Variations of volatile flavour compounds in finger citron (Citrus medica L. var. sarcodactylis) pickling process revealed by E-nose, HS-SPME-GC-MS and HS-GC-IMS

Influence of germination and roasting on the characteristic volatile organic compounds of quinoa using sensory evaluation, E-nose, HS-GC-IMS, and HS-SPME-GC-MS

This study aimed to investigate the effects of germination and roasting on the flavor of quinoa. Firstly, the aroma of quinoa and germinated quinoa roasted under different conditions was analyzed using sensory evaluation and electronic nose (E-nose). Results showed that the best favorable aroma of quinoa and germinated quinoa was obtained when roasted at 160 °C for 15 min. Then, a total of 34 and 80 volatile organic compounds (VOCs) of quinoa and germinated quinoa roasted at 160 °C for 15 min were determined using headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) and headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS), respectively. Germination and roasting effectively reduced the contents of VOCs that produced undesirable flavor. Moreover, germination improved the floral aromas, while roasting mainly produced caramel, cocoa, and roasted nut aromas of quinoa. This study indicated that germination and roasting treatments might serve as promising processing methods to improve the flavor of quinoa.

Effect of cooking methods on volatile compounds and texture properties in maize porridge

To investigate the optimal processing of maize porridge, the volatile compounds and texture under different cooking methods and time have been studied. A total of 51 volatile compounds were identified in maize porridge. Notably, the major volatiles, aldehydes and esters exhibited a relatively high content in electric pressure cooker (EPC), and esters tend to significantly increase after cooking. Among aldehydes, nonanal and hexanal played a great role in flavor due to their relatively high content. Volatile compounds of maize porridge in different cooking methods could be clearly distinguished by multiple chemometrics. Furthermore, texture analysis revealed that almost all the indicators in the EPC can reach the lowest value at 60 min. To summarize, different cooking methods had a more significant influence on the volatile compounds and texture compared to time. This study helps to improve the sensory attributes of maize porridge, and thus contributes to healthier and more sustainable production.

The grading detection model for fingered citron slices (citrus medica 'fingered') based on YOLOv8-FCS

Introduction

Fingered citron slices possess significant nutritional value and economic advantages as herbal products that are experiencing increasing demand. The grading of fingered citron slices plays a crucial role in the marketing strategy to maximize profits. However, due to the limited adoption of standardization practices and the decentralized structure of producers and distributors, the grading process of fingered citron slices requires substantial manpower and lead to a reduction in profitability. In order to provide authoritative, rapid and accurate grading standards for the market of fingered citron slices, this paper proposes a grading detection model for fingered citron slices based on improved YOLOv8n.

Methods

Firstly, we obtained the raw materials of fingered citron slices from a dealer of Sichuan fingered citron origin in Shimian County, Ya'an City, Sichuan Province, China. Subsequently, high-resolution fingered citron slices images were taken using an experimental bench, and the dataset for grading detection of fingered citron slices was formed after manual screening and labelling. Based on this dataset, we chose YOLOv8n as the base model, and then replaced the YOLOv8n backbone structure with the Fasternet main module to improve the computational efficiency in the feature extraction process. Then we redesigned the PAN-FPN structure used in the original model with BiFPN structure to make full use of the high-resolution features to extend the sensory field of the model while balancing the computation amount and model volume, and finally we get the improved target detection algorithm YOLOv8-FCS.

Results

The findings from the experiments indicated that this approach surpassed the conventional RT-DETR, Faster R-CNN, SSD300 and YOLOv8n models in most evaluation indicators. The experimental results show that the grading accuracy of the YOLOv8-FCS model reaches 98.1%, and the model size is only 6.4 M, and the FPS is 130.3.

Discussion

The results suggest that our model offers both rapid and precise grading for fingered citron slices, holding significant practical value for promoting the advancement of automated grading systems tailored to fingered citron slices.

Volatile aroma compounds of passion fruit seed Oils: HS-GC-IMS analysis and interpretation

The physicochemical properties, fatty acid composition and volatile aroma compounds of cold-pressed passion fruit seed oils were analyzed. The oils were rich in linoleic acid, oleic acid and volatile compounds. A total of 108 volatile compounds including 17 aldehydes, 23 alcohols, 21 esters, 19 ketones, 6 acids, 9 alkenes, 5 pyrazines and 8 others were identified using HS-GC-IMS. The significant differences of volatile compounds in the purple and yellow passion fruit seed oils were observed via the GalleryPlot graph and distinguished by principal component analysis. The results showed that acids, alcohols, esters and ketones were major aromatic compounds in purple passion fruit seed oils, which contribute to flavors such as flowery, fruity, creamy, yogurt. Whereas the contents of aldehydes, pyrazines, alkenes were higher in yellow passion fruit seed oils, which contributes to fatty and nutty odors. The findings filled in our understanding of volatilization characteristics in passion fruit seed oils.

