Volatolomics to Decrypt the Monophagous Nature of a Rice Pest, Scirpophaga Incertulas (Walker).

Scirpophaga incertulas Walker (Lepidoptera: Crambidae, yellow stem borer, YSB) is a monophagous insect pest that causes significant yield loss in rice (Oryza staiva L.). Semiochemical based pest management is being sought as an alternate to chemical pesticides to reduce pesticide footprints. We hypothesized differential release of volatiles from host rice and two companion non-host weeds, Echinochloa colona and Echinochloa crus-galli could be responsible for oviposition and biology of YSB and these chemicals could be used for YSB management. Number of eggs laid, and number of larvae hatched were significantly higher in rice plant as compared to weeds. YSB could only form dead hearts in rice plants. YSB significantly preferred host-plant volatiles compared to the non-host plants both in choice and no-choice tests in an Y-tube olfactometer. 2-Hexenal, hexanal, 2,4-hexadienal, benzaldehyde, nonanal, methyl salicylate and decanal were found in the leaf volatolomes of both the host and non-host plants in HS-SPME-GC-MS (Headspace-Solid phase micro extraction-Gas chromatography-Mass spectrometer). Pentene-3-one, 2-pentyl furan, 2,4-heptadienal, 2-octenal, 2-octenol and menthol were present only in the non-host plants. Fourteen rice unique compounds were also detected. The built-in PCA (Principal Component Analysis) and PLS-DA (Partial least squares-discriminant analysis) analysis in the MS-DIAL tool showed that the volatiles emitted from TN1 formed a cluster distinct from Echinochloa spp. and 2-octenal was identified as a unique compound. Olfactometer bioassays using synthetic compounds showed that rice unique compounds, like xylene, hexanal served as attractants whereas non-host unique compounds, like 2-pentylfuran, 2-octenal acted as repellent. The results indicate that the rice unique compounds xylene, hexanal along with other volatile compounds could be responsible for higher preference of YSB towards rice plants. Similarly, the non-host unique compounds 2-pentylfuran, 2-octenal could possibly be responsible for lower preference and defence against YSB. These compounds could be utilised for devising traps for YSB monitoring and management.

Fermentation Characteristics of Fermented Milk with Streptococcus thermophilus CICC 6063 and Lactobacillus helveticus CICC 6064 and Volatile Compound Dynamic Profiles during Fermentation and Storage.

The lactic acid bacteria Streptococcus thermophilus and Lactobacillus helveticus are commonly used as starter cultures in dairy product production. This study aimed to investigate the characteristics of fermented milk using different ratios of these strains and analyze the changes in volatile compounds during fermentation and storage. A 10:1 ratio of Streptococcus thermophilus CICC 6063 to Lactobacillus helveticus CICC 6064 showed optimal fermentation time (4.2 h), viable cell count (9.64 log10 colony-forming units/mL), and sensory evaluation score (79.1 points). In total, 56 volatile compounds were identified and quantified by solid-phase microextraction and gas chromatography-mass spectrometry (SPME-GC-MS), including aldehydes, ketones, acids, alcohols, esters, and others. Among these, according to VIP analysis, 2,3-butanedione, acetoin, 2,3-pentanedione, hexanoic acid, acetic acid, acetaldehyde, and butanoic acid were identified as discriminatory volatile metabolites for distinguishing between different time points. Throughout the fermentation and storage process, the levels of 2,3-pentanedione and acetoin exhibited synergistic dynamics. These findings enhance our understanding of the chemical and molecular characteristics of milk fermented with Streptococcus thermophilus and Lactobacillus helveticus, providing a basis for improving the flavor and odor of dairy products during fermentation and storage.

Effects of Non-Saccharomyces Yeasts and Their Pairwise Combinations in Co-Fermentation with Saccharomyces cerevisiae on the Quality of Chunjian Citrus Wine.

