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Additional file 1: Table S1 Correlations between gut microbiota taxa and blood pressure levels in female subjects. Table S2 Correlations between gut microbiota taxa and blood pressure levels in male subjects. Fig. S1 Relative abundances and comparative analysis of the annotated KEGG functions of gut microbiota in female and male subjects. The KEGG functions with significant differences between groups are presented by Wilcoxon rank-sum test. #P < 0.1, *P < 0.05, **P < 0.01.

Additional file 1: Table S1. Primer sequences used in qPCR.

Since economic reform in 1978, migration and the expansion of higher education have become important factors in China's modernization process and are closely linked with social mobility (Cebolla-Boado & Soysal, 2018): Rapid economic growth has stimulated massive migration both at home and abroad for educational and/or career opportunities. When market forces continue to permeate every sector, including education and the labor market, the special institutional arrangement (i.e. hukou system) and the structure of the labor market are still organizing the social structure of the entire society (Bian & Logan, 1996; Xiao & Bian, 2018).This background provides a context for studying the relationship among socioeconomic status attainment, higher education and migration, namely, how migration produces and maintains social inequality under the joint action of centralist state-control and market forces. At present, the research on “how mobility affects college graduates’ performance in China” mainly has the following shortcomings. First, in 2019, China’s Gini Coefficient was reported at 0.465 NA. The main investigation of previous research on individual social and economic status is ascribed factors (such as family background, residence, gender) (He & Wu, 2018), achieved status, such as level of education (Xiao & Bian, 2018), social capital (Bian, 1997), or the structure of the labor market (Li et al., 2015), while the geographical mobility and its interaction with other factors impact on individual socioeconomic status is ignored. Second, in terms of higher education, similar to many western developed countries in the 1950s, China's higher education began to expand in the late 1990s. Since 1999, the Chinese government has adopted the higher education expansion policy, resulting in the rapid growth of higher education opportunities. A striking example is that in 1998, the gross enrollment rate of higher education was 5.86% and by 2018, the ratio had reached 50.60 percent (World Bank, 2020). However, research on higher education focuses on the influence of family background and factors in the education process on the access to educational opportunities and academic performance (Liu,2015; Tam & Jiang, 2015), while there is a lack of research on the relationship between higher education and labor market. Third, in terms of migration, similar to many other developing countries, China has been experiencing the massive volume of internal migration. In 2017, 244 million people was estimated to move across regions within the country (Report on China’s Migrant Population Development, 2017), which is close to the total global international migration (United Nations, 2017). Because the rural-to-urban is quantitatively so important, many studies have been conducted to explore the labor market performance of low-skilled migrants in China (Fan, 2002; Wu & Treiman, 2004; Zhang & Wu, 2017), whereas research on higher-education and highly skilled migration within China is scarce. Research question This dissertation is composed of three empirical studies focusing on the effects of migration on the socioeconomic status of college graduates and whether such effects are limited by other structural factors. Specifically, Chapter 4 studies the interaction of migration and gender on college graduates’ starting salary and work organization entry. Chapter 5 explores the influence of migration and family background on college graduates' employment outcomes; examines the role of locality (cities) in differentiating socio-economic outcomes of migrants. The last empirical chapter, Chapter 6, examined whether Beijing, Shanghai, Guangzhou and Shenzhen, the first-tier cities, have emerged as an “upward social class escalator region” (Fielding, 1992) for the young adults in the Chinese graduate labor market. The research questions were as follows: 1. Is there an economic premium attached to graduate migration? If yes, do all young people with different characteristics benefit equally from the migration premium? 2. Is there a double negative effect between gender and migrant status on college graduates’ initial salaries and entry into the state sector for employment? 3. Is there migrant selectivity among graduate return migrants in terms of human capital characteristics? What is the impact of family background on graduate return migrants’ labor market outcomes? 