Characterization of the major aroma-active compounds in peach (Prunus persica L. Batsch) by gas chromatography-olfactometry, flame photometric detection and molecular sensory science approaches

Characterization of volatile compounds in mozzarella cheeses made from bovine and buffalo milk by different aroma extraction and identification methods

High-moisture mozzarella cheese is particularly popular because of its freshness and milky flavor; however, the difference in aroma compound composition between high-moisture mozzarella cheese made from bovine (BOC) and buffalo milk (BUC) remains unclear. Herein, the volatile compounds of 2 kinds of mozzarella cheese were qualitatively and quantitatively analyzed by solid-phase microextraction comprehensive two-dimensional gas chromatography olfactometry time-of-flight mass spectrometry (SPME-GC×GC-O-TOF-MS), solid-phase microextraction-Arrow gas chromatography mass spectrometry (SPME Arrow-GC-MS), and gas chromatography ion-mobility spectrometry (GC-IMS) for the first time. A total of 139 volatile compounds were identified (69 aroma active compounds were sniffed), of which 106 were identified in BOC and 96 in BUC. About 70.5% of these compounds can be identified by GC×GC-O-TOF-MS, exceeding 2.6 times that of GC-IMS. Particularly, 2-methyltetrahydrofuran-3-one (nutty flavor, odor intensity of 3) and methoxy-phenyl-oxime (burnt flavor, 689.47 ± 48.32 μg/kg, odor intensity of 5) were identified as aroma active compounds in BOC for the first time. The sensory evaluation confirmed that 2-methyltetrahydrofuran-3-one is one of the factors responsible for the differences in nutty flavor observed between BOC and BUC. Compared with the 3 aroma extract techniques (SPME, SPME-Arrow and headspace), SPME-Arrow can increase the adsorption capacity of volatile compounds in samples, but required the high separation and high sensitivity detection equipment for more efficient identification of volatile compounds. The combination of the GC×GC-O-TOF-MS, GC-MS, and GC-IMS had obtained a comprehensive aroma profile of mozzarella cheese, which laid a theoretical foundation for the construction of aroma fingerprints of mozzarella cheeses from different milk sources, and provided a basis for the development and application of new dairy products.

Characterization of perceptual interactions among aroma compounds found in Rose damascena and Angelica dahurica root essential oil with threshold, S-curve, σ-τ plot and molecular docking

The study investigated the perceptual interaction between two types of Rose damascena essential oil and two types of Angelica dahurica root essential oil. Using gas chromatography-olfactometer (GC-O) and gas chromatography-mass spectrometer (GC-MS), 24 and 25 aromatic compounds in Rose damascena essential oil and Angelica dahurica root essential oil were identified and quantified, respectively. Based on flavor dilution (FD) values and odor activity values (OAVs), 10 important aroma compounds in Rose damascena essential oil and 6 in Angelica dahurica root essential oil were identified. The perceptual interactions between these aroma compounds were explored by using the threshold method, S-curve, and σ-τ plot. Additionally, molecular docking analysis revealed changes in binding energy and binding sites. Notably, when aroma compounds shared similar structures and fragrances, they exhibited additive or synergistic effects. Conversely, dissimilar compounds showed different interactions. The molecular docking results aligned with our experimental findings. Overall, our study demonstrates that the threshold method, S-curve, σ-τ plot, and molecular docking enhance our understanding of aroma compound perceptual interactions between Rose damascena essential oil and Angelica dahurica root essential oil. These insights provide a theoretical foundation and practical guidance for improving the aroma of Angelica dahurica root essential oil and studying perceptual interactions among essential oils.

Floral infusions: Elevating the bouquet of non-alcoholic chardonnay wine beverage

This study explores the impact of natural flower extracts from Prunus persica, Rosa chinensis, and Lilium bulbiferum to enhance the aroma of dealcoholized Chardonnay wine, addressing the sensory deficiencies commonly associated with dealcoholized wine beverages (DWBs). The investigation revealed a richer bouquet of aromatic compounds, particularly higher alcohols, esters, and terpenes, which significantly elevated the aromatic profile of treated wines without altering their physicochemical properties. Principal Component Analysis (PCA) showed distinct aroma profiles between control and flower extract-DWBs, with the latter exhibiting enhanced floral and fruity characteristics. Additionally, Partial Least Squares Regression (PLSR) showed a positive correlation between specific volatile classes especially terpenes and esters, sensory attributes of floral and fruity notes, highlighting the crucial role of these compounds in enhancing overall aroma. These findings not only present a promising opportunity to improve the appeal of DWBs, but also suggest a potential for broader applications in the beverage industry.

Study on the Mechanisms of Flavor Compound Changes During the Lactic Fermentation Process of Peach and Apricot Mixed Juice

This study employed headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and liquid chromatography-mass spectrometry (LC-MS) for non-targeted metabolomics analyses to examine the impact of mixed fermentation with various lactic acid bacteria (LAB) on the flavor compounds and metabolites of peach and apricot mixed juice (PAMJ), specifically focusing on the alterations of volatile compounds and non-volatile metabolites, as well as their metabolic pathways during the fermentation process. A total of 185 volatiles were identified using HS-SPME-GC-MS analysis, revealing significant differential metabolites, including eugenol, benzaldehyde, and γ-decalactone etc. The results indicated that lactic fermentation significantly enhanced the overall flavor of the juice toward the end of the fermentation process. In the interim, untargeted metabolomics utilizing LC-MS identified 1846 divergent metabolites, with 564 exhibiting up-regulation and 1282 demonstrating down-regulation. The metabolic pathway study performed by the Kyoto Encyclopedia of Genes and Genomes (KEGG) revealed significant changes in the metabolic levels of amino acids and saccharides after the lactic fermentation of PAMJ. Primarily associated with amino acid metabolism and starch and sucrose metabolism pathways. This work establishes a theoretical foundation for advancing fermented fruit juices with superior quality.