Non-Saccharomyces (NSc) yeasts have great potential in improving wine qualities. In this study, two NSc and two Saccharomyces cerevisiae (Sc) samples were tested on their performance of mono-inoculated and composite culture in the fermentation of Chunjian citrus wine. The cell count, Brix degree, total sugar, total acidity, alcohol level, pH value, color intensity (CI), and tonality were determined to evaluate the contribution of NSc to the quality of citrus wine in the mixed fermentation. Volatile compounds were analyzed by HS-SPME-GC-MS, and sensory evaluation was carried out. During the 9-day fermentation, the mixed-culture wine exhibited a higher cell concentration than the pure culture. After the fermentation, mixed-culture wine specifically decreased the concentrations of unfavorable volatile compounds, such as isobutanol and octanoic acid, and increased favorable volatile compounds, including ethyl octanoate, ethyl decanoate, and phenylethyl acetate. The quality category of the citrus wine was improved compared with the Sc mono-inoculated wines, mainly in regard to aroma, retention, and sweetness. The study shows that the mixed fermentation of NSc and Sc has positive impacts on reducing alcohol level and total acidity and increasing CI. The present work demonstrates that the mixed fermentation of NSc and Sc has enormous beneficial impacts on improving the quality of citrus wine.

LVI and DI-SPME Combined with GC/MS and GC/MS for Volatile Chemical Profile Investigation and Cytotoxic Power Evaluation of Essential Oil and Hydrolate from Cannabis sativa L. cv. Carmagnola.

Cannabis sativa L. is a plant that has been cultivated since ancient times thanks to its various uses. Even its extraction products, such as essential oil and hydrolate, having a varied chemical composition and rich in bioactive components, find wide use in different sectors, gathering ever-increasing interest over time. In this work, the essential oil of Cannabis sativa L. cv. Carmagnola was characterized by using Gas Chromatography/Mass Spectrometry (GC/MS) and, for the first time, the chemical profile of the hydrolate was also described through different analytical techniques such as Large-Volume Injection Gas Chromatography/Mass Spectrometry (LVI-GC/MS) and Direct Immersion-Solid Phase Microextraction-Gas Chromatography/Mass spectrometry (DI-SPME-GC/MS), in order to provide a more complete compositional profile. The results of the analyses conducted on the hydrolate highlighted a high content of α-terpineol; on the other side, in the essential oil, a prevalence of monoterpenes, with α-pinene and limonene as the characterizing components, was detected. Both matrices were also investigated to evaluate their cytotoxic activity by using a panel of cancer cell lines derived from different histotypes such as melanoma (A375, LOX IMVI), non-small cell lung cancer (H1299, A549), colon (HT29) and pancreatic (L3.6) cancer cell lines. The obtained data demonstrated that essential oil was more effective than hydrolate in terms of reduction in cell viability.

Comparative Analysis of Hydrosol Volatile Components of Citrus × Aurantium 'Daidai' and Citrus × Aurantium L. Dried Buds with Different Extraction Processes Using Headspace-Solid-Phase Microextraction with Gas Chromatography-Mass Spectrometry.

This work used headspace solid-phase microextraction with gas chromatography-mass spectrometry (HS-SPME-GC-MS) to analyze the volatile components of hydrosols of Citrus × aurantium 'Daidai' and Citrus × aurantium L. dried buds (CAVAs and CADBs) by immersion and ultrasound-microwave synergistic-assisted steam distillation. The results show that a total of 106 volatiles were detected in hydrosols, mainly alcohols, alkenes, and esters, and the high content components of hydrosols were linalool, α-terpineol, and trans-geraniol. In terms of variety, the total and unique components of CAVA hydrosols were much higher than those of CADB hydrosols; the relative contents of 13 components of CAVA hydrosols were greater than those of CADB hydrosols, with geranyl acetate up to 15-fold; all hydrosols had a citrus, floral, and woody aroma. From the pretreatment, more volatile components were retained in the immersion; the relative contents of linalool and α-terpineol were increased by the ultrasound-microwave procedure; and the ultrasound-microwave procedure was favorable for the stimulation of the aroma of CAVA hydrosols, but it diminished the aroma of the CADB hydrosols. This study provides theoretical support for in-depth exploration based on the medicine food homology properties of CAVA and for improving the utilization rate of waste resources.

Evaluation of Aromatic Characteristics and Potential Applications of Hemerocallis L. Based on the Analytic Hierarchy Process.

