Important Aroma Compounds Research Articles

Combined analysis of transcriptome and metabolome reveals the effects of novel aroma-producing Naumovozyma castellii on Feng-flavor Baijiu

Feng-flavor Baijiu has an elegant and pleasant aroma and is one of the four traditional famous liquors in China. A strain of Naumovozyma castellii XF0241 with excellent fermentation performance and rich aroma compounds was isolated and screened from the Feng-flavor fermented grains. Metabolomic analysis showed that the main flavor compounds of XF0241 are esters, terpenes, and heterocyclic compounds, which are important aroma and flavor compounds in Feng-flavor Baijiu. Compared with the model strain N. castellii CBS4309, the yeast's ester, terpenes and heterocyclic compounds were up-regulated by 168.99±45.31 %, 103.54±28.45% and 108.46±36.78% respectively. After adding additional XF0241 to the Feng-flavor fermented grains, the flavor compounds became more abundant, among which the ester showed the highest increase, followed by terpenoids and heterocyclic compounds. Transcriptomic analysis showed that 1134 genes were differentially expressed. The combined analysis of transcriptome and metabolome revealed that 10 enzymes related to ester production and 3 enzymes related to terpenoid biosynthesis, and 1 enzyme related to heterocyclic formation were significantly upregulated. We believe that XF0241 is one of the core yeasts of Feng-flavor Baijiu. Its production of rich aroma compounds plays an important role in the formation of the special aroma of liquor.

Hydrazides: An Important Tool for the Synthesis of 1,3,4-Oxadiazole

Abstract: Hydrazides, derivatives of hydrazine, are widely used in pharmaceuticals, polymers, dyes, herbicides, and as chemical preservatives. A notable application is in synthesizing 1,3,4-oxadiazole, an important aromatic compound with a five-membered heterocyclic ring containing two nitrogen atoms and one oxygen atom. Among the four oxadiazole isomers, 1,3,4-oxadiazole is the most significant, used in drug discovery, pharmaceuticals, and dyes. It is synthesized from various substituted hydrazides or hydrazones using reagents like copper, cobalt, cerium, phosphorus oxychloride, mercury oxide, potassium iodide, triflic anhydride, and carbon disulfide. This study reviews the synthesis methods of 1,3,4-oxadiazole, highlighting the advantages and disadvantages of different catalysts and conditions, providing useful insights for researchers.

Changes in meat quality and volatile flavor compounds profile in beef loin during dry-aging

The objective of this study was to evaluate the effects of dry-aging on beef meat quality changes and flavor compound developments during dry-aging periods. The results showed increased pH and weight loss (P < 0.01), while decreased water content, drip loss, centrifugation loss, and cooking loss (P < 0.01) with dry-aging. The extension of dry-aging significantly improved shear force and myofibrillar protein fragmentation (P < 0.05) of beef loins. However, longer-term dry-aged (28 d) meat exhibited much lower a* values, and higher 2-thiobarbituric reactive substances and carbonyl content (P < 0.01) at the end of dry-aging and even subsequent display. A total of 62 volatile flavor compounds were detected with whole dry-aging periods, and aldehydes were the major potential contributors to cooked beef meat flavor. Principal component analysis indicated the difference in flavor compounds profiles between unaged and dry-aged beef. The content of Strecker aldehydes (2-methyl-butanal and 3-methyl-butanal), some acids, heterocyclic compounds, and ethyl acetate increased with the prolongation of dry-aging time. By combining partial least squares discrimination analysis, 34 compounds with variable importance projection (VIP) > 1 were screened as important aroma compounds changed during the dry-aging processing of beef.

Effects of different fixation methods on the aroma quality of Anjibai tea

Fixation is a crucial step in the processing of Anjibai tea. In this study, gas chromatography tandem with mass spectrometry was used to analyze the aroma compositions of Anjibai tea across three types of fixation methods: roller-electrical fixation (REF), carding machine fixation (CMF), and roller-hot air fixation (RHF). Nine key volatile compounds were found responsible for Anjibai tea's aroma variations. Results from quantitative descriptive analyses, along with aroma recombination and omission tests, showed that linalool and geraniol significantly contribute to the formation of the medium flowery, fruity, and honey aromas in the REF samples; hexanal has a significant impact on the green aroma in the CMF samples; and 2-ethyl-3,6-dimethylpyrazine is an important aroma compound for the strong roasty aroma in the RHF samples. These findings provide an important theoretical foundation for improving the aroma quality of Anjibai tea and selecting the optimal fixation method.

