Ethyl Heptanoate Research Articles

Metagenomic and Metabolomic Profiling Reveals the Differences of Flavor Quality between Hongqu Rice Wines Fermented with Gutian Qu and Wuyi Qu.

Jiuqu (starter) makes an important contribution to the formation of the flavor characteristics of Hongqu rice wine (HQW). Gutian Qu (GTQ) and Wuyi Qu (WYQ) are two kinds of Jiuqu commonly used in HQW brewing, but the comparison of the two kinds of HQW is still insufficient at present. The objective of this study was to compare the dynamic changes of amino acids (AAs), higher alcohols (HAs), bioamines (BAs), volatile flavor compounds (VFCs), and microbial communities in HQW fermentation, with GTQ and WYQ as starter. This study used an automatic amino acid analyzer, GC, HPLC, and GC-MS to detect AAs, HAs, Bas, and VFCs during fermentation; metagenomic sequencing technology was used to elucidate the microbial community and its functional characteristics. The results showed that the contents of AAs and HAs in HQW brewed with WYQ (WYW) were significantly higher than those in HQW brewed with GTQ (GTW). On the contrary, the majority of BAs in GTW were significantly higher than those in WYW. The composition of VFCs in WYW and GTW were obviously different, as most of the VFCs were notably enriched in WYW, while ethyl caproate, isoamyl acetate, ethyl heptanoate, ethyl nonanoate, 1-decanol, citronellol, phenethyl acetate, and hexanoic acid were more abundant in GTW. Burkholderia gladioli, Pantoea dispersa, Weissella cibaria, Monascus purpureus, and Saccharomyces cerevisiae were the predominant microbial populations in GTW brewing at the species level, while Sphingomonas sp., Kosakonia cowanii, Enterobacter asburiae, Leuconostoc lactis, Aspergillus niger, and Saccharomyces cerevisiae were the dominant microbial species in WYW brewing. The abundance of functional genes involved in BAs biosynthesis were much higher in GTW brewing, while the abundance of functional genes related to the metabolism of characteristic VFCs were much higher in WYW brewing. Collectively, these findings provided evidence for elucidating the effects of Jiuqu and microbial communities on HQW flavor quality, and laid a solid foundation for the improvement of HQW flavor quality.

Molecular Sensomics Combined with Random Forest Model Can Reveal the Evolution of Flavor Type of Baijiu Based on Differential Markers.

Baijiu is popular with a long history and balanced flavor. Flavor type is the most widely used classification mode for Baijiu. However, the evolutionary relationships of Baijiu flavor types and the differential markers between flavor types are still unclear, significantly impacting the development of the Baijiu industry. In this study, a total of 319 trace components were identified using gas chromatography-olfactometry-mass spectrometry and gas chromatography-mass spectrometry. Among them, 91 trace components with high odor active values or taste active values were recognized as flavor components. Then random forests were conducted to screen differential markers between the derived and basic flavor types, while a principal component analysis assessed their effectiveness in distinguishing the flavor types of Baijiu. Finally, 19 differential markers (including 3-methylbutyric acid, pentanoic acid, 2-butanol, 2,3-butanediol, ethyl pro-panoate, isobutyl acetate, ethyl butanoate, ethyl hexanoate, ethyl heptanoate, ethyl lactate, ethyl 2-hydroxy butanoate, isopentyl hexanoate, ethyl nonanoate, isopropyl myristate, ethyl tetradecanoate, ethyl benzoate, 2,4-di-t-butylphenol, 2-methylbutanal and 3-octanone) were screened and proven to effectively reveal the evolution of Baijiu flavor types; these were further verified as key differential markers using addition tests and a correlation analysis.