Effect of Ceramides Derivatives from the Peach on Skin Function Improvement in UV-Irradiated Hairless Mice

This study investigated the protective effects of a ceramides derivates from the peach (PF3) on photoaging by UV-irradiated hairless mice. Mice were randomly divided into seven groups: AIN93G without UVB exposure (normal control, NC), AIN93G with UVB exposure (control, C), AIN93G supplemented 100 mg/kg body weight (BW) of L-ascorbic acid with UVB exposure (AA), AIN93G supplemented 100 mg/kg BW of arbutin with UVB exposure (Arbutin), AIN93G supplemented 10 mg/kg BW of PF3 with UVB exposure (10PF3), AIN93G supplemented 20 mg/kg BW of PF3 with UVB exposure (20PF3), and AIN93G supplemented 40 mg/kg BW of PF3 with UVB exposure (40PF3). The study examined the impact of PF3 on skin hydration, wrinkle formation, and melanogenesis using enzyme-linked immunosorbent assay (ELISA), real-time polymerase chain reaction (real-time PCR), and Western blot analysis. The PF3 demonstrated significant protective effects against photoaging by reducing skin wrinkle formation, decreasing epidermal and dermal thickening, and improving skin hydration. It also enhanced the expression of moisture-related factors (hyaluronic acid synthase [HAS], long-chain ceramides [LCBs], dihydroceramide desaturase 1 [DEGS1], and type I collagen [COL1A]) and antioxidant enzyme activities while reducing pro-inflammatory cytokines and oxidative stress markers. The PF3 supplementation positively modulated skin wrinkle formation-related factors, increasing collagen-related gene expression and decreasing matrix metalloproteinases. Additionally, PF3 showed potential in regulating melanogenesis by reducing the nitric oxide and cAMP content, as well as the expression of melanogenesis-related proteins. These comprehensive findings suggest that PF3 supplementation may be an effective strategy for preventing and treating UVB-induced skin photoaging through multiple mechanisms, including improved skin structure, hydration, antioxidant defense, and reduced inflammation and pigmentation.

Comparative Investigation of Aroma-Active Volatiles in ("Ruixue", "Liangzhi", "Crystal Fuji," and "Guifei") Apples by Application of Gas Chromatography-Mass Spectrometry-Olfactometry (GC-MS-O) and Two-Dimensional Gas Chromatography-Quadrupole Mass Spectrometry (GC × GC-qMS) Coupled with Sensory Molecular Science

Aroma dramatically impacts the overall flavor profiles and consumer acceptance; therefore, it is necessary to conduct a comprehensive analysis of the aroma characteristics of apples. In this study, the aroma differences among four popular apple varieties ("Ruixue", "Liangzhi", "Crystal Fuji," and "Guifei") were compared using two extraction methods (headspace-solid phase microextraction, and solvent-assisted flavor evaporation) coupled with gas chromatography-mass spectrometry-olfactometry (GC-MS-O) and two-dimensional gas chromatography-quadrupole mass spectrometry (GC × GC-qMS). A total of 82 odorants were identified via GC-MS-O, and 143 volatiles were identified by GC× GC-qMS. Among them, 41 key aroma-active compounds (butanal, ethyl acetate, 3-methylbutanal, methyl butanoate, 2-methylpropyl acetate, ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, butyl acetate, hexanal, 2-methylbutyl acetate, 1-butanol, 2-methylpropyl butanoate, 3-methylbutyl acetate, (E)-2-hexenal, butyl butanoate, butyl 2-methylbutanoate, hexyl acetate, hexyl butanoate, hexyl, 2-methylbutanoate, 1-octen-3-ol, 3-methylthiopropanol, 1,3-octanediol, linalyl acetate, and so on) with high odor activity values (OAVs) and AI value (odor activity values ≥1 or aroma intensity ≥3) were identified. Partial least-squares-discriminant analysis showed that Ruixue exhibited a high "fruity" note, Guifei and Crystal Fuji had the greatest "wood," "floral," and "sweet" notes, while Liangzhi presented a significant "green" note. This study provided flavor chemistry support for the apple quality control and production.

