Identification of nonvolatile chemical constituents in Chinese Huangjiu using widely targeted metabolomics

Effects of aging years on taste attributes of Huangjiu and their correlation with non-volatile compounds: A study based on E-tongue, UPLC-MS untargeted metabolomics, and WGCNA

Aging plays a crucial role in enhancing the flavor of Huangjiu. This study aims to elucidate the changes in taste attributes of aged Huangjiu and explore the correlation between non-volatile compounds. It showed that aging made the sourness, bitterness, and astringency more pronounced. The content of organic acids and amino acids exhibited specific patterns with aging years. The total taste activity value of organic acids showed an increasing trend, peaking at 54.40 in Huangjiu aged 15 years, which served as a key indicator of sourness intensity. A total of 22 potential contributors to umami and 18 to bitterness were screened based on weighted gene coexpression network analysis. The total content of potential umami contributors was significantly higher in fresh Huangjiu and aging stage I, but declined in later periods, while bitterness contributors increased gradually throughout the aging process. This study provided theoretical support for the taste characteristics of aged Huangjiu.

Influence of phloem lectin CsPP2-A1 on aphid development via mediation of phenylpropanoid and flavonoid biosynthesis in cucumber

BACKGROUND

Aphid, Aphis gossypii Glover, is a pest that significantly affects cucumbers (Cucumis sativus L.). Phloem protein 2 (PP2) is a conserved phloem lectin. Our previous study showed that the expression of CsPP2-A1 under aphid attack affected the accumulation of flavonoids and total phenolics in cucumber. The novel mechanism of lectin CsPP2-A1 mediating secondary metabolites affecting aphid resistance in cucumbers needs to be investigated.

RESULTS

The weight and length of aphids on CsPP2-A1 overexpression (CsPP2-A1-OE) cucumber plants significantly reduced compared to wild-type (WT). Conversely, aphids on CsPP2-A1 RNA interference (CsPP2-A1-RNAi) plants showed the opposite trend. Using secondary metabolomics, small molecular weight secondary metabolites were qualitatively and quantitatively assessed in WT and transgenic cucumber plants after aphid inoculation. The overexpression of CsPP2-A1 resulted in the up-regulation of differential metabolites (DMs) in phenylpropanoid biosynthesis, whereas interference expression of CsPP2-A1 led to a down-regulation of DMs in the flavonoid biosynthesis. Concurrently, it was observed that the CAD activity and the expression of the CsPAL, and CsCAD in OE-2 were up-regulated significantly. A significant reduction in the activities of CHI, F3H, and the expression of CsF3H, CsCHS, CsFLS, and CsCCR was noted in RNAi-2.

CONCLUSION

CsPP2-A1 indirectly affects the growth and development of aphids via mediation of phenylpropanoid and flavonoid biosynthesis. The indirect effects of the interaction of CsPP2-A1 with aphids offer insights into plant-insect interaction studies. © 2025 Society of Chemical Industry.

A novel aggregation-induced emission-featured hyperbranched poly(amido amine)s stabilized copper nanoclusters‑cerium (III) sensor for detection of thiol flavor compounds in processed meat

Thiol flavor compounds are a class of flavoring ingredients that contribute significantly to food flavor. However, rapid discrimination of multiple thiol-flavor compounds remain a challenge. In this study, a ratiometric fluorescent sensor (TPE-ssHPA@Cu NCs-Ce3+) with dual-channel fluorescence features was developed using tetraphenylethene-embedded hyperbranched poly(amidoamine) as a template to stabilize the copper nanocluster‑cerium ions. The sensor was explored for the specific discrimination of six typical thiol flavor compounds, each producing diverse fluorescent fingerprints that were further identified using pattern recognition methods. The sensor achieved a rapid response in identifying thiol flavor compounds and multicomponent mixtures, with detection limits of 0.32-3.13 μM. Furthermore, it was successfully applied to differentiate between the different types and cooking times of meat broths.