An effective means to improve the flavor quality of traditional fermented sour meat: The salt reduction strategy

The flavor formation of fermented meat products is significantly influenced by salt. In this study, the flavor analysis methods of electronic tongue and nose, gas chromatography-mass spectrometry, and liquid chromatography-mass spectrometry were utilized to explore the effect of salt content on the formation of sour meat flavor. The results demonstrated a significant decrease in pH value with the reduction of salt content (P < 0.05), while there was a significant rise in thiobarbituric acid reactive substances (TBARS) value associated with the decline in salt content (P < 0.05). Alcohols, aldehydes, and esters such as 1-octen-3-ol, 3-methyl-1-butanol, hexanal, heptanal, ethyl octanoate, ethyl heptanoate, etc. were considered to have significant contributions to the overall flavor of sour meat. The rapid accumulation of these aroma compounds under low-salt conditions was regarded as one of the key factors in the overall flavor enhancement of sour meat products. Additionally, the low-salt fermentation also promoted the accumulation of free amino acids and free fatty acids in sour meat products, thereby facilitating the formation of more complex aroma compounds. This study offers new technological ways to improve the conventional method of fermenting sour meat and offers theoretical justification for studies on salt reduction in conventionally fermented meat products.

Inoculation of Zaopei with biofortification: Inducing variation in community structure and improving flavor compounds in Nongxiangxing baijiu.

The deterioration of the quality of raw liquor caused by the low content of ethyl hexanoate in Nongxiangxing baijiu has become a pervasive problem in the baijiu industry. Therefore, this study attempted to increase the synthesis of ethyl hexanoate by microorganisms with high esterase activity to increase Zaopei fermentation. The results showed that biofortification was a feasible and important way to improve the quality of the raw liquor and increase the ethyl hexanoate content. Adding Bacillus subtilis, Staphylococcus epidermidis, and Millerozyma farinosa for biofortified fermentation disturbed the microbial community structure of Zaopei and increased the abundance of Wickerhamomyces, Saccharomyces, and Thermoascus. The contents of ethyl hexanoate, ethyl valerate, ethyl caprylate, and ethyl heptanoate also increased noticeably in baijiu. The results of E-nose and sensory analysis tested and verified that the baijiu in the fortified group had better flavor characteristics.

Dynamic changes of physicochemical parameters, antioxidant activity, organic acids, polyphenols, and volatile components in prune vinegar during fermentation

To investigate the quality variations of prune vinegar during fermentation, multivariate statistical analysis (MSA) was used in conjunction with high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). The results showed that the pH decreased slightly, there was a rapid decline in sugar content, and a gradual increase in total acid content, which achieved stabilization at 3.68 g/100 mL. The content of organic acid increased, while the total phenol content decreased. The total flavonoid content did not change significantly. Furthermore, the antioxidant capacity initially decreased and then increased. Prune vinegar contains important phenolics such as rutin, resveratrol, salicylic acid, trans-ferulic acid, and (+)-catechin. In addition, the flavor of prune fruit vinegar underwent changes during the fermentation process. During the fermentation of fruit vinegar, large quantities of 2,3-butanediol, glacial acetic acid, nonanoic acid, ethyl acetate, ethyl heptanoate, ethyl caproate, and linalool were produced. These compounds give prune vinegar its distinctive fruity and floral aroma. This study provided a comprehensive framework for the efficient processing of prunes and a strategy for enhancing the quality characteristics of prune vinegar or other fermented products.

The Use of Hanseniaspora opuntiae to Improve 'Sideritis' Wine Quality, a Late-Ripening Greek Grape Variety.

In view of climate change and the increasingly antagonistic wine market, the exploitation of native genetic resources is revisited in relation to sustainable wine production. 'Sideritis' is a late-ripening Greek grape variety, which is quite promising for counteracting wine quality issues associated with the annual temperature rise. The aim of this study was to improve the quality and to enhance the aroma of 'Sideritis' wine through the use of native yeasts. To improve vinification, Hanseniaspora opuntiae L1 was used along with Saccharomyces cerevisiae W7 in mixed fermentations (SQ). The addition of H. οpuntiae significantly altered the chemical profile of the wine compared to the single-inoculated fermentations with W7 (IS). H. opuntiae increased all the acetate esters, except for hexyl acetate and (Z)-3-hexen-1-ol acetate. The concentration of 2-phenylethyl acetate, which imparts flowery and sweet notes, exhibited a 2.6-fold increase in SQ as compared to IS wines. SQ also showed higher levels in several ethyl esters, including ethyl butyrate, ethyl heptanoate and ethyl 7-octenoate, which are associated with fruity notes compared to IS. H. opuntiae produced citronellol, a terpene associated with rose and green notes, and increased the overall acceptance of the wine. Present results are thus quite promising for improving 'Sideritis' wine quality towards a sustainable wine production in Greece in view of global warming.