Ester-related volatile compounds reveal the diversity and commonalities of different types of late-ripening peaches

To recognize the key ester-related volatile compounds, 5 types of peaches including 54 late-ripening peach materials were examined by headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry and E-nose. Here, a large number of esters were identified to be released by ripe peach fruits and were mainly characterized by fruity, green, and fatty notes. The variety and content of esters had greatly changed within or between cultivars, indicating that the fruit volatiles were highly differentiated depending on the specific genotypes and cultivation conditions. The ester types showed that fatty acid-derived C6 alcohols and methyl-/ethyl- short-chain alcohol were the main ester precursors, which were more likely to be utilized and well selected by alcohol acyltransferases, whereas the preference of acyl donors was not observed. The common peach type, which exhibited a unique volatile profile, displayed broader diversity and more abundant characteristics in ester-related volatiles than the other four types. A total of 19 key esters were identified as the main components and the content of most esters showed no significant difference among different peach types. Some key esters had even been enriched in nectarines. Moreover, the multiple discriminant analysis revealed a possible relationship between peach types and the domestication of the peach evolution. This study investigated ester-related volatiles released by different types of peach fruits and can be further used to evaluate the peach qualities, providing an important reference for peach breeding and processing.

Insights into the volatile flavor and quality profiles of loquat (Eriobotrya japonica Lindl.) during shelf-life via HS-GC-IMS, E-nose, and E-tongue

Loquat fruits are among the most popular Chinese fruits because of their unique taste and aroma. The quality profiles of these fruits during 18 days of shelf-life at 20 °C were elucidated by headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS), E-nose, and E-tongue. During shelf-life period, the properties and variations of 43 (20 aldehydes, 7 esters, 6 ketones, 1 alcohol, and 1 furan) volatile flavored compounds were determined by GC-IMS, which showed that the contents of methyl 3-methyl butanoate, ethyl acetate, and dimethyl ketone gradually decrease with prolonged shelf-life time, while (E)-2-heptenal, heptanal, (E)-2-pentenal, 1-penten-3-one 3-pentanone and 2-pentylfuran increase. The PCA based on the signal intensity of GC-IMS and E-nose, revealed that loquat fruits are well distinguished at different shelf-life times. The taste profile alternates as the storage time increases, along with higher pH, and lower amounts of total soluble solids, vitamin C, and total phenolics. The visual plots of GC-IMS, E-nose, and E-tongue had good consistency, and they characterized the aroma characteristics of loquat fruits well during different shelf-life periods. The findings of this research provide a useful understanding of the flavors of loquat fruits during their prolonged shelf-life, and a potential research basis for advancements in the loquat industry.

Characteristic fingerprints and comparison of volatile flavor compounds in Morchella sextelata under different drying methods

Morchella sextelata is a precious and popular commercial edible fungus that was developed recently in China. This research aimed to characterize the volatile profiles of M. sextelata under three dehydration methods (freeze, hot air, and natural air drying). Comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC × GC-ToF-MS) was shown to the best choice to discriminate the volatile profiles of M. sextelata Characteristic flavor substances of M. sextelata were eight-carbon-containing (C8) compounds, hexanal, 2(5 h)-furanone, and benzaldehyde. Drying methods had significant influences on the volatile flavor profiles of M. sextelata, and 104 differential compounds were screened by multivariate statistical analysis. Freeze-dried samples had the most abundant volatile compounds and maintained more alcohols, ketones, aldehydes, and esters described as mushroom, sweet, and green flavor, like 1-octen-3-ol, 1-octen-3-one, nonanal, 2,3-butanedione, and so on. Hot air-drying promoted the production of heterocycles and ketones with roasted flavor due to the thermalreaction, such as 2-cyclohexen-1-one, furan, 3-phenyl-, etc. Natural air-drying resulted in acids releasing an unpleasant flavor, e.g., acetic acid, 2-methylbutanoic acid, etc. Overall, thermal reaction combined with vacuum conditions might be suitable for maintaining and enriching the aroma flavor of dried true morels.

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.

Gastroprotective Effects of the Aqueous Extract of Finger Citron Pickled Products against Ethanol-Induced Gastric Damage: In Vitro and In Vivo Studies

Finger citron pickled products (FCPP), as folk remedies, are famous in southern China for protecting gastric mucosa. However, the gastric mucosa protection of FCPP has not been reported yet, and its effective mechanism is unclear. In this study, the protective mechanism of FCPP aqueous extract on gastric mucosa was investigated in vitro and in vivo for the first time, using human gastric mucosa epithelial cells (GES-1) and acute alcoholic gastric ulcer rat model respectively. Furthermore, we also investigated the main substances in the aqueous extract that exert gastroprotective activity using a GES-1 scratch test and basic chemical composition analysis. FCPP aqueous extract was found to play a protective and reparative role in GES-1 by promoting the secretion of trefoil factor thyroid transcription factor 2 (TFF2) and inhibiting the secretion of tumor necrosis factor-α (TNF-α) in cells damaged by alcohol. The ulcer index of gastric tissue induced by alcohol was significantly decreased (p < 0.01) after pretreatment with FCPP aqueous extract, indicating that FCPP aqueous extract had a good protective effect on the stomach mucosa. Moreover, FCPP aqueous extract could increase superoxide dismutase (SOD) activity and inhibit malondialdehyde (MDA) content, exhibiting good antioxidant capacity. Aqueous extract of FCPP could also effectively inhibit the increase of cytokines TNF-α, interleukin-1β (IL-1β) and interleukin-6 (IL-6) in serum of rats, and promote the increase of anti-inflammatory cytokines interleukin-10 (IL-10) to some extent. Furthermore, FCPP aqueous extract could inhibit the expression of nuclear factor kappa-B (NF-κB/P65) protein, caspase-1 protein and IL-1β protein in the gastric tissue of rats, while promoting the expression of IκBα protein, indicating that the gastric mucosa protection effects of FCPP aqueous extract were mainly dependent on the NF-κB/caspase-1/IL-1β axis. The polysaccharides in FCPP aqueous extract might be the main components that exerted gastroprotective activity, as demonstrated by GES-1 cell scratch assay. This study confirmed that FCPP aqueous extract presented promising potential in protecting gastric mucosa and avoiding gastric ulcers, which could provide an experimental basis for further utilizing the medicinal value and developing new products of FCPP.