4. Is there a positive association between moving to first-tier cities (Beijing, Shanghai, Guangzhou, and Shenzhen) and college graduates’ monthly starting salaries in China’s labor market? Due to the stringent local hukou barrier in Beijing, Shanghai and Guangzhou and Shenzhen, do graduate migrants have equal access to employment opportunities in government organizations and public enterprises compared to their local peers? Data and methods Data Findings of the three empirical studies in this dissertation are based on second-hand data. The data came from the “China College Student Survey” (CCSS), which was conducted by China Data Center at Tsinghua University in 2010, 2013 and 2015. The project used stratified probability-proportional-to-size random sampling and 60 universities from 23 provinces participated in the survey. It is a nationally representative survey. This survey aimed to understand the academic performance of Chinese college students during school, as well as their performance in the labor market and personal career choices. The survey also included information on the students’ socioeconomic status, school education during the middle school, and college entrance examinations. Since undergraduate study in China is usually a four-year program, students in the last semester of undergraduate study (four-year program) were defined as a sample population. The selected respondents need to fill in their placement after graduation, and students who chose to seeking a job after graduation need to give some information about employment (such as number of offers, place of employment, income, etc.). Further, the data used in this dissertation was limited to a sample with the following characteristics: Students who had no experience of migration before college and chose to find a job after graduation. In addition, only those who had received (at least) one offer and provided income information in the survey were included. The final sample consisted of 5,906 eligible individual students. Data analyses Considering the sample selection problems caused by these abovementioned conditions, the dissertation used Heckman’s (1979) two-step sample selection models to test the effect of sample selection bias on the results. Specifically, in the first step, a probit model was fitted to estimate the selection into our analytical sample, based on which the inverse Mill’s ratio, λ, was calculated (Flippen, 2013). In the second step, the λ parameter was included in the model predicting starting salary. In migration studies, researchers also pointed out the migrant self-selection issues (Borjas, 1987; Chiswick, 1999). Chapter 6 also used the two-step selection model to identify the return migration selectivity. Besides, this dissertation adopted propensity score matching and weighting methods. The matching method was used to compare the aggregate impact of education migration and work migration on the salary outcome in the whole sample as well as in disaggregated samples according to hukou origin (rural or urban); while the latter was to reduce selectivity bias in regression models, following the argument from Ridgeway, Kovalchik, Griffin and Kabeto (2015), I include the product of a propensity score weight (correcting for graduate migration selection bias) and the sampling weight as the final weight in estimations of regression models. Overview of the findings Chapter 4 examines how internal graduate migration interacts with gender and play a key role in producing inequality among recent college graduates in China. Results show that, on one hand, female graduate migrants had less chance to enter governmental organizations which affords institutional protection against gender discrimination. On the other hand, the effect of geographical mobility (migration) varied by work organizations and female graduate migrants who ended up in the non-state sector were more likely to experience an income penalty in earnings attainment. The results suggest that although female graduate migrants are a highly selective group in terms of human capital characteristics, they are disadvantaged twice in the labor market because of the existing barriers based on gender and hukou locality. In Chapter 5, the impact of graduate return migration on initial salaries of college graduates in Chinese graduate labor market is investigated. Results reveal that graduates moving back to their pre-college hukou located cities had more opportunities to get a placement in government organizations and public enterprises, relative to onward migrants, and the advantage was enhanced by the introduction of family political capital. Besides, despite of the effect of migrant selectivity indicated that they were not much different than the onward migrants with respect to the characteristics that determine starting salaries, graduate return migrants had slightly higher earnings than onward migrants. The findings suggest that family background plays an important role in shaping differences in labor market outcomes among graduate migrating population and graduate return migration seems to be a strategy for upward social mobility taken by college graduates from privileged families. Chapter 6, the last empirical chapter of the dissertation, examined whether Beijing, Shanghai, Guangzhou and Shenzhen have emerged as an “upward social class escalator region” (Fielding, 1992) for young people in China. After accounting for observed demographic