Mingquan Huang

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.

Triple-channel comparative analysis of volatile flavour composition in raw whole and skim milk via electronic nose, GC-MS and GC-O

A novel triple-channel comparative analysis of volatile composition in raw whole and skim milk (RWM and RSM) was developed via an electronic nose (E-Nose), headspace solid-phase micro-extraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS), and gas chromatography-olfactometry (GC-O). Volatile flavour compounds from RWM and RSM caused the differences in mouthfeel characteristics by the human sensors, and also affected consumer preference. Solid state sensor technology, an E-Nose, was applied to distinguish the differences in volatiles between RWM and RSM. Headspace volatiles adsorbed by HS-SPME fiber (CAR/PDMS) were detected by GC-MS. Aroma compounds were identified by GC-O. Nine and three compounds were found to be aroma-active compounds from RWM and RSM, respectively. Octanoic acid, butanoic acid, and 3-hydroxy-2-butanone were found to be the most important aroma-active compounds in RWM, while the most important aroma-active compound of RSM was octanoic acid.

The Occurrence of Propyl Lactate in Chinese Baijius (Chinese Liquors) Detected by Direct Injection Coupled with Gas Chromatography-Mass Spectrometry

As one of the oldest distillates in the world, flavor compounds of Chinese Baijiu (Chinese liquor) were extremely complex. Propyl lactate was firstly detected by direct injection and gas chromatography-mass spectrometry (GC-MS) in 72 Chinese Baijius. The objectives were to detect the contents of propyl lactate and evaluate its contribution to the aroma of Chinese Baijiu based on odor activity values (OAVs). The levels of propyl lactate in these distillates were determined by internal standard method and selective ion monitoring (SIM), which ranged from 0.050 to 1.900 mg∙L−1 under investigation. Its detection threshold was determined by Three-Alternative Forced-Choice (3-AFC) and curve fitting (CF), which was 0.740 mg∙L−1 in 38% ethanol solution. The contribution of propyl lactate on the aroma of these distillate drinks was evaluated by their odor activity values (OAVs), which varied from 0.066 to 4.440. The OAVs of propyl lactate were found to exceed 1 in 13 Chinese Baijius, including 50° Jingzhi Guniang 5 years (4.440), 52° Jingzhi Guniang 10 years (3.024), Jingyanggang (2.568), Xianghe Ronghe Shaofang (2.313), and 1956 Laolang (1.431), which indicated that propyl lactate was one of odor-active components in these Chinese Baijius.

Preparation and aroma analysis of Chinese traditional fermented flour paste

Volatile compounds in Chinese fermented flour paste were extracted using simultaneous distillation and extraction (SDE) and analyzed using gas chromatography-mass spectrometry (GC-MS) with DB-5 and DB-WAX capillary columns. A total of 84 volatile compounds were identified, including 8 aldehydes, 19 esters, 14 acids, 17 hydrocarbons, 7 heterocycles, and 19 other trace compounds. The major volatiles included furfural, 5-methyl-2-phenyl-2-hexenal, 4-ethylguaiacol, 2-phenylacetaldehyde, ethyl hexadecanoate, isovaleraldehyde, palmitic acid, and 5-methylfurfural. Aroma compounds were investigated using gas chromatography-olfactometry (GC-O) and aroma extract dilution analysis (AEDA). A total of 27 olfactory regions were exposed and 18 aroma extracts were located. Altogether, 6 aroma compounds identified using GC-O showed higher flavor dilution factors (FD≥32), including isovaleraldehyde, furfural, pentanoic acid, 2-acetylfuran, 1-octen-3-ol, and 2-phenylacetaldehyde. Compared with soybean sauce, fermented flour paste has more esters and aldehydes, which contribute to the desired fruity, caramel, sweet, and roasted odors.

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.

Characterization of the Potent Odorants Contributing to the Characteristic Aroma of Beijing Douzhi by Gas Chromatography–Olfactometry, Quantitative Analysis, and Odor Activity Value

Beijing douzhi (BD) is a traditional snack in Beijing, China, and it has been listed as a part of Beijings intangible cultural heritage. The potent odorants that contribute to the characteristic aroma of BD were investigated by analyzing the isolates from solvent-assisted flavor evaporation (SAFE) and simultaneous distillation-extraction. Using aroma extract dilution analysis based on gas chromatography-mass spectrometry and gas chromatography-olfactometry, 31 aroma-active compounds with flavor dilution (FD) factors ranging from 1 to 2187 were identified by comparison of their odor characteristics, MS data, and retention indices with those of reference compounds. To further determine their contribution to the aroma of BD, the odorants isolated using SAFE with FD factors ≥9 were quantified, and their odor activity values (OAVs; ratio of concentration to the respective odor threshold in water) were calculated. Eleven compounds were found to have OAVs ≥ 1, which indicated they were the potent odorants that contributed substantially to the characteristic aroma of BD. Among the 11 odorants, (E,Z)-2,6-nonadienal, eugenol, methional, p-cresol, 1-octen-3-one, and 3-methylbutanoic acid were not previously identified in BD.

Isolation and identification of antibiotic albaflavenone from Dictyophora indusiata (Vent:Pers.) Fischer

A sesquiterpene antibiotic was isolated from the dried fruiting body of Dictyophora indusiata (Vent: Pers.) Fischer by solvent extraction and column chromatography and identified as albaflavenone by FTIR, GC-MS, HR-FIMS and NMR spectra. The content of albaflavenone in the dried fruiting body of Dictyophora indusiata (Vent: Pers.) Fischer (the content of water was 15.63%) was quantified by GC through an external standard method to be about 0.0063%. The compound isolated has an earthy, camphor-like odour.