Solid-phase Microextraction Gas Research Articles

Sensory and chemical characterization of chestnuts processed in different methods using instrumental analyses and the Check-all-that-apply method

Chestnuts are known for their unique sensory characteristics and nutritional value. However, the changes in their sensory attributes after processing remain unclear. This study used instrumental analysis and sensory evaluation combined with multivariate statistical analysis to investigate the effect of packaging and thermal sterilization procedures on the sensory characteristics of chestnuts. The results showed that the significant variations (p < 0.05) between the different processing methods for chestnuts were revealed via the texture analysis, headspace solid-phase microextraction gas chromatography × gas chromatography-time of flight-mass spectrometry (HS-SPME-GC×GC-TOF-MS), and check-all-that-apply (CATA) sensory evaluation. The packaging had a more significant influence on the sensory quality of the chestnuts than thermal sterilization procedures. The HS-SPME-GC×GC-TOF-MS identified 116 volatile compounds, and the partial least squares-discriminant analysis (PLS-DA) identified the 28 volatile compounds responsible for the similarities and differences among different processing methods of chestnuts. Principal component analysis (PCA) combined with texture analysis and the fingerprint of HS-SPME-GC×GC-TOF-MS, as well as the correspondence analysis (CA) analysis of CATA, could discriminate samples from different packaging of chestnuts. This study provides chestnuts processing recommendations for satisfying consumer preferences and predicting possible related quality changes.

An insight into trichomes-deficiency and trichomes-rich black teas by comparative metabolomics: The impact of oxidized trichomes on metabolic profiles and infusion color

Tea trichomes were regarded as an essential evaluation index for reflecting tea flavor quality in terms of aroma and influence on infusion color. This study reveals the impact of golden oxidized trichomes on the color, volatile and non-volatile metabolites of black teas through comparative metabolomics combined quantitative analysis on hongbiluo (trichomes-deficiency black teas), hongjinluo (trichomes-rich black teas), and trichomes (from hongjinluo). Forty-six volatile components were detected using headspace solid-phase microextraction gas chromatography-mass spectrometry, while the results suggested that the contribution of trichomes to black teas is limited. A total of 60 marker non-volatile compounds were identified, including catechins, catechin oxidation products, flavonoid glycosides, organic acids, hydrolysable tannins and amino acids. Notably, p-coumaroyl-kaempferol glucosides, and catechin dimers demonstrated high levels in independent trichomes and showed a positive correlation with the brightness and yellow hue of black tea infusions, specifically kaempferol 3-O-di-(p-coumaroyl)-hexoside. Furthermore, results from fractional extraction analysis of separated trichomes provided that N-ethyl-2-pyrrolidinone-substituted epicatechin gallates, acylated kaempferol glycosides, and chromogenic catechins dimers, such as theaflavins, were primary color contributors in oxidized trichomes. Especially, we found that epicatechin gallate (ECG) and its derivates, 3′-O-methyl-ECG and N-ethyl-2-pyrrolidinone-substituted ECG, highly accumulated in trichomes, which may be associated with the varieties of hongbiluo and hongjinluo black teas. Eventually, addition tests were applied to verify the color contribution of trichome mixtures. Our findings employed comprehensive information revealing that golden oxidized trichomes contributed significantly to the brightness and yellow hue of black tea infusion, but their contribution to the aroma and metabolic profile is limited. These findings may contribute to the effective modulation of the infusion color during black tea production by regulating the proportion of tea trichomes or screening trichomes-rich or deficiency varieties.

Impact of pre- and post-fermentation fining with polyvinylpolypyrrolidone on the chemical stability and aromatic profile of Viognier wine.

Polyvinylpolypyrrolidone (PVPP) is a synthetic, insoluble polymer that can be added to white wines to improve the chemical stability of the final product by precipitating unstable low molecular weight phenolic compounds responsible for visual defects and undesirable flavor characteristics (e.g., excessive bitterness and/or astringency). The objective of this study was to characterize the effects of PVPP on the quality characteristics of Viognier wine when added pre- or post-fermentation as compared to an untreated control wine. Both PVPP-treated wines contained significantly lower concentrations of monomeric phenolics and browning pigments than the control wine (p≤0.05). The addition of PVPP prior to fermentation conferred protection against oxidation of the wine as measured by acetaldehyde concentration (p≤0.05). Analysis of the volatile aroma profile of each wine by headspace solid phase microextraction gas chromatographymass spectrometry (HS-SPME-GC-MS)revealed that the overarching aroma profiles of the PVPP-treated wines were significantly different from the control wine, but there was no difference between wines treated with PVPP pre-fermentation versus those treated post-fermentation. Specifically, statistically significant differences were observed in 9 of the 22 quantified aroma compounds, including those notably associated with the "stone fruit" aroma of Viognier. A negative correlation was identified between aroma compound concentration removal and the hydrophobicity of each compound, suggesting that the observed differences in aroma may be due to adsorption of aroma compounds by PVPP. The findings from this study present risks and benefits to wine quality upon treatment with PVPP at commercially recommended levels, and provide potentially valuable information for industrial wine producers.