Quality Improvement of Garlic Paste by Whey Protein Isolate Combined with High Hydrostatic Pressure Treatment

Garlic, one of the most popular spices and medical herbs, has a unique pungent flavor and taste. Conventional homogenization and thermal treatment commonly lead to flavor and color deterioration in garlic paste, because allicin is highly susceptible to degradation and reaction. The present study was to investigate the effects of whey protein isolate (WPI) and different levels of high hydrostatic pressure (HHP, 200, 300, 400, 500, and 600 MPa) on the quality of garlic paste. Results showed that the addition of WPI in the homogenization of garlic significantly prevented green discoloration. Furthermore, WPI plus HHP under 500 MPa could better protect the color of garlic paste. Higher pressure (600 MPa) led to WPI aggregation, resulting in higher green color chroma of garlic paste. GC-MS results revealed that the application of WPI and HHP in garlic paste increased the relative level of pungent flavor compounds and decreased those of unpleasant odor compounds. The correlation analysis results revealed that WPI efficiently prevented garlic green discoloration, which is attributed to the thiol group in WPI exchanging the sulfonyl groups in allicin. In consideration of the microbial load, flavor and color quality of garlic paste, the optimal processing conditions were found at 500 MPa for 5 min with 2% WPI addition, extending shelf life to 25 days.

Discrimination and Characterization of Volatile Flavor Compounds in Fresh Oriental Melon after Forchlorfenuron Application Using Electronic Nose (E-Nose) and Headspace-Gas Chromatography-Ion Mobility Spectrometry (HS-GC-IMS)

Aroma is a crucial factor determining the market value and consumer satisfaction of fresh oriental melon. However, few studies focus on the volatile flavor of fresh oriental melon, and the effect of forchlorfenuron application on the aroma profile is unclear. This study characterized the volatile profile of fresh oriental melon fruit after forchlorfenuron application by E-nose and HS-GC-IMS. The holistic variation of volatile compounds exhibited evident distinction based on linear discriminant analysis (LDA) with E-nose. Forty-eight volatile compounds were identified from fresh oriental melon via GC-IMS, mainly esters, alcohols, aldehydes, and ketones, along with smaller quantities of sulfides and terpenes. Compared to pollination melon fruits, 13 critical different volatile flavor compounds were screened out in forchlorfenuron application groups by the PLS-DA model, imparting sweet fruity flavor. The results of the current study provide a valuable basis for evaluating the flavor quality of oriental melon after forchlorfenuron treatment.

Uncovering the effect of Moringa oleifera Lam. leaf addition to Fuzhuan Brick Tea on sensory properties, volatile profiles and anti-obesity activity

As a nutritious plant with valuable potential, the Moringa oleifera Lam. leaf addition to Fuzhuan Brick Tea (FBT) for co-fermentation is an industrial innovation and a new route to make full use of Moringa oleifera Lam. leaves. However, the sensory properties, volatile profiles and anti-obesity activity of Fuzhuan Brick (Moringa oleifera Lam.) tea (MFBT) are still unknown. The results demonstrated that MFBT has richer and more complex smell and taste, better color and higher overall acceptance scores. In total, 57 volatile flavor compounds, consisting of 3 acids, 16 hydrocarbons, 5 esters, 8 ketones, 13 aldehydes, 6 alcohols and others, were identified using HS-SPME-GC-MS. The characteristic odor components in MFBT were 3-buten-2-one, 4-(2,6,6-trimethyl-1-cyclohexen-1-yl)- and 1-cyclohexene-1-carboxaldehyde, 2,6,6-trimethyl-, which gave it a floral, woody, sweet, herbal and fruity aroma. 2-Octenal, (E) contributed significantly to the aroma of FBT, which could impart fresh, fatty and green aromas. In addition, MFBT could better regulate lipid accumulation, glucose tolerance, insulin tolerance and inflammation response more effectively than FBT. The mechanism is that MFBT could better regulate the dysbiosis of gut microbiota induced by HFFD, mainly increasing the abundance of beneficial bacteria such as SCFA-producing bacteria (Bacteroidetes, Lactobacillaceae, Bacteroidales_S24-7_group and Clostridiaceae_1) and decreasing the abundance of harmful bacteria such as pro-inflammatory/obesity and metabolic syndrome-related bacteria (Proteobacteria, Deferribacteres, Desulfovibrio, Catenibacterium and Helicobacter), which in turn increased feces short-chain fatty acids and lowered circulating lipopolysaccharides. These results suggested that co-fermentation with Moringa oleifera Lam. leaf could significantly improve the quality and enhance the anti-obesity effect of FBT.

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.