Hemerocallis L. possesses abundant germplasm resources and holds significant value in terms of ornamental, edible, and medicinal aspects. However, the quality characteristics vary significantly depending on different varieties. Selection of a high-quality variety with a characteristic aroma can increase the economic value of Hemerocallis flowers. The analytic hierarchy process (AHP) is an effective decision-making method for comparing and evaluating multiple characteristic dimensions. By applying AHP, the aromatic character of 60 varieties of Hemerocallis flowers were analyzed and evaluated in the present study. Headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) was employed to identify volatile components in Hemerocallis flowers. Thirteen volatile components were found to contribute to the aroma of Hemerocallis flowers, which helps in assessing their potential applications in essential oil, aromatherapy, and medical treatment. These components include 2-phenylethanol, geraniol, linalool, nonanal, decanal, (E)-ß-ocimene, α-farnesene, indole, nerolidol, 3-furanmethanol, 3-carene, benzaldehyde and benzenemethanol. The varieties with better aromatic potential can be selected from a large amount of data using an AHP model. This study provides a comprehensive understanding of the characteristics of the aroma components in Hemerocallis flowers, offers guidance for breeding, and enhances the economic value of Hemerocallis flowers.

Efficient Capture of Cannabis Terpenes in Olive Oil during Microwave-Assisted Cannabinoid Decarboxylation.

The development of selective extraction protocols for Cannabis-inflorescence constituents is still a significant challenge. The characteristic Cannabis fragrance can be mainly ascribed to monoterpenes, sesquiterpenes and oxygenated terpenoids. This work investigates the entrapment of Cannabis terpenes in olive oil from inflorescences via stripping under mild vacuum during the rapid microwave-assisted decarboxylation of cannabinoids (MW, 120 °C, 30 min) and after subsequent extraction of cannabinoids (60 and 100 °C). The profiles of the volatiles collected in the oil samples before and after the extraction step were evaluated using static headspace solid-phase microextraction (HS-SPME), followed by gas chromatography coupled to mass spectrometry (GC-MS). Between the three fractions obtained, the first shows the highest volatile content (~37,400 mg/kg oil), with α-pinene, ß-pinene, ß-myrcene, limonene and trans-ß-caryophyllene as the main components. The MW-assisted extraction at 60 and 100 °C of inflorescences using the collected oil fractions allowed an increase of 70% and 86% of total terpene content, respectively. Considering the initial terpene amount of 91,324.7 ± 2774.4 mg/kg dry inflorescences, the percentage of recovery after decarboxylation was close to 58% (mainly monoterpenes), while it reached nearly 100% (including sesquiterpenes) after extraction. The selective and efficient extraction of volatile compounds, while avoiding direct contact between the matrix and extraction solvents, paves the way for specific applications in various aromatic plants. In this context, aromatized extracts can be employed to create innovative Cannabis-based products within the hemp processing industry, as well as in perfumery, cosmetics, dietary supplements, food, and the pharmaceutical industry.

Comparison of Flavonoid Content, Antioxidant Potential, Acetylcholinesterase Inhibition Activity and Volatile Components Based on HS-SPME-GC-MS of Different Parts from Matteuccia struthiopteris (L.) Todaro.

Matteuccia struthiopteris is one of the most globally consumed edible ferns and widely used in folk medicine. Reports mainly focus on young fronds and the rhizome which are common edible medicinal parts. However, there are few detailed reports on other parts. Therefore, the volatile components of different parts based on HS-SPME-GC-MS were identified, and total flavonoid contents, antioxidant activities and acetylcholinesterase inhibitory activities were compared in order to reveal the difference of volatile components and potential medicinal value of different parts. The results showed that total flavonoid contents, antioxidant activities and volatile components of different parts were obviously different. The crozier exhibited the strongest antioxidant activities, but only underground parts exhibited a dose-dependent inhibition potential against AChE. Common volatile compounds were furfural and 2-furancarboxaldehyde, 5-methyl-. In addition, it was found that some volatile components from adventitious root, trophophyll, sporophyll and petiole were important ingredients in food, cosmetics, industrial manufacturing and pharmaceutical applications.

Profiling of Volatile Compounds in 'Muscat Hamburg' Contaminated with Aspergillus carbonarius before OTA Biosynthesis Based on HS-SPME-GC-MS and DLLME-GC-MS.

Aspergillus carbonarius is known to produce the carcinogenic ochratoxin A (OTA) in grapes. The metabolism process before OTA biosynthesis influences the content and composition of the volatile compounds in grapes. In this study, a self-established method based on QuEChERS coupled with high-performance liquid chromatography-fluorescence detection (HPLC-FLD) was used to determine the OTA levels during a seven-day contamination period. The results showed that OTA was detected on the second day after contamination with A. carbonarius. Thus, the first day was considered as the critical sampling timepoint for analyzing the volatiles in grapes before OTA biosynthesis. Additionally, the volatile compounds in grapes were analyzed using headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and dispersive liquid-liquid microextraction gas chromatography-mass spectrometry (DLLME-GC-MS). The corresponding data were evaluated via multivariate data analysis using projection methods, including PCA and OPLS-DA. The results indicated significant differences in the nine volatile compounds in grapes contaminated with A. carbonarius before OTA biosynthesis. The results of the Pearson correlation analysis showed positive correlations between ethyl acetate, styrene, 1-hexanol and OTA; (E)-2-hexenal and nerolic acid were negatively correlated with OTA. Overall, these findings provide a theoretical basis for the early prediction of OTA formation in grape and grape products using GC-MS technology.

