Inflammatory macrophage reprogramming strategy of fucoidan microneedles-mediated ROS-responsive polymers for rheumatoid arthritis.

During the pathogenesis of rheumatoid arthritis, inflammatory cells usually infiltrate synovial tissues, notably, M1-type macrophages, whose redox imbalance leads to the degradation of joint structures and deterioration of function. Natural active products play a vital role in immune modulation and antioxidants. In this study, we constructed a ROS-responsive nanoparticle called FTL@SIN, which consists of fucoidan (Fuc) and luteolin (Lut) connected by a ROS-responsive bond, Thioketal (TK), and encapsulated with an anti-rheumatic drug, Sinomenine (SIN), for synergistic anti-inflammatory effects. The FTL@SIN is then dispersed in high molecular weight Fuc-fabricated dissolvable microneedles (FTL@SIN MNs) for local administration. Therapy of FTL@SIN MNs afforded a significant decrease in macrophage inflammation while decreasing key pro-inflammatory cytokines and repolarizing M1 type to M2 type, thereby ameliorating synovial inflammation, and promoting cartilage repair. Additionally, our investigations have revealed that Fucoidan (Fuc) demonstrates synergistic effects, exhibiting superior mechanical strength and enhanced physical stability when compared to microneedles formulated solely with hyaluronic acid. This study combines nanomedicine with traditional Chinese medicine, a novel drug delivery strategy that presents a promising avenue for therapeutic intervention in rheumatoid arthritis.

Taste-Active Peptides from Triple-Enzymatically Hydrolyzed Straw Mushroom Proteins Enhance Salty Taste: An Elucidation of Their Effect on the T1R1/T1R3 Taste Receptor via Molecular Docking.

The objective of our study was to analyze and identify enzymatic peptides from straw mushrooms that can enhance salty taste with the aim of developing saltiness enhancement peptides to reduce salt intake and promote dietary health. We isolated taste-related peptides from the straw mushroom extract using ultrafiltration and identified them using UPLC-Q-TOF-MS/MS. The study found that the ultrafiltration fraction (500-2000 Da) of straw mushroom peptides had a saltiness enhancement effect, as revealed via subsequent E-tongue and sensory analyses. The ultrafiltration fractions (500-2000 Da) were found to contain 220 peptides, which were identified through UPLC-Q-TOF-MS/MS analysis. The interaction of these peptides with the T1R1/T1R3 receptor was also assessed. The investigation highlighted the significant involvement of Asp223, Gln243, Leu232, Asp251, and Pro254 in binding peptides from triple-enzymatically hydrolyzed straw mushrooms to T1R1/T1R3. Based on the binding energy and active site analysis, three peptides were selected for synthesis: DFNALPFK (-9.2 kcal/mol), YNEDNGIVK (-8.8 kcal/mol), and VPGGQEIKDR (-8.9 kcal/mol). Importantly, 3.2 mmol of VPGGQEIKDR increased the saltiness level of a 0.05% NaCl solution to that of a 0.15% NaCl solution. Additionally, the addition of 0.8 mmol of YNEDNGIVK to a 0.05% NaCl solution resulted in the same level of saltiness as a 0.1% NaCl solution.

Rejection Sensitivity and Reactive Aggression in Early Adults: The Mediating Role of Loneliness and Maladaptive Coping.

Reactive aggression is an aggressive response to a perceived threat or provocation. It has detrimental effects on individuals and society. Rejection sensitivity, a disposition that one tends to anxiously expect, readily perceive, and intensely react to social rejection, has been associated with reactive aggression. Considering that the mechanism underlying this link remains unclear, this study explores the mediating role of loneliness and maladaptive coping. Participants included 1104 early adults between the ages of 17-23 (Mage = 20.35, SD = 1.11, 33.6% men) in China who completed the Chinese version of the Tendency to Expect Rejection Scale, Loneliness Scale, Ways of Coping Questionnaire, and Reactive-Active Aggression Questionnaire. The serial mediation model revealed that loneliness and maladaptive coping independently mediated the association of rejection sensitivity with reactive aggression. More importantly, the chain mediating effect of "loneliness-maladaptive coping" also accounted for this link. The above findings contribute to a deeper understanding of the relationships among these factors and suggested that rejection sensitivity could positively be related to reactive aggression through loneliness and maladaptive coping.

Exploring novel Kokumi peptides in Agaricus bisporus: selection, identification, and tasting mechanism investigation through sensory evaluation and computer simulation analysis.

