Characterization of the aromatic profile of purple passion fruit (Passiflora edulis Sims) during ripening by HS-SPME-GC/MS and RNA sequencing

Comprehensive Analysis on Physicochemical Properties and Characteristic Compounds of Insect-Infested Ziziphi Spinosae Semen

Objectives: Ziziphi spinosae semen (ZSS), an edible and medicinal substance, was easily infested by Plodia interpunctella (P. interpunctella) during storage. However, there was no identification method for insect-infested ZSS based on its chemical composition. Therefore, the characteristic compounds in ZSS before and after being infested by P. interpunctella were discovered based on the comparison of volatile organic compounds (VOCs), untargeted metabolomics, and other quality characters. Methods: Color, total flavonoid content (TFC), and main active compound content were measured to explore the change of physicochemical properties in ZSS after being infested by P. interpunctella. Non-targeted metabolomic techniques, including ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) were used to assess molecular-level alterations. Results: The color changed significantly. The TFC and main active compounds of spinosin, jujuboside A, jujuboside B, and betulinic acid were decreased significantly. A total of nine VOCs and twenty-one metabolites were screened out that could be used to identify whether ZSS was infested. And some metabolites, such as uric acid, gluconic acid, hypoxanthine, and xanthine, were discovered as characteristic compounds in ZSS after being infested by P. interpunctella. Conclusions: The study provided the basis and reference for the identification of insect-infested ZSS and offered an example for the identification of other insect-infested edible and medicinal materials.

Molecular Networking from Volatilome of Theobroma grandiflorum (Copoazu) at Different Stages of Maturation Analyzed by HS-SPME-GC-MS

Theobroma grandiflorum (copoazu) is a plant native to South America, widely cultivated in countries within the Amazon region. Its unique phytochemical composition imparts distinctive organoleptic properties, making it an exotic fruit. In this study, headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) was used to identify the volatile organic compounds (VOCs) produced by copoazu. The optimal conditions for sample pretreatment were first determined using a Design of Experiments (DoE) approach. Analysis of the volatile profiles enabled the identification of 96 copoazu VOCs across three ripening stages. Of these, 79 VOCs were classified into chemical compound families using spectral correlation analysis across various libraries and databases, as well as molecular network analysis. Additionally, a volatilomic analysis was conducted to examine the changes in VOCs throughout the ripening process. Molecular network analysis showed that the VOCs emitted by the fruit are linked to the interconversion of compounds, which can be observed through the study of the metabolic pathways. These findings provide a comprehensive analysis of the copoazu volatilome, providing valuable insights into the organoleptic characteristics of this Amazonian fruit. Esters and terpenes such as α-terpineol, trans-4-methoxythujane, linalool, 2-methylbutyl butanoate, 3-methylbut-2-enoic acid, 2-methylpentyl ester, and 2-methylpropyl hexanoate were identified as potential biomarkers associated with the copoazu ripening process.

Microbiome and Metabolome Illustrate the Correlations Between Endophytes and Flavor Metabolites in Passiflora ligularis Fruit Juice

This study investigates the interplay between volatile and non-volatile flavor metabolites and endophytic microbial communities during three developmental stages of Passiflora ligularis fruit juice. Using bioinformatics and metabolomics, we characterize microbial diversity and metabolic variations to understand flavor development. A total of 1490 bacterial and 1158 fungal operational taxonomic units (OTUs) were identified. Young fruits had higher microbial diversity, dominated by Proteobacteria and Firmicutes (bacteria) and Ascomycota and Basidiomycota (fungi). As the fruit matured, Proteobacteria increased while Firmicutes decreased, indicating that microbial succession is tied to development. Metabolomic profiling identified 87 volatile and 1002 non-volatile metabolites, with distinct chemical classes varying across stages. Saturated hydrocarbons and fatty alcohols were the main volatile metabolites, while organic acids and lipids among non-volatile metabolites showed stage-dependent changes, influencing flavor complexity. Correlation analysis showed microbial-flavor interactions: Proteobacteria negatively correlated with metabolites, while Firmicutes positively correlated with metabolites. Ascomycota positively correlated with volatile metabolites, whereas Basidiomycota showed an inverse relationship, highlighting their differential contributions to flavor biosynthesis. This study enhances understanding of microbial and metabolic factors shaping P. ligularis fruit flavor, highlighting the importance of microbial influence on fruit metabolomics. The findings suggest the potential for microbiome engineering to improve flavor quality, aiding postharvest management and industrial processing in the food and beverage industry.

Analysis of Volatile Metabolome and Transcriptome in Sweet Basil Under Drought Stress

Basil, renowned for its aromatic properties, exhibits commendable drought tolerance and holds significant value as an edible and medicinal plant. Recognizing the scarcity of studies addressing basil's response to drought stress, we performed physiological experiments and omics analyses of sweet basil across four distinct levels of drought stress. During drought stress, basil showed increased activity of antioxidant enzymes and accumulated more osmoregulatory compounds. Our metabolic analysis meticulously identified a total of 830 metabolites, among which, 215 were differentially accumulated. The differentially accumulated metabolites under drought stress were predominantly esters and terpenes; however, none were identified as the primary volatile compounds of basil. Transcriptome analyses highlighted the pivotal roles of phenylpropanoid and flavonoid biosynthesis and lipid metabolism in fortifying the resistance of sweet basil against drought stress. α-linolenic acid, lignin, flavonoid, and flavonol contents significantly increased under stress; the essential genes involved in the production of these compounds were confirmed through quantitative real-time PCR (qRT-PCR), and their variations aligned with the outcomes from sequencing. This holistic approach not only enriches our understanding of the molecular intricacies underpinning basil's drought resistance but also furnishes valuable insights for the molecular breeding of basil varieties endowed with enhanced drought tolerance.

Metabolome and transcriptome analysis reveal the pigments biosynthesis pathways in different color fruit peels of Clausena lansium L. Skeels

Introduction

The color of Clausena lansium L. Skeels cv. Jixin fruit peel is brown (BP), while the mutant cv. Zijin had purple fruit peels (PP). The coloration of the peels was attributed to significant differences in chlorophyll, carotenoid, and anthocyanin content between BP and PP.

Methods

This study investigates the biosynthetic metabolic activities in the brown and purple peels of Clausena lansium L. Skeels using metabolomics and transcriptomics. It aims to identify metabolic pathways and differentially expressed genes related to flavonoids and anthocyanins biosynthesis.

Results

The PP (purple peel) has higher levels of a-carotene and b-carotene but lower levels of chlorophyll a, chlorophyll b, and lutein compared to BP. Zeaxanthin was absent from both peels, suggesting that the b-carotene hydroxylase enzyme is not active. Both peels contain delphinidin-based (Dp) and cyanidin-based (Cy) anthocyanins, but not pelargonidin-based (Pg). The total anthocyanin content and the Dp/Cy ratio are higher in PP than in BP. The delphinidin, cyanidin, and mallow derivatives in the PP were significantly higher than in the BP. The increase of total anthocyanin content and Dp/Cy ratio may be the main reason for the peel color changing from brown to purple. The significant increase of F3H expression in purple peels suggested a higher efficiency of catalyzing the conversion of naringenin into dihydroflavonols in the PP, leading to the higher content of total anthocyanin. Despite the significant increase of FLS expression in PP, the contents of kaempferol, quercetin, and myricetin significantly decreased, suggesting that the increase of FLS expression did not lead to an increase in flavonol biosynthesis.