Aroma profiles of sweet cherry juice fermented by different lactic acid bacteria determined through integrated analysis of electronic nose and gas chromatography-ion mobility spectrometry

Sweet cherries are popular among consumers, with a recent explosion in sweet cherry production in China. However, the fragility of these fruits poses a challenge for expanding production and transport. With the aim of expanding the product categories of sweet cherries that can bypass these challenges, in this study, we prepared sweet cherry juice fermented by three different lactic acid bacteria (LAB; Lactobacillus acidophilus, Lactobacillus plantarum, and Lactobacillus rhamnosus GG), and evaluated the growth, physiochemical, and aroma characteristics. All three strains exhibited excellent growth potential in the sweet cherry juice; however, Lactobacillus acidophilus and Lactobacillus plantarum demonstrated more robust acid production capacity and higher microbial viability than Lactobacillus rhamnosus GG. Lactic acid was the primary fermentation product, and malic acid was significantly metabolized by LAB, indicating a transition in microbial metabolism from using carbohydrates to organic acids. The aroma profile was identified through integrated analysis of electronic nose (E-nose) and headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) data. A total of 50 volatile compounds characterized the aromatic profiles of the fermented juices by HS-GC-IMS. The flavor of sweet cherry juice changed after LAB fermentation and the fruity odor decreased overall. Lactobacillus acidophilus and Lactobacillus plantarum significantly increased 2-heptanone, ethyl acetate, and acetone contents, bringing about a creamy and rummy-like favor, whereas Lactobacillus rhamnosus GG significantly increased 2-heptanone, 3-hydroxybutan-2-one, and 2-pentanone contents, generating cheesy and buttery-like odors. Principal component analysis of GC-IMS data and linear discriminant analysis of E-nose results could effectively differentiate non-fermented sweet cherry juice and the sweet cherry juice separately inoculated with different LAB strains. Furthermore, there was a high correlation between the E-nose and GC-IMS results, providing a theoretical basis to identify different sweet cherry juice formulations and appropriate starter culture selection for fermentation. This study enables more extensive utilization of sweet cherry in the food industry and helps to improve the flavor of sweet cherry products.

Identification and Analysis of Metabolites That Contribute to the Formation of Distinctive Flavour Components of Laoxianghuang

In addition to volatile compounds, metabolites also have a great effect on the flavour of food. Fresh finger citron cannot be eaten directly because of its spicy and bitter taste, so it is made into a preserved fruit product known as Laoxianghuang (LXH). To investigate the metabolites that have an effect on the flavour of LXH, untargeted metabolomics was performed using an ultrahigh-performance liquid chromatography with tandem mass spectrometry (UPLC-MS/MS), and the metabolites of the Laoxianghuang samples from different locations in the Chaoshan area were compared and analysed. A total of 756 metabolites were identified and distinct differences were revealed among the different Laoxianghuang samples. A total of 33 differential metabolites with the most significant changes were screened through further multivariate analytical steps, and each group of samples had unique metabolites. For instance, pomolic acid had the highest content in the JG sample, while L-glycyl-L-isoleucine was rich in the QS sample. Moreover, flavonoid metabolites made the greatest contribution to the unique flavour of Laoxianghuang. The metabolic pathways involved are the biosynthetic pathways of flavonoids, isoflavonoids, flavones, and flavonols. This study can provide some creative information for distinguishing the quality differences of Laoxianghuang from the perspective of metabolites and offer preliminary theoretical support to characterise the formation of flavour substances in Laoxianghuang.

Qualitative determination of volatile substances in different flavored cigarette paper by using headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) combined with chemometrics

In order to investigate the difference of volatile substances among flavored cigarette paper, which are supplied by several manufacturers with different batches, the stability of the complex system of scented cigarette paper was analyzed and evaluated. In this study, Headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) was used to detect the aroma compounds of 23 flavored cigarette paper samples. Based on fingerprint analysis, the differences and changes of aroma compounds of different samples were studied in the form of data visualization. Principal component analysis, partial least squares regression analysis, cluster heatmap analysis and artificial neural network analysis were used to evaluate the stability of different cigarette paper. The results show that: A total of 29 volatile substances were identified from different scented cigarette paper. Fingerprint analysis revealed that the volatile substances of different cigarette paper samples were roughly the same, but not the content. The results of chemometrics analysis showed that there were significant differences in the characteristic aroma compounds of cigarette paper from different manufacturers. HS-GC-IMS technology combined with chemometrics method could be applied to determine the difference of volatile substances among different flavored cigarette paper, which theoretically and technically supported the quality stability maintenance and identification of flavored cigarette paper processed in different places.

Investigation of volatile flavor compounds and characterization of aroma-active compounds of water-boiled salted duck using GC-MS-O, GC-IMS, and E-nose

To clarify the characteristic aroma substances of water-boiled salted duck (WSD), headspace-gas chromatography-mass spectrometry-olfactometry (HS-GC-MS-O), gas chromatography-ion mobility spectrometry (GC-IMS) combined with an electronic nose (E-nose) were used to analyze the volatile flavor profile of three types of WSD (containing four samples). Thirty-one and fifty volatile flavor components were identified by GC-MS and GC-IMS, including aldehydes, alcohols, esters, ketones, hydrocarbons, and others. The characteristic aroma compounds of WSD, including pentanal, hexanal, heptanal, octanal, nonanal, (E)-2-octenal, benzaldehyde, (E)-2-nonenal, decanal, 1-octen-3-ol, 1-octanol, 1-pentanol, ethyl acetate, d-limonene, and 2-pentylfuran, were confirmed by GC-O, odor activity values (OAVs), and aroma-recombination and omission experiments. The aroma description of these aroma-active compounds can be divided into 6 categories, namely, "fruity", "mushroom", "fat", "sweet", "faint scent" and "potato, scorch" aromas. The difference between samples was mainly caused by the differential volatile compounds, followed by the identification method.