Characterization of Free and Glycosidically Bound Volatile and Non-Volatile Components of Shiikuwasha (Citrus depressa Hayata) Fruit

Shiikuwasha, a citrus fruit native to Okinawa, Japan, has various cultivation lines with distinct free volatile and non-volatile components. However, the glycosylated volatiles, which are sources of hidden aromas, remain unknown. This study aimed to characterize the chemical profiles of free and glycosidically bound volatile as well as non-volatile components in the mature fruits of six Shiikuwasha cultivation lines: Ishikunibu, Izumi kugani-like, Kaachi, Kohama, Nakamoto seedless, and Ogimi kugani. Free volatiles were analyzed using solid-phase microextraction-gas chromatography-mass spectrometry. Glycosides were collected via solid-phase extraction and hydrolyzed with β-glucosidase, and the released volatiles were measured. Additionally, the non-volatile components were determined using non-targeted proton nuclear magnetic resonance analysis. Total free and bound volatiles ranged from 457 to 8401 µg/L and from 104 to 548 µg/L, respectively, and the predominant free volatiles found were limonene, γ-terpinene, and p-cymene. Twenty volatiles were released from glycosides, including predominant 1-hexanol and benzyl alcohol, with Kaachi and Ogimi kugani showing higher concentrations. Principal component analysis (PCA) revealed that taste-related compounds like sucrose, citrate, and malate influenced line differentiation. The PCA of the combined data of free and bound volatile and non-volatile components showed flavor component variances across all lines. These findings provide valuable insights into the chemical profiles of Shiikuwasha fruits for fresh consumption and food and beverage processing.

Dynamic Changes in Aroma Compounds during Processing of Flat Black Tea: Combined GC-MS with Proteomic Analysis

Flat black tea (FBT) has been innovatively developed to alleviate homogenisation competition, but the dynamic changes in aroma components during the process remain unclear. This study employed HS-SPME-GC-MS to analyse the aroma components of tea samples from various processing stages of FBT, and to make a comparative assessment with conventional strip-like Congou black tea (SBT). Additionally, a proteomic analysis was conducted on fresh leaves, withered leaves, and frozen-thawed leaves. Significant changes were observed in the aroma components and proteins during the processing. The results of the multivariate and odour activity value analysis demonstrated that the principal aroma components present during the processing of FBT were linalool, (E)-2-hexen-1-al, methyl salicylate, geraniol, hexanal, benzeneacetaldehyde, (Z)-3-hexenyl butyrate, dimethyl sulphide, 2-methylbutanal, 2-ethylfuran, nonanal, nonanol, 3-methylbutanal, (Z)-3-hexen-1-ol, 2-pentylfuran, linalool oxide I, and β-myrcene. Freezing-thawing and final roasting are the key processing steps for forming the aroma quality of FBT. The final roasting yielded a considerable quantity of pyrazines and pyrroles, resulting in a high-fried aroma, but caused a significant reduction in linalool, geraniol, β-myrcene, and esters, which led to a loss of floral and fruity aromas. The freezing-thawing treatment resulted in an accelerated loss of aroma substances, accompanied by a decrease in the expression level of lipoxygenase and 2-C-methyl-D-erythritol 2,4-cyclodiphosphate synthase. The formation of aroma substances in the linoleic acid metabolic pathway and terpenoid metabolic process was hindered, which had a negative impact on tea aroma. This study elucidates the causes of unsatisfactory aroma quality in tea products made from frozen tea leaves, providing theoretical support for the utilisation of frostbitten tea leaves, and helps us to understand the mechanism of aroma formation in black tea.

The shaking and standing processing improve the aroma quality of summer black tea

Black teas harvested during the summer season usually have the defect of low aroma intensity, resulting in unacceptability from consumers. The shaking and standing (SS) process is key to the production of oolong tea and is believed to significantly improve the aroma quality. However, the specific effects of the shaking process on the aroma quality of black tea have not been elucidated. SSBT has a higher aroma intensity than BT, especially floral and sweet odors. By Aroma Extract Dilution Analysis (AEDA), 27 volatiles with flavor dilution factor (FD) above 8 were selected, of which 20 had odor activity values (OAV) values above 1; among them, 9 floral and sweet volatiles with high OAV were linalool (485 for BT, 918 for SSBT), (E)-β-ionone (389, 699), geraniol (315, 493), β-myrcene (25, 62), (E)-2-hexenal (2, 7), phenylacetaldehyde (44, 75), (Z)-3-hexenyl hexanoate (19, 41), 1-hexanol (9, 26), and 2-phenylethanol (2,3). Aroma reconstitution of these 20 volatiles showed reliable results of floral, sweet, fruity, and roasted odors, further validating the aroma and intensity profiles of the key odorants. Overall, our results reveal that the metabolite mechanism of the SS process improves the aroma quality of black tea, providing a theoretical basis and guiding measures for the production of high-aroma black tea.

Effect of postharvest grape dehydration on chemical composition, antioxidant activity and sensory characeteristics of Marselan wines

To explore the effect of postharvest dehydration on grape berries and wine quality, we determined physicochemical properties, polyphenols, antioxidant activities, volatile compounds and sensory characteristics for wines brewed by 'Marselan' (Vitis vinifera L.) grapes with 0%, 10%, 15%, 20%, and 25% of water loss. The result showed that postharvest dehydration improved the alcohol content, residual sugar and titratable acidity of Marselan wine. Phenolic compounds and antioxidant activities in wines with a dehydration of 20% have significantly increased. Postharvest dehydration increased the contents of isobutanol, isoamyl alcohol, phenylethyl alcohol, ethyl acetate, isoamyl acetate and ethyl butyrate in Marselan wines, and enhanced the floral, fruity and sweet taste of wines. Marselan wine had the lowest acceptability score under the condition of severe dehydration (25% dehydration), which was related to the significant increase of tannins content. In summary, postharvest dehydration was beneficial in improving the quality of Marselan wine.