and human capital characteristics and migrant selectivity, migrating into Beijing, Shanghai, Guangzhou and Shenzhen has been found to be positively associated with earnings attainment, and the economic benefit from relocation was greater than that experienced by migrants elsewhere in the system. However, in-migrants to Beijing, Shanghai, Guangzhou and Shenzhen have fewer opportunities to work in the state sector (government organizations in particular). These results suggest that migration to Beijing, Shanghai, Guangzhou and Shenzhen can only bring short-term economic benefits, but it cannot guarantee the upward social mobility of migrants. It remains to be further investigated as to whether such a region has the potential to become an escalator region in China. Implication of the findings Findings above demonstrate the impact of internal migration on the socioeconomic status of graduates in China’s labor market. Based on these findings, there are some policy recommendations and theoretical directions that can be pointed out. Theoretical implications Overall, through nuanced investigation of the influence of migration on labor market outcomes, my dissertation makes an important contribution to the field of social mobility literature on labor market performance of highly-educated migrants. 1. The impact of internal migration on the socioeconomic status of college graduates In the field of higher education, the relationship between education and employment is a topic that scholars and policy makers have long been concerned about (Schomburg & Teichler, 2007). Research in the field of higher education is focused on the impact of education-related mechanisms (national education system, school type or major, etc.) on employment outcomes. In this study, the influence of higher education related factors has been verified（academic performance at college such as undergraduate GPA, awards, CCP membership, English language certification; fields of study and college type (whether “Project 211” or not) . More importantly, findings indicate that graduate migration has a non-negligible impact on the employment results of college graduates. The results of this dissertation also show that in China, as economic reforms continue to advance, students have more freedom to make use of geographical mobility to find the most suitable job for themselves, so as to maximize the economic return brought by work. The labor market performance of migrants also reflects the socio-economic integration of migrants. The findings challenge the idea of self-selection of migrants. Results from the empirical chapters show that in general, there is a positive association between geographical mobility and the initial salaries of college graduates, even after controlling for their migration-related characteristics. Migrant experience itself, rather than migrant selectivity, helps graduate migrants to achieve higher earnings. My dissertation suggests that although there is a positive association between migration and salary outcome, migration has an inhibiting effect on entering the primary sector in the labor market. The existing institutional and structural factors in the society have an important impact on the consequences of migration. Different from the segmented mechanism in developed countries, China’s labor market is divided by state-owned and non-state-owned sectors and the hukou system is the main channel for sending workers into different sectors. Hukou hinders the free movement of college graduates, making it impossible for migrants to achieve upward mobility through migration. Besides, the results of this dissertation prove that cities play an important role in creating unequal consequences of migration. High-skilled migrants have often been associated with global elite, as free-floating mobiles that are disembodied from localities and moving outside of the constraints of nation states (Hannerz 1996, 129; Sklair 2005). In China, these highly educated migrants are not “free-floating mobiles”, instead, their mobility and its consequences are constrained by institutions and structures. Results show that, despite of a substantial income premium from migration that in-migrants to Chinese megacities (Beijing, Shanghai, Guangzhou, and Shenzhen) experience, they face more restrictions from the hukou system (comparing migrants elsewhere in the system) when seeking employment in government organizations and public enterprises. Last, in China, citizenship has been found to be stratified in terms of hukou locality. In the Chinese context, citizenship has been interlocked with the hukou (household registration) system for more than 50 years. With the reform of the household registration system，the hukou location，rather than the hukou classification, has become more important in determining access to resources and defining one’s life chances. The larger the city is, the more valuable is its hukou because there are more government-provided benefits. Beijing, Shanghai, Guangzhou and Shenzhen, where the barriers or social boundaries associated with hukou are stronger than any other cities (Wang et al., 2017; Zhang & Tao, 2012), as a result, migrants encounter more difficulties in labor market if they want to settle down in these cities. 