Relatively reliable and rapid identification of colorant compounds in food matrices by HPLC-DAD-QTOF-MS combined with theoretical calculation

A new convenient method for identifying colorant compounds (CCs) in food matrices was developed using high-performance liquid chromatography with a diode array detector and quadrupole-time-of-flight mass spectrometer (HPLC-DAD-Q/TOF-MS) combined with theoretical calculations. A model sample containing three typical CCs was completely separated via HPLC-DAD. The obtained 3D ultraviolet-visible (UV-vis) spectra revealed the maximum absorption wavelengths (MAWs) of all CCs (yellow, 430 nm; red, 520 nm; blue, 620 nm) in the range of 400-800 nm, and their colors were determined based on their MAWs. Temporary structures of the CCs were obtained using Q/TOF-MS analysis. Theoretical calculations were then performed to obtain the theoretical MAWs and colors of the CCs according to their calculated UV-vis spectra based on temporary structures. The structures of the CCs were confirmed without the need for authoritative standards by comparing the consistency between their experimental and theoretical MAWs and colors. This method is particularly suitable for identifying CCs or compounds with UV-Vis absorption, including new compounds, compounds for which standards are difficult to obtain, and known compounds without reporting relevant molecular information.

Decoding of the enhancement of saltiness perception by aroma-active compounds during Hunan Larou (smoke-cured bacon) oral processing

The enhancement of saltiness induced by odrants perceived from the retronasal cavity during Larou oral processing was analyzed. During the oral processing of Xiangtan Larou, the smoky attribute was the dominant when chewing 0-15 times, followed by the savory (15-24 times) and meaty (24-42 times). Partial least squares analysis predicted 33 aroma compounds from the retronasal cavity significantly (p < 0.05) contributing to the aroma perception. A total of 12 aroma compounds with saltiness-enhancement ability were confirmed by odorant-NaCl mixture model experiments. Results revealed that 2-methoxy-4-vinylphenol (1.00-1000.00 μg/L) had the strongest enhancing effect on saltiness at NaCl (2969.85 mg/L), followed by diallyl sulfide (0.156-2.50 μg/L), 2,5-dimethylthiophene (0.156-50.00 μg/L), 2,6-dimethylphenol (1.00-100.00 μg/L), 2,5-dimethylpyrazine (0.391-50.00 μg/L), and 2,3-butanedione (0.50-100.0 μg/L). The sulfur-containing, nitrogen-containing, and phenolic odorants with savory, roasty, sulfide, meaty or smoky, attributes showed the better ability in saltiness enhancement.

Preparation of Fangxian traditional Xiaoqu and its evolution of microbial communities and aroma compounds during fermentation

Fangxian traditional Xiaoqu (FTXQ) is an important factor in the formation of unique aroma of Fangxian Huangjiu. FTXQ with only Polygonum hydropiper L. and FTXQ with Polygonum hydropiper L. and multiple herbs were prepared. Together with their seed Qu, three fermentation broths (FBs) were obtained and used during brewing to investigate differences in microorganisms, aroma compounds, and sensory evaluation. The results indicated that the core communities, including Enterococcus, and Saccharomyces, and 150 volatile aroma compounds, such as phenethyl alcohol were identified, and they showed close relationships. Twenty-three bacterial genera, including Enterococcus, 10 fungal genera like Saccharomyces, and 58 compounds, such as isoamyl octanoate, were the microorganisms and compounds responsible for the differences in the three FBs at different fermentation stages. The herbs added to Xiaoqu could enhance the overall aroma intensities of FBs and probably benefit in inhibiting the production of foodborne pathogens like Cronobacter during brewing.