Effect of gamma irradiation on sensory and aroma compounds of soaked bayberry jiu

Soaked bayberry jiu is a homely fruit alcoholic beverage that produced by soaking bayberry in Baijiu, a traditional Chinese distilled spirit. To investigate the changes in the sensory and aroma compounds of soaked bayberry jiu following gamma irradiation, the sensory evaluation, electron nose, electron tongue, and headspace solid-phase microextraction gas chromatography mass spectrometry (HS-SPME-GC-MS) were conducted. The results showed that the different irradiation doses of samples could be well separated. The taste and smell of 6 kGy irradiated soaked bayberry jiu were significantly improved, but the color of irradiated samples was deteriorated. Moreover, a total of 53 differential products (21 decreased and 32 increased products) were detected compared 6 kGy irradiated soaked bayberry jiu to unirradiated sample, including some important aroma compounds of Baijiu, indicating that the active free radicals produced by gamma irradiation promote the oxidation-reduction reaction in soaked bayberry jiu and lead to the mutual transformation and equilibrium among the compounds. These findings suggest that gamma irradiation can improve the quality of soaked bayberry jiu.

Comparison of Aroma Profiles of Whiskeys Fermented from Different Grain Ingredients.

Different grain sources of whiskey have great potential for aroma expression. In this paper, four whiskeys fermented from different raw materials (barley, wheat, highland barley, and sorghum) were compared. Gas chromatography-mass spectrometry (GC-MS) and sensory evaluation were used to determine the composition of the aromatic compounds. A correlation analysis was further conducted between the aromatic compounds and sensory evaluations. Barley whiskey and wheat whiskey had more pronounced fruity, floral, and grain aromas, attributed to esters and terpenes. Barley whiskey had the most compounds (55), followed by highland barley whiskey (54). Highland barley whiskey had the greatest number of unique aroma compounds (seven). It exhibited a unique cocoa aroma related to concentrations of trans-2-nonenal, γ-nonanolactone, 1-nonanol, isoamyl lactate, 2-butanol, and 6-methyl-5-hepten-2-one. Sorghum whiskey had a specific leather and mushroom aroma attributed to 6-methyl-5-hepten-2-one, ethyl lactate, ethyl caprate, phenethyl octanoate, farnesol, α-terpineol, 3-methyl-1-pentanol, and methyleugenol. Alcohols were the main aroma components of grain whiskeys. Isoamyl alcohol (231.59~281.39 mg/L), phenylethyl alcohol (5.755~9.158 mg/L), citronellol (0.224~4.103 mg/L), β-damascenone (0.021~2.431 mg/L), geraniol (0.286~1.416 mg/L), isoamyl acetate (0.157~0.918 mg/L), phenylacetaldehyde (0.162~0.470 mg/L), linalool (0.024~0.148 mg/L), 1-octen-3-ol (0.016~0.145 mg/L), trans-2-nonenal (0.027~0.105 mg/L), and trans-2-octen-1-ol (0.011~0.054 mg/L) were all important aroma compounds in the whiskeys.

Impact of indigenous Oenococcus oeni and Lactiplantibacillus plantarum species co-culture on Cabernet Sauvignon wine malolactic fermentation: Kinetic parameters, color and aroma

Malolactic fermentation (MLF) is a crucial process to enhance wine quality, and the utilization of indigenous microorganisms has the potential to enhance wine characteristics distinct to a region. Here, the MLF performance of five indigenous Oenococcus oeni strains and six synthetic microbial communities (SynComs), were comparatively evaluated in Cabernet Sauvignon wine. In terms of malate metabolism rate and wine aroma diversity, the strain of O. oeni Oe114–46 demonstrated comparable MLF performance to the commercial strain of O. oeni Oe450 PreAc. Furthermore, the corresponding SynComs (Oe144–46/LpXJ25) exhibited improved fermentation properties, leading to increased viable cell counts of both species, more rapid and thorough MLF, and increased concentrations of important aroma compounds, such as linalool, 4-terpinenol, α-terpineol, diethyl succinate, and ethyl lactate. These findings highlight the remarkable MLF performance of indigenous O. oeni and O. oeni-L. plantarum microbial communities, emphasizing their immense potential in improving MLF efficiency and wine quality.