Screening and tentatively identifying of volatile hazards of desiccant and deoxidizer in food package

Food desiccant and deoxidizer are becoming more prevalent in food preservation, where they keep food in good quality for longer periods of time by absorbing moisture and oxygen. In such a way that they are in direct contact with the food inside the food package. However, their safety is still unclear and they must be fully screened and identified. In this study, the volatiles in five representative desiccants and two deoxidizers in the market were screened and tentatively identified by headspace solid-phase microextraction gas chromatography coupled with mass spectrometry (HS-SPME-GC-MS), compared with NIST spectral libraries, and combined with manual analysis. Specific migration limits are provided in accordance with EU NO 10/2011. Risk classes are predicted for substances lacking toxicological data through toxtree software. More than half of the substances were initially screened with toxicological data, seven with specific migration limits, three Cramer III substances, the remainder being Cramer I substances and substances with no risk level. The high-risk substances were further analyzed and traced back to their potential sources. However, there are a few substances for which the potential sources are still unclear and require further research. Despite this, this study has established the safety of desiccant and deoxidizer for use in food to a large extent, providing a solid basis for the future development of the industry.

Correlation between physicochemical properties, flavor characteristics and microbial community structure in Dushan shrimp sour paste

Dushan shrimp sour paste (DSSP), a traditional Guizhou condiment, and its unique flavor is determined by the fermentation microbiota. However, the relationship between the microbiota structure and its flavor remains unclear. This study identified 116 volatile flavor compounds using electronic nose and headspace solid-phase microextraction-gas chromatography mass spectrometry (HS-SPME-GC–MS) techniques, of which 19 were considered as key flavor compounds, mainly consisting of 13 esters and 1 alcohol. High-throughput sequencing technique, the bacterial community structure of nine groups of DSSPs was determined. Further analysis revealed Vagococcus, Lactococcus, and Tepidimicrobium as key bacteria involved in flavor formation. This study contributes to our understanding of the relationship between bacterial communities and the flavor formation, and provides guidance for screening starter culture that enhance the flavor of DSSP in industrial production.

Flavor release from walnut kernels in an in-vitro mastication model with decoupled oral parameters

Consumer preferences for walnut products are largely determined by the flavors released during mastication. In this study, a peeled walnut kernel (PWK) model was established with oral parameters decoupled using a Hutchings 3D model. The model explored in vitro variations using head-space solid-phase microextraction-gas chromatography-mass spectrometry and intelligent sensory techniques. The fracture strength, hardness, particle size, adhesiveness, springiness, gumminess, and chewiness were significantly reduced during mastication. We identified 61 volatile compounds and found that 2,5-dimethyl-3-ethylpyrazine is a key component, releasing predominantly baking and milky notes. Glutamic acid, alanine, arginine, and sucrose were identified as the key compounds in taste perception. The method can help establish a mastication model for nuts and facilitate breakthroughs in the development of walnut products and processing methods.

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

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

Revealing the microbial diversity and volatile flavor formation in finger citron kombucha by metagenomic and GC-MS analysis