Discussion

The competition between F3'H and F3'5'H may determine the ratio of Dp/Cy, the higher levels of F3'H, F3'5'H, and UFGT expression, lead to the increase accumulation of total anthocyanin and Dp/Cy in PP. The deficiency of Pg in both peels resulted from the substrate specificity of the DFR enzyme. The research also describes the transition in color from BP to PP and details of the biosynthetic pathways for carotenoids and anthocyanins, elucidating the molecular processes underlying anthocyanin production.

Characterization of the aroma and flavor profiles of guava fruit (Psidium guajava) during developing by HS-SPME-GC/MS and RNA sequencing

The flavor of guava, an important tropical fruit, is influenced by secondary metabolites. However, the mechanisms and processes underlying flavor formation in guava remain unclear. In this study, dynamic changes in volatile organic compounds (VOCs), sugars, and organic acids in guava peel and flesh across different developmental stages were investigated using headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC). Here, we identified 90 VOCs, three sugars and eight organic acids. The dynamics of VOCs differ between the flesh and peel. The early developmental stages are more critical in influencing the variation of VOCs in the flesh, while VOC changes in peel occur more progressively across the developmental stages. By integrating transcriptomic and metabolomic analyses, we identified several key genes involved in VOC, sugar, and acid metabolism. This is the first study to describe the expression patterns of these genes throughout guava development, providing new insights into guava flavor development.

Metabolomics revealed the characteristics of the unique flavor substances of Alxa Allium mongolicum

Allium mongolicum is a wild vegetable with high nutritional value and is famous for its taste and aroma. This study used headspace solid-phase microextraction-mass spectrometry coupled with gas chromatography-mass spectrometry techniques to study the metabolic profile of A. mongolicum in different ecological environments. A total of 624 volatile organic compounds (VOCs) were identified. Ester compounds, heterocyclic compounds and terpenoids are the key metabolites that determine flavor differences. KEGG analysis showed that monoterpenoid biosynthesis, zein biosynthesis, α-linolenic acid metabolism and secondary metabolite biosynthesis were the most important metabolic pathways. Compared with Minqin A. mongolicum and Tengger A. mongolicum, Alxa A. mongolicum flavor substance notes sensory flavor has more green, fruity, sweet, floral, spicy, metallic, rose, almond, apple, grassy, tropical, citrus, fresh, herbal and other flavor combinations. Overall, this study reveals the main reason for the unique flavor of Alxa A. mongolicum through metabolomic evidence.

Formulation of Hydrogel Beads to Improve the Bioaccessibility of Bioactive Compounds from Goldenberry and Purple Passion Fruit and Evaluation of Their Antiproliferative Effects on Human Colorectal Carcinoma Cells

Goldenberry and purple passion fruit contain bioactive compounds (BCs) that can prevent gastrointestinal cancers; hydrogel beads can protect and control their release in the gastrointestinal tract. This study aimed to develop an encapsulating material for fruit hydrogel beads (FHBs) to increase their bioaccessibility and to assess antiproliferative effects. A blend of goldenberry-purple passion fruit was encapsulated using ionic gelation and electrospraying. Through a mixture experimental design with sodium alginate (SA), hydroxypropylmethylcellulose (HPMC) and arabic gum (AG) as components, the following response variables were optimized: polyphenol bioaccessibility and encapsulation efficiency. Polyphenols and antioxidant activity were quantified before and after digestion. Antiproliferative effect was evaluated on Caco-2 colon cancer cells. Variations in formulation proportions had a significant effect (p < 0.05) on most responses. An SA-AG mixture in a 0.75:0.25 ratio maximized polyphenol bioaccessibility to 213.17 ± 19.57% and encapsulation efficiency to 89.46 ± 6.64%. Polyphenols and antioxidant activity were lower in FHBs than in the fruit blend (F). Both F and FHBs inhibited tumor cell proliferation by 17% and 25%, respectively. In conclusion, encapsulating BCs in hydrogel beads with SA-AG can enhance the effectiveness of polyphenols in food applications by improving their bioaccessibility and showing a more pronounced effect in inhibiting tumor cell proliferation.

Headspace Solid-Phase Microextraction and Gas Chromatography-Mass Spectrometry Combined with Sensory Evaluation for the Analysis of Volatile Aromatic Compounds in Apricot (Prunus armeniaca L.) Germplasm Resources Cultivated in Xinjiang, China

The volatile compounds in the fruits of 24 apricot cultivars were quantitatively and qualitatively determined via headspace solid-phase microextraction and gas chromatography-mass spectrometry (HS-SPME-GC-MS). A total of 429 volatile compounds were detected in these fruits, and the greatest number of detected terpenoids was 77. Significant differences were found among the cultivars in terms of the total volatile compound content of the fruits, with variation from 112.76 ('ZSHYX') to 317.36 µg/g ('JNL'). Using relative odor activity value (rOAV) analysis, 42 key aroma compounds were identified. The rOAVs of (2S,4R)-4-methyl-2-(2-methylprop-1-enyl)oxane, (E)-non-2-enal, (3-methyl-3-sulfanylbutyl) formate, and thiophen-2-ylmethanethiol were above 1000, and most had green, fruity, and woody odors; these results indicated that these substances were important contributors to the overall aroma of the apricot fruits. Our study provides a comprehensive analysis of the volatile compounds from 24 representative apricot cultivars and can aid in the further scientific understanding of the metabolites and aroma in apricots. These findings provide a reference for controlling fruit quality and for future apricot cultivar breeding.

Analysis of Volatile Compounds' Changes in Rice Grain at Different Ripening Stages via HS-SPME-GC-MS

Aroma is a crucial determinant of rice taste quality, with volatile organic compounds (VOCs) playing a key role in defining this characteristic. However, limited research has explored the dynamic changes in these aromatic substances during the ripening stages of rice grains. In this study, we analyzed VOCs in rice grains across four ripening stages post-flowering using headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS). A total of 417 VOCs were identified, among which 65 were determined to be key aroma-active compounds based on relative odor activity value (rOAV) analysis. Most of these aroma-active compounds exhibited an accumulation pattern as the grains matured. Notably, 5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone and 2-Methyloxolan-3-one had the largest rOAV values. Additionally, (Z)-6-nonenal, (Z,Z)-3,6-nonadienal, 2-thiophenemethanethiol, 5-methyl-2-furanmethanethiol, 2,2,6-trimethyl-cyclohexanone, and 3-octen-2-one were identified as potential key markers for distinguishing rice-grain maturity stages. Moreover, 2-acetyl-1-pyrroline (2-AP), heptanal, and 1-nonanol were identified as marker metabolites differentiating aromatic from non-aromatic brown rice. These findings contribute to a deeper understanding of the dynamic variation and retention of aroma compounds during rice-grain ripening, and they offer valuable insights into the improvement of fragrant rice varieties.