Comparative Analysis of Volatile Compounds in the Flower Buds of Three Panax Species Using Fast Gas Chromatography Electronic Nose, Headspace-Gas Chromatography-Ion Mobility Spectrometry, and Headspace Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry Coupled with Multivariate Statistical Analysis.

The flower buds of three Panax species (PGF: P. ginseng; PQF: P. quinquefolius; PNF: P. notoginseng) widely consumed as health tea are easily confused in market circulation. We aimed to develop a green, fast, and easy analysis strategy to distinguish PGF, PQF, and PNF. In this work, fast gas chromatography electronic nose (fast GC e-nose), headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS), and headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) were utilized to comprehensively analyze the volatile organic components (VOCs) of three flowers. Meanwhile, a principal component analysis (PCA) and heatmap were applied to distinguish the VOCs identified in PGF, PQF, and PNF. A random forest (RF) analysis was used to screen key factors affecting the discrimination. As a result, 39, 68, and 78 VOCs were identified in three flowers using fast GC e-nose, HS-GC-IMS, and HS-SPME-GC-MS. Nine VOCs were selected as potential chemical markers based on a model of RF for distinguishing these three species. Conclusively, a complete VOC analysis strategy was created to provide a methodological reference for the rapid, simple, and environmentally friendly detection and identification of food products (tea, oil, honey, etc.) and herbs with flavor characteristics and to provide a basis for further specification of their quality and base sources.

Volatile compounds produced in smoked bacon inoculated with potential spoilage bacteria.

BACKGROUND: Volatile organic compounds (VOCs) produced during meat storage are mainly derived from the decomposition of meat components and the metabolism of spoilage bacteria. VOCs produced in sterile bacon model substrate inoculated or un-inoculated with spoilage bacteria, Staphylococcus xylosus (P2), Leuconostoc mesenteroides (P6), Carnobacterium maltaromaticum (P9), Leuconostoc gelidum (P16) and Serratia liquefaciens (P20), previously isolated, were identified by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Furthermore, combinations of the strains (Pm) were also obtained. RESULTS: In total, 54 volatile compounds, including aldehydes, alcohols, phenols, ketones, alkanes, alkanes, organic acids, esters and so forth, were determined after 45 days of storage in bacon inoculated with potential spoilage bacteria using the HS-SPME/GC-MS method. VOC concentrations of alcohols and organic acids in groups inoculated with bacteria were remarkably higher (P < 0.05) compared to that in control samples. Specifically, some VOCs are closely related to the metabolic activity of the inoculated bacterial strains; for example, 2,3-butanediol was associated with P2, P16 and P20, and acetic acid was mainly related to P6 and P9. CONCLUSION: The results of partial least squares regression indicated that there was a high correlation between the electronic nose sensors and VOCs of smoked inoculated potential spoilage bacteria. These compounds are potentially important for predicting deterioration of smoked bacon. © 2023 Society of Chemical Industry.

Revealing the spoilage characteristics of refrigerated prepared beef steak by advanced bioinformatics tools.

BACKGROUND: Although microorganisms are the main cause of spoilage in prepared beef steaks, very few deep spoilage mechanisms have been reported so far. Aiming to unravel the mechanisms during 12 days of storage at 4 °C affecting the quality of prepared beef steak, the present study investigated the changes in microbial dynamic community using a combined high-throughput sequencing combined and bioinformatics. In addition, gas chromatography-mass spectrometry combined with multivariate statistical analysis was utilized to identify marker candidates for prepared steaks. Furthermore, cloud platform analysis was applied to determine prepared beef steak spoilage, including the relationship between microbiological and physicochemical indicators and volatile compounds. RESULTS: The results showed that the dominant groups of Pseudomonas, Brochothrix thermosphacta, Lactobacillus and Lactococcus caused the spoilage of prepared beef steak, which are strongly associated with significant changes in physicochemical properties and volatile organic compounds (furan-2-pentyl-, pentanal, 1-octanol, 1-nonanol and dimethyl sulfide). Metabolic pathways were proposed, among which lipid metabolism and amino acid metabolism were most abundant. CONCLUSION: The present study is helpful with respect to further understanding the relationship between spoilage microorganisms and the quality of prepared beef steak, and provides a reference for investigating the spoilage mechanism of dominant spoilage bacteria and how to extend the shelf life of meat products. © 2024 Society of Chemical Industry.