Kombucha is a kind of health drink formed by the metabolism of Symbiotic Culture of Bacteria and Yeast (SCOBY) composed of yeast, acetic acid bacteria and lactic acid bacteria, which is popular among researchers and fond of consumers because of its antioxidant and hypoglycemic effects. In this study, the finger citron kombucha with different fermentation time (2, 4, 6, 8 day) were analyzed by headspace solid phase micro-extraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and metagenomic sequencing. The results showed that a total of 76 volatiles were identified, including 15 key volatiles, such as linalool, geraniol, α-terpinene, and limonene, which had a great influence on the flavor of kombucha. Metagenomic analysis showed that unclassified-g-Gluconobacter, Komagataeibacter saccharivorans, Gluconobacter-sp.-R71656 and other microorganisms were the dominant species in finger citron kombucha. Through the correlation heat map analysis of volatiles and microbial composition, it was found that Gluconobacter had a positive effect on the formation of most volatiles of kombucha. In addition, Novacetimonas hansenii, Brettanomyces bruxellensis and Wickerhamiella sorbophila were also closely related to the flavor formation of kombucha. This study provided a theoretical basis for finding the key aroma-producing microorganisms in the fermentation process of finger citron kombucha and the subsequent construction of SCOBY.

Integration of transcriptome and metabolome reveals regulatory mechanisms of volatile flavor formation during tomato fruit ripening

Tomato is an important economic crop all over the world. Volatile flavors in tomato fruit are key factors influencing consumer liking and commercial quality. However, the regulatory mechanism controlling the volatile flavors of tomatoes is still not clear. Here, we integrated the metabolome and transcriptome of the volatile flavors in tomato fruit to explore the regulatory mechanism of volatile flavor formation, using wild and cultivated tomatoes with significant differences in flavors. A total of 35 volatile flavor compounds were identified, based on the solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS). The content of the volatiles, affecting fruit flavor, significantly increased in the transition from breaker to red ripe fruit stage. Moreover, the total content of the volatiles in wild tomatoes was much higher than that in the cultivated tomatoes. The content variations of all volatile flavors were clustered into 10 groups by hierarchical cluster and Pearson correlation analysis (PCC). The fruit transcriptome was also patterned into 10 groups, with significant variations both from the mature green to breaker fruit stage and from the breaker to red ripe fruit stage. Combining the metabolome and the transcriptome of the same developmental stage of fruits by co-expression analysis, we found that the expression level of 1 182 genes was highly correlated with the content of volatile flavor compounds, thereby constructing two regulatory pathways of important volatile flavors. One pathway is tetrahydrothiazolidine N-hydroxylase (SlTNH1)-dependent, which is regulated by two transcription factors (TFs) from the bHLH and AP2/ERF families, controlling the synthesis of 2-isobutylthiazole in amino acid metabolism. The other is lipoxygenase (SlLOX)-dependent, which is regulated by one TF from the HD-Zip family, controlling the synthesis of hexanal and (Z)-2-heptenal in fatty acid metabolism. Dual-luciferase assay confirmed the binding of bHLH and AP2/ERF to their structural genes. The findings of this study provide new insights into volatile flavor formation in tomato fruit, which can be useful for tomato flavor improvement.

Identification of Organic Solvents in Agrochemicals Intoxication Cases

In South Korea, deaths caused by poisoning are mostly suicides due to drug overdoses, or agrochemical poisonings. Even though the latter is becoming less frequent, they are still occurring in large numbers across the country. In some cases, deaths result from toxicity of organic solvents contained in the agrochemical products. In this study, we identified organic solvents in post-mortem blood of acute agrochemical poisoning cases using solid phase microextraction-gas chromatography/mass spectrometry with black fiber. Out of 42 cases, organic solvents were detected in 29, with toluene and butanol detected simultaneously in 13 cases. In these 13 cases, the original pesticides were of various types, including organophosphorus compounds, carbamate, nicotine, and oxadiazine. Xylene and ethyl benzene were simultaneously detected six times. In these six cases, the original pesticides were mainly pyrethroid-based pesticides, such as cypermethrin and deltamethrin. Methoxypropanol was detected in five cases in which the water-soluble pesticide glufosinate was detected. These organic solvents may cause acute poisoning and even death in some agrochemical poisoning cases.

Integrative metagenomics, volatilomics and chemometrics for deciphering the microbial structure and core metabolic network during Chinese rice wine (Huangjiu) fermentation in different regions