Study on Evaluation of Fruit Aroma of Plum Variety Resources Based on Headspace Solid-Phase Microextraction Combined with Gas Chromatography-Mass Spectrometry

To explore the characteristics of and variations in aroma components across different plum varieties and maturity stages, this study employed headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS). This method was used to systematically analyze the aroma components of 12 early-maturing, 15 medium-maturing, and 11 late-maturing plum varieties. The variations in volatile components among these three germplasm types were then compared using multivariate statistical methods. The examination revealed that 138 aromatic components were meticulously identified and quantified, such as 26 aldehydes, 63 esters, 13 ketones, 30 alcohols, and six other compounds. Thirteen main aroma compounds including acetic acid hexyl ester, (Z)-3-hexen-1-ol acetate, hexanal, 1-hexanol, 3-hexenal, butanoic acid butyl ester, (E)-2-hexen-1-ol, hexanoic acid butyl ester, propanoic acid butyl ester, (E)-2-hexenal, L-.alpha.-terpineol, (Z)-2-hexen-1-ol acetate, and 1-butanol were considered dominant. The orthogonal partial least squares discriminant analysis (OPLS-DA) combined with variable importance projection (VIP) results showed that 24 differential aroma compounds were screened out from 38 varieties of plum fruits based on their differences in aroma components, which can be used to distinguish plum fruits at different ripening times. Twenty-four aroma-contributing compounds were identified based on their odor activity values (OAVs). Among these, 14 key aroma components with OAVs ≥ 10 were highlighted. In summary, the aroma compounds of early- and late-maturing plum germplasm exhibited rich diversity, with significant differences in aroma components between plums of varying maturity and germplasm. These differences can serve as indicators for identifying different plum germplasm.

Combining with E-nose, GC-MS, GC-IMS and chemometrics to explore volatile characteristics during the different stages of Zanthoxylum bungeanum maxim fruits

To explore the volatile characteristics of Z. bungeanum fruits during different developmental stages, the dynamical changes of volatile organic compounds (VOCs) were detected by E-nose, GC-MS and GC-IMS, respectively. The results showed that terpenes, alcohols, esters and aldehydes played the important roles in the aroma formation of Z. bungeanum. Meanwhile, these VOCs also exhibited the high abundance levels among five growth stages of Z. bungeanum. According to the analysis of odor activity value (OAV) and relative odor activity value (ROAV), 37 VOCs can be recognized as the important aroma compounds. Thereinto, β-myrcene and linalool were the most key aroma compounds. Multi-factor analysis exhibited that the combination of GC-MS and GC-IMS was a better strategy to clarify the volatile characteristics comprehensively. Using the above combined VOC datasets, six positively correlated modules and 32 hub VOCs were finally identified by weighted correlation network analysis among five growth stages of Z. bungeanum.

Integration of full-length Iso-Seq, Illumina RNA-Seq, and flavor testing reveals potential differences in ripened fruits between two Passiflora edulis cultivars

Background

Passion fruit (Passiflora edulis) is loved for its delicious flavor and nutritious juice. Although studies have delved into the cultivation and enhancement of passion fruit varieties, the underlying factors contributing to the fruit's appealing aroma remain unclear.

Methods

This study analyzed the full-length transcriptomes of two passion fruit cultivars with different flavor profiles: "Tainong 1" (TN1), known for its superior fruit flavor, and "Guihan 1" (GH1), noted for its strong environmental resilience but lackluster taste. Utilizing PacBio Iso-Seq and Illumina RNA-Seq technologies, we discovered terpene synthase (TPS) genes implicated in fruit ripening that may help explain the flavor disparities.

Results

We generated 15,913 isoforms, with N50 lengths of 1,500 and 1,648 bp, and mean lengths of 1,319 and 1,463 bp for TN1 and GH1, respectively. Transcript and isoform lengths ranged from a maximum of 7,779 bp to a minimum of 200 and 209 bp. We identified 14,822 putative coding DNA sequences (CDSs) averaging 1,063 bp, classified 1,007 transcription factors (TFs) into 84 families. Additionally, differential expression analysis of ripening fruit from both cultivars revealed 314 upregulated and 43 downregulated unigenes in TN1 compared to GH1. The top 10 significantly enriched Gene Ontology (GO) terms for the differentially expressed genes (DEGs) indicated that TN1's upregulated genes were primarily involved in nutrient transport, whereas GH1's up-regulated genes were associated with resistance mechanisms. Meanwhile, 17 PeTPS genes were identified in P. edulis and 13 of them were TPS-b members. A comparative analysis when compared PeTPS with AtTPS highlighted an expansion of the PeTPS-b subfamily in P. edulis, suggesting a role in its fruit flavor profile.

Conclusion

Our findings explain that the formation of fruit flavor is attributed to the upregulation of essential genes in synthetic pathway, in particular the expansion of TPS-b subfamily involved in terpenoid synthesis. This finding will also provide a foundational genetic basis for understanding the nuanced flavor differences in this species.

Analysis of Aroma Characteristics of 'Binzi' and 'Xiangguo' Apple-Ancient Cultivars in China

'Binzi' (BZ) (Malus domestica subsp. chinensis var. binzi Li Y.N.) and 'Xiangguo' (XG) (Malus domestica subsp. chinensis var. xiangguo Li Y.N.) are the ancient cultivars in China. The BZ fruits have a low-fragrant flavor on harvest day but a high-fragrant flavor after storage at room temperature, while the XG fruits have a stronger flavor when mature. 'Starking' (SK) and 'Golden Delicious' (GD) fruits have a rich flavor and are recognized by all countries in the world. However, information on the differences between ancient Chinese cultivars and Western apple cultivars in aroma compounds remains unknown. The apple fruits were collected for continuous two years. Aroma compounds in the skin and pulp of the fruits were detected at room temperature (20 ± 1 °C) during storage. The dynamics of VOCs in BZ and SK fruits were more similarly reflected in esters, while those of XG and GD fruits were reflected in aldehydes and alcohols. Ethyl 2-methylbutyrate, with an extremely low odor threshold, was the main source of typical apple flavor in SK, BZ, and XG fruits, while hexyl acetate was the source of the banana flavor in GD fruits. 6-methyl-5-hepten-2-one and β-damascenone were the important ketones produced in the later stage of storage, derived from the carotenoid metabolism pathway and providing a citrus and rose flavor to the four apple cultivars. SK had the highest number of characteristic aroma components, which were mainly derived from the amino acid metabolism pathway, providing fruits with a sweet and fruity flavor. Although the characteristic aroma components of GD were derived from the fatty acid metabolic pathway, the number of volatile esters was lower. Ethyl butyrate, derived from the saturated fatty acid metabolism, had the highest content in BZ, providing a pineapple flavor; the flavor of XG was mainly derived from ethyl 2-methylbutyrate, 6-methyl-5-hepten-2-one, and β-damascenone. Therefore, we suggest BZ and XG apples as the aroma-breeding material with which to enrich new cultivars' aroma components, derived from the fatty acid metabolism and carotenoid metabolism pathways, respectively.

Infestation of Rice Striped Stem Borer (Chilo suppressalis) Larvae Induces Emission of Volatile Organic Compounds in Rice and Repels Female Adult Oviposition

Plants regulate the biosynthesis and emission of metabolic compounds to manage herbivorous stresses. In this study, as a destructive pest, the pre-infestation of rice striped stem borer (SSB, Chilo suppressalis) larvae on rice (Oryza sativa) reduced the subsequent SSB female adult oviposition preference. Widely targeted volatilomics and transcriptome sequencing were used to identify released volatile metabolic profiles and differentially expressed genes in SSB-infested and uninfested rice plants. SSB infestation significantly altered the accumulation of 71 volatile organic compounds (VOCs), including 13 terpenoids. A total of 7897 significantly differentially expressed genes were identified, and genes involved in the terpenoid and phenylpropanoid metabolic pathways were highly enriched. Correlation analysis revealed that DEGs in terpenoid metabolism-related pathways were likely involved in the regulation of VOC biosynthesis in SSB-infested rice plants. Furthermore, two terpenoids, (-)-carvone and cedrol, were selected to analyse the behaviour of SSB and predators. Y-tube olfactometer tests demonstrated that both (-)-carvone and cedrol could repel SSB adults at higher concentrations; (-)-carvone could simultaneously attract the natural enemies of SSB, Cotesia chilonis and Trichogramma japonicum, and cedrol could only attract T. japonicum at lower concentrations. These findings provide a better understanding of the response of rice plants to SSB and contribute to the development of new strategies to control herbivorous pests.