Evaluation of fifteen processing methods of hellgrammites based on the flavor characteristics.

To investigate suitable processing methods for improve the flavor while maintaining quality, hellgrammites were subjected to fifteen different processing methods. The samples were tested by sensory evaluation and were analyzed using HS-SPME-GC-MS. The sensory evaluation revealed that five methods for head and chest removal, three wine-fried methods, and three vinegar-roasting methods significantly reduced the levels of hexanal (3129.05 ± 45.77 µg/kg) and heptanal (436.72 ± 7.42 µg/kg), compounds responsible for fishy and earthy flavors, compared to raw samples. The latter two methods exhibited increased aroma flavor. PCA and OPLS-DA analyses suggested that acids, alcohols, and esters played a crucial role in flavor modification. Notably, vinegar-roasting methods demonstrated the highest acid content and had a substantial impact on volatile compounds. Additionally, boiling methods effectively reduced the levels of hazardous compounds, such as toluene and 1,3-Dimethyl-benzene. However, other methods did not exhibit similar efficacy in reducing hazardous compounds. The accumulation of hazardous compounds showed a decreasing trend in the whole insect, head removal, and head and chest removal groups. Moreover, the relative odor activity value consistently identified aldehyde compounds, including hexanal and heptanal, as the main contributors to aroma. Overall, boiling and head and chest removal procedures were suggested as precautionary measures during the initial processing of hellgrammites-based food products. The vinegar-roasting and wine-fried methods could be employed to impart desired flavors, aligning with consumers' preferences. These findings lay the foundation for standardizing processing techniques and ensuring the quality control of products derived from hellgrammites.

Comprehensive study of volatile compounds and transcriptome data providing genes for grape aroma.

BACKGROUND: Fruit aroma is an important quality with respect to consumer preference, but the most important aroma compounds and their genetic regulatory mechanisms remain elusive. RESULTS: In this study, we qualitatively analysed volatile compounds in the pulp and skin of five table grape cultivars with three aroma types (muscat, strawberry, and neutral) using solid-phase microextraction gas chromatography/mass spectrometry. We identified 215 aroma compounds, including 88 esters, 64 terpenes, and 29 alcohols, and found significant differences in the number of compounds between the pulp and skin, especially for terpenes. Skin transcriptome data for the five grape cultivars were generated and subjected to aroma compound-gene correlation analysis. The combined transcriptomic analysis and terpene profiling data revealed 20 candidate genes, which were assessed in terms of their involvement in aroma biosynthetic regulation, including 1 VvCYP (VIT_08s0007g07730), 2 VvCCR (VIT_13s0067g00620, VIT_13s0047g00940), 3 VvADH (VIT_00s0615g00010, VIT_00s0615g00030, VIT_ 00s0615g00020), and 1 VvSDR (VIT_08s0040g01200) in the phenylpropanoids synthesis pathway, and 1 VvDXS (VIT_05s0020g02130) and 6 VvTPS (VIT_13s0067g00370, Vitis_vinifera_newGene_3216, VIT_13s0067g00380, VIT_13s0084g00010, VIT_00s0271g00010, and VIT_13s0067g00050) in the methylerythritol phosphate pathway (involved in the production and accumulation of aromatic compounds). Additionally, 2 VvMYB (VIT_17s0000g07950, VIT_03s0063g02620) and 1 VvGATA (VIT_15s0024g00980) transcription factor played important regulatory roles in the accumulation of key biosynthetic precursors of these compounds in grapes. Our results indicated that downstream genes, specifically 1 VvBGLU (VIT_03s0063g02490) and 2 VvUGT (VIT_17s0000g07070, VIT_17s0000g07060) are involved in regulating the formation and volatilization of bound compounds in grapes. CONCLUSIONS: The results of this study shed light on the volatile compounds and "anchor points" of synthetic pathways in the pulp and skin of muscat and strawberry grapes, and provide new insight into the regulation of different aromas in grapes.