Huangjiu is a spontaneously fermented alcoholic beverage, that undergoes intricate microbial compositional changes. This study aimed to unravel the flavor and quality formation mechanisms based on the microbial metabolism of Huangjiu. Here, metagenome techniques, chemometrics analysis, and headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC–MS) metabolomics combined with microbial metabolic network were employed to investigate the distinctions and relationship between the microbial profiles and the quality characteristics, flavor metabolites, functional metabolic patterns of Huangjiu across three regions. Significant variations (P < 0.05) were observed in metabolic rate of physicochemical parameters and biogenic amine concentration among three regions. 8 aroma compounds (phenethyl acetate, phenylethyl alcohol, isobutyl alcohol, ethyl octanoate, ethyl acetate, ethyl hexanoate, isoamyl alcohol, and diethyl succinate) out of 448 volatile compounds were identified as the regional chemical markers. 25 dominant microbial genera were observed through metagenomic analysis, and 13 species were confirmed as microbial markers in three regions. A metabolic network analysis revealed that Saccharomycetales (Saccharomyces), Lactobacillales (Lactobacillus, Weissella, and Leuconostoc), and Eurotiales (Aspergillus) were the predominant populations responsible for substrate, flavor (mainly esters and phenylethyl alcohol) metabolism, Lactobacillales and Enterobacterales were closely linked with biogenic amine. These findings provide scientific evidence for regional microbial contributions to geographical characteristics of Huangjiu, and perspectives for optimizing microbial function to promote Huangjiu quality.

Yeasts volatile organic compounds (VOCs) as potential growth enhancers and molds biocontrol agents of mushrooms mycelia

Volatile organic compounds (VOCs) produced by yeasts can positively affect crops, acting as antifungals or biostimulants. In this study, Aureobasidium pullulans and Metschnikowia pulcherrima were evaluated as potential antagonists of Trichoderma spp., common fungal pathogen in mushroom cultivation. To assess the biocontrol ability and biostimulant properties of the selected yeast species, in vitro co-culture and VOCs exposure assays were conducted. In both assays, VOCs produced by Aureobasidium spp. showed the stronger antifungal activity with a growth inhibition up to 30 %. This result was further confirmed by the higher volatilome alcohol content revealed by solid phase microextraction-gas chromatography mass spectrometry (SPME/GC–MS). Overall, Aureobasidium strains can be potentially used as biocontrol agent in Pleorotus ostreatus and Cyclocybe cylindracea mycelial growth, without affecting their development as demonstrated by VOCs exposure assay and Fourier-transform infrared spectroscopy (FT-IR). Conversely, M. pulcherrima was characterized by a lower or absent antifungal properties and by a volatilome composition rich in isobutyl acetate, an ester often recognized as plant growth promoter. As confirmed by FT-IR, Lentinula mycelia exposed to M. pulcherrima VOCs showed a higher content of proteins and lipids, suggesting an improvement of some biochemical properties. Our study emphasizes that VOCs produced by specific yeast strains are potentially powerful alternative to synthetic fungicide in the vegetative growth of mushroom-forming fungi and also able to modify their biochemical composition.

Accentuation of the browning characteristics and functional properties of aged tomatoes (Solanum lycopersicum cv.)

Moisture-assisted aging technology (MAAT) is a green process that improves browning characteristics and functionalities. This study investigated the physicochemical and functional characteristics of aged tomatoes. MAAT modulated carotenoids biotransformation from esterified to free form (Fourier-transform infrared spectroscopy 1738, 2851, and 2922 cm−1) and generated primary and secondary oxidation volatiles, such as 4-terpineol, α-terpineol, and γ-terpineol (Headspace solid-phase microextraction gas chromatography-mass), which contributed woody and clove odors. Total flavonoids and α-glucosidase activity inhibitory were significantly increased from 1207.729 to 2318.204 mg RE/100 g DW and 77.703% to 86.851%, respectively. We discovered different synthesis pathways of 5-HMF and furfural under different water activities; this breakthrough may set furfural as an important factor in quality control of MAAT products in the future. Thus, MAAT can modulate the chemical form of tomato carotenoids, improve functionalities, and generate unique woody odor volatiles. These results may be applied to health food development in the food industry.

EXPLORING THE IMPACT OF DIFFERENT PACKAGING TYPES AND REPEATED PACKAGE OPENING ON VOLATILE COMPOUND CHANGES IN GROUND ROASTED COFFEE

In this study, the dynamics of volatile compound alterations during the storage of ground roasted coffee in various packaging were investigated using solid-phase microextraction-gas chromatography-mass spectrometry. Each type of packaging underwent repeated opening and closing, simulating the gradual consumption behavior of the consumer who consumes ground coffee in smaller doses over time. The experimental results revealed that after 30 days of storage, 35 to 45% of the volatile substances originally present in the coffee were lost regardless of the type of packaging used. Notably, storing coffee in a paper sachet proved to be the least effective method, resulting in a loss of over 80% of all volatile coffee substances during this storage period.