Metabolomic analysis reveals the changing trend and differential markers of volatile and nonvolatile components of Artemisiae argyi with different aging years

INTRODUCTION

Artemisia argyi Folium (AAF) is a traditional medicinal herb and edible plant. Analyzing the differential metabolites that affect the efficacy of AAF with different aging years is necessary.

OBJECTIVE

The aim of the study was to investigate the changing trend and differential markers of volatile and nonvolatile metabolites of AAF from different aging years, which are necessary for application in clinical medicine.

METHODOLOGY

Metabolites were analyzed using a widely targeted metabolomic approach based on ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and gas chromatography tandem mass spectrometry (GC-MS).

RESULTS

A total of 153 volatile metabolites and 159 nonvolatile metabolites were identified. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) could clearly distinguish AAF aged for 1 year (AF-1), 3 years (AF-3), and 5 years (AF-5). Seven flavonoids and nine terpenoids were identified as biomarkers for tracking the aging years.

CONCLUSIONS

The metabolomic method provided an effective strategy for tracking and identifying biomarkers of AAF from different aging years. This study laid the foundation for analysis of the biological activity of Artemisia argyi with different aging years.

Multi-omic applications for understanding and enhancing tropical fruit flavour

Consumer trends towards nutrient-rich foods are contributing to global increasing demand for tropical fruit. However, commercial cultivars in the breeding pipeline that are tailored to meet market demand are at risk of possessing reduced fruit flavour qualities. This stems from recurrent prioritised selection for superior agronomic traits and not fruit flavour, which may in turn reduce consumer satisfaction. There is realisation that fruit quality traits, inclusive of flavour, must be equally selected for; but currently, there are limited tools and resources available to select for fruit flavour traits, particularly in tropical fruit species. Although sugars, acids, and volatile organic compounds are known to define fruit flavour, the specific combinations of these, that result in defined consumer preferences, remain unknown for many tropical fruit species. To define and include fruit flavour preferences in selective breeding, it is vital to determine the metabolites that underpin them. Then, objective quantitative analysis may be implemented instead of solely relying on human sensory panels. This may lead to the development of selective genetic markers through integrated omics approaches that target biosynthetic pathways of flavour active compounds. In this review, we explore progress in the development of tools to be able to strategically define and select for consumer-preferred flavour profiles in the breeding of new cultivars of tropical fruit species.

Evaluation of Dynamic Changes of Volatile Organic Components for Fishmeal during Storage by HS-SPME-GC-MS with PLS-DA

Headspace solid-phase microextraction, combined with gas chromatography-mass spectrometry and partial least squares discriminant analysis, was adopted to study the rule of change in volatile organic compounds (VOCs) for domestic and imported fishmeal during storage with different freshness grades. The results showed that 318 kinds of VOCs were detected in domestic fishmeal, while 194 VOCs were detected in imported fishmeal. The total relative content of VOCs increased with storage time, among which acids and nitrogen-containing compounds increased significantly, esters and ketones increased slightly, and phenolic and ether compounds were detected only in domestic fishmeal. Regarding the volatile base nitrogen, acid value, pH value, and mold counts as freshness indexes, the freshness indexes were significantly correlated with nine kinds of VOCs (p < 0.05) through the correlation analysis. Among them, volatile base nitrogen had a significant correlation with VOCs containing nitrogen, acid value with VOCs containing carboxyl group and hydrocarbons, pH value with acids which could be used to adjust pH value, and mold counts with part of acids adjusting pH value and VOCs containing nitrogen. Due to the fact that the value of all freshness indexes increased with freshness degradation during storage, based on volatile base nitrogen and acid value, the fishmeal was divided into three freshness grades, superior freshness, corrupting, and completely corrupted. By using partial least squares discriminant analysis, this study revealed the differences in flavor of the domestic and imported fishmeal during storage with different freshness grades, and it identified four common characteristic VOCs, namely ethoxyquinoline, 6,7,8,9-tetrahydro-3H-benzo[e]indole-1,2-dione, hexadecanoic acid, and heptadecane, produced by the fishmeal samples during storage, as well as the characteristic VOCs of fishmeal at each freshness grade.

Integrative multiomics profiling of passion fruit reveals the genetic basis for fruit color and aroma

Passion fruit (Passiflora edulis) possesses a complex aroma and is widely grown in tropical and subtropical areas. Here, we conducted the de novo assembly, annotation, and comparison of PPF (P. edulis Sims) and YPF (P. edulis f. flavicarpa) reference genomes using PacBio, Illumina, and Hi-C technologies. Notably, we discovered evidence of recent whole-genome duplication events in P. edulis genomes. Comparative analysis revealed 7.6∼8.1 million single nucleotide polymorphisms, 1 million insertions/deletions, and over 142 Mb presence/absence variations among different P. edulis genomes. During the ripening of yellow passion fruit, metabolites related to flavor, aroma, and color were substantially accumulated or changed. Through joint analysis of genomic variations, differentially expressed genes, and accumulated metabolites, we explored candidate genes associated with flavor, aroma, and color distinctions. Flavonoid biosynthesis pathways, anthocyanin biosynthesis pathways, and related metabolites are pivotal factors affecting the coloration of passion fruit, and terpenoid metabolites accumulated more in PPF. Finally, by heterologous expression in yeast (Saccharomyces cerevisiae), we functionally characterized 12 terpene synthases. Our findings revealed that certain TPS homologs in both YPF and PPF varieties produce identical terpene products, while others yield distinct compounds or even lose their functionality. These discoveries revealed the genetic and metabolic basis of unique characteristics in aroma and flavor between the 2 passion fruit varieties. This study provides resources for better understanding the genome architecture and accelerating genetic improvement of passion fruits.

Volatile metabolomics reveals the characteristics of the unique flavor substances in oats

Oats is a cereal well known for its high nutritional value and unique flavor. This study investigated the metabolomics data from oats, wheat, and barley using broadly targeted GC-MS metabonomic techniques. A total of 437 volatile organic compounds (VOCs) were identified, of which 414 were shared metabolites, with three metabolites unique to oats. Three hundred and seven differentially accumulated metabolites (DAMs) were screened from all the comparison groups, of which 27 metabolites were shared by oats and barley, and 121 shared by oats and wheat. Terpenoids and esters were the key metabolites determining the differences in flavor. A KEGG analysis indicated that the alpha-linolenic acid and phenylalanine pathways were the most significant metabolic pathways. The 42 DAMs found may be the main substances leading to the flavor differences between the different varieties. Overall, this study reveals the main reasons for the unique flavor of oats through metabolomic evidence.

A comparative analysis of morphology, microstructure, and volatile metabolomics of leaves at varied developmental stages in Ainaxiang (Blumea balsamifera (Linn.) DC.)