Characterization of a novel flavored yogurt enriched in γ-aminobutyric acid fermented by Levilactobacillus brevis CGMCC1.5954.

This study developed and characterized a γ-aminobutyric acid (GABA)-enriched yogurt fermented by Levilactobacillus brevis CGMCC1.5954. The GABA content in the yogurt was 147.36 mg/100 mL, which was 317.06% higher than that of the control group. Furthermore, there was a significant improvement in the aroma, hardness, adhesion, cohesiveness, and gelatinousness of yogurt. The chromatography and metabolomics analyses further confirmed the high GABA content in yogurt and its nutritional value, and the metabolic pathway for GABA production by L. brevis 54 was identified. A total of 58 volatile flavor compounds were identified using headspace solid-phase microextraction-gas chromatography-mass spectrometry, of which 2-nonanone and 2-heptanone may be responsible for the high odor score of GABA-enriched yogurt. This study developed a nutritious and unique GABA-enriched flavored yogurt, summarized the metabolic pathway of GABA, and provided a flavor fingerprint that could guide the production of specifically flavored yogurts.

A useful species identification and quality control using volatile patterns of ssajuari-ssuk and sajabal-ssuk (Artemisia princeps Pamp. cv. ssajuari and Artemisia princeps Pamp. cv. sajabal; Korean mugwort) according to air-drying term by fast gas chromatography with uncoated surface acoustic wave sensor.

INTRODUCTION: Ssajuari-ssuk and sajabal-ssuk have many clinical benefits. It is difficult to discriminate between these two species based on general characteristics aside from the shapes of the leaves. Thus, species identification and quality control between ssajuari-ssuk and sajabal-ssuk are of great concern in plant science and clinical therapy. OBJECTIVE: The aim of this study is to determine whether fast gas chromatography with uncoated surface acoustic wave sensor (GC-SAW) can be a useful technique for performing species identification and quality control using volatile patterns of ssajuari-ssuk and sajabal-ssuk air-dried for 4 months and 2 years and 4 months. METHODOLOGY: Fast GC-SAW sensor provides second unit analysis, simple, on-line measurements that do not require pretreatment of the sample and rapid sensory information. Headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) was employed to confirm the identification of the volatiles and compared to fast GC-SAW sensor. RESULTS: In air-dried sajabal-ssuk, the concentration of 1,8-cineole was higher than that in air-dried ssajuari-ssuk, while the level of α-thujone was considerably lower than that of air-dried ssajuari-ssuk. Each of ssajuari-ssuk and sajabal-ssuk air-dried for 4 months and 2 years and 4 months has its own characteristic volatile pattern owing to its individual chemotypes or chemical compositions. CONCLUSION: Consequently, the fast GC-SAW sensor can be a useful technique for species identification and quality control using volatile patterns of ssajuari-ssuk and sajabal-ssuk air-dried for 4 months and 2 years and 4 months. This method can be used for the standardisation of quality control using volatile patterns of herbal medicines.

Volatile-Based Diagnosis for Pathogenic Wood-Rot Fungus Fulvifomes siamensis by Electronic Nose (E-Nose) and Solid-Phase Microextraction/Gas Chromatography/Mass Spectrometry.

Wood rot fungus Fulvifomes siamensis infects multiple urban tree species commonly planted in Singapore. A commercial e-nose (Cyranose 320) was used to differentiate some plant and fungi volatiles. The e-nose distinctly clustered the volatiles at 0.25 ppm, and this sensitivity was further increased to 0.05 ppm with the use of nitrogen gas to purge the system and set up the baseline. Nitrogen gas baseline resulted in a higher magnitude of sensor responses and a higher number of responsive sensors. The specificity of the e-nose for F. siamensis was demonstrated by distinctive clustering of its pure culture, fruiting bodies collected from different tree species, and in diseased tissues infected by F. siamensis with a 15-min incubation time. This good specificity was supported by the unique volatile profiles revealed by SPME GC-MS analysis, which also identified the signature volatile for F. siamensis-1,2,4,5-tetrachloro-3,6-dimethoxybenzene. In field conditions, the e-nose successfully identified F. siamensis fruiting bodies on different tree species. The findings of concentration-based clustering and host-tree-specific volatile profiles for fruiting bodies provide further insights into the complexity of volatile-based diagnosis that should be taken into consideration for future studies.