Identifying potential breath biomarkers for early diagnosis of papillary thyroid cancer based on solid-phase microextraction gas chromatography-high resolution mass spectrometry with metabolomics.

Thyroid cancer incidence rate has increased substantially worldwide in recent years. Fine needle aspiration biopsy (FNAB) is currently the golden standard of thyroid cancer diagnosis, which however, is invasive and costly. In contrast, breath analysis is a non-invasive, safe and simple sampling method combined with a promising metabolomics approach, which is suitable for early cancer diagnosis in high volume population. This study aims to achieve a more comprehensive and definitive exhaled breath metabolism profile in papillary thyroid cancer patients (PTCs). We studied both end-tidal and mixed expiratory breath, solid-phase microextraction gas chromatography coupled with high resolution mass spectrometry (SPME-GC-HRMS) was used to analyze the breath samples. Multivariate combined univariate analysis was applied to identify potential breath biomarkers. The biomarkers identified in end-tidal and mixed expiratory breath mainly included alkanes, olefins, enols, enones, esters, aromatic compounds, and fluorine and chlorine containing organic compounds. The area under the curve (AUC) values of combined biomarkers were 0.974 (sensitivity: 96.1%, specificity: 90.2%) and 0.909 (sensitivity: 98.0%, specificity: 74.5%), respectively, for the end-tidal and mixed expiratory breath, indicating of reliability of the sampling and analysis method CONCLUSION: This work not only successfully established a standard metabolomic approach for early diagnosis of PTC, but also revealed the necessity of using both the two breath types for comprehensive analysis of the biomarkers.

Comprehensive analysis of the dynamic changes of volatile and non-volatile metabolites in boletus edulis during processing by HS-SPME-GC–MS and UPLC-MS/MS analysis

In order to investigate the dynamic changes of flavor compounds, Ultra Performance Liquid Chromatography Tandem Mass Spectrometry (UPLC-MS/MS) combined with Headspace Solid Phase Microextraction Gas Chromatography Mass Spectrometry (HS-SPME-GC–MS) was used to detect the metabolites in different drying processes. A total of 80 volatile compounds and 1319 non-volatile compounds were identified. The trend in the changes of C-8 compounds and sulfur-containing compounds were generally consistent with the trend of key enzyme activities. 479 differential metabolites were identified and revealed that metabolic profiles of compounds in Boletus edulis were altered with increased organic acids and derivatives and lipids and lipid-like molecules. Fatty acids and amino acids were transformed into volatile compounds under the action of enzymes, which played a significant role in the formation of the distinctive flavor of Boletus edulis. Our study provided a theoretical support for fully comprehending the formation mechanism of flavor from Boletus edulis during drying processes.

Volatile flavor behavior characterization of Hericium erinaceus during postharvest storage using E-nose, HS-GC-IMS, and HS-SPME-GC–MS after treated with electron-beam generated X-ray irradiation

Flavor alteration is a crucial factor affecting the quality of mushrooms during preservation. The dynamic variations of volatile profiles of fresh Hericium erinaceus with electron-beam generated X-ray irradiation were investigated by combining E-nose, headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS), and headspace solid-phase microextraction gas chromatography–mass spectrometry (HS-SPME-GC–MS). E-nose analysis achieved rapid discrimination in all treatments over storage time. 65 and 73 volatile organic compounds (VOCs) were identified by HS-GC-IMS and HS-SPME-GC–MS, respectively. Thereinto, 1-octen-3-ol, 1-octen-3-one, and 2-octanone were screened out as the characteristic VOCs, which contents declined during storage. While the contents of (E)-2-octenal, (E)-2-nonenal, and 1-octanol increased. The flavor profile changes from distinct mushroom and floral odor to an intense alcohol and fatty odor. Notably, one-kGy irradiation remained more volatiles and denser mushroom odor after storage. Multivariate analysis further confirmed that 1.0 kGy irradiation contributed to the overall aroma retention during postharvest storage of H. erinaceus.