Introduction

Ainaxiang (Blumea balsamifera (Linn.) DC.) is cultivated for the extraction of (-)-borneol and other pharmaceutical raw materials due to its abundant volatile oil. However, there is limited knowledge regarding the structural basis and composition of volatile oil accumulation in fresh B. balsamifera leaves.

Methods

To address this problem, we compare the fresh leaves' morphology, microstructure, and volatile metabonomic at different development stages, orderly defined from the recently unfolded young stage (S1) to the senescent stage (S4).

Results and discussion

Distinct differences were observed in the macro-appearance and microstructure at each stage, particularly in the B. balsamifera glandular trichomes (BbGTs) distribution. This specialized structure may be responsible for the accumulation of volatile matter. 213 metabolites were identified through metabolomic analysis, which exhibited spatiotemporal accumulation patterns among different stages. Notably, (-)-borneol was enriched at S1, while 10 key odor metabolites associated with the characteristic balsamic, borneol, fresh, and camphor aromas of B. balsamifera were enriched in S1 and S2. Ultra-microstructural examination revealed the involvement of chloroplasts, mitochondria, endoplasmic reticulum, and vacuoles in the synthesizing, transporting, and storing essential oils. These findings confirm that BbGTs serve as the secretory structures in B. balsamifera, with the population and morphology of BbGTs potentially serving as biomarkers for (-)-borneol accumulation. Overall, young B. balsamifera leaves with dense BbGTs represent a rich (-)-borneol source, while mesophyll cells contribute to volatile oil accumulation. These findings reveal the essential oil accumulation characteristics in B. balsamifera, providing a foundation for further understanding.

Integrative analysis of non-targeted metabolome and transcriptome reveals the mechanism of volatile formation in pepper fruit

Introduction: Aroma is a key inherent quality attributes of pepper fruit, yet the underlying mechanisms of aroma compound biosynthesis remain unclear. Methods: In this study, the volatile profile of the QH (cultivated Capsicum chinense) and WH (cultivated Capsicum annuum) pepper varieties were putatively identified during fruit development using gas chromatography-mass spectrometry (GC-MS). Results and discussion: The results identified 203 volatiles in pepper, and most of the esters, terpenes, aldehydes and alcohols were significantly down-regulated with fruit ripening. The comparison of volatile components between varieties revealed that aldehydes and alcohols were highly expressed in the WH fruit, while esters and terpenes with fruity or floral aroma were generally highly accumulated in the QH fruit, providing QH with a fruity odor. Transcriptome analysis demonstrated the close relationship between the synthesis of volatiles and the fatty acid and terpene metabolic pathways, and the high expression of the ADH, AAT and TPS genes was key in determining the accumulation of volatiles in pepper fruit. Furthermore, integrative metabolome and transcriptome analysis revealed that 208 differentially expressed genes were highly correlated with 114 volatiles, and the transcription factors of bHLH, MYB, ARF and IAA were identified as fundamental for the regulation of volatile synthesis in pepper fruit. Our results extend the understanding of the synthesis and accumulation of volatiles in pepper fruit.

Insights into the Isolation, Identification, and Biological Characterization Analysis of and Novel Control Strategies for Diaporthe passiflorae in Postharvest Passion Fruit

Postharvest diseases seriously restrict developments in the passion fruit industry. In this study, we aimed to identify the postharvest pathogen affecting passion fruit, investigate its pathogenicity, and explore relevant control methods. The pathogen was isolated from rotting passion fruit and identified using morphological characteristics, ITS sequences, and phylogenetic tree analyses. Additionally, preliminary studies were conducted to assess the biological characteristics of the pathogen and evaluate the efficacy of various treatments for disease control. The fungus on the passion fruit called B4 was identified as Diaporthe passiflorae. Optimal conditions for mycelial growth were observed at 25-30 °C and pH 5-6, with starch as the carbon source and peptone as the nitrogen source. Infection by D. passiflorae accelerated fruit decay, reduced the h° value of the peel, and increased the peel cell membrane permeability when compared to the control. Notably, treatments with appropriate concentrations of ɛ-poly-l-lysine, salicylic acid, and melatonin showed inhibitory effects on the pathogen's growth in vitro and may thus be potential postharvest treatments for controlling brown rot caused by D. passiflorae in passion fruit. The results provide a scientific basis for the development of strategies to control postharvest decay and extend the storage period of passion fruit.

Characterization of Key Compounds of Organic Acids and Aroma Volatiles in Fruits of Different Actinidia argute Resources Based on High-Performance Liquid Chromatography (HPLC) and Headspace Gas Chromatography-Ion Mobility Spectrometry (HS-GC-IMS)

Actinidia arguta, known for its distinctive flavor and high nutritional value, has seen an increase in cultivation and variety identification. However, the characterization of its volatile aroma compounds remains limited. This study aimed to understand the flavor quality and key volatile aroma compounds of different A. arguta fruits. We examined 35 A. arguta resource fruits for soluble sugars, titratable acids, and sugar-acid ratios. Their organic acids and volatile aroma compounds were analyzed using high-performance liquid chromatography (HPLC) and headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS). The study found that among the 35 samples tested, S12 had a higher sugar-acid ratio due to its higher sugar content despite having a high titratable acid content, making its fruit flavor superior to other sources. The A. arguta resource fruits can be classified into two types: those dominated by citric acid and those dominated by quinic acid. The analysis identified a total of 76 volatile aroma substances in 35 A. arguta resource fruits. These included 18 esters, 14 alcohols, 16 ketones, 12 aldehydes, seven terpenes, three pyrazines, two furans, two acids, and two other compounds. Aldehydes had the highest relative content of total volatile compounds. Using the orthogonal partial least squares discriminant method (OPLS-DA) analysis, with the 76 volatile aroma substances as dependent variables and different soft date kiwifruit resources as independent variables, 33 volatile aroma substances with variable importance in projection (VIP) greater than 1 were identified as the main aroma substances of A. arguta resource fruits. The volatile aroma compounds with VIP values greater than 1 were analyzed for odor activity value (OAV). The OAV values of isoamyl acetate, 3-methyl-1-butanol, 1-hexanol, and butanal were significantly higher than those of the other compounds. This suggests that these four volatile compounds contribute more to the overall aroma of A. arguta. This study is significant for understanding the differences between the fruit aromas of different A. arguta resources and for scientifically recognizing the characteristic compounds of the fruit aromas of different A. arguta resources.

Post-harvest ripening affects drying behavior, antioxidant capacity and flavor release of peach via alteration of cell wall polysaccharides content and nanostructures, water distribution and status

Effect of post-harvest ripening on cell wall polysaccharides nanostructures, water status, physiochemical properties of peaches and drying behavior under hot air-infrared drying was evaluated. Results showed that the content of water soluble pectins (WSP) increased by 94 %, while the contents of chelate-soluble pectins (CSP), Na₂CO₃-soluble pectins (NSP) and hemicelluloses (HE) decreased during post-harvest ripening by 60 %, 43 %, and 61 %, respectively. The drying time increased from 3.5 to 5.5 h when the post-harvest time increased from 0 to 6 days. Atomic force microscope analysis showed that depolymerization of hemicelluloses and pectin occurred during post-harvest ripening. Time Domain -NMR observations indicated that reorganization of cell wall polysaccharides nanostructure changed water spatial distribution and cell internal structure, facilitated moisture migration, and affected antioxidant capacity of peaches during drying. This leads to the redistribution of flavor substances (heptanal, n-nonanal dimer and n-nonanal monomer). The current work elucidates the effect of post-harvest ripening on the physiochemical properties and drying behavior of peaches.