Targeted/untargeted metabolomics and antioxidant properties distinguish Citrus reticulata 'Chachi' from Citrus reticulata Blanco

Dried citrus peel (DCP), also called "Chen Pi", has edible and medicinal value. However, the specific differences among various sources remain unknown. Herein, we collected six DCP species, namely, one Citrus reticulata 'Chachi' (CZG) and five Citrus reticulata Blanco (CRB). Targeted high-performance liquid chromatography and untargeted ultra-high-performance liquid chromatography-tandem mass spectrometry were employed to comprehensively compare the phenolic compounds and metabolites in DCP. Interestingly, 13 different phenolic compounds were noted in DCP. The total phenolic compound content in all CRB samples (58.86-127.65 mg/g) was higher than that of CZG (39.47 mg/g). Untargeted metabolomic revealed 1495 compounds, with 115 differentially expressed metabolites for CRBs and CZG, particularly flavonoids (38), terpenoids (15), and phenolic acids and derivatives (9). Lastly, antioxidant assays revealed that all CRB samples exhibited higher antioxidant activities compared with CZG. Therefore, our study results provide a theoretical basis for the high-value utilization of citrus peels and their metabolites.

Integrated microbiomic and metabolomic dynamics of Yi traditional fermented liquor

This study examines the microbial community composition, metabolite characteristics, and the relationship between the two during the fermentation process of Yi traditional fermented liquor. Yi traditional fermented foods have a profound historical and cultural background, with significant ethnic characteristics. As a case in point, Yi traditional fermented liquor is typically prepared using local plants or traditional Chinese herbs as fermentation substrates and undergoes a lengthy fermentation process, resulting in a fermented beverage that is reputed to have beneficial effects on human health. These foods are not only characterised by a distinctive flavor profile, but are also perceived to possess certain health benefits in the context of traditional ethnic medicine and wellness practices. The community composition of bacteria and fungi was analyzed using 16S rRNA and ITS1 sequencing technologies, which revealed that microbial diversity was higher in the early stages of fermentation but gradually decreased as fermentation progressed. A total of 130 major volatile flavor compounds and 26 key metabolites were identified at different stages of fermentation. These included acids, sugars, amino acids and flavonoids, which significantly influence the flavor and nutritional value of the fermented products. The study indicates a significant correlation between specific microbial populations (such as yeasts) and key metabolites (such as flavonoids and amino acids). These findings emphasise the significance of the interplay between microbial communities and metabolites in shaping the quality and efficacy of fermented products. They offer a scientific foundation for optimizing traditional fermented food production processes.

The Microbial Diversity and Flavor Metabolism Regulation of Xiangzao During Different Natural Fermentation Time Periods

Xiangzao brine is a special flavored food produced by the natural fermentation of Huangjiu lees. To clarify fermentation time on its quality, this study integrated flavoromics analysis, macro-genomics, and polypeptide omics to analyze the volatile flavor components, microbial species, and flavor peptide distributions of four groups of samples (XZ-1Y, XZ-2Y, XZ-3Y, and XZ-4Y) fermented for 1-4 years. The results showed that the samples fermented for 1 year had the highest contents of umami amino acids and umami peptides, and the samples fermented for 4 years had the highest contents of organic acids and fruity components. In addition, 42 volatile flavor components and 532 peptides were identified, including 393 umami taste peptides and only 37 bitter taste peptides. Correlation analysis showed that ethyl lactate and furfural were positively correlated with the abundance of Nocardioides and Stenotrophomonas, respectively. The abundance of Pseudomonas was positively correlated with four previously unreported umami peptides (FATPR, RELER, FNLERP, and RSSFLGQ) screened by molecular docking. This study provides a reference for the flavor metabolism regulation of Xiangzao brine.

Anti-oxidant activity of 1-(1H-imidazo[4,5-c]pyridin-4-yl)ethenone, a Maillard reaction product derived from fructose and histidine

BACKGROUND

The Maillard reaction involves the interaction of various amino acids and reducing sugars, resulting in food browning. It often produces appealing aromas and flavors. The complexities of the reaction are such that it can be challenging to identify the often numerous and frequently volatile products formed by it. In the present study, we sought to identify and evaluate an unusual product with anti-oxidant activity arising from a fructose-histidine Maillard reaction model. The anti-oxidant profile of this product was assessed by computational means.