Agaricus bisporus contains amino acids associated with thickness and full-mouthfeel, making it a potential candidate for salt substitutes and flavor enhancers in various food applications. Kokumi peptides were isolated from the enzymatic digest of Agaricus bisporus using ultrafiltration nanofiltration, gel chromatographic separation, and RP-HPLC, coupled with sensory evaluation. Subsequently, the peptides, EWVPVTK and EYPPLGR, were selected for solid-phase synthesis based on molecular docking. Sensory analysis, including thresholds, time intensity, and dose-configuration relationships, indicated that EWVPVTK and EYPPLGR exhibited odor thresholds of 0.6021 mmol L-1 and 2.332 mmol L-1 in an aqueous solution. Molecular docking scores correlated with low sensory thresholds, signifying strong taste sensitivities. EWVPVTK, in particular, demonstrated a higher sense of richness at lower concentrations compared to EYPPLGR. Molecular docking and dynamics simulations elucidated that the interactions between Kokumi peptides and the CaSR receptor primarily involved hydrogen bonding, electrostatic interactions, and hydrophobic interactions. Both EWVPVTK and EYPPLGR exhibited stable binding to the CaSR receptor. Active binding sites were identified, with EWVPVTK interacting at Arg 66, Asp 216, Gln 245, and Asn 102, while EYPPLGR engaged with Ser 272, Gln 193, Glu 297, Ala-298, Tyr-2, and Agr-66 in hydrophilic interactions through hydrogen bonds. Notably, these two Kokumi peptides were found to be enriched in umami and sweet amino acids, underscoring their pivotal role in umami perception. This study not only identifies novel Kokumi peptides from Agaricus bisporus but also contributes theoretical foundations and insights for future studies in the realm of Kokumi peptides.

Connectivity-based neuromarker for children's inhibitory control ability and its relevance to body mass index.

Preserving a normal body mass index (BMI) is crucial for the healthy growth and development of children. As a core aspect of executive functions, inhibitory control plays a pivotal role in maintaining a normal BMI, which is key to preventing issues of childhood obesity. By studying individual variations in inhibitory control performance and its associated connectivity-based neuromarker in a sample of primary school students (N = 64; 9-12 yr), we aimed to unravel the pathway through which inhibitory control impacts children's BMI. Utilizing resting-state functional MRI scans and a connectivity-based psychometric prediction framework, we found that enhanced inhibitory control abilities were primarily associated with increased functional connectivity in brain structures vital to executive functions, such as the superior frontal lobule, superior parietal lobule, and posterior cingulate cortex. Conversely, inhibitory control abilities displayed a negative relationship with functional connectivity originating from reward-related brain structures, such as the orbital frontal and ventral medial prefrontal lobes. Furthermore, we revealed that both inhibitory control and its corresponding neuromarker can moderate the association between food-related delayed gratification and BMI in children. However, only the neuromarker of inhibitory control maintained its moderating effect on children's future BMI, as determined in the follow-up after one year. Overall, our findings shed light on the potential mechanisms of how inhibitory control in children impacts BMI, highlighting the utility of the connectivity-based neuromarker of inhibitory control in the context of childhood obesity.

Novel kokumi peptides from yeast extract and their taste mechanism via an in silico study.

Yeast extract, a widely utilized natural substance in the food industry and biopharmaceutical field, holds significant potential for flavor enhancement. Kokumi peptides within yeast extracts were isolated through ultrafiltration and gel chromatography, followed by identification using liquid chromatography tandem mass spectrometry (LC-MS/MS). Two peptides, IQGFK and EDFFVR, were identified and synthesized using solid-phase methods based on molecular docking outcomes. Sensory evaluations and electronic tongue analyses conducted with chicken broth solutions revealed taste thresholds of 0.12 mmol L-1 for IQGFK and 0.16 mmol L-1 for EDFFVR, respectively, and both peptides exhibited kokumi properties. Additionally, through molecular dynamics simulations, the binding mechanisms between these peptides and the calcium-sensing receptor (CaSR) were explored. The findings indicated stable binding of both peptides to the receptor. IQGFK primarily interacted through electrostatic interactions, with key binding sites including Asp275, Asn102, Pro274, Trp70, Tyr218, and Ser147. EDFFVR mainly engaged via van der Waals energy and polar solvation free energy, with key binding sites being Asp275, Ile416, Pro274, Arg66, Ala298, and Tyr218. This suggests that both peptides can activate the CaSR, thereby inducing kokumi activity. This study provides a theoretical foundation and reference for the screening and identification of kokumi peptides, successfully uncovering two novel kokumi peptides derived from yeast extract.