Efficacy and Mechanisms of Action of Essential Oils' Vapours against Blue Mould on Apples Caused by Penicillium expansum.

Biofumigation with slow-release diffusers of essential oils (EOs) of basil, oregano, savoury, thyme, lemon, and fennel was assessed for the control of blue mould of apples, caused by Penicillium expansum. In vitro, the ability of the six EOs to inhibit the mycelial growth was evaluated at concentrations of 1.0, 0.5, and 0.1%. EOs of thyme, savoury, and oregano, at all three concentrations, and basil, at 1.0 and 0.5%, were effective in inhibiting the mycelial growth of P. expansum. In vivo, disease incidence and severity were evaluated on 'Opal' apples artificially inoculated with the pathogen and treated at concentrations of 1.0% and 0.5% of EOs. The highest efficacy in reducing blue mould was observed with EOs of lemon and oregano at 1.0% after 60 days of storage at 1 ± 1 °C (incidence of rot, 3 and 1%, respectively) and after a further 14 days of shelf-life at 15 ± 1 °C (15 and 17%). Firmness, titratable acidity, and total soluble solids were evaluated at harvest, after cold storage, and after shelf-life. Throughout the storage period, no evident phytotoxic effects were observed. The EOs used were characterised through GC-MS to analyse their compositions. Moreover, the volatile organic compounds (VOCs) present in the cabinets were characterised during storage using the SPME-GC-MS technique. The antifungal effects of EOs were confirmed both in vitro and in vivo and the possible mechanisms of action were hypothesised. High concentrations of antimicrobial and antioxidant compounds in the EOs explain the efficacy of biofumigation in postharvest disease control. These findings provide new insights for the development of sustainable strategies for the management of postharvest diseases and the reduction of fruit losses during storage.

Characterization of Volatile Organic Compounds in Five Celery (Apium graveolens L.) Cultivars with Different Petiole Colors by HS-SPME-GC-MS.

Celery (Apium graveolens L.) is an important vegetable crop cultivated worldwide for its medicinal properties and distinctive flavor. Volatile organic compound (VOC) analysis is a valuable tool for the identification and classification of species. Currently, less research has been conducted on aroma compounds in different celery varieties and colors. In this study, five different colored celery were quantitatively analyzed for VOCs using HS-SPME, GC-MS determination, and stoichiometry methods. The result revealed that γ-terpinene, d-limonene, 2-hexenal,-(E)-, and ß-myrcene contributed primarily to the celery aroma. The composition of compounds in celery exhibited a correlation not only with the color of the variety, with green celery displaying a higher concentration compared with other varieties, but also with the specific organ, whereby the content and distribution of volatile compounds were primarily influenced by the leaf rather than the petiole. Seven key genes influencing terpenoid synthesis were screened to detect expression levels. Most of the genes exhibited higher expression in leaves than petioles. In addition, some genes, particularly AgDXS and AgIDI, have higher expression levels in celery than other genes, thereby influencing the regulation of terpenoid synthesis through the MEP and MVA pathways, such as hydrocarbon monoterpenes. This study identified the characteristics of flavor compounds and key aroma components in different colored celery varieties and explored key genes involved in the regulation of terpenoid synthesis, laying a theoretical foundation for understanding flavor chemistry and improving its quality.

Natural Variation Confers 'Aiyuan 38' Citrus Mutant a New Color and Unique Flavor.

Citrus exhibits unique nutritional values. Most citrus cultivars are derived from mutations. However, the effect of these mutations on fruit quality is unclear. We have previously found a yellowish bud mutant in the citrus cultivar 'Aiyuan 38'. Therefore, this study aimed to determine the effect of the mutation on fruit quality. 'Aiyuan 38' (WT) and a bud mutant variant (MT) were used to analyze variations in fruit color variation and flavor substances using colorimetric instruments, high-performance liquid chromatography (HPLC), headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS), and odor activity values (OAVs). The mutation in MT conferred yellowish characteristics to its peel. Although the differences in total sugar and acid content of the pulp were not statistically significant between WT and MT, the MT glucose content was significantly lower and the malic acid level was significantly higher. HS-SPME-GC-MS analysis revealed that the MT pulp released more types and contents of volatile organic compounds (VOCs) than the WT, whereas the opposite trend was observed for the peel. Analysis of the OAV revealed that the MT pulp contains 6 unique VOCs, whereas the peel contains only 1. This study provides a useful reference for the study of flavor substances associated with citrus bud mutations.