Comparison of Aroma Compounds and Sensory Characteristics between Two Different Types of Rice-Based Baijiu.

Rice-based Baijiu has gained popularity in the Chinese market. Qingya-flavored Baijiu, a variant of Xiaoqu-fermented Baijiu, employs rice as its primary raw material, with an improved production process compared to traditional rice-flavored Baijiu. We comprehensively characterized and compared the aroma profiles of these two rice-based Baijiu types using static sensory experiments (QDA, quantitative descriptive analysis) and dynamic sensory experiments (TDS, temporal dominance of sensations). Qingya-flavored Baijiu exhibited pronounced plant, oily, and roasted aromas, while traditional rice-flavored Baijiu displayed more prominent fruity, floral, and sour notes. Utilizing GC-O-MS (gas chromatography-olfactometry-mass spectrometry) and multi-method quantification, we qualitatively and quantitatively analyzed 61 key aroma compounds, identifying 22 compounds with significant aroma contributions based on odor activity values (OAVs). Statistical analyses, combining sensory and chemical results, were conducted to predict important aroma compounds responsible for the aroma differences between the two Baijiu types. Aroma Recombination and Omission experiments showed that seven compounds play key roles in the aroma of Qingya-flavored Baijiu, including (2E,4E)-Deca-2,4-dienal, linalool, apricolin, ethyl acetate, ethyl isobutyrate, ethyl caprylate, and ethyl isovalerate.

Impact of argon dielectric barrier discharge cold plasma on the physicochemical and cooking properties of lightly-milled rice

This study investigated the influence of argon dielectric barrier discharge-cold plasma (DBD-CP) applied at different voltage settings (1 kV and 2 kV) and exposure durations (5 min and 10 min) on the physicochemical properties, cooking behavior, textural attributes, and flavor characteristics of lightly-milled-rice (LMR). The DBD-CP treatment increased the brightness of untreated LMR from 62.93 to 76.69, and reduced the water droplet contact angle from 66.66° to 58.99° following a treatment of 2 kV-10 min. Moreover, the treatment enhanced the crystallinity and gelatinization enthalpy of LMR starch by 8.93% and 60.55%, respectively. Conversely, it led to a decrease in the amylose content by 7.66% when compared to the control group. Metabolomic analysis revealed a decrease in the content of key compounds involved in metabolic pathways, including amino acids, α-hydroxy acids, and GABA. The cooking experiment demonstrated a substantial reduction by 5.4 min in optimal cooking time, along with water absorption capacity and volume expansion rate increased by 54.19% and 68.42% in 2 kV-10 min DBD-treated LMR, respectively. Notably, DBD-CP treatment positively influenced the production of important aroma compounds such as alcohols, aldehydes, and ketones. Overall, DBD-CP proved to be an effective physical processing method for significantly enhancing the edible quality and aroma of LMR.

Craig‐Hückel Hybrid Aromatic Metalla‐dehydro[11]annulenes Constructed by a Formal [10+1] Cycloaddition Reaction

AbstractAromatic metalla‐annulenes are important aromatic compounds, research into which has been mainly concentrated on metal‐benzenes and their lower homologues. Reports on their superior homologs are rare, and this has greatly limited the systematic study of their properties. In this work, a series of osma‐dehydro[11]annulenes with good air and thermal stability were prepared in high yields through a simple [10+1] strategy, by incorporating a metal fragment into conjugated ten‐carbon chains in a one‐pot reaction. They are the first monometallic aromatic metalla‐[n]annulenes with the ring size larger than 6, and their Craig‐Hückel hybrid aromaticity is supported by various physical and computational parameters. Besides, these complexes show versatile reactivities, not only giving further evidence for their aromaticity, but also demonstrating their physical and chemical properties can easily be regulated. This work enriches the metalla‐aromatic chemistry, and provides a new avenue for the synthesis of large metalla‐annulenes with different ring sizes.