2.Maintenance of inequality: the interaction between migration and other social and demographic characteristics The findings of this dissertation indicate that although graduate migration is generally considered to be “a process wherein higher-education students …for the purpose of career advancement or upward social mobility” (Li, et al. 2020, p.4); however, mobility did not play a role in reducing existing inequalities. In the Chinese context, The reason why migration is associated with inequality lies in its mechanism: Exclusion (Immigration Policy and Citizenship at the societal level) and opportunity hoarding (Opportunity structures in employment markets at the societal level). The hukou system in China, is a typical example of exclusion based on legal boundaries enforced by the state. This dissertation also wants to emphasize the socio-economic differentiation brought about by the classification of hukou system (especially local-nonlocal). Just as immigration policy measures and citizenship which is closely related to legal affiliation in international migration, the nature of legal exclusion provided by hukou restricts their access to the same job opportunities as local residents, although it does not limit the migration behavior of graduates. The linked mechanism is opportunity structure in the labor market. For graduate migrants, the hukou system does shape the opportunity structure in the labor market, that is, compared with local people, migrants have fewer job opportunities. But more importantly, it is important to note that the hukou system works in conjunction with the segmented labor market: what migrants lack is not jobs that are generally available, but jobs in the primary sector of the segmented labor market. Therefore, migration produced inequality through exclusion (in the sense of legal aspect) and opportunity structure. Additionally, this dissertation suggests that, migrant status interacts with pre-existing inequalities such as hukou status(rural/urban) and gender and shapes outcomes among college graduates in China’s urban labor market. Rather than being natural, categories, such as gender and race, are socially constructed, and they not only influence individual identities but also provide principles of organization in the social system (Browne & Misra, 2003). Thus, these results imply that migration may serve to entrench pre-existing socioeconomic inequalities between rural and urban hukou holders, as well as between men and women. 3. Family background, education and migration: The reproduction of social inequality In the field of stratification research and higher education, one of the focal points of debate is the extent to which higher education reduces the influence of family background on an individual's economic success (Bloome, Dyer, & Zhou, 2018; Hout, 1988; Torche, 2011; Witteveen & Attewell, 2017, 2020). Findings of the study support the reproduction hypothesis, that is, family background still has a very important influence on the employment outcomes of college graduates: Family income is significantly positively correlated with graduate starting salaries. In addition, although the political capital of parents has no significant impact on the salary of a graduate, it has a significant impact on whether college migrants can enter into the employment of primary sectors. This shows that power maintenance still plays an important role in the graduate labor market. Political elites are more likely to pass on their dominant position to their children, and the formation of elites is exclusive. Another important finding of this dissertation is that the influence of family background on one's economic achievement can also be realized by influencing one's migration behavior. The return migration behavior in particular, is a resource and power of dominant families: graduate return migrants are more likely to be singletons from one-child urban families with higher family income, cadre parents, and more familial political capital. Furthermore, those with more political capital are more likely to enter government organizations and public enterprises. By influencing their children's migration choice, the children from the advantaged families obtain higher socioeconomic status by means of mobility, thus realizing the intergenerational transmission of class. Therefore, geographical mobility becomes a tool for the reproduction of social class. Practical implications In terms of the labor market, the findings of this dissertation suggest that the government needs to establish policy evaluation and supervision mechanisms for gender equality. At the same time, laws and regulations related to the labor market should be established to enhance the awareness of labor equality and the ability to protect rights, so that female workers can learn to use legal means to fight for and protect their rights. Moreover, such local protectionism should be corrected in policy design, given the unequal employment opportunities for locals and outsiders brought about by the hukou system. In the field of higher education, students should have more freedom of choice in their educational