Effect of incubation temperature on identification of key odorants of sewage sludge using headspace GC analysis

Currently, headspace gas chromatography-mass spectrometry is a widely used method to identify the key odorants of sludge. However, the effect of incubation temperature on the generation and emission of key odorants from sludge was still uncertain. Thus, in this paper, headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and headspace gas chromatography-coupled ion mobility spectrometry (HS-GC-IMS) were carried out to analyze the volatiles emitted from the sludge incubated at different temperatures (30 °C, 50 °C, 60 °C, and 80 °C). The results indicated that the total volatile concentration of the sludge increased with temperatures, which affected the identified proportion of sludge key odorants to a certain extent. Differently from the aqueous solutions, the variation of volatile emission from the sludge was inconsistent with temperature changes, suggesting a multifactorial influence of incubation temperature on the identification of sludge odorants. The microbial community structure and adenosine triphosphate (ATP) metabolic activity of the sludge samples were analyzed at the initial state, 30 °C, and 80 °C. Although no significant effect of incubation temperature on the microbial community structure of the sludge, the incubation at 80 °C led to a noticeable decrease in microbial ATP metabolic activity, accompanied by a significant change in the proportion of odor-related microorganisms with low relative abundances. Changes in the composition and activity of these communities jointly contributed to the differences in odor emission from sludge at different temperatures. In summary, the incubation temperature affects the production and emission of volatiles from sludge through physicochemical and biochemical mechanisms, by which the microbial metabolism playing a crucial role. Therefore, when analyzing the key odorants of sludge, these factors should be considered.

Identification of volatile and non-volatile migrants released during sous vide cooking by UPLC-IMS-QTOF and DI-SPME-GC-MS using a design of experiments approach

The rise of new culinary advances combined with science has made it possible to find new optimum methods of cooking, such as vacuum cooking (Sous Vide), that allow achieving pleasant textures, preserving the genuine nature of the food and also its original flavour. Sous Vide involves the direct contact of plastic materials with food during cooking, causing the possible release of chemical compounds that may alter the properties of the food and pose a risk to human health. In this work, the migration kinetics that takes place during this cooking process have been estimated thanks to a design of experiments (DoE). DoE has been applied to 4 samples of vacuum cooking bags containing 3 food simulants (ethanol 10%, acetic acid 3% and isooctane) under typical cooking conditions of the culinary technique. The study also allowed the identification of the main volatile and non-volatile migrants that can be transferred from this particular packaging. Twenty-nine non-volatile species were identified by ultra-high performance liquid chromatography coupled to a quadrupole-time-of-flight ion-mobility separation mass spectrometer (UPLC-IMS-QTOF) and sixty-four volatile species were identified by solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS). Furthermore, a comprehensive literature analysis was conducted to explore the applications, origins, and potential toxicity of these compounds.

Impact of salt content on Douchi metabolites: biogenic amines, non-volatile compounds and volatile compounds.

The excessive salt intake associated with Douchi has become a topic of controversy. Addressing this concern and enhancing its market competitiveness necessitates the application of salt reduction fermentation in Douchi. Therefore, to promote the application of salt reduction fermentation in Douchi, a comprehensive study was undertaken aiming to investigate the differences in biogenic amines, volatile compounds and non-volatile compounds in Douchi with varying salt content. The findings unequivocally demonstrate that salt hampers the formation of metabolites in Douchi. As the salt content increased, there was a significant decrease (P < 0.05) in the levels of total acid, amino-type nitrogen and free amino acids in Douchi. Notably, when the salt content exceeded 80 g kg-1, there was a substantial reduction (P < 0.05) in putrescine, lactic acid and malic acid levels. Similarly, when the salt content surpassed 40 g kg-1, β-phenethylamine and oxalic acid levels exhibited a significant decline (P < 0.05). Furthermore, the results of E-nose and principal component analysis based on headspace solid phase microextraction gas chromatography-mass spectrometry revealed notable discrepancies in the volatile compound content between Douchi samples with relatively low salt content (40 and 80 g kg-1) and those with relatively high salt content (120, 160 and 200 g kg-1) (P < 0.05). By employing partial least squares discriminant analysis, eight distinct volatile compounds, including o-xylene, benzaldehyde and 1-octen-one, were identified. These compounds exhibited higher concentrations in Douchi samples with relatively low salt content (40 and 80 g kg-1). The sensory results showed that Douchi samples with lower salt content exhibited higher scores in the soy sauce-like and Douchi aroma attributes. In conclusion, this study significantly enhances our understanding of the impact of salt on metabolites in Douchi and provides invaluable insights for the development of salt reduction fermentation in this context. © 2024 Society of Chemical Industry.