Hehe Li

Characterization of the Key Odorants in Chinese Zhima Aroma-Type Baijiu by Gas Chromatography-Olfactometry, Quantitative Measurements, Aroma Recombination, and Omission Studies.

Zhima aroma-type Baijiu with typical sesame aroma is particularly popular in northern China. To our knowledge, it is still uncertain which components are important to make contributions to its unique aroma, although a few pieces of research have reported many volatile compounds in this Baijiu. The aroma-active compounds from the Baijiu were researched in this paper. A total of 56 odorants were identified in Chinese Zhima aroma-type Baijiu by aroma extract dilution analysis (AEDA). Their odor activity values (OAVs) were determined by different quantitative measurements, and then 26 aroma compounds were further confirmed as important odorants due to their OAVs ≥ 1, and these had higher values, such as ethyl hexanoate (OAV 2691), 3-methylbutanal (2403), ethyl pentanoate (1019), and so on. The overall aroma of Zhima aroma-type Baijiu could be simulated by mixing of the 26 key odorants in their measured concentrations. The similarity of the overall aroma profiles between the recombination model and the commercial sample was judged to be 2.7 out of 3.0 points. Omission experiments further corroborated the importance of methional and ethyl hexanoate for the overall aroma of Chinese Zhima aroma-type Baijiu.

Characterization of key aroma compounds in Gujinggong Chinese Baijiu by gas chromatography–olfactometry, quantitative measurements, and sensory evaluation

One of famous Chinese Baijiu, Gujinggong (GJG) that is produced in Anhui province, belongs to the famous Luzhou-aroma type of Baijiu in regards of its unique flavor characteristics. However, its key aroma-impact volatiles have not been clearly characterized. In this study, a total of 60 aroma compounds of GJG were identified by GC-O and GC-MS, and 35 of them were further recognized as important aroma compounds owing to their OAVs≥1 and sensory evaluation. As a result, its aroma profile was successfully simulated by reconstitution of those 35 and other 11 aroma compounds based on their measured concentrations in the GJG. Moreover, omission test was applied to investigate the effects of the important aroma compounds on the whole aroma profile of GJG. In this context, 9 aroma compounds were confirmed as the key aroma compounds of GJG.

Cytoprotective effects of a tripeptide from Chinese Baijiu against AAPH-induced oxidative stress in HepG2 cells via Nrf2 signaling

Antioxidant peptides have been widely reported, whereas the intracellular antioxidant activity of a tripeptide (Pro-His-Pro, PHP), which was newly isolated and identified from Chinese Baijiu in our previous study, are still poorly understood. This study investigated the protective effects of PHP on 2,2′-azobis (2-methyl-propanimidamidine) dihydrochloride (AAPH)-induced oxidative stress in HepG2 cells and the involved molecular mechanisms. Pretreatment with PHP suppressed the generations of reactive oxygen species (ROS), malondialdehyde (MDA) and oxidized glutathione (GSSG), prevented a decrease in reduced glutathione (GSH), and up-regulated the activities of cellular antioxidant enzymes. Moreover, PHP treatment stimulated the mRNA and protein expression levels of antioxidant enzymes and nuclear factor E2 related factor 2 (Nrf2). Meanwhile, PHP markedly reduced the level of Kelch-like ECH-associated protein 1 (Keap1), suggesting that PHP effectively activated Nrf2/antioxidant response element (ARE)-mediated activity. These findings provide the first molecular basis for the health-promoting effects of PHP to prevent AAPH-induced oxidative stress.

Joint direct injection and GC–MS chemometric approach for chemical profile and sulfur compounds of sesame-flavor Chinese Baijiu (Chinese liquor)

Sesame-flavor Chinese Baijiu (SFCB) is a popular type of Chinese Baijiu because of its unique sesame-like aroma. Direct injection combined with gas chromatography–mass spectrometry (GC–MS) was successfully applied to determine volatile compounds in 36 sesame-flavor Chinese Baijiu (SFCB) samples and total of 125 volatile compounds were detected, 30 volatiles were further identified as impact aroma compounds of Guojing SFCB by aroma extract dilution analysis (AEDA). As a category of characteristic aroma compounds of SFCB, five sulfur compounds detected were quantified by internal standard method followed by GC–MS with Selected Ion Monitor (GC–MS/SIM). The contents of dimethyl disulfide and dimethyl trisulfide in most SFCB samples were extremely higher than their olfactory thresholds, which indicated these sulfur compounds made significant contribution to the aroma profile of SFCB. Composition differences between the SFCB samples of various brands were investigated. Statistical analyses on the contents of sulfur compounds and peak area data were used to distinguish SFCB samples from different brands. The results of correlation cluster analysis and principal component analysis (PCA) showed that a group of common volatile compounds appeared to occur in the SFCB samples of different brands and may constitute the aromatic skeleton for SFCB although a few particular volatiles were found to be specific for the samples of a certain brand. Therefore, differences between SFCB samples were more likely due to the distinguishing balance states established by the group of common volatiles with different concentrations rather than the presence of specific volatiles with unique aromas.