Descriptive temporal sensory properties and volatile composition of Pinot noir wines produced with contrasting alcoholic fermentation temperatures and cap management regimes

Pinot noir is rapidly becoming a winemaking staple in the Central Coast of California. Therefore, it is important to understand how factors such as fermentation temperature and cap management affect the chemical and sensory impact of such wines. Herein, Pinot noir wines were made with three contrasting alcoholic fermentation temperature regimes (Cold, Cold/Hot, Hot) and combined factorially with two cap management regimes (with or without punch downs). The impact of these factors on colour, aroma, and the temporal retronasal aroma and mouthfeel profile was assessed by a trained sensory panel (n = 13) using descriptive analysis (DA) and time-intensity (TI), respectively. Combining a hot fermentation temperature and no punch downs led to wines with higher colour saturation and purple hue. In contrast, wines fermented at cold fermentation temperatures with no punch downs showed reduction aromas. In terms of individual main effects, wines fermented at cold temperatures had more orthonasal aroma, while wines fermented at hot temperatures had higher astringency. To understand the relationship between selected volatile aromas and perceived sensory results, a partial least square regression (PLSR) was conducted. PLSR indicated that cold fermentation temperature wines with punch downs were associated with esters, including ethyl hexanoate and ethyl heptanoate, as well as β-damascenone, which aligned with sensory results. The effect of salivary flow rate on the temporal sensory profile post-expectoration was also analysed. Low salivary flow rate panellists perceived both astringency and length significantly later and more intensely than high salivary flow rate panellists. However, the time of maximum intensity was perceived significantly later for high salivary flow rate panellists. Overall, fermentation temperature had a more significant impact on the sensory and volatile composition of Pinot noir wines than the cap management regime. However, cap management still appeared to affect sensory and volatile chemistry results through significant interactions. Therefore, the relationship between fermentation temperature and cap management was not straightforward from avolatile chemistry or sensory perspective. The importance of accounting for salivary flow rate in panellists when using time-based sensory analysis was also highlighted.

Bioturbation effect of artificial inoculation on the flavor metabolites and bacterial communities in the Chinese Mao-tofu fermentation

A comparison between artificially inoculated Mao-tofu (CC) and naturally fermented Mao-tofu (MM) indicated that artificially adding Mucor plasmaticus to Mao-tofu dramatically enhanced the essential amino acid (EAA) content, as well as umami and sweet amino acids. Gas chromatography-tandem mass spectrometry (GC–MS/MS) analysis revealed that phenol (3.226 μg/g), 1-octen-3-ol (5.031 μg/g), ethyl heptanoate (1.646 μg/g), and indole (3.422 μg/g) were the key flavor components in Mao-tofu. Unlike MM, CC displayed a substantial increase in esters and a considerable decrease in foul odor substances, including sulfur-containing compounds and indole. Lactococcus raffinolactis, Enterobacter sp. 638, and Streptococcus parauberis KCTC 11537 represented the key bacterial species altering the amino acids and flavor of Mao-tofu according to PacBio single-molecule real-time (SMRT) sequencing and correlation analysis. This study presents the technical feasibility of artificially inoculating Mao-tofu to regulate the core bacterial communities and control the quality of fermented soybean products.