Discovery of peptides with saltiness-enhancing effects in enzymatic hydrolyzed Agaricus bisporus protein and evaluation of their salt-reduction property.

This study aimed to screen peptides with saltiness-enhancing effects from enzymatic hydrolyzed Agaricus bisporus protein and quantify their salt-reduction. The saltiness evaluation standard curve was first established to evaluate salinity. The peptide fractions (U-1, U-2, and U-3) were obtained from enzymatic hydrolyzed Agaricus bisporus protein by ultrafiltration. Quantitative calculations showed that the U-2 fraction (200-2000 Da) had the strongest saltiness-enhancing effect, and its perceived saltiness in 50 mmol NaCl solution was 60.24 ± 0.10 mmol/L. The peptide sequences were identified by liquid chromatography/mass spectrometry (LC-MS/MS). Results suggested that the potential peptides with saltiness-enhancing effects were umami peptides. Molecular docking with the umami receptor T1R1/T1R3 revealed that the key amino acid residues were Asp82, Glu392, Glu270, and Asp269. Furthermore, peptide YDPNDPEK (976.4138 Da), DDWDEDAPR(1117.4312 Da), and DVPDGPPPE (1058.4668 Da) were synthesized for salt-reduction quantification. 0.4 % peptide YDPNDPEK in NaCl solution was found to have a salt-reduction of 30 %, which provided the basic theory and data for the salt-reduction of peptide in enzymatic hydrolyzed Agaricus bisporus protein.

Resting-state functional network connectivity underlying conscientiousness in school-aged children.

Conscientiousness is a personality trait that matures from early childhood to late adolescence, yet little is known about its underlying brain mechanisms during this period. To investigate this, our study examined the resting-state functional network connectivity (rsFNC) of 69 school-aged children (mean age = 10.12 years, range = 9-12) using a whole-brain region-of-interest (ROI) based analysis, based on functional magnetic resonance imaging (fMRI). The results indicated a positive association between conscientiousness and the rsFNC between the fronto-parietal network (FPN) and two brain networks: the somatosensory motor-hand network (SMHN) and the auditory network (AN). However, conscientiousness was negatively associated with the rsFNC between FPN and two other networks: the salience network (SN); the default mode network (DMN). Moreover, our results suggest that the FPN may play a hub role in the neural performance of children's conscientiousness. Intrinsic brain networks, particularly those involved in higher-order cognitive functions, impact children's conscientiousness. Therefore, FPN plays an important role in the development of children's personality, providing insight into the neural mechanisms underlying children's personality.

Light-Colored Maillard Peptides: Formation from Reduced Fluorescent Precursors of Browning and Enhancement of Saltiness Perception.

The browning formation and taste enhancement of peptides derived from soybean, peanut, and corn were studied in the light-colored Maillard reaction compared with the deep-colored reaction. The fluorescent compounds, as the browning precursors, were accumulated during the early Maillard reaction of peptides and subsequently degraded into dark substances, which resulted in a higher browning degree of deep-colored Maillard peptides (MPs), especially for the MPs derived from corn peptide. However, the addition of l-cysteine in light-colored Maillard reaction reduced the formation of deoxyosones and short-chain reactive α-dicarbonyls, thereby weakening the generation of fluorescent compounds and inhibited the browning of MPs. Synchronously, the peptides were thermally degraded into small peptides and amino acids, which were consumed less during light-colored thermal reaction due to its shorter reaction time at high temperature compared with deep-colored ones, thus contributing to a stronger saltiness perception of light-colored MPs than deep-colored MPs. Besides, the Maillard reaction products derived from soybean and peanut peptides possessed an obvious "kokumi" taste, making them suitable for enhancing the soup flavors.

Impact of Leavening Agents on Flavor Profiles and Microbial Communities in Steamed Bread: A Comparative Analysis of Traditional Chinese Sourdough and Commercial Yeast.