Insight into the Characterization of Volatile Compounds in Smoke-Flavored Sea Bass (Lateolabrax maculatus) during Processing via HS-SPME-GC-MS and HS-GC-IMS

The present study aimed to ascertain how the volatile compounds changed throughout various processing steps when producing a smoke-flavored sea bass (Lateolabrax maculatus). The volatile compounds in different production steps were characterized by headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS). A total of 85 compounds were identified, and 25 compounds that may be considered as potential key compounds were screened by principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA). Results indicated that aldehydes were the major volatile compounds throughout the processing. The characteristic volatile compound in fresh samples was hexanol, and curing was an effective method to remove the fishy flavor. The concentration of volatile compounds was significantly higher in dried, smoked, and heated samples than in fresh and salted samples. Aldehydes accumulated because of the drying process, especially heptanal and hexanal. Smoke flavoring was an important stage in imparting smoked flavor, where phenols, furans and ketones were enriched, and heating leads to the breakdown of aldehydes and alcohols. This study will provide a theoretical basis for improving the quality of smoke-flavored sea bass products in the future.

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.

Discrimination of Black and White Sesame Seeds Based on Targeted and Non-Targeted Platforms with Chemometrics: From Profiling towards Identification of Chemical Markers

The present study was conducted to clarify the differences in the multi-element, volatile organic compound, fatty acid, and metabolite fingerprints between black and white sesame seeds. A total of 53 chemical elements, 32 volatile flavor compounds, 40 fatty acids, and 283 metabolites were identified and evaluated in the two groups of sesame seeds. Univariate and multivariate statistics indicated a distinct separation between the two groups of sesame seeds. A panel of 16 chemical elements, 3 volatile compounds, 8 individual fatty acids, and 54 metabolites with p value < 0.05 and variable importance in projection score > 1 were selected as the most important discriminants for the two types of sesame seeds. Overall, these data reveal the influence of genotype on the chemical composition of sesame seeds. Our findings also demonstrate that the hybrid model of instrumental analysis and chemometrics is feasible for the discrimination of black and white sesame seeds.

Discrimination and Characterization of the Volatile Organic Compounds in Schizonepetae Spica from Six Regions of China Using HS-GC-IMS and HS-SPME-GC-MS

Volatile organic compounds (VOCs) are the main chemical components of Schizonepetae Spica (SS), which have positive effects on the quality evaluation of SS. In this study, HS-SPME-GC-MS (headspace solid-phase microextraction-gas chromatography-mass spectrometry) and HS-GC-IMS (headspace-gas chromatography-ion mobility spectrometry) were performed to characterize the VOCs of SS from six different regions. A total of 82 VOCs were identified. In addition, this work compared the suitability of two instruments to distinguish SS from different habitats. The regional classification using orthogonal partial least squares discriminant analysis (OPLS-DA) shows that the HS-GC-IMS method can classify samples better than the HS-SPME-GC-MS. This study provided a reference method for identification of the SS from different origins.

Vibration mill-assisted complex enzyme hydrolysis for flavoring of freeze-dried sea cucumber powder

This study aims to analyze the flavor differences of freeze-dried sea cucumber powder, processed for different time intervals, under vibration mill-assisted complex enzyme hydrolysis using electronic nose (E-nose) and gas chromatography-ion mobility spectrometry (GC-IMS). The results of principal component analysis by E-nose showed distinction among the four groups of freeze-dried sea cucumber powder (papain-neutral protease (PN) and flavorzyme-neutral protease (FN), processed for 60 and 80 min). The GC-IMS revealed 35 volatile compounds. Subsequently, based on the fingerprint and heat map results, the flavor differences among the samples were clearly distinguished. When compared to the other three groups, the 60-FN group exhibited a greater variety and quantity of volatile compounds such as octanal, heptanal, hexanal, (E, Z)-2,6-nonadienal, and nonanal. The 80-PN group exhibited high amounts of 2-propanone, ethylbenzene, ethyl acetate, and 2,5-dimethylpyrazine. In addition, the vibration mill technique was considered to be a mild enzyme-assisted method. PRACTICAL APPLICATIONS: This study found that different enzyme types and physical technology operation time can affect the different volatile flavor compounds of freeze-dried sea cucumber powder, which can be quickly and effectively be identified by E-nose and GC-IMS technology to improve the flavor and quality of the product, while facilitating the rapid adjustment and development of the industry. Meanwhile, the results of the study could provide a reference for the deep processing and flavor improvement of the sea cucumber industry and make an important contribution to the related literature. In addition, this could also promote the development and application of non-thermal processing technologies such as vibratory mill in the freeze-dried sea cucumber powder industry.