RESULTS

The fructose-histidine Maillard reaction products (FH-MRPs) were generated by heating a 2:1 mixture of the sugar and the amino acid at 140 °C for 2 h. Chromatographically separable fractions, labelled DM-1 to DM-8, were obtained using silica gel as the stationary phase and dichloromethane/methanol (DCM/MeOH) mixtures as the mobile one. Fraction DM-5 exhibited the highest 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, and further bio-assay guided fractionation led to isolation and identification of 1-(1H-imidazo[4,5-c]pyridin-4-yl)ethenone (IMPE) as the active principal, the structure of which was established by nuclear magnetic resonance (NMR) spectroscopic and mass spectral techniques. A mechanism for the formation of IMPE from its precursors is proposed. Density functional theory (DFT) calculations suggest this novel heterocyclic compound exerts its anti-oxidant effects by interacting with DPPH and 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals. Essentially, IMPE was non-toxic below 300 ug mL-1, showing a concentration-dependent free radical clearance capacity and reducing power within the 100-1000 μg mL-1 range, and moreover, exhibiting significant Fe2+ chelating abilities wihin the 50-200 μg mL-1 range.

CONCLUSION

This study identified the unique FH-MRP, IMPE, and found that it acts as food antioxidant through the chelation of metal ions. © 2024 Society of Chemical Industry.

Recent advances in photoluminescent fluorescent probe technology for food flavor compounds analysis

The real-time, precise qualitative and quantitative sensing of food flavor compounds is crucial for ensuring food safety, quality, and consumer acceptance. As indicators for food flavor labeling, it is vital to delve deep into the specific ingredient and content of food flavor compounds to assess the food flavor quality, but still facing huge challenges. Photoluminescent fluorescent probe technology, with fast detection and high sensitivity, has shown immense potentials in detecting food flavor compounds. In this review, the classification and optical sensing mechanism of photoluminescent fluorescent probe technology are described in detail. Besides, challenges in applying photoluminescent fluorescent probe technology to analyze food flavor compounds are outlined to indicate future research directions. We hope this review can provide an insight for the applications of photoluminescent fluorescent probe technology in the evaluation of food flavor quality in future.

Decoding the aroma changes of stir-fried shredded potatoes with different soy sauces using thermal desorption combined with gas chromatography-mass spectrometry and sensory evaluation

The aroma changes of stir-fried shredded potatoes (SFSP) were investigated using thermal desorption combined with sensory evaluation and chemometrix analysis. The intensity of the sauce aroma, savory, fatty, and roasty attributes were significantly increased, while the intensity of beany and green attributes were significantly (p < 0.001) inhibited after soy sauce added. Ninety-nine aroma compounds were detected in SFSPs, and aldehydes were the most abundant (relative concentration ratio, 59.18 %-88.80 %). The pH value changes confirmed that soy sauce increased the aroma variances by migration but decreased the total aroma content due to the high oxidation inhibition of unsaturated fatty acids. Eleven aroma compounds contributing to aroma attribute variances were confirmed by partial least squares analysis and aroma-change pattern analysis. Addition test further verified that β-pinene, acetic acid, methanethiol, methional, limonene, 2-acetylpyrrole, ethyl acetate, 1-pentanol, dimethyl trisulfide, dimethyl disulfide, and phenylethanol played a key role in promoting the aroma profiles of SFSP.

Exploring microbial dynamics and metabolic pathways shaping flavor profiles in Huangjiu through metagenomic analysis

In the production of Huangjiu (Chinese rice wine), fermentation microbiota plays a crucial role in flavor formation. This study investigates the microbial dynamics and metabolic pathways that shape the flavor profiles of Huangjiu using different starters. Sensory evaluation and metabolite analysis of six starters revealed significant differences in ester, fruity, and sweet aromas. Saccharomyces, Aspergillus, and Rhizopus were identified as the dominant genera significantly impacting fermentation. Metagenomic species and functional gene annotations of Huangjiu starters elucidated the metabolic pathways for key flavor compounds synthesis pathways. Enzyme genes involved in these pathways were classified and annotated to microbial genera using the NR database, identifying 231 classes of relevant catalytic enzymes and 154 microbial genera. A metabolic relationship between flavor compound formation and different microbial genera was established using catalytic enzymes as a bridge. This study highlights the impact of starter composition on the final product and provides new insights for optimizing starters to enhance Huangjiu flavor quality.