mobility. For rural students, attention should be paid to the improvement of rural educational resources, including teachers and schools. In the college application stage, teachers or organizations should fully explain the situation of each higher education institution (including education and employment), so that students and parents can have a deeper understanding of the school. What’s more, the establishment of various types of colleges and universities, such as vocational skills schools, and the further improvement of the higher education system will enable students to have more choices when applying for colleges and universities. In terms of the household registration system, the welfare and rights attached to the household registration system should be removed to break the institutional bottleneck of social mobility of the floating population. Given the important role of first-tier cities in China's economic system, how to solve the problem of floating population in first-tier cities has become a key issue for policy makers to solve in the future. Limitations and directions for future research Finally, several important limitations need to be considered. First, the dissertation was limited by the use of a cross-sectional design conducted, and it was not able to investigate the long-term impact of migration on college graduates’ labor market outcomes. Future research should attempt to collect longitudinal data that trace a representative sample of higher education leavers after graduation in order to have a better understanding of the long-term consequences of migration. Second, although this dissertation tried best to include as many variables as possible to correct for migrant self-selection bias, it should be acknowledged that there is still a possibility that unobserved traits, such as personality, risk-taking, and confidence, are also related to the labor market outcomes of graduates. It is suggested that the association of these factors is investigated in future studies. Third, this dissertation was exclusively focused on the effect of graduate migration on the labor market outcomes among bachelor’s degree holders. However, migration is associated with education, and individuals with the different educational background may benefit differently from geographic mobility. Future work from China to include individuals at different education levels (such as B.A., M.A., and PhD.) would be of great help in knowing the same issue in the Chinese context. Fourth, this dissertation merely examined the economic outcomes of migration. While both earnings attainment and work organization entry are essential indicators of the social and economic status in China (Li et al., 2015; Xiao & Bian, 2018), the consequence of migration is related to other aspects of life, including housing ownership, marriage, and family support (Cui et al., 2016; Qian & Qian, 2017). One possible area of future research would be to conduct follow-up surveys of the college-educated cohorts of the current CCSS sample. This could help researchers gain a more complete picture of the graduate migration process and its importance for determining individuals’ life opportunities.

The meat-like reactions of l-cysteine and d-(+)-xylose with or without glycine were investigated. LC-MS was used to quantitatively determine the initial stage intermediates including 2-threityl-thiazolidine-4-carboxylic acid, Cys-Amadori, and Gly-Amadori in the reaction mixtures. The results showed that the addition of glycine was only in positive correlation with the browning feature of cyseine-xylose reaction. When excessive glycine was added, a high browning rate would be achieved, but it did not benefit the formation of meaty compounds. For a complex meat-like reaction system containing cysteine, reducing sugars and glycine, to overcome the low rate of reaction, and particularly, to minimize the inhibitive effect of cysteine in the generation of meaty flavors, selection of an appropriate ratio between cysteine and glycine is important in an effort to make amounts of the intermediates of Cys-Amadori and Gly-Amadori approximately equally consist in the reaction mixture.

Pork of black-pig in China is well known for its quality and preferred by consumers. However, there is a lack of research on its flavors. By solvent assisted flavor evaporation combined with GC-MS, 104 volatile compounds in the stewed pork broth of black-pig were identified with the dominant amounts of fatty acids, alcohols, and esters. By aroma extract dilution analysis-GC-O method, 27 odor-active compounds were characterized, including 2-methyl-3-furanthiol, 3-(methylthio)propanal, 2-furfurylthiol, γ-decalactone, nonanal, (E)-2-nonenal, and (E,E)-2,4-decadienal that had high FD factors. Compared to the common white-pig, the aroma compounds in both pork broths were almost the same, but the aroma profile of potent odorants for the black-pig pork broth showed less fatty and more roasted notes, which were partially attributed to the higher monounsaturated fatty acids and lower polyunsaturated fatty acids in meat. With aid of authentic chemicals and selected reaction monitoring mode of GC-MS/MS, 19 aroma compounds were quantitated.