Craig-Hückel Hybrid Aromatic Metalla-dehydro[11]annulenes Constructed by a Formal [10+1] Cycloaddition Reaction.

Aromatic metalla-annulenes are important aromatic compounds, research into which has been mainly concentrated on metal-benzenes and their lower homologues. Reports on their superior homologs are rare, and this has greatly limited the systematic study of their properties. In this work, a series of osma-dehydro[11]annulenes with good air and thermal stability were prepared in high yields through a simple [10+1] strategy, by incorporating a metal fragment into conjugated ten-carbon chains in a one-pot reaction. They are the first monometallic aromatic metalla-[n]annulenes with the ring size larger than 6, and their Craig-Hückel hybrid aromaticity is supported by various physical and computational parameters. Besides, these complexes show versatile reactivities, not only giving further evidence for their aromaticity, but also demonstrating their physical and chemical properties can easily be regulated. This work enriches the metalla-aromatic chemistry, and provides a new avenue for the synthesis of large metalla-annulenes with different ring sizes.

Characterization of Key Odorants in Chinese Texiang Aroma and Flavor Type Baijiu (Chinese Liquor) by Means of a Molecular Sensory Science Approach.

The popularity of texiang aroma type baijiu (liquor), known for its unique production technology and multilayered flavor, has been steadily increasing among consumers. So far, no research has determined its key aroma compounds for characterizing the unique flavor, which is the purpose of this paper. Using gas chromatography-olfactometry (GC-O) coupled with the GC-mass spectrometry (GC-MS) method, 87 aroma-active compounds were identified and screened out with intensity values ≥2.0. 1,1,6-Trimethyl-1,2-dihydronaphthalene (TDN) was first confirmed by GC-O in Chinese liquor. According to a quantitative study and odor activity values (OAVs), 42 odorants were determined as important aroma compounds. These odorants were recombined based on quantitative concentrations, successfully simulating the overall aroma profile. Omission experiments verified ethyl hexanoate, β-damascenone, and 2-furfuryl ethyl ether as the key aroma compounds and revealed that ethyl acetate, furfural, and ethyl 2-phenylacetate were important aroma compounds to the overall flavor of texiang aroma and flavor type liquor.

Investigation on the key factors associated with flavor quality in northern strong aroma type of Baijiu by flavor matrix.

The strong aroma type of Baijiu is popular with its balanced flavor. However, the flavor characteristics of strong aroma type of Baijiu in different regions have significant diversities. Among them, the key aroma compounds in northern strong aroma type of Baijiu and the factors affecting the aroma profile and flavor quality are still unclear. In this study, a total of 78 aroma compounds were identified by gas chromatography-olfactometry-mass spectrometry (GC-O-MS). The quantitative analysis was completed and ethyl hexanoate (1003.24-4506.04mg/L) was the highest. Aroma profile was successfully simulated by reconstitution, and omission test was applied to investigate the effects of the important aroma compounds on the aroma profile. Additionally, the relationship between expression of aroma compounds and sensory characteristics of samples was illustrated by flavor matrix. The overall aroma profile of northern strong aroma type of Baijiu was formed by the key aroma compounds with different aroma expression.

Generation of Meaty Aroma from Onion (Allium cepa L.) with Polyporus umbellatus: Fermentation System, Sensory Profile, and Aroma Characterization.

One of the main reasons for consumer rejection of plant-based meat alternatives is the lack of meaty flavor after cooking. In this study, a platform was developed to generate meaty flavors solely from Allium substrates (chives, leeks, ramsons, and onions) using basidiomycete-mediated submerged fermentations. Polyporus umbellatus-mediated fermentation of onions resulted in an intense meaty and liver sausage-like flavor under proper fermentation parameters. Using multisolvent and solvent-free aroma extractions coupled with gas chromatography-mass spectrometry-olfactometry, 5 odorants with high assigned flavor dilution (FD) factors (≥ 256) were identified in the fermented sample that have been reported in the literature as important aroma compounds of meat products: methyl palmitate, bis(2-methyl-furyl) disulfide, (E,E)-2,4-decadienal, γ-nonalactone, and eugenol. Using selected ion monitoring, the presence of bis(2-methyl-furyl) disulfide (meaty, savory, FD 256) after fermentation was confirmed. It was proposed that P. umbellatus enzymatically forms bis(2-methyl-furyl) disulfide from intermediates derived from the thermal degradation of thiamine.