Widely targeted metabolomics analysis reveals the effect of soybean hull polysaccharides on nonvolatile components of plant-based yogurt and its metabolic pattern

Soybean hull polysaccharides (SHPS) enhance the physicochemical properties of plant-based yogurt. However, their effects on the nutritional profile and biochemical mechanisms remain unclear. This study aimed to assess the impact of SHPS addition on the nonvolatile components of plant-based yogurt and its underlying mechanisms through widely targeted metabolomics analysis. The results demonstrated that the addition of SHPS (0.2 %-1.0 % w/v) enhanced the levels of free amino acids, sugars, and organic acids, with the addition of 0.6 % w/v being particularly effective in improving yogurt quality. Widely targeted metabolomics analysis revealed 278 differential metabolites between yogurt supplemented with 0.6 % SHPS (SPY) and the control sample. SHPS increased the content of various metabolites, including amino acids and derivatives, saccharides, organic acids, and flavonoids, among others. Key metabolic pathways affected by SHPS included pantothenate and CoA biosynthesis; valine, leucine, and isoleucine biosynthesis; and benzoate degradation. As the primary component of SHPS, galacturonic acid affected the metabolic products in yogurt by participating in the pentose and glucuronate interconversions and ascorbate and aldarate metabolism pathways. These findings elucidate the role of SHPS in modulating the nutritional composition of plant-based yogurt, offering valuable insights into its functional mechanisms in food processing.

A comprehensive foodomics analysis of rambutan seed oils: Focusing on the physicochemical parameters, lipid concomitants and lipid profiles

A foodomics approach was employed to systematically characterize and compare the quality parameters, antioxidant activity, minor-components, fatty acid composition, and lipid profiles of the seed oils from the three most popular rambutan varieties in China. The total lipid content ranged from 23.40 to 25.77 g/100 g. The fatty acids 9cC18:1 (39.84%-40.92%) and C20:0 (28.45%-30.23%) were identified as the dominant ones, which are uncommon among higher plants. All oil samples exhibited low AI and TI values. BR-7 exhibited the highest levels of squalene (21.48 mg/kg), cholesterol (144.43 mg/kg), and tocopherol (17.42 mg/kg), and the lowest levels of polyphenols (24.21 mg GAE/kg). Additionally, a total of 807 lipid species were identified, with TAG, DGTS, and PE being the predominant ones. Multivariate statistical analyses revealed significant variations in lipid profiles among the varieties, particularly in glycerophospholipids and sphingolipids. Fifty-seven distinct lipids were identified as potential markers for distinguishing between rambutan varieties. Furthermore, a hypothetical scenario was developed by linking relevant lipid metabolism pathways. These findings establish a theoretical framework for comprehending rambutan seed oil in depth and unlocking its high-value potential.

The Addition of Glutamine Enhances the Quality of Huangjiu by Modifying the Assembly and Metabolic Activities of Microorganisms during the Fermentation Process

In this study, the effects of adding glutamate (Glu), glutamine (Gln), aspartate (Asp), and asparagine (Asn) on the flavor formation of Huangjiu were investigated, and the effect of Gln concentration on the quality, microbial community structure, and flavor development of Huangjiu was further explored. Varied Gln concentrations influenced yeast growth, sugar utilization, microbial communities, and quality attributes. Additional Gln promoted yeast cell counts and sugar depletion. It increased the complexity of bacterial co-occurrence networks and reduced the impact of stochastic processes on assembly. Correlation analysis linked microorganisms to flavor compounds. Isolation experiments verified the role of Saccharomyces cerevisiae, Aspergillus chevalieri, Bacillus altitudinis, and Lactobacillus coryniformis in flavor production under Gln conditions. This research elucidated the microbiological mechanisms by which amino acid supplementation, especially Gln, enhances Huangjiu quality by modulating microbial metabolic functions and community dynamics during fermentation. This research is significant for guiding the production of Huangjiu and enhancing its quality.