The thermal stability and migration resistance of light stabilizers are vital for their applications in plastics. Herein, a novel nano organic–inorganic hybrid light stabilizer with high thermal stability and low solubility was prepared by intercalating a synthesized hindered amine light stabilizer (HALS) with UV absorption capability into the interlayer galleries of MgAl layered double hydroxides (LDH) through co-precipitation method. The prepared HALS–LDH was characterized by XRD, FT–IR, SEM, TG–DTA and UV–vis, and was incorporated into the matrix of polypropylene (PP) via solvent casting method to prepare LDH/PP composite for light stability test. It was found that the synthesized HALS was successfully intercalated into the interlayer galleries of MgAl–LDH, forming an organic–inorganic hybrid material HALS–LDH with a mean size of 63 nm. HALS–LDH nanosheets were evenly dispersed in the matrix of PP, and the addition of HALS–LDH can retard the thermal decomposition of PP. Moreover, the incorporation of HALS–LDH significantly improved the light stability of PP and reduced the photo degradation of PP by about 83.2%. Therefore, the prepared novel HALS–LDH has potential application in the field of PP as an efficient and promising light stabilizer.

The different actions of abscisic acid (ABA) in the aboveground and belowground parts of plants suggest the existence of a distinct perception mechanism between these organs. Although characterization of the soluble ABA receptors PYR1/PYL/RCAR as well as core signaling components has greatly advanced our understanding of ABA perception, signal transduction, and responses, the environment-dependent organ-specific sensitivity of plants to ABA is less well understood.By performing real-time quantitative PCR assays, we comprehensively compared transcriptional differences of core ABA signaling components in response to ABA or osmotic/dehydration stress between maize (Zea mays L.) roots and leaves. Our results demonstrated up-regulation of the transcript levels of ZmPYLs homologous to dimeric-type Arabidopsis ABA receptors by ABA in maize primary roots, whereas those of ZmPYLs homologous to monomeric-type Arabidopsis ABA receptors were down-regulated. However, this trend was reversed in the leaves of plants treated with ABA via the root medium. Although the mRNA levels of ZmPYL1-3 increased significantly in roots subjected to polyethylene glycol (PEG)-induced osmotic stress, ZmPYL4-11 transcripts were either maintained at a stable level or increased only slightly. In detached leaves subjected to dehydration, the transcripts of ZmPYL1-3 together with ZmPYL5, ZmPYL6, ZmPYL10 and ZmPYL11 were decreased, whereas those of ZmPYL4, ZmPYL7 and ZmPYL8 were significantly increased. Our results also showed that all of the evaluated transcripts of PP2Cs and SnRK2 were quickly up-regulated in roots by ABA or osmotic stress; conversely they were either up-regulated or maintained at a constant level in leaves, depending on the isoforms within each family.There is a distinct profile of PYR/PYL/RCAR ABA receptor gene expression between maize roots and leaves, suggesting that monomeric-type ABA receptors are mainly involved in the transmission of ABA signals in roots but that dimeric-type ABA receptors primarily carry out this function in leaves. Given that ZmPYL1 and ZmPYL4 exhibit similar transcript abundance under normal conditions, our findings may represent a novel mechanism for species-specific regulation of PYR/PYL/RCAR ABA receptor gene expression. A difference in the preference for core signaling components in the presence of exogenous ABA versus stress-induced endogenous ABA was observed in both leaves and roots. It appears that core ABA signaling components perform their osmotic/dehydration stress response functions in a stress intensity-, duration-, species-, organ-, and isoform-specific manner, leading to plasticity in response to adverse conditions and, thus, acclimation to life on land. These results deepen our understanding of the diverse biological effects of ABA between plant leaves and roots in response to abiotic stress at the stimulus-perception level.