Formation of key aroma-active and off-flavor components in concentrated peach puree

Non-volatiles offer some insight into the formation of aroma-active components in peach puree (PP), but more depth investigation is still needed. Formation pathways of key aroma-active and off-flavor components in PP during thermal concentration (PP + C) and sterilization (PP + C + S) are unclear. Therefore, GC-O-MS combined with UPLC-MS/MS was used to identify the volatile and nonvolatile components and their formation pathways. Among the 36 aroma-active compounds, the contents of γ-decalactone, hexyl acetate, leaf acetate, hexanal, and 1-hexanol (odor activity value ≥ 1) decreased by 46 %, 100 %, 100 %, 92 %, and 100 % between PP and PP + C + S, causing the weakening of "green" and "fruity" attributes. Off-flavor components including 1-octen-3-one, isobutyric acid, isothiazole, and isovaleric acid were identified during thermal processing. 1-Octen-3-one content increased by 75 % from PP to PP + C + S through linolenic acid metabolism, which contributed to "cooked"; the formation of isobutyric and isovaleric acids, isothiazole, resulted in the enhancement of "sour/rancid" via serine and leucine metabolism.

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

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

Changes of Volatile Organic Compounds of Different Flesh Texture Pears during Shelf Life Based on Headspace Solid-Phase Microextraction with Gas Chromatography-Mass Spectrometry

Aroma is an important sensory factor in evaluating the quality of pear fruits. This study used headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) to analyze the volatile organic compounds (VOCs) of three crispy pears and five soft pears during shelf life, and the changes in soluble solids content (SSC) were analyzed. The results showed that the SSC of the soft pears such as Nanguoli, Jingbaili and Louis was always higher than that of the crispy pears throughout shelf life. A total of 160 VOCs were detected in the eight pear varieties. Orthogonal partial least squares discriminant analysis (OPLS-DA) and hierarchical cluster analysis (HCA) combined with predictor variable importance projection (VIP) showed that the eight pear varieties could be obviously classified into six groups according to the differences in their VOCs, and 31 differential VOCs were screened out, which could be used to differentiate between pears with different flesh textures. The results of clustering heat map analysis showed that, with the extension of shelf life, the content of each different VOC did not change much in crispy pears, whereas the difference in soft pears was larger. This study confirmed the potential of determining the optimal shelf life of different pear varieties about aroma evaluation and studying the mechanism of differences in VOCs in the future.

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.

Application and prospect of metabolomics-related technologies in food inspection

BACKGROUND

Food inspection covers a broad range of topics, including nutrient analysis, food pollutants, food auxiliary materials, additives, and food sensory identification. The foundation of diverse subjects like food science, nutrition, health research, and the food industry, as well as the desired reference for drafting trade and food legislation, makes food inspection highly significant. Because of their high efficiency, sensitivity, and accuracy, instrumental analysis methods have gradually replaced conventional analytical methods as the primary means of food hygiene inspection.

SCOPE AND APPROACH

Metabolomics-based analysis technology, such as nuclear magnetic resonance (NMR), gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), and capillary electrophoresis-mass spectrometry (CE-MS), has become a widely used analytics platform. This research provides a bird's eye view of the application and future of metabolomics-related technologies in food inspection.

KEY FINDINGS AND CONCLUSIONS

We have provided a summary of the features and the application range of various metabolomics techniques, the strengths and weaknesses of different metabolomics platforms, and their implementation in specific inspection procedures. These procedures encompass the identification of endogenous metabolites, the detection of exogenous toxins and food additives, analysis of metabolite alterations during processing and storage, as well as the recognition of food adulteration. Despite the widespread utilization and significant contributions of metabolomics-based food inspection technologies, numerous challenges persist as the food industry advances and technology continues to improve. Thus, we anticipate addressing these potential issues in the future.

Cinnamon essential oil vapor alleviates the reduction of aroma-related volatiles in cold-stored "Feicheng" peach using HS-GC-IMS

"Feicheng" peach is popular for its unique aroma, but its defect of being highly sensitive to chilling injury (CI) often leads to aroma loss and internal browning. Essential oils (EOs) are often used to enhance the antioxidant capacity of plants and fruits, as well as to trigger their defense against biotic/abiotic stresses. This study aimed to examine the effect of cinnamon essential oil (CEO) vapor treatment on the aroma quality of peach fruit during cold storage using HS-GC-IMS. The results showed that 50 μL/L CEO vapor reduced the severity of internal browning (IB) in peaches at the stage of 7 ~ 21 d during refrigeration (Significantly, the L* value was higher and the IB index was lower than that of control, p < 0.05). Meanwhile, the evident reduction or loss of aroma content caused by CI was restored to a higher level than the control (p < 0.05). Furthermore, CEO treatment promoted the release of aroma-related volatiles as evidenced by more propyl acetate, and the dimer of amyl acetate, isoamyl acetate, butyl acetate detected than that on harvest day and no-treated group after 21 d of cold storage plus 2 d of shelf life. Genes of PpLOX1, PpLOX2, PpHPL1 and PpADH1 associated with aroma-related volatile biosynthesis revealed higher transcript abundance in peach fruits treated with CEO than the control (p < 0.05). Overall, our study demonstrated that CEO in vapor phase may be beneficial to alleviate the quality deterioration in aroma and flesh color of "Feicheng" peaches caused by CI, which lays a theoretical reference for maintaining postharvest quality of peach fruits.