Moisturizing and aroma-enhancing effects of low molecular weight fenugreek polysaccharides in cigarettes

Polysaccharides possess excellent moisturizing effects due to their abundance of hydrophilic groups and film-forming properties. Additionally, they can produce a refreshing aroma during the pyrolysis process. However, there is scarce research on their application in the tobacco field. Herein, we investigated the effects of low molecular weight fenugreek polysaccharide (FP) obtained through ethanol fractionation and DEAE-52 cellulose column chromatography on moisture retention and aroma enhancement in tobacco. The moisture retention test revealed that the addition of FP increased the moisture retention index (MRI) of tobacco by 11.72 %–16.69 %, indicating that the hydrophilic nature of polysaccharides facilitated the migration of free water in tobacco to bound water, resulting in reduced water activity. Moreover, the contact angle between polysaccharide and tobacco was <90°, enabling better infiltration into tobacco and slowing down tobacco shrinkage caused by water loss. Among all the components, EFP-20 and EFP-40 demonstrated superior performance. Furthermore, FP exhibited excellent thermal stability below 200 °C and can decomposed to produce aromatic substances at high temperatures. It also demonstrated the ability to adsorb ethyl heptanoate and thermally decompose to produce a substantial amount of heptanoic acid. Consequently, the incorporation of FP in tobacco demonstrated favorable effects on both moisturization and aroma enhancement.

Effect of Maturation with American Oak Chips on the Volatile and Sensory Profile of a Cabernet Sauvignon Rosé Wine and Its Comparison with Commercial Wines

Rosé wines are commonly consumed as young wines mainly due to their freshness and fruity character. Nevertheless, in recent years a new market looking for alternatives to traditional wines has emerged. Considering this, the study of the volatile and sensory profiles of a varietal rosé wine aged with oak chips was carried out. Two Cabernet Sauvignon rosé wines were made: one was maturated with oak chips and the other without. Both wines were physicochemically characterized. Then, their volatile and sensory profiles were analyzed, also including two commercial wines. The results showed that the produced wines complied with Mexican regulations. Also, they showed greater relative areas in compounds such as ethyl (E)-2-hexenoate, ethyl heptanoate, ethyl nonanoate, ethyl 3-nonenoate, β-citronellol, (±)-trans-nerolidol, and β-damascenone. In their sensory profile, they were mostly related to attributes such as berries, prune, bell pepper, and herbaceous notes. Among the compounds related to barrel maturation, only cis-oak-lactone was identified in the rosé wine matured with chips. However, it was associated with vanilla, woody, smoky, and spicy attributes. According to the results, the maturation of rosé wines with oak chips could be a good alternative to provide them with unusual notes and thus offer new alternatives to traditional and new wine consumers.

Identification on regional-markers based on the flavor molecular matrix analysis of sauce-aroma style Baijiu.

Baijiu is a very complex system and its flavor substances are endogenous influenced by raw materials, starter, production process, production region and other factors. The production region directly affects the composition of flavor substances and quality of Baijiu. However, identification of Baijiu region is challenging because the corresponding relationship between the production region and Baijiu quality is not clear, and the identification of regional-markers is indeterminate. In this study, the difference on volatile components of sauce-aroma style Baijiu from four representative regions were investigated. Consequently, a total of 94 volatile compounds were identified in samples tested. Additionally, it was verified that 35 potential flavor substances had important contributions to the aroma of sauce-aroma style Baijiu. Meanwhile, 9 potential regional-markers were screened through multivariate analysis. Further, based on distribution of volatile compounds and the results of sensory evaluation combined with multivariate analysis, molecular matrix and correlation network were established according to the result of addition experiments, which showed that 6 substances had a significant impact on the flavor of the tested samples. In this study, 6 key flavor substances (including ethyl octanoate, ethyl 2-methyl propanoate, propyl acetate, ethyl heptanoate, 2-nonanone and butyl hexanoate) were considered as important regional-markers to effectively identify the production region of sauce-aroma style Baijiu. This article is protected by copyright. All rights reserved.

Effect of Drying Process on the Formation of the Characteristic Flavor of Oyster (Crassostrea hongkongensis).