Structural Characterization and Anti-inflammatory Activity of a Galactorhamnan Polysaccharide From Citrus medica L. var. sarcodactylis

This study aimed to extract polysaccharides from Citrus medica L. var. sarcodactylis (finger citron fruits) and analyze their structures and potential bioactivities. A new polysaccharide named K-CMLP was isolated and purified by Diethylaminoethylcellulose (DEAE)-Sepharose Fast Flow and DEAE-52 cellulose column chromatography with an average molecular weight of 3.76 × 10³ kDa. Monosaccharide composition analysis revealed that K-CLMP consisted of rhamnose, galactose, and glucose, with a molar ratio of 6.75:5.87:1.00. Co-resolved by methylation and two-dimensional nuclear magnetic resonance (NMR), K-CLMP was alternately connected with 1, 2-Rha and 1, 4-Gal to form the backbone, and a small number of glucose residues was connected to O-4 of rhamnose. The results of DPPH⋅ and ABTS⁺⋅ radical scavenging assays indicated that both crude polysaccharide Citrus medica L. var. polysaccharide (CMLP) and K-CLMP exhibited strong free-radical-scavenging properties in a dose-dependent manner. In addition, K-CMLP significantly inhibited the production of pro-inflammatory cytokines (IL-6 and TNF-α) and reactive oxygen species (ROS) in RAW 264.7 cells treated with LPS. These results provide a basis for further use as one of the potential functions of food or natural medicine.

Progress of Research on the Application of Nanoelectronic Smelling in the Field of Food

In the past 20 years, the development of an artificial olfactory system has made great progress and improvements. In recent years, as a new type of sensor, nanoelectronic smelling has been widely used in the food and drug industry because of its advantages of accurate sensitivity and good selectivity. This paper reviews the latest applications and progress of nanoelectronic smelling in animal-, plant-, and microbial-based foods. This includes an analysis of the status of nanoelectronic smelling in animal-based foods, an analysis of its harmful composition in plant-based foods, and an analysis of the microorganism quantity in microbial-based foods. We also conduct a flavor component analysis and an assessment of the advantages of nanoelectronic smelling. On this basis, the principles and structures of nanoelectronic smelling are also analyzed. Finally, the limitations and challenges of nanoelectronic smelling are summarized, and the future development of nanoelectronic smelling is proposed.

Compositional Analysis of Four Kinds of Citrus Fruits with an NMR-Based Method for Understanding Nutritional Value and Rational Utilization: From Pericarp to Juice

Citrus is one of the most important economic crops and is widely distributed across the monsoon region. Citrus fruits are deeply loved by consumers because of their special color, fragrance and high nutritional value. However, their health benefits have not been fully understood, especially the pericarps of citrus fruits which have barely been utilized due to their unknown chemical composition. In the present study, the pericarp and juices of four typical varieties of citrus fruits (lemon, dekopon, sweet orange and pomelo) were analyzed by NMR spectroscopy combined with pattern recognition. A total of 62 components from the citrus juices and 87 components from the citrus pericarps were identified and quantified, respectively. The different varieties of the citrus fruits could be distinguished from the others, and the chemical markers in each citrus juice and pericarp were identified by a combination of univariate and multivariate statistical analyses. The nutritional analysis of citrus juices offers favorable diet recommendations for human consumption and data guidance for their potential medical use, and the nutritional analysis of citrus pericarps provides a data reference for the subsequent comprehensive utilization of citrus fruits. Our results not only provide an important reference for the potential nutritional and medical values of citrus fruits but also provide a feasible platform for the traceability analysis, adulteration identification and chemical composition analysis of other fruits.

Detection of Volatiles by HS-SPME-GC/MS and Biological Effect Evaluation of Buddha's Hand Fruit

The present work aimed to chemically characterize and evaluate the antiradical power and biological effects of Citrus medica var. sarcodactylus essential oil (EO) and hydrolate (Hy) from exocarp as well as methanol extracts, from both exocarp and mesocarp (EEX and MEX). The whole fresh fruit was also investigated by SPME-GC/MS to describe its volatile composition. EO and Hy were analyzed by GC/MS and HS-GC/MS techniques, respectively. Limonene and γ-terpinene were found to be the most abundant compounds both in the fresh parts of the fruit and in the EO, while α-terpineol and terpinen-4-ol were in the Hy. The extracts were also rich in furan and coumarin derivatives. A good antiradical activity of all samples except Hy was detected both against ABTS·+ than DPPH·, removed up to about 50%. The antibacterial activity against Bacillus cereus and Escherichia coli was evaluated by microwell dilution method to determine MIC and MBC values. EEX and MEX showed efficacy at very high concentrations against both tested bacteria. The MIC value of EO against B. cereus was 0.5% v/v, while Hy was not able to inhibit the bacterial growth at the tested concentrations. Cytotoxicity investigated on the HL60 leukemia cell line by MTT assay provided an EC₅₀ of 1.24% v/v for EO. Interesting activity of Hy was also observed.

Effect of blend oil on the volatile aroma profile and storage quality of garlic paste

The aim of this study was to evaluate the effect of edible oil on the volatile aroma profile and storage quality of garlic paste, and to explore the underlying mechanisms. The administration of blend oil at 40 °C in a garlic to oil ratio of 1.8 had a higher overall acceptance by affective sensory test. Compared with the original garlic paste, the sensory aroma profile of the oil-immersed garlic paste was characterized by suppressed pungency, garlic scent and garlic odor, and enhanced oil scent. SPME-GC-MS and HS-GC-IMS showed that the application of blend oil caused great changes in the level of some compounds, which could explain its role in the oil-immersed garlic paste. Furthermore, the blend oil also reduced the growth rate of the total number of colonies and browning intensity, and inhibited the loss of allicin. Therefore, the application of blend oil in garlic paste improved the sensory aroma and delayed the deterioration of the product quality.