Chinese steamed bread (CSB) made with commercial yeasts and traditional Chinese sourdoughs was analyzed for the flavor and microbial communities. Sensory attributes were assessed using quantitative descriptive analysis (QDA). Results showed that commercial yeast CSB-1 (JMMT1), a yeast-based sample, had stronger milky and sweet attributes, while commercial yeast CSB-2 (JMMT2) had more pronounced yeasty attributes. Among the sourdough-based samples, Shandong traditional sourdough steamed bread (SDMT) exhibited a winelike character with a weak sweet aftertaste, whereas Shanxi traditional sourdough steamed bread (SXMT) had a distinct sour attribute and a less prominent floury taste. SAFE-GC-O-MS analysis identified 40 aroma compounds with FD values ≥2, including 33 key aroma compounds with an OAV of ≥1. Compounds such as 2,3-butanediol, decanal, methyl isobutenyl ketone, gamma-nonanolactone, ethyl caprate, 2-ethylhexyl acetate, vanillin, and indole contributed significantly to the diverse aroma profiles. High-throughput sequencing revealed dominant strains: Bacillus in JMMT1, Lactobacillus in JMMT2, Bacillus in SDMT, and Lactobacillus in SXMT. Over two-thirds of the aroma compounds showed correlations with microorganisms. Notably, Acetobacter exhibited a highly significant correlation with butanoic acid, while Lactobacillus played a significant role in the formation of ester flavors. These findings contribute to the flavor evaluation and microbial community analysis of steamed bread made with different leavening agents, providing valuable insights into their relationship.

Analysis of umami taste and their contributing compounds in edible fungi based on electronic tongue, sensory evaluation, and chemical analysis.

Edible fungi are rich in nutrients and have unique umami taste, which varies with genotypes, growth conditions, and harvest time. In this study, umami compounds in 12 species of edible fungi are analyzed and identified by electronic tongue. Through principal component analysis and discriminant factor analysis, these 2 methods could be successfully distinguished the variety of 12 edible fungi. Besides, the umami intensity of edible fungi soup is also evaluated by sensory and chemical analysis methods, for example, Tricholoma matsutake is 5.60 ± 0.34 and 5.17 ± 0.38, Coprinus comatus is 7.70 ± 0.23 and 9.83 ± 0.34 through sensory evaluation and electronic tongue respectively, followed by establishing the correlation from the response data by PLS (partial least squares analysis). According to the PLS model, with a correlation coefficients of calibration models greater than 0.7 and the low root mean square error of calibration and root mean square error of prediction values, the results correlate well with each other. Therefore, we can indicate that the electronic tongue is able to analyze and evaluate the umami intensity of edible fungi to some extent.

Preparation of Saltiness-Enhancing Enzymatic Hydrolyzed Pea Protein and Identification of the Functional Small Peptides of Salt Reduction.

According to the correlation of saltiness determined by electronic tongue and perceived NaCl concentration, favorable enzymatic hydrolysis parameters were achieved to prepare the saltiness enhancing mixture peptides from pea protein. Six peptide fractions (F1, F2, F3, F4, F5, and F6) were isolated using Sephadex G-10 gel filtration. Among them, fraction F4 (0.1%) exhibited the highest saltiness (5.90 ± 0.03). The amino acid sequences of five main peptides identified by time-of-flight mass spectrometry were Tyr-Trp (367.40 Da), Gly-Glu-His-Glu (470.43 Da), Glu-Arg-Phe-Gly-Pro (604.65 Da), Gly-Ala-Gly-Lys (331.37 Da), and Pro-Gly-Ala-Gly-Asn (414.41 Da). Tyr-Trp (0.01%) in 0.4% NaCl solution had a 20% saltiness-enhancement compared with 0.4% NaCl solution. More salivary aldosterone was secreted after tasting hydrolysate or Tyr-Trp solutions via enzyme-linked immunosorbent assay, reflecting the improvement of human sensitivity to saltiness. Thereby, the saltiness-enhancing effect was confirmed for the small peptides from hydrolyzed pea protein and the main contributor was further identified.

Revealing the influence of microbiota on the flavor of kombucha during natural fermentation process by metagenomic and GC-MS analysis.

In this work, raw Pu-erh tea (RAPT) was employed for kombucha preparation, and the microbial composition and volatile flavor compounds of the fermented tea had been investigated during natural fermentation process. The head space-solid phase microextraction-gas chromatograph mass spectrometry (HS-SPME-GC-MS) was performed for volatiles analysis of unfermented tea and kombucha fermented for 3 days (KF-3) and 6 days (KF-6). Meanwhile, the microbial community of KF-3 and KF-6 were evaluated by metagenomic analysis. A total of 72 volatile compounds were identified and obvious changes in volatiles were observed during the fermentation process based on the results of GC-MS and principal component analysis (PCA). Metagenomic sequencing analysis demonstrated that bacterium Komagataeibacter saccharivorans and unclassified-g-komagataeibacter and yeast Saccharomyces cerevisiae and Brettanomyces bruxellensis were the most common microbes contained in the sampled kombucha communities. Furthermore, the relevance among microbial community and volatile compounds was evaluated through correlation heatmap analysis. The results suggested that the main flavor volatiles of kombucha (i.e., acids, esters and terpenes) were closely related to species of genus Komagataeibacter, Gluconacetobacter, Saccharomyces, Brettanomyces, Acetobacter, Novacetimonas and Pichia microorganisms. The obtained results would help to better understand microbial communities and volatile compounds of kombucha, which could provide useful information for enhancing the flavor quality of kombucha products.