Understanding the role of lipids in aroma formation of circulating non-fried roasted chicken using UHPLC-HRMS-based lipidomics and heat transfer analysis

The role of lipids in aroma formation of circulating non-fried roasted (CNR) chicken with different roasting times was studied using ultra-high performance liquid chromatography high-resolution mass spectrometry (UHPLC-HRMS)-based lipidomics and heat transfer analysis. Thirteen odorants were confirmed as important aroma compounds of CNR chicken, including dimethyl trisulfide, 3,5-dimethyl-2-ethylpyrazine, nonanal, and 1-octen-3-ol. A comprehensive lipidomics analysis identified 1254 lipids in roasted chickens, classified into 23 distinct lipid categories that included 281 phosphatidylcholines (PC), 223 phosphatidylethanolamines (PE), and 202 triglycerides (TG). Using OPLS-DA analysis, the lipid PG (18:1_18:1) showed promise as a potential biomarker for distinguishing between chickens subjected to CNR treatments with varying roasting times. The lipids PC, PE, and their derivatives are likely to play a crucial role in the formation of aroma compounds. In addition, TGs that contributed to the retention of key odorants in roasted chicken included TG (16:0_16:0_18:1), TG (16:0_16:0_18:0), and TG (16:0_18:1_18:1). Findings further showed that lower water activity and specific heat capacity promoted the formation and retention of aroma compounds during the CNR process. This study contributed to a better understanding of the formation of aroma compounds through lipid oxidation in roasted chicken.

3-Alkyl-2-methoxypyrazines: Overview of Their Occurrence, Biosynthesis and Distribution in Edible Plants.

Pyrazines are ubiquitous in nature - biosynthesized by microorganisms, insects, and plants. Due to their great structural diversity, they own manifold biological functions. Alkyl- and alkoxypyrazines for instance play a key role as semiochemicals, but also as important aroma compounds in foods. Especially 3-alkyl-2-methoxypyrazines(MPs) have been of great research interest. MPs are associated with green and earthy attributes. They are responsible for the distinctive aroma properties of numerous vegetables. Moreover, they have a strong influence on the aroma of wines, in which they are primarily grape-derived. Over the years various methods have been developed and implemented to analyse the distribution of MPs in plants. In addition, the biosynthetic pathway of MPs has always been of particular interest. Different pathways and precursors have been proposed and controversially discussed in the literature. While the identification of genes encoding O-methyltransferases gave important insights into the last step of MP-biosynthesis, earlier biosynthetic steps and precursors remained unknown. It was not until 2022 that in vivo feeding experiments with stable isotope labeled compounds revealed L-leucine and L-serine as important precursors for IBMP. This discovery gave evidence for a metabolic interface of the MP-biosynthesis and photorespiration.

Identification of Important Aroma Components and Sensory Profiles of Minimally Processed (Unroasted) and Conventionally Roasted Dark Chocolates.

Roasting is an important unit operation for the development of characteristic chocolate aroma during manufacturing. However, there is an increase in interest in minimally processed chocolate products due to their potential positive health benefits. The odor-important compounds and sensory characteristics of minimally processed (unroasted) and conventionally roasted dark chocolates were determined by gas chromatography-olfactometry, aroma extract dilution analysis (AEDA), and stable isotope dilution analysis (SIDA). Except for acetic acid, all odorants had higher odor-activity values (OAVs) in roasted chocolate. Acetic acid, developed during fermentation and drying, had the highest OAV in both chocolates but was better preserved in unroasted chocolate. Compounds making a greater aroma impact on roasted chocolate compared with unroasted chocolate included dimethyl trisulfide, 2-ethyl-3,5-dimethylpyrazine, and 3-methylbutanal. Nine significant sensory attributes in unroasted and roasted chocolates were identified. Vinegar (aroma) and roasted (aroma and aroma by mouth), sweet (taste), and hardness (texture) attributes differed between unroasted and roasted chocolates. The results of this study enforce the embracement of low thermal processes to showcase the inherent flavor potential of cacao beans but also to support the concept of chocolate "terroir" by potentially preserving important aroma compounds developed during fermentation.