Revealing the mechanism of post-harvest processing on rose quality based on dynamic changes in water content, enzyme activity, volatile and non-volatile metabolites

Existing studies on post-harvest processing of edible roses have mainly focused on processing techniques and physicochemical properties of the final dried products, with limited studies on how changes in metabolites during processing affect the quality of these products. This study investigated changes in water content and status, enzyme activity, phenolic compounds, and volatile and non-volatile compounds during processing and revealed the mechanisms by which post-harvest processing (drying without blanching (WBD) and drying with blanching (BD)) affects the quality of dried roses by establishing their correlations. Results showed that the blanching reduced the relative content of free water and water activity, thus reducing the subsequent drying time and enzyme activity. The BD method caused higher levels of phenolic compounds than the WBD method in terms of gallic acid, ellagic acid, epicatechin, and quercetin. The OPLS-DA analysis identified 6 differential volatiles out of 72 detected volatiles, contributing to the unique aroma of dried roses by activating olfactory receptors through hydrogen bonding and hydrophobic interactions. 58 differential metabolites were screened from 964 non-volatile metabolites. KEGG pathway analysis revealed that the changes in volatile and non-volatile metabolites induced by different processing methods were due to the effect of blanching on glutathione and fatty acid metabolism. These findings provide a comprehensive understanding of how post-harvest processing affects the quality of dried roses.

Integration of widely targeted metabolomics and the e-tongue reveals the chemical variation and taste quality of Yunnan Arabica coffee prepared using different primary processing methods

UPLC-Q-TOF-MS and electronic tongue analysis were applied to analyse the metabolic profile and taste quality of Yunnan Arabica coffee under seven primary processing methods. The total phenolic content ranged from 34.44 to 44.42 mg/g DW, the e-tongue results revealed the strongest umami sensor response value in the sample prepared with traditional dry processing, while the samples prepared via honey processing II had the strongest astringency sensor response value. Metabolomics analysis identified 221 differential metabolites, with higher contents of amino acids and derivatives within dry processing II sample, and increased contents of lipids and phenolic acids in the honey processing III sample. The astringency and aftertaste-astringency of the coffee samples positively correlated with the trigonelline, 3,5-di-caffeoylquinic acid and 4-caffeoylquinic acid content. The results contributed to a better understanding of how the primary processing process affects coffee quality, and supply useful information for the enrichment of coffee biochemistry theory.

Widely targeted metabolomics-based analysis of the impact of L. plantarum and L. paracasei fermentation on rosa roxburghii Tratt juice

Rosa roxburghii Tratt fruits (RRT) exhibit extremely high nutritional and medicinal properties due to its unique phytochemical composition. Probiotic fermentation is a common method of processing fruits. Variations in the non-volatile metabolites and bioactivities of RRT juice caused by different lactobacilli are not well understood. Therefore, we aimed to profile the non-volatile components and investigate the impact of L. plantarum fermentation (LP) and L. paracasei fermentation (LC) on RRT juice (the control, CG). There were both similarities and differences in the effects of LP and LC on RRT juice. Both of the two strains significantly increased the content of total phenolic, total flavonoid, and some bioactive compounds such as 2-hydroxyisocaproic acid, hydroxytyrosol and indole-3-lactic acid in RRT juice. Interestingly, compared with L. paracasei, L. plantarum showed better ability to increase the content of total phenolic and these valuable compounds, as well as certain bioactivities. The antioxidant capacity and α-glucosidase inhibitory activity of RRT juice were notably enhanced after the fermentations, whereas its cholesterol esterase inhibitory activity was reduced significantly. Moreover, a total of 1466 metabolites were identified in the unfermented and fermented RRT juices. There were 278, 251 and 134 differential metabolites in LP vs CG, LC vs CG, LC vs LP, respectively, most of which were upregulated. The key differential metabolites were classified into amino acids and their derivatives, organic acids, nucleotides and their analogues, phenolic acids and alkaloids, which can serve as potential markers for authentication and discrimination between the unfermented and lactobacilli fermented RRT juice samples. The KEGG enrichment analysis uncovered that metabolic pathways, purine metabolism, nucleotide metabolism and ABC transporters contributed mainly to the formation of unique composition of fermented RRT juice. These results provide good coverage of the metabolome of RRT juice in both unfermented and fermented forms and also provide a reference for future research on the processing of RRT or other fruits.