Intracellular antioxidant effect of vanillin, 4-methylguaiacol and 4-ethylguaiacol: three components in Chinese Baijiu

Vanillin, 4-methylguaiacol, and 4-ethylguaiacol, three bioactive components in Chinese Baijiu (Chinese liquor), were evaluated in terms of their possible antioxidant activities by DPPH, ABTS, ORAC, reducing power, metal chelation assays, and AAPH-induced HepG2 cell model. In in vitro chemical assays, vanillin, 4-methylguaiacol, and 4-ethylguaiacol exhibited stronger antioxidant activities than Trolox in ABTS, ORAC, and reducing power assays. Furthermore, three levels of treatment (1000, 500 and 10 mg L−1) of vanillin, 4-methylguaiacol, and 4-ethylguaiacol were assessed in the AAPH-induced HepG2 cell model. The results show that vanillin, 4-methylguaiacol, and 4-ethylguaiacol exerted similar antioxidant activities in a dose-dependent manner, and relieved the increased reactive oxygen species (ROS) quickly and efficiently; they also markedly improved AAPH-induced alterations in oxidative stress biomarkers and antioxidant enzymes, and were even more effective than Trolox. These findings indicate that vanillin, 4-methylguaiacol, and 4-ethylguaiacol are potent natural antioxidants in Chinese Baijiu, and this lays the foundation for better illustrating the health benefits of Chinese Baijiu.

Quantification and cytoprotection by vanillin, 4-methylguaiacol and 4-ethylguaiacol against AAPH-induced abnormal oxidative stress in HepG2 cells

Vanillin, 4-methylguaiacol, and 4-ethylguaiacol, three phenolic compounds in Gujinggong (GJG) Chinese baijiu (Chinese liquor), were quantified by liquid–liquid extraction (LLE) combined with gas chromatography-mass spectrometry (GC-MS) and evaluated for their possible cytoprotective effects by AAPH-induced HepG2 cell model. To confirm whether vanillin, 4-methylguaiacol, and 4-ethylguaiacol protected HepG2 cells against AAPH-induced abnormal oxidative stress via motivating the Keap1–Nrf2 pathway, the gene and protein expression of Nrf2, Keap1, SOD, CAT, and GPx from the Keap1–Nrf2 pathway were measured with real-time PCR and western blot. Three levels of treatment doses (1000, 500, and 100 mg L−1) were applied. Results showed that vanillin, 4-methylguaiacol, and 4-ethylguaiacol exhibited potent cytoprotective effect in a dose-dependent manner, greatly alleviating or reversing the increased oxidative stress induced by AAPH through up-regulating the mRNA and protein expression levels of Nrf2, SOD, CAT, and GPx, and thereby, significantly improving the intracellular antioxidant defense system in HepG2 cells (p < 0.05). Based on these findings, it was confirmed that vanillin, 4-methylguaiacol, and 4-ethylguaiacol, natural components of Chinese baijiu, were able to modulate the expression of Nrf2 and its downstream antioxidative enzymes (i.e., SOD, CAT, and GPx) against AAPH-induced abnormal oxidative stress. Further, this study lays the foundation for better illustrating the health benefits of Chinese baijiu.

Characterization of key aroma compounds in Meilanchun sesame flavor style baijiu by application of aroma extract dilution analysis, quantitative measurements, aroma recombination, and omission/addition experiments