Electronic Nose and Head Space GC-IMS Provide Insights into the Dynamic Changes and Regularity of Volatile Compounds in Zangju (Citrus reticulata cv. Manau Gan) Peel at Different Maturation Stages

Zangju (Citrus reticulata cv. Manau Gan) is the main citrus cultivar in Derong County, China, with unique aroma and flavour characteristics, but the use of Zangju peel (CRZP) is limited due to a lack of research on its peel. In this study, electronic nose, headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS), and partial least squares-discriminant analysis (PLS-DA) methods were used to rapidly and comprehensively evaluate the volatile compounds of dried CRZP and to analyse the role of dynamic changes at different maturation stages. The results showed that seventy-eight volatile compounds, mainly aldehydes (25.27%) and monoterpenes (55.88%), were found in the samples at four maturity stages. The contents of alcohols and aldehydes that produce unripe fruit aromas are relatively high in the immature stage (October to November), while the contents of monoterpenoids, ketones and esters in ripe fruit aromas are relatively high in the full ripening stage (January to February). The PLS-DA model results showed that the samples collected at different maturity stages could be effectively discriminated. The VIP method identified 12 key volatile compounds that could be used as flavour markers for CRZP samples collected at different maturity stages. Specifically, the relative volatile organic compounds (VOCs) content of CRZP harvested in October is the highest. This study provides a basis for a comprehensive understanding of the flavour characteristics of CRZP in the ripening process, the application of CRZP as a byproduct in industrial production (food, cosmetics, flavour and fragrance), and a reference for similar research on other C. reticulata varieties.

Analysis of Important Volatile Organic Compounds and Genes Produced by Aroma of Pepper Fruit by HS-SPME-GC/MS and RNA Sequencing

Pepper is an important condiment, and its aroma affects its commercial value. In this study, transcriptome sequencing and combined headspace solid-phase microextraction and gas chromatography-mass spectrometry (HS-SPME-GC-MS) were used to analyze the differentially expressed genes and volatile organic compounds in spicy and non-spicy pepper fruits. Compared with non-spicy fruits, there were 27 up-regulated volatile organic compounds (VOCs) and 3353 up-regulated genes (Up-DEGs) in spicy fruits. The results of KEGG enrichment analysis of the Up-DEGs combined with differential VOCs analysis showed that fatty acid biosynthesis and terpenoid biosynthesis may be the main metabolic pathways for aroma differences between non-spicy and spicy pepper fruits. The expression levels of the fatty acid biosynthesis-related genes FAD, LOX1, LOX5, HPL, and ADH and the key terpene synthesis gene TPS in spicy pepper fruits were significantly higher than those in non-spicy pepper fruits. The differential expression of these genes may be the reason for the different aroma. The results can provide reference for the development and utilization of high-aroma pepper germplasm resources and the breeding of new varieties.

Analysis of Volatile Aroma Components and Regulatory Genes in Different Kinds and Development Stages of Pepper Fruits Based on Non-Targeted Metabolome Combined with Transcriptome

Aroma is a crucial attribute affecting the quality of pepper and its processed products, which has significant commercial value. However, little is known about the composition of volatile aroma compounds (VACs) in pepper fruits and their potential molecular regulatory mechanisms. In this study, HS-SPME-GC-MS combined with transcriptome sequencing is used to analyze the composition and formation mechanism of VACs in different kinds and development stages of pepper fruits. The results showed that 149 VACs, such as esters, alcohols, aldehydes, and terpenoids, were identified from 4 varieties and 3 development stages, and there were significant quantitative differences among different samples. Volatile esters were the most important aroma components in pepper fruits. PCA analysis showed that pepper fruits of different developmental stages had significantly different marker aroma compounds, which may be an important provider of pepper's characteristic aroma. Transcriptome analysis showed that many differential genes (DEGs) were enriched in the metabolic pathways related to the synthesis of VACs, such as fatty acids, amino acids, MVA, and MEP in pepper fruits. In addition, we identified a large number of differential transcription factors (TFs) that may regulate the synthesis of VACs. Combined analysis of differential aroma metabolites and DEGs identified two co-expression network modules highly correlated with the relative content of VACs in pepper fruit. This study confirmed the basic information on the changes of VACs in the fruits of several Chinese spicy peppers at different stages of development, screened out the characteristic aroma components of different varieties, and revealed the molecular mechanism of aroma formation, providing a valuable reference for the quality breeding of pepper.

Characterization of volatile organic compounds with anti-atherosclerosis effects in Allium macrostemon Bge. and Allium chinense G. Don by head space solid phase microextraction coupled with gas chromatography tandem mass spectrometry

Introduction

Allium macrostemon Bge. (AMB) and Allium chinense G. Don (ACGD) are both edible Allium vegetables and named officinal Xiebai (or Allii Macrostemonis Bulbus) in East Asia. Their medicinal qualities involve in lipid lowering and anti-atherosclerosis effects. And steroidal saponins, nitrogenous compounds and sulfur compounds are like the beneficial components responsible for medicinal functions. Sulfur compounds are the recognized main components both in the volatile oils of AMB and ACGD. Besides, few researches were reported about their holistic chemical profiles of volatile organic compounds (VOCs) and pharmacodynamic effects.

Methods

In this study, we first investigated the lipid-lowering and anti-atherosclerotic effects of volatile oils derived from AMB and ACGD in ApoE ^-/- mice with high fat and high cholesterol diets.

Results

The results showed the volatile oils of AMB and ACGD both could markedly reduce serum levels of TG, TC, and LDL-C (p < 0.05), and had no alterations of HDL-C, ALT, and AST levels (p > 0.05). Pathological results displayed they both could obviously improve the morphology of cardiomyocytes and the degree of myocardial fibrosis in model mice. Meanwhile, oil red O staining results also proved they could apparently decrease the lesion areas of plaques in the aortic intima (p < 0.05). Furthermore, head space solid phase microextraction coupled with gas chromatography tandem mass spectrometry combined with metabolomics analysis was performed to characterize the VOCs profiles of AMB and ACGD, and screen their differential VOCs. A total of 121 and 115 VOCs were identified or tentatively characterized in the volatile oils of AMB and ACGD, respectively. Relative-quantification results also confirmed sulfur compounds, aldehydes, and heterocyclic compounds accounted for about 85.6% in AMB bulbs, while approximately 86.6% in ACGD bulbs were attributed to sulfur compounds, ketones, and heterocyclic compounds. Multivariate statistical analysis showed 62 differentially expressed VOCs were observed between AMB and ACGD, of which 17 sulfur compounds were found to be closely associated with the garlic flavor and efficacy.

Discussion

Taken together, this study was the first analysis of holistic chemical profiles and anti-atherosclerosis effects of AMB and ACGD volatile oils, and would benefit the understanding of effective components in AMB and ACGD.