Flavor Characterization of Native Xinjiang Flat Peaches Based on Constructing Aroma Fingerprinting and Stoichiometry Analysis

The flat peach is a high economic value table fruit possessing excellent quality and a unique aroma. This article investigated the quality characteristics and aroma fingerprinting of flat peaches (Qingpan, QP; Ruipan 2, R2; Ruipan 4, R4; Wanpan, WP) from Xinjiang in terms of taste, antioxidant capacity, and volatile aroma compounds using high-performance liquid chromatography (HPLC) and HS-SPME-GC-MS. The results showed that the flat peaches had a good taste and high antioxidant capacity, mainly due to the high sugar-low acid property and high levels of phenolic compounds. This study found that sucrose (63.86~73.86%) was the main sugar, and malic acid (5.93~14.96%) and quinic acid (5.25~15.01%) were the main organic acids. Furthermore, chlorogenic acid (main phenolic compound), epicatechin, rutin, catechin, proanthocyanidin B1, and neochlorogenic acid were positively related to the antioxidant activity of flat peaches. All flat peaches had similar aroma characteristics and were rich in aromatic content. Aldehydes (especially benzaldehyde and 2-hexenal) and esters were the main volatile compounds. The aroma fingerprinting of flat peaches consisted of hexanal, 2-hexenal, nonanal, decanal, benzaldehyde, 2,4-decadienal, dihydro-β-ionone, 6-pentylpyran-2-one, 2-hexenyl acetate, ethyl caprylate, γ-decalactone, and theaspirane, with a "peach-like", "fruit", and "coconut-like" aroma. Among them, 2,4-decadienal, 2-hexenyl acetate, and theaspirane were the characteristic aroma compounds of flat peaches. The results provide a theoretical basis for the industrial application of the special aroma of flat peaches.

Identification of Key Components Responsible for the Aromatic Quality of Jinmudan Black Tea by Means of Molecular Sensory Science

A fruity aroma is regarded as an important factor in the evaluation of black tea quality. However, the compounds contributing to a particularly fruity aroma still garner less attention. In this study, we aimed to identify the aroma-active compounds of the peach-like aroma of Jinmudan black tea (JBT). We used gas chromatography-mass spectrometry (GC-MS) to reveal the profile of the chemical compounds integrated into JBT and identified terpenoids, heterocyclic, and esters that contribute to its floral and fruity aroma. Under the PCA and PLS-DA modes, JBT and Fuyun NO. 6 black tea (FBT) can be divided into two classes, respectively (class 1 and class 2); several compounds, including indole, methyl salicylate, and δ-decalactone, have a higher VIP value (Variable Importance in Projection), and it has been found that δ-decalactone was the characteristic aromatic compound of peach fruit. Gas chromatography-olfactometry (GC-O) and the odor activity value (OAV) indicated that, in JBT, linalool, phenylacetaldehyde, and δ-decalactone could be considered aroma-active compounds (AACs). However, in FBT, the high content of heterocyclic compounds contribute to its caramel-like aroma. As for the biochemical compounds measurement, JBT has a higher content of theaflavins (TFs), thearubigins (TRs), and flavonoids. These results provide a theoretical basis for the quality and processing improvement in JBT.

Investigation of Lactone Chiral Enantiomers and Their Contribution to the Aroma of Longjing Tea by Odor Activity Value and S-Curve

Odor activity value (OAV) and S-curve were used to study the content, proportion, and contribution of lactone chiral enantiomers in Longjing tea. A total of 10 enantiomers were identified in this study, among which (S)-(-)-δ-decalactone (45.4-84.4 μg/L), (S)-(-)-γ-decalactone (31.5-109 μg/L), (S)-(-)-γ-nonanolactone (23.4-72.8 μg/L), and (S)-(-)-γ-undecalactone (21.1-56.2 μg/L) presented the highest concentrations. Furthermore, (R)-(+)-γ-nonanolactone (OAV: 2-7), (S)-(-)-γ-nonanolactone (OAV: 1-5), (S)-(-)-δ-decalactone (OAV: 2-4), (R)-(+)-δ-decalactone (OAV: 1-3), and (R)-(+)-γ-undecalactone (OAV: 1-5) were determined as enantiomeric compounds that play an important role in the perceived aroma of Longjing tea. Compared with the aromatic reconstitution (AR), the threshold increased to different degrees after adding γ-nonanolactone, γ-decalactone, δ-decalactone, γ-undecalactone, and their chiral enantiomers. This finding indicated that these compounds exert significant effects on the overall aroma of the AR. The contribution of racemates and chiral enantiomers to the AR threshold and aroma is completely different. In view of the difference between racemic and enantiomers' aroma characteristics in Longjing tea, the analysis and identification of chiral enantiomers are necessary to enrich and improve the accurate analysis of the flavor profile of Longjing tea.