GC/MS-based untargeted metabolomics reveals the differential metabolites for discriminating vintage of Chenxiang-type baijiu

The "outstanding and unique aged aroma" of Chinese Chenxiang-type baijiu (CXB)-Daoguang 25 (DG25) mainly originates from a "extraordinary storage technology" of Mujiuhai (a wooden container), so it is mysterious and interesting. In this study, an untargeted GC/MS-based metabolomics was used to reveals the volatile differential metabolites for discriminating six different vintages of DG25 combing with chemometrics. A total of 100 volatile metabolites (including unknowns) were extracted and identified, including esters (41%), alcohols (10%) and acids (7%) so on. Finally, 33 differential metabolites were identified as aging-markers. Among them, 25 aging-markers showed a downtrend, including 17 esters such as ethyl acetate, ethyl hexanoate and ethyl palmitate so on. Moreover, it was interesting and to further study that furans showed a significant downtrend. Statistically speaking, ethyl benzoate played an important role in discriminating vintage of 1Y and 3Y, and the other 24 differential metabolites with downtrend discriminating the unstored (0Y-aged) DG25. Eight differential metabolites, such as ethyl octanoate, benzaldehyde, 3-methylbutanol and 1,1-diethoxyaccetal so on increased during aging of DG25, and they played a statistical role in discriminating the 5Y-, 10Y- and 20Y-aged DG25. This study provides a theoretical basis way for the formation mechanism of aging aroma for CXB.

Comparative study on key odorants of Jiujiang Fenggang Huangjiu and their succession regularities during aging using sensory-directed flavor analysis

Huangjiu was a Chinese national alcohol with a unique flavor. The key odorants in Jiujiang Fenggang Huangjiu (JJFG) and their succession regularities during aging were systematically researched by a sensomics analysis approach. The volatiles of JJFG were isolated by solvent-assisted flavor evaporation, 77 odorants were identified using gas chromatography-olfactometry-mass spectrometry combined with odor-specific magnitude estimation. Three aroma recombinants, prepared using odorants with odor activity values ≥ 1, all showed good similarities with their corresponding samples (92.1%∼97.5%). After omission/addition tests, 7 new key aroma compounds were found in JJFG, including 1-octen-3-one, 1-pentanol, guaiacol, ethyl 2-hydroxy-4-methylpentanoate, 2-phenethyl acetate, ethyl butanoate, and (E,Z)-2,6-nonadienal. Using orthogonal partial least squares-discriminant analysis, 20 compounds with VIP ≥ 1 were found to be important indicators during aging of JJFG. Among them, sotolon, 3-methylsulfanylpropanal, et al. increased with aging. The improved solid-phase extraction can effectively quantify sotolon, with a recovery rate of 80.96%∼91.75%.

Comprehensive metabolomic variations of hawthorn before and after insect infestation based on the combination analysis of 1H NMR and UPLC-MS

Hawthorn, the sliced and dried ripe fruits of Crataegus pinnatifida Bge. Var. Major N. E. Br. (Rosaceae), is an edible and medicinal substance with a variety of health-promoting benefits. Hawthorn needs to be stored in warehouses after harvesting to meet people's perennial demand. However, it is easily infested by insects of Plodia interpunctella and Tribolium castaneum during storage, which inevitably leads to poor quality and causes adverse effects on people's health. So far, there has been no report on insect-infested hawthorn. In this study, we analyzed the changes of metabolites in hawthorn before and after insect infestation and screened out potential biomarkers to effectively and quickly detect the occurrence of insect infestation. A combination analysis of 1H nuclear magnetic resonance (NMR) and ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) was used to identify the primary and secondary metabolites. By the comparison of hawthorn and insect-infested hawthorn samples, it was found that the differences were mainly manifested in the content of metabolites. The metabolites of 32 and 1463 were identified by 1H NMR and UPLC-MS analysis, respectively. According to the parameters of VIP >1 and P < 0.05, 10 differential metabolites were screened from 1H NMR analysis. Based on the parameters of VIP >1.0, P < 0.05, and (FC) > 1 or < 1, 47 differential metabolites were screened from UPLC-MS analysis. Therefore, a total of 57 differential metabolites were considered as differential biomarkers. The heat map analysis showed that the content of some differential biomarkers with significant pharmacological activities decreased after insect infestation. Through receiver operating characteristic (ROC) curve assessment, 52 differential biomarkers (6 of 1H NMR analysis and 46 of UPLC-MS analysis) were screened to distinguish whether insect infestation occurred in hawthorn. This is the first report on the changes of metabolites between hawthorn and insect-infested hawthorn and on the screening of differential biomarkers for monitoring insects. These results contributed to evaluate quality of hawthorn and ensure food safety for consumers. It also laid a foundation for further research on the infestation mechanism and safe storage monitoring in hawthorn.