Insights into the Edible and Biodegradable Ulvan-Based Films and Coatings for Food Packaging.

Recently, edible films or coatings that are made from algal polysaccharides have become promising candidates for replacing plastic-based packaging materials for food storage due to their non-toxic, biodegradable, biocompatible, and bioactive characteristics. Ulvan, a significant biopolymer with unique functional properties derived from marine green algae, has been extensively used in various sectors. However, there are fewer commercial applications of this sugar in the food packaging industry compared to many other algae-derived polysaccharides, such as alginates, carrageenan, and agar. This article aims to review the unparalleled chemical composition/structure and physiochemical properties of ulvan and the latest developments in ulvan-based edible films and coatings, thus highlighting their potential applications in the food packaging industry.

Characteristic flavor fingerprint disclosure of dzo beef in Tibet by applying SAFE-GC-O-MS and HS-GC-IMS technology.

To understand the overall flavor of the dzo beef, fatty acids, volatile compounds and aroma profiles of dzo beef samples (raw beef (RB), broth (BT) and cooked beef (CB)) were investigated by head-space-gas chromatography-ion mobility spectrometry (HS-GC-IMS) and gas chromatography-mass spectrometry (GC-MS). The fatty acid analysis showed a decrease in the ratio of polyunsaturated fatty acids, such as linoleic acid, which decreased from 2.60 % in RB to 0.51 % in CB. The principal component analysis (PCA) showed that HS-GC-IMS was able to distinguish different samples. A total of 19 characteristic compounds with odor activity value (OAV) > 1 were identified by gas chromatography-olfactometry (GC-O). Fruity, caramellic, fatty and fermented attributes were enhanced after stewing. Butyric acid and 4-methylphenol were responsible for the stronger off-odor in RB. 3-Hydroxy-2-butanone and 2,5-dimethyl-4-hydroxy-3(2H)-furanone with buttery and caramellic attributes were dominated in BT, while (E)-2-nonenal, (E,E)-2,4-decadienal and (E,E)-2,4-nonadienal prominently conferred fatty attribute on CB. Furthermore, anethole with anisic aroma was first identified in beef, which may be one of the typical chemical markers that distinguish dzo beef from other varieties.

The inferior frontal gyrus spontaneous activity mediates the association of early life adversity with self-control ability in late adolescents.

Self-control, the ability to regulate prepotent desires or impulses in order to realize one's valued goal, has been found to be associated with early life adversity. However, the neural correlates underlying this relationship remain poorly understood. The present study employed resting-state functional magnetic resonance imaging (fMRI) to investigate this issue among late adolescents (N = 538). Results showed that family unpredictability rather than family harshness of early life adversity was negatively correlated with self-control ability. The whole brain analysis showed that self-control was associated with enhanced ALFF in the right middle and inferior frontal gyrus, the left anterior insula, and with decreased ALFF in the left precuneus. Moreover, the mediating analysis showed that ALFF in the inferior frontal gyrus could partially mediated the association of family unpredictability with self-control ability. These findings suggested that the brain regions implicating in executive control might be the neural correlates underlying the relationship between early life adversity and self-control ability, which advances the mechanistic understanding of how early family environment relates to the development of self-regulation in late adolescence.

Novel umami peptide from Hypsizygus marmoreus hydrolysate and molecular docking to the taste receptor T1R1/T1R3.