Evaluation of Dynamic Changes and Regularity of Volatile Flavor Compounds for Different Green Plum (Prunus mume Sieb. et Zucc) Varieties during the Ripening Process by HS-GC-IMS with PLS-DA

Headspace gas chromatography-ion mobility spectrometry and partial-least-squares discriminant analysis (PLS-DA) were adopted to analyze the rule of change in flavor substances for different varieties of green plums at different levels of maturity (S1-immature, S2-commercially mature, and S3-fully mature). The results showed that 68 kinds of volatile flavor substances were identified in all green plum samples. The types and contents of such volatile substances experienced a V-shaped trend with an increasing degree of green plum maturity. During the S1 and S2 stages, aldehydes, ketones, and a small amount of alcohols were the main volatile flavor substances in the green plum samples. During the S3 stage, esters and alcohols were the most important volatile flavor components in the green plum pulp samples, followed by terpenes and ketones. YS had the most types and highest contents of volatile flavor substances in three stages, followed by GC and DZ. By using the PLS-DA method, this study revealed the differences in flavor of the different varieties of green plums at different maturity stages, and it identified eight common characteristic volatile flavor substances, such as ethyl acetate, 3-methylbutan-1-ol, and 2-propanone, produced by the different green plum samples during the ripening process, as well as the characteristic flavor substances of green plums at each maturity stage (S1-S3).

Dynamic Changes of Volatile Compounds during the Xinyang Maojian Green Tea Manufacturing at an Industrial Scale

Xinyang Maojian (XYMJ) is one of the premium green teas and originates from Xinyang, which is the northernmost green tea production area in China. The special geographic location, environmental conditions, and manufacturing process contribute to the unique flavor and rich nutrition of XYMJ green tea. Aroma is an important quality indicator in XYMJ green tea. In order to illustrate the aroma of XYMJ green tea, the key odorants in XYMJ green tea and their dynamic changes during the manufacturing processes were analyzed by headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS). A total of 73 volatile compounds of six different chemical classes were identified in the processed XYMJ green tea samples, and the manufacturing processes resulted in the losses of total volatile compounds. Among the identified volatile compounds, twenty-four aroma-active compounds, such as trans-nerolidol, geranylacetone, nonanal, (+)-δ-cadinene, linalool, (Z)-jasmone, cis-3-hexenyl butyrate, cis-3-hexenyl hexanoate, methyl jasmonate, and β-ocimene, were identified as the key odorants of XYMJ green tea based on odor activity value (OAV). The key odorants are mainly volatile terpenes (VTs) and fatty acid-derived volatiles (FADVs). Except for (+)-δ-cadinene, copaene, cis-β-farnesene, (Z,E)-α-farnesene and phytol acetate, the key odorants significantly decreased after fixing. The principal coordinate analysis (PCoA) and the hierarchical cluster analysis (HCA) analyses suggested that fixing was the most important manufacturing process for the aroma formation of XYMJ green tea. These findings of this study provide meaningful information for the manufacturing and quality control of XYMJ green tea.

SPME-GC-MS combined with chemometrics to assess the impact of fermentation time on the components, flavor, and function of Laoxianghuang

Laoxianghuang, fermented from Citrus medica L. var. Sarcodactylis Swingle of the Rutaceae family, is a medicinal food. The volatiles of Laoxianghuang fermented in different years were obtained by solid-phase microextraction combined with gas chromatography–mass spectrometry (SPME-GC–MS). Meanwhile, the evolution of its component-flavor function during the fermentation process was explored in depth by combining chemometrics and performance analyses. To extract the volatile compounds from Laoxianghuang, the fiber coating, extraction time, and desorption temperature were optimized in terms of the number and area of peaks. A polydimethylsiloxane/divinylbenzene (PDMS/DVB) with a thickness of 65 μm fiber, extraction time of 30 min, and desorption temperature of 200 °C were shown to be the optimal conditions. There were 42, 44, 52, 53, 53, and 52 volatiles identified in the 3rd, 5th, 8th, 10th, 15th, and 20th years of fermentation of Laoxianghuang, respectively. The relative contents were 97.87%, 98.50%, 98.77%, 98.85%, 99.08%, and 98.36%, respectively. Terpenes (mainly limonene, γ-terpinene and cymene) displayed the highest relative content and were positively correlated with the year of fermentation, followed by alcohols (mainly α-terpineol, β-terpinenol, and γ-terpineol), ketones (mainly cyclohexanone, D(+)-carvone and β-ionone), aldehydes (2-furaldehyde, 5-methylfurfural, and 1-nonanal), phenols (thymol, chlorothymol, and eugenol), esters (bornyl formate, citronellyl acetate, and neryl acetate), and ethers (n-octyl ether and anethole). Principal component analysis (PCA) and hierarchical cluster analysis (HCA) showed a closer relationship between the composition of Laoxianghuang with similar fermentation years of the same gradient (3rd-5th, 8th-10th, and 15th-20th). Partial least squares discriminant analysis (PLS-DA) VIP scores and PCA-biplot showed that α-terpineol, γ-terpinene, cymene, and limonene were the differential candidate biomarkers. Flavor analysis revealed that Laoxianghuang exhibited wood odor from the 3rd to the 10th year of fermentation, while herb odor appeared in the 15th and the 20th year. This study analyzed the changing pattern of the flavor and function of Laoxianghuang through the evolution of the composition, which provided a theoretical basis for further research on subsequent fermentation.

HS-SPME-GC/MS Analysis for Revealing Carob's Ripening

Carob's recognized nutritional and medicinal value next to its unique agriculture importance is associated with an array of social, economic, and cultural activities. The carob fruit is popular for its intense aroma due to the emitted volatile organic compounds (VOCs). The composition of VOCs released from carob fruits changes during ripening, rendering it a non-invasive tool for the determination of the ripening period and freshness of the fruit. Therefore, headspace solid-phase microextraction gas chromatography/mass spectrometry (HS-SPME-GC/MS) was applied to reveal the respective gaseous signal molecules related to fruit maturity. The sampling was implemented during weeks 26-36 from five different locations in Cyprus. Additionally, the gaseous emissions of total VOCs (TVOCs) and carbon dioxide (CO₂) were recorded next to the moisture content of the fruit. The major chemical classes in the ripening are acids, followed by esters, and ketones. More specifically, the most abundant VOCs during ripening are propanoic acid, 2-methyl-(isobutyric acid), 2-heptanone, propanoic acid, 2-methyl-, 2-methylbutyl ester, acetic acid, methyl isobutyrate, propanoic acid, 2-methyl-, 3-methylbutyl ester, 2-pentanone, butanoic acid and propanoic acid, 2-methyl-ethyl ester. Finally, CO₂ emissions and moisture content showed a rapid decline until the 31st week and then stabilized for all examined areas. The methodology revealed variations in VOCs' profile during the ripening process.