Oysters are nutritious and tasty but difficult to store. Drying can extend the storage period of oysters and give them a unique flavor. In this study, the effects of four drying procedures, namely, vacuum freeze drying (VFD), vacuum drying (VD), natural sun-drying (NSD), and hot air drying (HAD), on the flavor characteristics of oysters (Crassostrea hongkongensis) were investigated using blanched oysters as a control (CK). Results showed that HAD produced more free amino acids than the other methods, but VFD retained the most flavor nucleotides. Compared with cold drying (VFD), hot drying (VD, NSD, and HAD) increased the abundance of organic acids, betaine, and aroma substances. Glutamic acid, alanine, AMP, hexanal, octanal, heptanal, (E, E)-2,4-heptadienal, (E)-2-decenal, nonanal, etc., are defined as the characteristic flavor compounds of dried oysters, with umami, sweet, green, fatty, and fruity aromas being the main organoleptic attributes of dried oysters. Glutamic acid, glycine, betaine, IMP, pentanal, ethyl heptanoate, (E, Z)-2,4-nonadienal, 1-octen-3-one, 2-hexenal, 2-octenal, hexanal, decanal were defined as markers to distinguish different drying methods. Overall, HAD showed improved flavor qualities and characteristics and was better suited for the highly commercialized production of dried oysters.

Flavor evolution of normal- and low-fat Chinese sausage during natural fermentation

This work compared the flavor evolution of normal-fat (NF) with that of low-fat (LF) Chinese sausage during natural fermentation. Higher degree of lipid oxidation occurred in NF sausages, resulting in its faster formation of stable volatile profiles. Faster formation of esters occurred in NF sausage in the initial 10 days, whereas prolonged fermentation reduced the level of ethyl lactate-M, ethyl heptanoate, ethyl hexanoate-D and ethyl pentanoate-D. Gradual reduction of alcohols was observed in both groups, and surge in aldehydes occurred in LF samples during day 20–30 period. Faster formation of taste characteristics and larger amount of 2-methylfuran as well as 2,3-dimethylpyrazine were found in LF sausages, since more free amino acids were liberated in LF sausages. Umami and aftertaste tastes formed in the first 20 days, whereas prolonged fermentation reduced these favorable taste. These results highlight that the choice of proper fermentation duration should largely depend on the fat content in Chinese sausages.

Development of attractants and repellents for Tuta absoluta based on plant volatiles from tomato and eggplant

IntroductionTuta absoluta is currently considered one of the most devastating invasive pests of solanaceous plants worldwide, causing severe damage to the tomato industry. Insects use volatile organic compounds (VOCs) to locate host plant for feeding and oviposition. Those VOCs could be developed as lures for pest monitoring and control.MethodsIn this study, the differentially accumulated VOCs between the preferred host (tomato) and non-preferred host (eggplant) were analyzed by GC–MS method, and their roles on female T. absoluta host selection and egg laying behaviors were investigated using electroantennography (EAG), olfactometer and cage experiments.ResultsA total of 39 differentially accumulated VOCs were identified in tomato and eggplant. Strong EAG signals were obtained in 9 VOCs, including 5 VOCs highly accumulated in tomato and 4 VOCs highly accumulated in eggplant. Further olfactometer bioassays showed that 4 compounds (1-nonanol, ethyl heptanoate, ethyl octanoate and o-nitrophenol) were attractive to T. absoluta females, while 5 compounds (2-phenylethanol, 2-pentylfuran, trans,trans-2,4-nonadienal, 2-ethyl-5-methylpyrazine and trans-2-nonenal) were repellent, indicating that VOCs from host plants play important roles in host plant preferences. The attractive activities of 1-nonanol and ethyl octanoate, as well as the repellent activities of trans,trans-2,4-nonadienal and trans-2-nonenal, were further confirmed in cage experiments.DiscussionIn this study, two attractants and two repellents for T. absoluta were developed from plant released VOCs. Our results could be useful to enhance the development of eco-friendly and sustainable pest management strategies for T. absoluta.