Hypsizygus marmoreus is an edible variety of mushroom with a distinct umami taste, which might be contributed by amino acids and umami peptides. Umami peptides have been widely studied, except for those from Hypsizygus marmoreus. Therefore, the main purpose of this study was to find new umami peptides in it. After the mushrooms were enzymatically hydrolyzed, they were separated and characterized by UF, GFC, RP-HPLC, UPLC-Q-TOF MS/MS and the umami peptide EGTAG was obtained. Sensory evaluation found that EGTAG had distinct umami taste with thresholds of 8.26 mmol/L and 10.04 mmol/L in water and chicken consommé, respectively. Molecular docking results showed that Glu120, Ser142, Asp162 and Gln361 of T1R1/T1R3 may play critical roles. Hydrogen and hydrophobic interactions were the main binding forces between T1R1/T1R3 and the umami peptide. We proposed umami peptide from Hypsizygus marmoreus may be used as savory enhancer in the salt-reducing foods in the future. HYPOTHESES: Edible fungi generally have umami taste and umami peptides from edible fungi had been reported in the literature. Hypsizygus marmoreus belongs to edible fungi and has umami characteristics, so it can be inferred that Hypsizygus marmoreus contains umami peptides.

Identification of novel umami peptides from Boletus edulis and its mechanism via sensory analysis and molecular simulation approaches.

The study aimed to identify umami peptides from Boletus edulis and explore their umami mechanism. 421, 713 and 616 peptides identified by LC-MS/MS from control sample (CS), enzymatically extracted sample (EES) and high-pressure cooking sample (HPCS), respectively. According to molecular docking study, three potential umami peptides (DGF, KCGQ and HHYE) were chemically synthesized for sensory evaluation. DGF/HHYE had the lowest umami recognition threshold values in the absence (0.37 mmol/L for DGF)/presence (0.21 mmol/L for HHYE) of monosodium l-glutamate. KCGQ exhibited the strongest synergistic umami effect. Molecular dynamic simulation revealed that hydrogen bonds and hydrophobic interactions were the major intermolecular interaction forces and the charged amino acid residues (D1, E4 and K1) in umami peptides were dominate in the molecular recognition of umami peptides and the receptor. This study lays the groundwork for the efficient screening of umami peptides from edible fungi and contributes to the umami peptides structure-activity relationship research.

Characteristic volatile fingerprints of three edible marine green algae (Ulva spp.) in China by HS-GC-IMS and evaluation of the antioxidant bioactivities.

In this study, the volatile compounds fingerprinting as well as the relationship between phytochemical composition and antioxidant bioactivity of U. prolifera, U. linza and U. clathrata were investigated. The significant differences of volatile compounds in three dehydrated seaweeds were observed by headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS), and the type of volatile compounds in U. clathrata (83 compounds) was highest, followed by U. linza (75 compounds) and U. prolifera (57 compounds). Furthermore, a variety of polarity solvents were used to extract Ulva spp. in order to determine the influence of total phenolics (TPC), flavonoids (TFC) and carbohydrates content (TCC) on antioxidant activities. The results showed that ethyl acetate extracts of U. prolifera had the highest antioxidant activity (IC50 = 143.18 µg/mL) in ABTS assay, and methanol extracts of U. clathrata revealed the highest scavenging activity (IC50 = 95.32 µg/mL) against OH radicals as well as the aqueous extracts of U. prolifera exhibited the strongest radical scavenging capacity (IC50 = 527.75 µg/mL) against DPPH radicals. Pearson correlation analysis revealed that the antioxidant capacity of Ulva spp. was significantly impacted by TFC and TPC. The findings presented in this thesis add to our understanding of volatilization characteristics and biological properties in edible marine green seaweeds.

Variation in Volatile Compounds of Raw Pu-Erh Tea upon Steeping Process by Gas Chromatography-Ion Mobility Spectrometry and Characterization of the Aroma-Active Compounds in Tea Infusion Using Gas Chromatography-Olfactometry-Mass Spectrometry.

Steeping process is an important factor for aroma release of tea, which has rarely been investigated for the aroma changes of raw Pu-erh tea (RAPT). In addition, the comprehensive aroma characteristics identification of RAPT infusion is necessary. In this study, GC-IMS coupled with principal component analysis (PCA) was used to clarify the difference of volatile profiles during the steeping process of RAPT. Furthermore, the volatiles contained in the RAPT infusion were extracted by three pretreatment methods (HS-SPME, SBSE, and SAFE) and identified using GC-O-MS. According to the odor activity value, 28 of 66 compounds were categorized as aroma-active compounds. Aroma recombination and omission experiments showed that "fatty", "green", "fruity", and "floral" are considered to be the main aroma attributes of RAPT infusion with a strong relationship with 1-octen-3-one, 1-octen-3-ol, (E)-2-octenal, ß-ionone, linalool, etc. This study will contribute a better understanding of the mechanism of the RAPT steeping process and volatile generation.