Synthesis of isoamyl acetate using protein-coated microcrystals of different lipases

Abstract The goal of this study was the immobilization of different lipases as protein-coated microcrystals on K2SO4 and their uses in the synthesis of isoamyl acetate in n-hexane medium. The optimum conditions, such as lipase variety, temperature, the initial molar ratio of vinyl acetate/isoamyl alcohol, immobilized lipase amount, and reaction time were determined. The highest conversion was obtained when protein-coated microcrystals of Thermomyces lanuginosus lipase (TLL-PCMCs) was used for the synthesis of isoamyl acetate. The optimum temperature, the initial molar ratio of vinyl acetate/isoamyl alcohol, immobilized lipase amount, and reaction time were determined to be 50 °C, 3.0, 30 mg, and 360 min, respectively. Under the optimized conditions, isoamyl acetate yield was obtained as 95%. TLL-PCMCs retained 90% of their initial activity after five repeat use in the isoamyl acetate synthesis. TLL-PCMCs may be used in the preparation of industrially important aroma compounds due its ease of preparation and efficiency.

Evaluation of volatile and thermal properties of boza, a traditional fermented beverage

Although boza is widely preferred and consumed, there is no detailed study on volatile and thermal characteristics. A liquid–liquidextraction (LLE) method has been proposed for the volatile extraction of boza using GC-MS. DB-Wax column from 50 °C to 250 °C at a rate of 4 °C/min with a final hold at 250 °C for 10 min. A helium gas was selected as a carrier gas with a 3.2 ml/min linear velocity. The retention time of the internal standard (4-nonanol) used in our study, was detected in the middle of the chromatogram, and the peak response was relatively stable. The odor activity values (OAVs) were utilized to elucidate the aroma and key odorant substances. Based on OAVs, the most important aroma compounds identified in boza were hexanoic acid [25.1, cheesy goat], 4-vinyl phenol [12.1, phenolic/burnt], acetoin [9.1, buttery/creamy], acetic acid [6.7, vinegary/irritant] and octan-2-ol [3.5, coconut]. The high-performance liquid chromatography (HPLC) system was used to determine the organic acids in boza. The quality parameters of the method were established in terms of the linearity of the calibration, the limit of quantification, the limit of detection, and recovery experiments. The proposed method showed a good recovery from 79.47 to 109.96%. The proposed method was found to be specific as no interference peaks were observed for blank samples. Regarding thermal properties, onset temperature (To), peak temperature (Tp), and end set temperature (Te) increase with the heating rate. In contrast, with increasing temperature, there was a slight decrease in the endothermic peak width (EPW) and peak height index (PHI) values. The level of alcohol was 0.06% below the criteria of the Turkish Boza Standard (TSE 9778).

Metabolic Engineering of Escherichia coli for the Biosynthesis of 3-Phenylpropionic Acid and 3-Phenylpropyl Acetate

3-Phenylpropionic acid (3PPA) and its derivative 3-phenylpropyl acetate (3PPAAc) are important aromatic compounds with broad applications in the cosmetics and food industries. In this study, we constructed a plasmid-free 3PPA-producing Escherichia coli strain and designed a novel 3PPAAc biosynthetic pathway. A module containing tyrosine ammonia lyase and enoate reductase, evaluated under the control of different promoters, was combined with phenylalanine-overproducing strain E. coli ATCC31884, enabling the plasmid-free de novo production of 218.16 ± 43.62 mg L-1 3PPA. The feasibility of the pathway was proved by screening four heterologous alcohol acetyltransferases, which catalyzed the transformation of 3-phenylpropyl alcohol into 3PPAAc. Afterward, 94.59 ± 16.25 mg L-1 3PPAAc was achieved in the engineered E. coli strain. Overall, we have not only demonstrated the potential of de novo synthesis of 3PPAAc in microbes for the first time but also provided a platform for the future of biosynthesis of other aromatic compounds.