Effects of fermentation on flavor and antioxidant activity in ginkgo rice wine

Ginkgo seed is a kind of food and medicine homologous goods. It is a feasible method to use Saccharomyces cerevisiae and Non-Saccharomyces yeast to ferment ginkgo rice wine (GRW) to remove the bitter taste and retain the biological activity. In order to better explore the formation of the unique flavor and taste of GRW, the volatile flavor compounds and sensory properties of GRWs fermented at different time were analyzed by GC-MS, GC-IMS and electronic sensory evaluation techniques. In addition, the changes of phenols in GRW were determined by LC-MS, and the antioxidant activity was dynamically monitored. GC-MS analysis showed the content of ethyl laurate, isoamyl acetate, ethyl heptanoate, 1-pentanol, ethanol and 1-propanol increased significantly with the progress of fermentation, among which ethyl acetate (OAV = 23.0), ethyl heptanoate (OAV = 44.4) and isoamyl acetate (OAV = 34.7) were the key flavor compounds of GRW at 60 h. GC-IMS analysis suggested some alcohols and ketones were significantly enriched at 60 h, including 2-pentanone, acetone, 1-butanol, 1-hexanol. Electronic sensory technology showed GRW at 60 h had strong mellow and fruity aroma due to benzoic acid, butyric acid and 2-methylbutyric acid. The bitterness and umami intensity in GRW gradually decreased, while the astringency and aftertaste increased. Furthermore, LC-MS results indicated the types of phenols increased, including quinic acid, shikimic acid, sorbic acid, etc., which significantly improved the antioxidant activity of GRW. Together, the flavor quality and biological activity of GRW had been effectively improved through microbial fermentation, which indicated that GRW had potential market prospects.

Olfactory Responses of Anastrepha obliqua (Diptera: Tephritidae) to Mango Fruits as Influenced by Cultivar and Ripeness Stages.

Anastrepha obliqua Macquart (Diptera: Tephritidae) is a polyphagous species with hog plums (Spondias spp.) (Sapindales: Anacardiaceae) and mangoes (Mangifera indica L.) (Sapindales: Anacardiaceae) as primary host fruits. In this study, the olfactory preference of A. obliqua for three stages of ripeness of two mango cultivars ('Coche' and 'Ataulfo') was investigated. The female flies were more attracted to ripe 'Coche' fruits compared to those ripe 'Ataulfo'. Further, they were more attracted to the 'Coche' half-ripe and ripe fruits than to the unripe ones, but they did not discriminate among the stages of ripeness of 'Ataulfo' fruits. The male flies did not show preference for any specific mango cultivars or ripeness stage tested. Four compounds from ripe 'Coche' mangoes, and two from ripe 'Ataulfo' fruits were identified using coupled gas chromatography-electroantennographic (GC-EAD) recording and gas chromatography-mass spectrometry (GC-MS) analysis. 'Coche' mango volatiles eliciting responses from the female antennae were ethyl butyrate, ethyl hexanoate, ethyl heptanoate, and ethyl octanoate. The two 'Ataulfo' mango volatiles were identified as 3-carene and ethyl octanoate. These compounds were absent in unripe mangoes of both cultivars. Synthetic blends of these compounds were attractive to females as mango extracts in field cage tests. Our results suggest that the olfactory preference of A. obliqua for attractive hosts is based on the presence or absence of the compounds associated with fruit maturity.

Characterization of the aroma release from retronasal cavity and flavor perception during baijiu consumption by Vocus-PTR-MS, GC×GC-MS, and TCATA analysis

This experiment investigated the dynamic sensory profile and changes in retronasal aroma during the drinking process of baijiu (53%Alcohol by Volume). The Temporal Check-All-That-Apply (TCATA) method was used to characterize the dynamic sensory changes of baijiu. The use of Vocus proton transfer reaction mass spectrometry (Vocus-PTR-MS) in combination with GC × GC-MS revealed 83 potentially dominant volatile aroma compounds that associated with 69 Vocus-PTR-MS ions. The contribution of the compounds to the perception of baijiu was found to be related with their compound type and hydrophobicity. Hydrophilic compounds dominated the aroma burst-stage, with small molecule alcohols, aldehydes, and phenols etc. contributed a variety of aromas and enriched the baijiu drinking experience. Hydrophobic compounds dominated the aftertaste-stage, particularly C7-9 esters, alcohols, and aldehydes, dominating flavor perception of baijiu drinking. Finally, 1-butanol, ethyl lactate, phenylacetaldehyde, octanoic acid, ethyl hexanoate, and ethyl heptanoate were selected as the key aroma compounds contribute to the changes in sensory perception during baijiu drinking.