Characterisation of Flavour Attributes in Egg White Protein Using HS-GC-IMS Combined with E-Nose and E-Tongue: Effect of High-Voltage Cold Plasma Treatment Time

Egg white protein (EWP) is susceptible to denaturation and coagulation when exposed to high temperatures, adversely affecting its flavour, thereby influencing consumers' decisions. Here, we employ high-voltage cold plasma (HVCP) as a novel nonthermal technique to investigate its influence on the EWP's flavour attributes using E-nose, E-tongue, and headspace gas-chromatography-ion-mobilisation spectrometry (HS-GC-IMS) due to their rapidness and high sensitivity in identifying flavour fingerprints in foods. The EWP was investigated at 0, 60, 120, 180, 240, and 300 s of HVCP treatment time. The results revealed that HVCP significantly influences the odour and taste attributes of the EWP across all treatments, with a more significant influence at 60 and 120 s of HVCP treatment. Principal component analyses of the E-nose and E-tongue clearly distinguish the odour and taste sensors' responses. The HS-GC-IMS analysis identified 65 volatile compounds across the treatments. The volatile compounds' concentrations increased as the HVCP treatment time was increased from 0 to 300 s. The significant compounds contributing to EWP characterisation include heptanal, ethylbenzene, ethanol, acetic acid, nonanal, heptacosane, 5-octadecanal, decanal, p-xylene, and octanal. Thus, this study shows that HVCP could be utilised to modify and improve the EWP flavour attributes.

Characterization of the Flavor Profile of Bigeye Tuna Slices Treated by Cold Plasma Using E-Nose and GC-IMS

To avoid heat, treatment induces numerous physicochemical changes under severe conditions in the tuna, cold plasma (CP), as a non-thermal technology, possess objective potential on tuna processing. The effect of cold plasma on the volatile flavor compounds of bigeye tuna (Thunnus obesus) sashimi has been evaluated using electronic nose (E-nose) and gas chromatography-ion mobility spectrometry (GC-IMS). GC–IMS results revealed a total of 33 volatile compounds in tuna slices. The effect of CP treatment on tuna flavor was not significant, furthermore CP could protect volatile freshness compounds such as 1-hexanol. Principal component analysis (PCA) of the E-nose and GC–IMS results could effectively differentiate the effect of storage to tuna sashimi. There was a high correlation between the E-nose and GC–IMS results, providing a theoretical basis for establishing the flavor fingerprint of tuna sashimi.

Investigation of fermentation-induced changes in the volatile compounds of Trachinotus ovatus (meixiangyu) based on molecular sensory and interpretable machine-learning techniques: Comparison of different fermentation stages

Fermented golden pomfret (Trachinotus ovatus) is appreciated by local consumers owing to its distinct flavor. Electronic nose (E-nose) and gas chromatography-ion mobility spectrometry (GC-IMS) technologies were used to analyze the changes in volatile compounds responsible for evolution of the golden pomfret odor profile during fermentation. Forty-five ion peaks were detected using GC-IMS. Although aldehydes represented the major initial volatile compound group, their levels decreased as fermentation proceeded. Between 3 and 15 days, increased levels of esters contributed to a stable volatile organic compounds profile. After 18 days, high levels of indole and pyrazines were detected. Eleven key volatile compounds were screened based on partial least squares discriminant analysis (PLS-DA). Back propagation artificial neural network (BP-ANN) predicted the fermentation stage enabling the development of better strategies to regulate golden pomfret fermentation. This study provided a theoretical basis for real-time monitoring and quality control of Chinese fermented golden pomfet.

The Aroma Fingerprints and Discrimination Analysis of Shiitake Mushrooms from Three Different Drying Conditions by GC-IMS, GC-MS and DSA

The aroma fingerprints and discrimination analysis of shiitake mushrooms under different drying conditions were performed by GC-IMS, GC-MS, and descriptive sensory analysis (DSA) with advanced chemometric methods. Three samples (A, B, and C) were treated with varied drying degree and rate. The sample A and C were at the same drying degree and the sample B and C were at the same drying rate. The GC-IMS volatile fingerprints, including the three-dimensional topographic map, topographic map, and gallery plot, showed that 29 compounds showed higher signal intensities in sample B. Moreover, 28 volatile compounds were identified by HS-SPME-GC-MS and only 8 compounds were ever detected by GC-IMS. The sample B not only had more varieties of volatile compounds, but also showed significant higher contents than sample A and C, especially C8 compounds (p < 0.05). Additionally, sample B showed the highest intensity in mushroom-like, chocolate-like, caramel, sweat, seasoning-like, and cooked potato-like odors by DSA. PCA, fingerprint similarity analysis (FSA) and PLSR further demonstrated that the sample B was different from sample A and C. These results revealed that samples with different drying degree were different and drying degree exerted more influence on the volatile flavor quality than the drying rate. This study will provide a foundation and establish a set of comprehensive and objective methods for further flavor analysis.