Combined Metabolome and Transcriptome Analyses Reveal the Flavonoids Changes and Biosynthesis Mechanisms in Different Organs of Hibiseu manihot L

Hibiseu manihot L. (Jinhuakui, JHK), also known as a garden landscape plant, is widely cultivated as a landscape plant having pharmacological effects due to its high flavonoids content. Although flavonoids were the main active pharmaceutical ingredients in JHK, little information was obtained about the content, composition, and accumulation pattern of flavonoids in different tissues. Most studies only identified a few kinds of flavonoids in JHK limited by separation and identification problems. Therefore, combined metabolome and transcriptome analysis was performed to explore the accumulation patterns and biosynthesis mechanisms of flavonoids in JHK. In this study, we identified 160 flavonoids in 15 samples of JHK (flower, leaf, root, stem, and seeds) by using LC-MS/MS. Consistent with the total flavonoid content determination, these flavonoids were significantly accumulated in flowers, followed by leaves, stems, roots, and seeds. Among them, certain flavonoids, with high content, were also identified for the first time in JHK, such as tricetin, catechin, hesperidin, ncyanidin-3-O-sambubioside, astragalin, procyanidin B2/B3/C1, apigenin-5-O-glucoside, etc. Different tissues underwent significantly reprogramming of their transcriptomes and metabolites changes in JHK, particularly in the flavonoid, flavone, and flavonol biosynthesis pathways. We conducted a correlation analysis between RNA-seq and LC-MS/MS to identify the key genes and related flavonoids compounds, rebuild the gene-metabolites regulatory subnetworks, and then identified 15 key genes highly related to flavonoids accumulation in JHK. These key genes might play a fine regulatory role in flavonoids biosynthesis by affecting the gene expression level in different organs of JHK. Our results could be helpful for the improvement of the market/industrial utilization value of different parts of JHK, to pave the way for the regulatory mechanism research of flavonoids biosynthesis, and provide insight for studying the production quality improvement of JHK.

Comparison of the Effects of High Pressure Processing, Pasteurization and High Temperature Short Time on the Physicochemical Attributes, Nutritional Quality, Aroma Profile and Sensory Characteristics of Passion Fruit Purée

The study investigated the effects of high-pressure processing (HPP) (600 MPa/5 min), pasteurization (PT) (85 °C/30 s), and high-temperature short time (HTST) (110 °C/8.6 s) on physicochemical parameters (sugar, acid, pH, TSS), sensory-related attributes (color, aroma compounds), antioxidants (phenolics, vitamin C, carotenoids, antioxidant capacity), and sensory attributes of yellow passion fruit purée (PFP). Compared to the PT and HTST, HPP obtained the PFP with better color, sugar, and organic acid profiles. Although PT was equally effective preservation of antioxidants and antioxidant capacity of PFP compared to HPP, high temperature inevitable resulted in the greater degradation of the aroma profile. The amounts of esters, alcohols, and hydrocarbon in PFP were significantly increased by 11.3%, 21.3%, and 30.0% after HPP, respectively. All samples were evaluated by a panel comprising 30 panelists according to standard QDA (quantitative descriptive analysis) procedure, and the result showed that HPP-treated PFP was rated the highest overall intensity score with 7.06 for its sensory attributes, followed by control (6.96), HTST (6.17), and PT (6.16). Thus, HPP is a suitable alternative technology for achieving the good sensory quality of PFP without compromising their nutritional properties.

Branched-Chain Volatiles in Fruit: A Molecular Perspective

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.

Configuration of the Volatile Aromatic Profile of Carob Powder Milled From Pods of Genetic Variants Harvested at Progressive Stages of Ripening From High and Low Altitudes

Carob powder is increasingly valued as a substitute for cocoa and as a flavor-enhancing component of processed foods. However, little is known about the impact of preharvest factors such as fruit maturity, genotype and altitude on its volatile organic compounds (VOCs) composition. The current study examined the VOCs composition of powder milled from pods of two genotypes cultivated at 15 and 510 m altitude and harvested at six progressive stages of maturity, ranging from fully developed immature green (RS1) to late ripe (RS6). Fifty-six VOCs categorized into acids, esters, aldehydes, ketones, alcohols, furans, and alkanes were identified through HS-SPME GC-MS analysis. Maturity was the most influential factor, followed by altitude and least by genotype. Aldehydes and alcohols correlated positively (r = 0.789; p < 0.001), both accumulated in immature carobs and decreased with progressive ripening, resulting in the attenuation of green grassy aroma. Conversely, acids increased with ripening and dominated the carob volatilome at full maturity, correlating negatively with aldehydes and alcohols (r = −0.835 and r = −0.950, respectively; p < 0.001). The most abundant VOC throughout ripening (17.3-57.7%) was isobutyric acid, responsible for the characteristic cheesy-acidic-buttery aroma of carob powder. The pleasurable aroma detected at the immature stages (RS2 and RS3) was traced to isobutyrate and methyl isobutyrate esters, rendering unripe green carob powder a potential admixture component for improving the aroma of novel food products. Lower altitude favored the accumulation of acids linked to less pleasant aroma, whereas isobutyric acid was more abundant at higher altitude. This constitutes a significant indication that higher altitude enhances the characteristic carob-like aroma and sensory quality of carob powder.

Evidences of Colletotrichum fructicola Causing Anthracnose on Passiflora edulis Sims in China

Passion fruit (Passiflora edulis) is a tropical and subtropical plant that is widely cultivated in China due to its high nutritional value, unique flavor and medicinal properties. In August 2020, typical anthracnose symptoms with light brown and water-soaked lesions on Passiflora edulis Sims were observed, which result in severe economic losses. The incidence of this disease was approximately 30%. The pathogens from the infected fruit were isolated and purified by the method of tissue isolation. Morphological observations showed that the colony of isolate BXG-2 was gray to celadon and grew in concentric circles. The orange conidia appeared in the center after 14 days of incubation. The pathogenicity was verified by Koch’s postulates. The internal transcribed spacer (ITS), chitin synthase (CHS-1), actin (ACT), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were amplified by relevant PCR programs. The multi-gene (ITS, GAPDH, ACT, CHS-1) phylogeny analysis confirmed that isolate BXG-2 belongs to Colletotrichum fructicola. The inhibitory effect of six synthetic fungicides on the mycelial growth of the pathogen was investigated, among which difenoconazole 10% WG showed the best inhibitory effect against C. fructicola with an EC₅₀ value of 0.5579 mg·L⁻¹. This is the first report of anthracnose on Passiflora edulis Sims caused by Colletotrichum fructicola in China.

An Optimized SPME-GC-MS Method for Volatile Metabolite Profiling of Different Alfalfa (Medicago sativa L.) Tissues

Solid-phase microextraction (SPME) was coupled to gas chromatography mass spectrometry (GC-MS) and a method optimized to quantitatively and qualitatively measure a large array of volatile metabolites in alfalfa glandular trichomes isolated from stems, trichome-free stems, and leaves as part of a non-targeted metabolomics approach. Major SPME extraction parameters optimized included SPME fiber composition, extraction temperature, and extraction time. The optimized SPME method provided the most chemically diverse coverage of alfalfa volatile and semi-volatile metabolites using a DVB/CAR/PDMS fiber, extraction temperature of 60 °C, and an extraction time of 20 min. Alfalfa SPME-GC-MS profiles were processed using automated peak deconvolution and identification (AMDIS) and quantitative data extraction software (MET-IDEA). A total of 87 trichome, 59 stem, and 99 leaf volatile metabolites were detected after background subtraction which removed contaminants present in ambient air and associated with the fibers and NaOH/EDTA buffer solution containing CaCl₂. Thirty-seven volatile metabolites were detected in all samples, while 15 volatile metabolites were uniquely detected only in glandular trichomes, 9 only in stems, and 33 specifically in leaves as tissue specific volatile metabolites. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) of glandular trichomes, stems, and leaves showed that the volatile metabolic profiles obtained from the optimized SPME-GC-MS method clearly differentiated the three tissues (glandular trichomes, stems, and leaves), and the biochemical basis for this differentiation is discussed. Although optimized using plant tissues, the method can be applied to other types of samples including fruits and other foods.