Analysis of the Volatile Flavor Compounds of Pomegranate Seeds at Different Processing Temperatures by GC-IMS

This study sought to reveal the mechanism of flavor generation when pomegranate seeds are processed, as well as the contribution of volatile organic components (VOCs) to flavor formation. Gas chromatography–ion mobility spectrometry (GC-IMS), combined with relative odor activity (ROAV) and statistical methods, was used for the analysis. The results showed that 54 compounds were identified from 70 peaks that appeared in the GC-IMS spectrum. Then, the ROAV results showed 17 key volatile components in processing pomegranate seeds, and 7 flavor components with large differential contributions were screened out using statistical methods. These included γ-butyrolactone, (E)-3-penten-2-one (dimer), pentanal, 1-propanethiol, octanal, and ethyl valerate (monomer). It is suggested that lipid oxidation and the Maillard reaction may be the main mechanisms of flavor formation during the processing of pomegranate seeds. Furthermore, this study lays the experimental and theoretical foundations for further research on the development of flavor products from pomegranate seeds.

Comparative analysis of volatile aromatic compounds from a wide range of pear (PyrusL.) germplasm resources based on HS-SPME with GC-MS

Aroma is one of the most important sensory characteristics of fruit quality. Here, the aroma composition of mature fruits of 202 pear cultivars was detected by headspace solid-phase microextraction (HS-SPME) with gas chromatography-mass spectrometry (GC-MS). As a result, 221 major volatile components were detected, among which aldehydes, esters and alcohols were the most dominant aroma components. We also found Pyrus communis L. had the highest volatile content, followed by Pyrus sinkiangensis Yu, Pyrus ussuriensis Maxim., Pyrus bretschneideri Rehd., Hybrid Breeding cultivar group, Chinese sand pears (Pyrus pyrifolia Nakai), and Japanese and Korean (J&K) sand pears (Pyrus pyrifolia Nakai). In addition, the aroma composition and contents varied greatly among the different ripening-period groups. Finally, the fruits of pear germplasms also showed geographical flavor characteristics. These basic data and results could help us better understanding the variations of aroma quality among pear varieties and promote the development of pear breeding program.

Characterization of aroma compounds and effects of amino acids on the release of esters in Laimao baijiu

BACKGROUND

Laimao baijiu is a typical soy-sauce aroma-type baijiu in China. Amino acids are non-volatile compounds in baijiu and are beneficial to human health. Aroma is one of the important indicators that are used to evaluate the quality of baijiu. The interaction between aroma-active compounds and non-volatile compounds can also affect the release of aroma compounds. In this study, we identified the active-aroma compounds and amino acids in Laimao baijiu by stir bar sorptive extraction (SBSE), gas chromatography-olfactometry (GC-O), gas chromatography-mass spectrometry (GC-MS), and ultra-performance liquid chromatography-mass spectrometry (UPLC-MS). The interaction between amino acids and key esters was investigated by sensory analysis and partition coefficients.

RESULTS

A total of 63 aroma compounds and 21 amino acids were identified. Twenty-one esters were identified from them as major aroma-active ester compounds with odor activity values ≥ 1. Finally, sensory analysis revealed that l-alanine had a significant effect on the strength of the aromas of esters, suggesting that low concentrations of amino acids were more likely to promote the release of esters and high concentrations were more likely to inhibit this. The partition coefficient can be a good explanation for this phenomenon.

CONCLUSION

l-Alanine can significantly affect the aroma intensity of key ester aroma compounds in Laimao baijiu, and the effects of different concentrations of amino acids are different. This work shows that amino acids, as non-volatile compounds, have a regulatory effect on the release of aroma compounds in alcoholic beverages, which may provide new technical support for the aroma modulation of alcoholic beverages. © 2022 Society of Chemical Industry.

Identification of the key off-flavor odorants for undesirable spoiled odor in thermally sterilized fermented soymilk

Spoiled odors are a problem in thermally sterilized fermented soymilk. This study aims to clarify production conditions and key odorants of spoiled odors. The sensory evaluation showed that thermal sterilization caused a decrease in the sensory intensity of yogurt and fruity odors while significantly increasing undesirable aromas including beany, acidic, cooked-beans and spoiled odors. The spoiled odors increased with increasing acidity and heating temperatures. The strongest spoiled odor was observed in fermented soymilk at titratable acidity of 5.4 g/kg, sterilized at 90 °C. Apart from common volatiles that were inherent in soymilk and generated from lactic fermentation, 2-methyltetrahydrothiophen-3-one was found for the first time in soybean foods and was found to cause the spoiled odor. 44 volatiles found in thermally sterilized fermented soymilk were jointly formed its flavor wheel. This study provides important theoretical support for solving the problem of spoiled odor restricting the popularization of plant-based fermented soymilk.