Effect of Microbial Fermentation on the Fishy-Odor Compounds in Kelp (Laminaria japonica)

Kelp (Laminaria japonica) is an important marine resource with low cost and rich nutrition. However, its fishy odor has compromised consumer acceptance. In this study, the effects of fermentation with Lactobacillus plantarum FSB7, Pediococcus pentosaceus CICC 21862 and Saccharomyces cerevisiae SK1.008 on fishy notes in kelp was studied using gas chromatography-mass spectrometry (GC-MS), gas chromatography-ion mobility spectrometry (GC-IMS) and odor activity values (OAVs). Forty-four volatile organic compounds (VOCs) were identified in unfermented kelp, most of which were aldehydes, followed by alkanes, alcohols and ketones. Among them were 19 volatile compounds with OAV greater than one. Substances containing α,β-unsaturated carbonyl structure (1-Octen-3-one, (E,Z)-2,6-nonadienal, (E,E)-2,4-decadienal, etc.) are the main contributors to kelp fishy odor. The number of VOCs in kelp samples fermented by L. plantarum, P. pentosaceus and S. cerevisiae were decreased to 22, 24 and 34, respectively. GC-IMS shows that the fingerprint of the S. cerevisiae fermented sample had the most obvious changes. The disappearance of 1-octen-3-one and a 91% decrease in unsaturated aldehydes indicate that S. cerevisiae was the most effective, while L. plantarum and P. pentosaceus only reached 43-55%. The decrease in kelp fishy notes was related to the decrease in α,β-unsaturated carbonyl groups. The experimental results show that odor reduction with fermentation is feasible.

Discrimination of rice varieties using smartphone-based colorimetric sensor arrays and gas chromatography techniques

A smartphone-based colorimetric sensor array system was established for discrimination of rice varieties having different geographical origins. Purposely, aroma profiling of nine rice varieties was performed using solid-phase microextraction gas chromatography-mass spectrometry. Alcohols, aldehydes, alkanes, ketones, heterocyclic compounds, and organic acids represent the abundant compounds. Colorimetric sensor array system produced a characteristic color difference map upon its exposure to volatile compounds of rice. Discrimination of rice varieties was subsequently achieved using principal component analysis, hierarchical clustering analysis, and k-nearest neighbors. Rice varieties from same geographical source were clustered together in the scatter plot of principal component analysis and hierarchical clustering analysis dendrogram. The k-nearest neighbors algorithm delivered optimal results with discrimination rate of 100% for both calibration and prediction sets using sensor array system. The smartphone-based colorimetric sensor array system and gas chromatography technique were able to effectively differentiate rice varieties with the advantage of being simple, rapid, and low-cost.

Effect of different fertilizers on the physicochemical properties, chemical element and volatile composition of cucumbers

The main purpose of the present study was to investigate the effect of different fertilizers on the physicochemical properties, multi-element and volatile composition of cucumbers. All samples were divided into five groups according to different combinations and amounts of chicken manure, NPK 17-17-17 fertilizer and microbial fertilizer. The co-application of chicken manure (120,000 kg/ha) and NPK 17-17-17 fertilizer (750 kg/ha) achieved the best texture properties, whereas the addition of the microbial fertilizer at 6000 kg/ha significantly improved the color quality of cucumbers. Similarly, the co-application of chicken manure, NPK 17-17-17 fertilizer and microbial fertilizer at 6000 kg/ha enhanced the number and abundance of volatile components detected in the cucumbers. Cucumbers from the control group contained the highest levels of most of the determined elements. Overall, a combination of chicken manure, NPK 17-17-17 fertilizer and 6000 kg/ha microbial fertilizer is recommended as a relatively efficient fertilizer utilization for cucumbers.

Aroma characteristics of traditional Huangjiu produced around Winter Solstice revealed by sensory evaluation, gas chromatography-mass spectrometry and gas chromatography-ion mobility spectrometry

Traditional Huangjiu (a kind of traditional Chinese rice wine) produced around Winter Solstice has higher quality and a more harmonious aroma than those produced during other periods. To determine the specific differences in aroma characteristics, sensory evaluation, gas chromatography-mass spectrometry (GC-MS) and gas chromatography-ion mobility spectrometry (GC-IMS) were used to analyze the volatile profiles of the traditional Huangjiu samples produced under different ambient temperature conditions. The sensory evaluation results showed that the aroma attributes of wheat, sweet, ester, alcoholic and sauce were stronger for the samples fermented near Winter Solstice than those for the other samples. GC-MS combined with heatmap analysis showed that with the decrease in average ambient temperature, the contents of esters such as diethyl succinate and ethyl butanoate gradually increased, and the contents of alcohols such as phenylethyl alcohol, 2-methylpropanol and 3-methylbutanol gradually decreased. Some key aroma compounds, such as ethyl butyrate (OAV: 97-151), nonanal (OAV: 189-200), ethyl octanoate (OAV: 859-1134) and ethyl phenylacetate (OAV: 307-353), were more abundant in the samples fermented near Winter Solstice than the other samples. The visualization of GC-IMS suggested that isoamyl acetate, 2-methylpropyl acetate, ethyl 3-methylbutyrate, and ethyl 2-methylbutanoate were enriched near Winter Solstice. Together, the results suggested that the traditional Huangjiu produced around Winter Solstice contained more flavor volatiles and had better aroma quality than those produced during other periods.