The aroma components in Meilanchun sesame flavor style baijiu were identified by aroma extract dilution analysis (AEDA), quantitative analysis, aroma active compound recombination, and omission/addition experiments. 92 components in Meilanchun were identified. Among them, 47 odor active compounds were further confirmed by GC-MS/O with aroma extract dilution analysis (AEDA). Ethyl pentanoate, 3-methy-1-butanol, methional, ethyl 3-phenylpropanoate, phenethyl alcohol had the highest flavor dilution (FD) factors (FD = 2187). Among the 88 components that were determined in terms of their odor activity values (OAVs), 35 compounds showed OAVs ≥ 1. Furthermore, a reconstitution model was prepared by mixing the above mentioned 35 compounds, lactic acid, phenethyl alcohol and 2-methoxy-1,3-dioxolane, and showed a good similarity to the aroma of Meilanchun baijiu. Omission/addition experiments further confirmed that ethyl hexanoate (OAV 1945), ethyl butanoate (OAV 838), 3-methyl-1-butanol (OAV 2), 3-methylbutanal (OAV 618), methional (OAV 59), and dimethyl trisulfide (OAV 44), might be the most important compounds for the unique flavor of Meilanchun baijiu. In addition, phenols and acetoin (OAV 66) were confirmed to be the key odorants and the odorless compound lactic acid played a significant role in the roasted sesame flavor baijiu by the omission experiments.

Interactions between p-cresol and Ala-Lys-Arg-Ala (AKRA) from Sesame Flavor-type Baijiu

The objective of this study was to investigate the influence of Ala-Lys-Arg-Ala (AKRA), a tetrapeptide newly identified from Chinese Sesame flavor-type Baijiu in our previous work, on its binding ability with aroma compounds. A method using headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC/MS) was employed to determine the corresponding binding ability between different concentrations of AKRA (10 - 1000 μg/L) and aromas in Baijiu. In comparison, the aroma molecules in Baijiu before and after adding AKRA were almost the same; only their volatility was altered, with mostly the esters, alcohols, and phenolic compounds being decreased. Additionally, AKRA slightly changed the whole aroma profile of Baijiu, especially with respect to p-cresol (an off-odor in sesame-flavor-type Baijiu), which was verified by systematic sensory experiments including gas chromatography-olfactometry (GC-O) and odor activity values (OAVs) analysis. The nonvolatile tetrapeptide favored the hydrogen bond interactions with p-cresol, forming the AKRA- p-cresol complex, thus reducing the headspace concentration of phenolic off-flavors as evidenced by HS-SPME-GC/MS, ultraviolet (UV) absorption spectroscopy, and nuclear magnetic resonance spectrum (1H NMR) analysis. Meanwhile, the hydrogen bond interaction was further confirmed with the intermolecular cross-peaks between the carboxyl hydrogen of AKRA and the phenolic hydroxyl of p-cresol by nuclear Overhauser effect spectroscopy (1H-1H NOESY).

Validation of a QuEChERS-Based Gas Chromatography-Mass Spectrometry (GC-MS) Method for Analysis of Phthalate Esters in Grain Sorghum: PAEs analyzation in GS by QuEChERS/GC-MS…

A modified QuEChERS method coupled with gas chromatography-mass spectrometry (GC-MS) was developed for analysis of 14 phthalate esters (PAEs) in grain sorghum (GS). Chemical extraction was done with acetonitrile followed by dispersive-solid phase extraction technique with a mixture of sorbents including primary secondary amine and octadecyl silica. Under the optimized condition, the matrix-matched calibration curves for all PAEs showed good linear relationship in the concentration range between 5 and 500 μg/L with correlation coefficients (R2 ) better than 0.99. Mean recoveries were between 82.0% and 120.2% at spiking levels of 0.06, 0.6, and 2.0 mg/kg with RSD of 0.3% to 7.8% (n = 5) for intra-day precision and 1.2% to 7.6% (n = 5) for inter-day precision. The LODGS and LOQGS for 14 PAEs were between 0.4 and 10.0 μg/kg and 0.5 and 20.0 μg/kg, respectively. Analysis of 32 commercial GS samples revealed that dimethyl-, diethyl-, diisobutyl-, dibutyl-, and di- (2-ethylhexyl) phthalate esters were detected in all of the analytes. In addition, content-color scale model was applied to visualize the concentration differences of PAEs in real GS samples. Principal component analysis of PAEs revealed that the GS samples did not have a distinctive cluster based on their geographic origins. The established method was proven to be simple, accurate, and effective for analysis of PAEs in GS, which might also be applied for analysis of PAEs in other matrices. PRACTICAL APPLICATION A modified QuEChERS-based GC-MS method was developed for the determination of phthalate esters (PAEs) in grain sorghum (GS). The ubiquitous presence of PAEs can migrate into GS. Therefore, evaluation of the total content of PAEs in GS is helpful to understand its impact of overall pollution level on other foods. This study has provided some basic information in terms of the content and contamination of PAEs in GS, which is helpful to establish relevant standards and risk assessment of GS for the government.