Engineering an Enzymatic Cascade Catalytic Smartphone-Based Sensor for Onsite Visual Ratiometric Fluorescence-Colorimetric Dual-Mode Detection of Methyl Mercaptan

Precise and reliable onsite detection of methyl mercaptan (CH₃SH) is of great significance for environmental surveillance. Here, we synthesized a novel blue fluorescence nanozyme CeO₂@TPE with high peroxidase-like activity by employing aggregation-induced emission (AIE) tetraphenylethene (TPE) to embed into hollow CeO₂ nanospheres. In the presence of ethanol oxidase (AOX) and o-phenylenediamine (OPD), we engineered an enzymatic cascade activation ratiometric fluorescence-colorimetric dual-mode system AOX/CeO₂@TPE + OPD toward CH₃SH. In this design, CH₃SH initiated AOX catalytic activity to convert it into H₂O₂ for activating the peroxidase-like activity of CeO₂@TPE, producing ^•OH for oxidizing the naked-eye colorless OPD into deep yellow 2,3-diaminophenazine (DAP) with an absorption enhancement at ∼425 nm, companied by a new emission peak at ∼550 nm to match with the intrinsic emission at ∼441 nm for observing ratiometric fluorescence response, enabling a ratiometric fluorescence-colorimetric dual-mode analysis. Interestingly, both the ratiometric fluorescence and colorimetric signals could be gathered for being converted into the hue parameter on a smartphone-based sensor, achieving the onsite visual fluorescence-colorimetric dual-mode detection of CH₃SH in real environmental media with acceptable results. This study gave a novel insight into designing target-responsive enzymatic cascade activation system-based efficient and reliable dual-mode point-of-care sensors for safeguarding environmental health.

Physicochemical Characteristics, Antioxidant Activities, and Aroma Compound Analysis of Seven Peach Cultivars (Prunus persica L. Batsch) in Shihezi, Xinjiang

Peaches are tasty and juicy, with a unique flavor. The flavors of peaches always vary with cultivars. To investigate the physicochemical and aroma characteristics of peaches, the sugars, organic acids, total flavonoids, phenols, antioxidant activities, and aroma compounds of seven peach cultivars in Xinjiang were determined using high-performance liquid chromatography (HPLC) and headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME–GC–MS). The results showed that sucrose (59.83 to 87.34%), malic acid (32.41 to 59.14%), and chlorogenic acid (10.43 to 45.50%) were the dominant sugar, organic acid, and phenolic compound in peaches, respectively. The antioxidant activity varied between 147.81 and 394.55 μmol TEs/100 g. The analysis of the aroma structure of peaches found that the volatile composition of peaches was relatively consistent, though the concentration of total aroma and certain separate compounds were different between cultivars. Meanwhile, the aroma fingerprint of the peaches consisted of hexyl acetate, cis-3-hexenyl acetate, γ-decalactone, n-hexanal, 2-hexenal, nonanal, decanal benzaldehyde and 6-pentylpyran-2-one, providing a clear green, sweet, floral, and fruity odor. These results provide complete information on the physicochemical properties, functional ingredients and aroma of the peaches.

Characterization of volatile constituents and odorous compounds in peach (Prunus persica L) fruits of different varieties by gas chromatography-ion mobility spectrometry, gas chromatography-mass spectrometry, and relative odor activity value

The aim of this study is to acquire information for future breeding efforts aimed at improving fruit quality via effects on aroma by comparing the diversity of Chinese local peach cultivars across 10 samples of three varieties (honey peach, yellow peach, and flat peach). The volatile components of peach fruits were analyzed and identified by gas chromatography–ion mobility spectrometry (GC-IMS) combined with gas chromatography–mass spectrometry (GC-MS), and the main flavor components of peach fruit were determined by relative odor activity value (ROAV) and principal component analysis (PCA). A total number of 57 volatile components were detected by GC-IMS, including eight aldehydes, nine alcohols, eight ketones, 22 esters, two acids, two phenols, two pyrazines, one thiophene, one benzene, and two furans. The proportion of esters was up to 38.6%. A total of 88 volatile components were detected by GC-MS, among which 40 were key aroma compounds, with an ROAV ≥ 1. The analysis results showed that alcohols, ketones, esters, and aldehydes contributed the most to the aroma of peach fruit. PCA demonstrated that (E,E)-2, 6-non-adienal, γ-decalactone, β-ionone, and hexyl hexanoate were the key contributors to the fruit aroma. A reference for future directional cultivation and breeding could be provided by this study through evaluating the aroma quality of the peach at the cultivar level. The possible reasonable application of these peach fruits pulp will be guided through these research.

Research progress on the formation mechanism and detection technology of bread flavor

With a long history of fermentation technology and rich flavors, bread is widely consumed by people all around the world. The consumer market is huge and the demand is wide. However, the formation mechanism of bread baking flavor has not been completely defined. In order to improve the breadmaking process and the quality of bread, the main flavor substances produced in bread baking, the formation mechanism, and the detection technology of bread baking flavor are carefully summarized in this paper. The generation conditions and formation mechanism of flavor substances during the bread baking process are expounded, and the limitations of some current bread flavor detection technologies are proposed, which will provide theoretical basis for effectively regulating the generation of flavor substances in the bread baking process and making bread with good flavor and rich nutrition in the future.