Decoding the Different Aroma-Active Compounds in Soy Sauce for Cold Dishes via a Multiple Sensory Evaluation and Instrumental Analysis

Screening the suitability of soy sauce for specific cooking methods from various products is beneficial for the fine development of the soy sauce industry. Multiple sensory evaluation and gas chromatography-mass spectrometry/olfactometry (GC-MS/O) analysis were combined to decode the suitability of soy sauces for cold dishes and characterize their differential aroma-active compounds. Thirty-two kinds of soy sauce with 42 sensory descriptors were determined via a check-all-that-apply analysis, and werefurther classified into six categories via a cluster analysis. The sensory evaluation results showed that seven soy sauce samples had the highest acceptance in each category. Solid-phase microextraction and solid phase extraction results combined with the GC-MS/O analysis results showed that a total of 38 aroma-active compounds were identified in seven soy sauce samples, among which 2-methoxy-phenol (6-93), ethyl acetate (2-48), 3-methyl-1-butanol (4-30), 3-methyl-butanal (5-24), methional (0-22), dimethyl trisulfide (5-19) and dimethyl disulfide (0-8) showed a higher relative odor activity value (ROAV). A partial least squares regression prediction combined with additional tests further confirmed that 2,5-dimethyl-pyrazine; 2,6-dimethyl-pyrazine; and 2-ethyl-6-methyl-pyrazine significantly contributed to the roasted attributes, methional significantly contributed to the sauce-like notes, ethanol significantly contributed to the alcoholic notes and 2-methoxy-phenol significantly contributed to the smoky notes. 2,5-Dimethyl-pyrazine; methional; 2,6-dimethyl-pyrazine and 2-ethyl-6-methyl-pyrazine significantly contributed to the caramel-like attributes.

The Production of Intensified Qu and Its Microbial Communities and Aroma Variation during the Fermentation of Huangjiu (Chinese Rice Wine)

In recent years, intensified Qu (IQ) has been gradually applied to brewing in order to improve the aroma of Huangjiu (Chinese rice wine). In this study, Saccharomyces cerevisiae and Wickerhamomyces anomalus solutions were added to Fengmi Qu (FMQ) from Fangxian, China to produce IQ, and brewing trial was conducted. High-throughput sequencing (HTS) was used to analyze the microbial community in fermentation broth of IQ (IQFB). Headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) and sensory evaluation were performed to analyze volatile aroma compounds (VACs) in sample without Qu and both fermentation broths. The results showed that Pediococcus, Cronobacter, Enterococcus, Weissella, and Acinetobacter and Saccharomycopsis, Wickerhamomyces, and Saccharomyces were dominant bacterial and fungal groups, respectively. A total of 115 VACs were detected, and the content of esters including ethyl acetate, isoamyl acetate, and so on was noticeably higher in IQFB. The finding of sensory evaluation reflected that adding pure yeast to Qu could enhance fruit and floral aromas. Correlation analysis yielded 858 correlations between significant microorganisms and different VACs. In addition, prediction of microbial community functions in IQFB revealed global and overview maps and carbohydrate metabolism to be the main one. This study is advantageous for further regulation of the fermentation process of Huangjiu by microbial means.