Key aroma-active compounds identification of Ziziphus jujuba cv. Huizao: Effect of pilot scale freeze-drying

Aroma profile and key aroma-active of red jujube subjected to pilot scale freeze drying (FD) were investigated based on molecular sensory science. After FD, 41 aroma compounds were identified through gas chromatography-olfactometry-mass spectrometry (GC-O-MS) and quantified through calibration curves. The total aroma compounds content was decreased 26.71% compared with raw red jujube, of which ketones and acids contents were decreased 63.33% and 62.88%, while, the esters, lactones and alcohols contents were increased 34.10%, 8.52% and 480.17%, respectively. Through the GC-O-MS, odor active values combined with recombination and omission tests, 14 key aroma-active compounds were identification in freeze-dried red jujube. In which, 2-ethyl-3,5-dimethyl-pyrazine had the highest OAV (2687.00) and dominated the roast note of aroma profile. In addition, ethyl heptanoate, hexyl acetate, 2,3-butanediol, ethyl dodecanoate and 5-heptyloxolan-2-one were newly identified as the key aroma-active compounds in freeze-dried red jujube.

Effects of bio-augmented Daqu on microbial community, aroma compounds and physicochemical parameters of fermented grains during the brewing of Chinese special-flavor baijiu.

Bio-augmented Daqu is used to improve the microbial community and physicochemical parameters of fermented grains, thus affecting the flavor and quality of baijiu. This study investigated the effects of bio-augmented Daqu inoculated with Aspergillus niger NCUF413.1 and Saccharomyces cerevisiae NCUF304.1 on the microbial community, aroma compounds, and physicochemical parameters of fermented grains during special-flavor baijiu brewing. Compared with the control group (CG), the utilization of starch and production of ethanol in the inoculated group (IG) increased by 3.55% and 12.59%, respectively. The use of bio-augmented Daqu changed the bacterial communities. For example, Kroppenstedsia was the dominant bacterial genus (the relative abundance was about 22%) in the CG while Lactobacillus was the main dominant genus (the relative abundance was more than 30%) in the IG on days 20-30. Lactobacillus showed a significant positive correlation with the aroma compounds. The use of bio-augmented Daqu increased the aroma compound content - such as the ethyl heptanoate and ethyl hexanoate content. The addition of bio-augmented Daqu with A. niger and S. cerevisiae could change microbial communities, resulting in an increase in the yield of ethanol and the aroma compound content of fermented grains, thus improving the quality of baijiu. © 2022 Society of Chemical Industry.

Characterization and correlation of dominant bacteria and volatile compounds in post-fermentation process of Ba-bao Douchi

Ba-bao Douchi, traditionally produced and spontaneously fermented for 1–2 years, has a unique flavor. However, little information is known about microorganisms and volatile flavors, particularly their relationship. In this study, the aroma profiles including the key aroma compounds, and bacterial communities were characterized and the correlations between dominant bacterial genera with key aroma compounds were studied during the post-fermentation of Ba-bao Douchi. The research showed that 12 bacterial genera were identified as the dominant genus by high-throughput sequencing. A total of 84 volatile compounds were detected by HS-GC-IMS and HS-SPME-GC–MS. Odor activity value (OAV) and gas chromatography-Mass spectrometry-olfactometry (GC–MS-O) were combined to determine the key volatile compounds, and the main volatile compounds including ethyl hexanoate, ethyl heptanoate, isovaleraldehyde, (+)-α-pinene, beta-phellandrene, were found to be responsible for the strong fruitiness, chocolate fragrance, fresh scent flavor, and ginger flavor of Ba-bao Douchi. Pearson correlation analysis showed that 5 dominant bacterial genera were positively associated with > 6 key volatile compounds (p < 0.01, |r| > 0.7). Thus, these bacterial genera might have an effect on the biosynthesis of volatile components. This study provides a theoretical reference for revealing the functional microorganisms and improving the flavor quality of Ba-bao Douchi.