Consensual Regression of Soluble Solids Content in Peach by Near Infrared Spectrocopy

In order to reduce the uncertainty of the genetic algorithm (GA) in optimizing the near-infrared spectral calibration model and avoid the loss of spectral information of the unselected variables, a strategy of fusing consensus models is proposed to measure the soluble solids content (SSC) in peaches. A total of 266 peach samples were collected at four arrivals, and their interactance spectra were scanned by an integrated analyzer prototype, and then an internal index of SSC was destructively measured by the standard refractometry method. The near-infrared spectra were pre-processed with mean centering and were selected successively with a genetic algorithm (GA) to construct the consensus model, which was integrated with two member models with optimized weightings. One was the conventional partial least square (PLS) optimized with GA selected variables (PLS_GA), and the other one was the derived PLS developed with residual variables after GA selections (PLS_RV). The performance of PLS_RV models showed some useful spectral information related to peaches’ SSC and someone performed close to the full-spectral-based PLS model. Among these 10 runs, consensus models obtained a lower root mean squared errors of prediction (RMSEP), with an average of 1.106% and standard deviation (SD) of 0.0068, and performed better than that of the optimized PLS_GA models, which achieved a RMSEP of average 1.116% with SD of 0.0097. It can be concluded that the application of fusion strategy can reduce the fluctuation uncertainty of a model optimized by genetic algorithm, fulfill the utilization of the spectral information amount, and realize the rapid detection of the internal quality of the peach.

Analysis of key precursor peptides and flavor components of flaxseed derived Maillard reaction products based on iBAQ mass spectrometry and molecular sensory science

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Peptides-MRPs had high umami, mouthfulness, and continuity enhancement.

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DLSFIP and ELPGSP accounted for 42.22% and 20.41% of total consumption.

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Sulfur and nitrogen flavors was dependent on cysteine and peptides, respectively.

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This study also revealed the flavor formation mechanism of flaxseed derived MRPs.

Flaxseed derived Maillard reaction products (MRPs) have typical meaty flavor, but there is no report on comparison of their amino acids and peptides reactivity. The peptides and amino acids of flaxseed protein hydrolysates were separately collected by G-15 gel chromatography. Taste dilution analysis (TDA) showed that peptides-MRPs had high umami, mouthfulness, and continuity enhancement. Further, LC-MS/MS revealed that flaxseed protein hydrolysates consumed 41 peptides after Maillard reaction. Particularly, DLSFIP (Asp-Leu-Ser-Phe-Ile-Pro) and ELPGSP (Glu-Leu-Pro-Gly-Ser-Pro) accounted for 42.22% and 20.41% of total consumption, respectively. Aroma extract dilution analysis (AEDA) indicated that formation of sulfur-containing flavors was dependent on cysteine, while peptides were more reactive than amino acids for nitrogen-containing heterocycles. On the other hand, 11 flavor compounds with flavor dilution (FD) ≥ 64 were identified for flaxseed derived MRPs, such as 2-methylthiophene, 2-methyl-3-furanthiol, furfural, 2-furfurylthiol, 3-thiophenethiol, thieno[3,2-b] thiophene, 2,5-thiophenedicarboxaldehyde, 2-methylthieno[2,3-b] thiophene, 1-(2-methyl-3-furylthio)-ethanethiol, 2-methylthieno[3,2-b] thiophene, and bis(2-methyl-3-furyl)-disulfide. In addition, we further demonstrated the flavors formation mechanism of flaxseed derived MRPs.

Urinary volatomic profile of traditional tobacco smokers and electronic cigarettes users as a strategy to unveil potential health issues

Many harmful and potentially harmful constituents are present in tobacco products. Cigarette smoke is known to cause different forms of cancer and trigger the development of chronic diseases. In the last decade, electronic cigarettes have emerged as a healthier alternative associated to less harmful effects in comparison to traditional tobacco. However, the lack of standardization of electronic cigarettes products makes it difficult to establish and compare the real effects on health of products from different manufacturers. To better understand the impact of smoking and vaping, the volatomic composition of urine samples from traditional tobacco smokers and electronic cigarette users was established and compared with nonsmokers (control group), using headspace solid-phase microextraction combined with gas chromatography-mass spectrometry. A total of 45 urinary volatile organic metabolites belonging to different chemical families were identified in the urine of the studied groups. Benzene derivatives, terpenes, and aromatics were the chemical families that contributed the most to the urinary profile of smokers. The vapers urinary volatomic pattern was also dominated by terpenes and aromatics, in addition to alcohols. The orthogonal partial least squares-discriminant analysis of the data obtained indicated that the urinary profile of vapers is more closely related to the control group, reinforcing the hypothesis of the lowest harmfulness of electronic cigarettes. Further studies recruiting a higher number of subjects are therefore necessary to consolidate the data obtained.

Characterization of the Aroma-Active Compounds in Banana (Musa AAA Red green) and Their Contributions to the Enhancement of Sweetness Perception

"Hongmeiren" bananas are popular because of their red peel. Two extraction methods solvent-assisted flavor evaporation and headspace solid-phase microextraction, combined with gas chromatography-olfactometry and gas chromatography-mass spectrometry (GC-MS), were used to analyze the volatile components of "Hongmeiren" bananas. A total of 86 aroma compounds were identified by GC-MS, 62 of which were identified as the major aroma-active compounds with an odor activity value ≥ 1 or modified frequency ≥ 30%. Ethyl (E)-2-butenoate, 4-undecanone, and α-phellandrene were found in bananas for the first time. Sensory experiments showed that eight sweet-associated odorants could significantly achieve the sweetness enhancement effect at 30 g/L sucrose solution by odor-induced changes in taste perception. These experiments suggest that selected odorants can achieve sugar reduction, but with consideration of the sugar concentration. The study of the sweetness enhancement effect of individual compounds provides a more direct theoretical support for sugar reduction in the food industry.