Distributed teams have become increasingly prevalent. However, distance brings challenges in practice, and chief among them is the development of trusting and cohesive relationships. By contrast, in co-located settings, informal social interactions beyond purely task-oriented communication support trust and cohesion building. This research fills the gap by exploring, in two related studies, how to use online playful activities to encourage informal social interactions at work and at a distance. The first study identifies the potential to use open-ended, freeform drawing to jumpstart trust, cohesion, and positive emotions in a distributed team setting. The results reveal that there are four core facets of the experience afforded by online playful activities: expressivity, reflection, interactivity, and playfulness. These results suggest that designing around the four facets could contribute to an engaging playful experience that would help teams build a common ground, support subjective affective expressions and experience, build up team knowledge in a relaxing social context, and promote positive emotional contagions. Thus, a prototype based on these findings was developed and tested in a short-term, in-situ study with five teams from industry contexts. The prototype supported asynchronous, anonymous, collaborative online drawing. We found that participants obtained an increased engaging experience and perceived trust, cohesion, and transient positive emotions over five days. Findings also identified the relationship between the four facets; namely, how each was influenced by the others. Based on findings from the two studies, as well as insights from previous, related research, we developed a theoretical model to capture the characteristics of online playful activities for distributed teams. This model leads to a design framework with eight concrete design guidelines that form a basis for system design for online playful activities for distributed teams.

To explore initial Maillard reaction pathways and mechanisms for maximal formation of meaty flavors in heated cysteine-xylose-glycine systems, model reactions with synthesized initial Maillard intermediates, Gly-Amadori, TTCA (2-threityl-thiazolidine-4-carboxylic acids) and Cys-Amadori, were investigated. Relative relativities were characterized by spectrophotometrically monitoring the development of colorless degradation intermediates and browning reaction products. Aroma compounds formed were determined by solid-phase microextraction combined with GC–MS and GC-olfactometry. Gly-Amadori showed the fastest reaction followed by Cys-Amadori then TTCA. Free glycine accelerated reaction of TTCA, whereas cysteine inhibited that of Gly-Amadori due to association forming relatively stable thiazolidines. Cys-Amadori/Gly had the highest reactivity in development of both meaty flavors and brown products. TTCA/Gly favored yielding meaty flavors, whereas Gly-Amadori/Cys favored generation of brown products. Conclusively, initial formation of TTCA and pathway involving TTCA with glycine were more applicable to efficiently produce processed-meat flavorings in a cysteine-xylose-glycine system.

Shanxi aged vinegar is one of the most famous Chinese traditional cereal vinegars produced by spontaneous solid-state fermentation. However, the aroma composition of Shanxi aged vinegar is still ambiguous. The Shanxi vinegars before and after aging were both analyzed by solvent-assisted flavor evaporation combined with gas chromatography-mass spectrometry (GC-MS) as well as gas chromatography-olfactometry (GC-O) in aroma extract dilution analysis. A total of 87 odor-active regions were found by GC-O, and 80 odor-active compounds were identified. By GC-MS/MS, in selected reaction monitoring mode, 30 important identifications were quantitated using authentic standards. In comparison, the aroma molecules for the vinegars before and after aging were almost the same; only their levels were altered, with mostly the esters and some compounds that produce pungent smells being lost and the levels of those from the Maillard reaction, especially the pyrazines (e.g., tetramethylpyrazine), being greatly increased. As for the aged vinegar, the compounds found to have high flavor dilution factors (128) were 3-(methylthio)propanal, vanillin, 2,3-butanedione, tetramethylpyrazine, 3-methylbutanoic acid, γ-nonalactone, guaiacol, 3-(methylthio)propyl acetate, dimethyl trisulfide, phenylacetaldehyde, 2-ethyl-6-methylpyrazine, 2-acetylpyrazine, 2,3-dimethylpyrazine, furfural, and 3-hydroxy-2-butanone. However, the aroma compounds found at high concentrations (25 μg/L) in the aged vinegar were acetic acid, followed by 2,3-butanedione, furfural, 3-hydroxy-2-butanone, tetramethylpyrazine, furfuryl alcohol, and 3-methylbutanoic acid.