucipersica; cv. Maria Laura) were picked weekly from 57 days after full bloom (DAFB) to complete ripening on the tree in order to study the changes in volatile composition during fruit growth and ripening. Volatile substances were sampled from sliced pulp by dynamic headspace and analyzed by capillary Gas Chromatography (cGC) and gas chromatography/mass spectrometry. Volatile composition varied greatly, both quantitatively and qualitatively over time and between cultivars. Aldehydes, alcohols and esters showed a decreasing trend during fruit growth, with the exception of acetoin and (Z)-3-hexenol which reached the highest amounts in mature fruits. Glohaven peaches produced great amounts of lactones, mainly γ- and δ-decalactone, and γ- and δ-dodecalactone. Maria Laura nectarines produced less volatiles but more of esters and terpenoids (linalool and terpinolene) than peaches. As a consequence, nectarine aroma was more floral and fruity.
Article
Among the volatiles isolated by solvent extraction from cactus pear fruit (Opuntia ficus indica) and identified by HRGC–MS, selected chiral and achiral constituents were characterized by enantiodifferentiation and 13C/12C isotope ratio analysis, using multidimensional gas chromatography–mass spectrometry (MDGC–MS) and on-line gas chromatography–combustion isotope ratio mass spectrometry (HRGC-C-IRMS), respectively. While the enantiodistributions determined for methyl 2-methylbutanoate (98 : 2%, S : R), methyl 3-hydroxybutanoate (73 : 27%, R : S), 1-phenyl-ethanol (74 : 26%, R : S), linalool (68 : 32%, R : S), γ-nonalactone (65 : 35%, S : R), γ-deca-lactone (79 : 21%, R : S) and γ-dodecalactone (>99% R) can be discussed in relation to data previously provided for these compounds from various plant origins, the δ13C values of −22.0‰, −21.8‰, −19.1‰ and −20.9‰, measured for 1-hexanol, E-2-hexenol, E-2-nonenol and E,Z-2,6-nonadienol, respectively, are clear-cut indicators for their origin from plants with Crassulaceae acid metabolism (CAM), and thus may helpful for authenticity evaluations. Copyright © 2001 John Wiley & Sons, Ltd.
Article
Isoprenoid biosynthesis in plants proceeds via two independent pathways: 1) t