Flavor Compounds Research Articles

Effect of Different Probiotic Fermentations on the Quality of Plant-Based Hempseed Fermented Milk

This study investigated the effects of three different single-strain probiotics Lactiplantibacillus plantarum XD117, Lacticaseibacillus paracasei LC-37, and Lacticaseibacillus rhamnosus LGG, on the quality of hempseed fermented milk. The main findings were that adding probiotics increased the inhibition rate of α-glucosidase and pancreatic lipase in hempseed fermented milk significantly. Non-targeted metabolomic correlation analysis results confirmed that 14 substances, including three flavonoids, six amino acids and their derivatives, and five short peptides, were positively correlated with the hypoglycemic and hypolipidemic activities of hempseed fermented milk. Furthermore, a total of 59 volatile flavor compounds were identified, including aldehydes, alcohols, ketones, acids, and esters, and the role mapping of different probiotic communities was provided. These results can guide the development of hempseed fermented milk with unique flavor, rich probiotic content, and significant functional characteristics.

Genome-Wide Identification and Biochemical Characterization of Alcohol Acyltransferases for Aroma Generation in Wickerhamomyces subpelliculosus Isolates from Fermented Food.

The importance of nonconventional yeasts has increasingly been highlighted, particularly for aroma formation in fermented foods. Here, we performed de novo whole-genome sequencing of Wickerhamomyces subpelliculosus, which produces a variety of volatile flavor compounds, leading to the identification of the alcohol acyltransferase (AATase) family of genes. The genome of W. subpelliculosus contains seven AATase genes, encoding alcohol-O-acetyltransferases (ATFs) and ethanol acetyltransferase 1 (EAT1) for acetate ester formation, along with ethanol hexanoyl transferase 1 (EHT1) for ethyl ester formation. Among five ATF homologues, only WsATF5 showed acetyltransferase activity toward myriocin, a structural analogue of sphingosine. In contrast, heterologous expression of WsEHT1 and WsEAT1 in Saccharomyces cerevisiae promoted the production of ethyl decanoate and ethyl acetate, respectively, supporting their AATase activity. The enzymatic activity analyses revealed the additional alcoholysis activity of WsEAT1 and the thioesterase activity of WsEHT1. Subcellular localization analysis indicated that WsEAT1 was localized in the mitochondria, WsEHT1 in the endoplasmic reticulum and lipid droplets (LDs), and WsATF5 in the LDs. The novel W. subpelliculosus AATases could be usefully applied to produce flavor components in various food industries.

Enhancing Brioche Bread with Emulsified Seed and Nut Oils: Nutritional and Sustainable Benefits

This study evaluates the effectiveness of an oil-in-water emulsion formulated from water and seed and nut oils as a substitute for butter in the formulation of brioche bread. First, the selected oils were physicochemically characterized. In the brioche, animal fat was fully and partially replaced, and the effects were analyzed at the physical, chemical, and sensory levels. The new formulations exhibited increased lightness, a softer crumb, improved cohesiveness, and greater expansion compared to the control, resulting in fluffier and lighter brioches. Nutritionally, the seed and nut oil brioches showed a lower fat content and lower energy value, but higher protein and carbohydrate levels. The lipid profile was enhanced, with a higher proportion of unsaturated fatty acids, which positively impacted two heart-friendly indices and increased the vitamin E content. This improvement potentially allows the food industry to apply health claims to product labeling. Regarding sensory analysis, in all cases, the reformulated brioches scored higher than the control sample in terms of external appearance, although there remained a preference for the flavor and aroma of the traditional version, which could be mitigated by adding flavor compounds such as diacetyl. This study differs from previous research by using a seed and nut oil emulsion instead of non-emulsified oils, improving the texture and stability of brioche bread, an achievement not consistently reported in prior studies. Additionally, it emphasizes sustainability by offering a plant-based alternative that addresses the growing consumer demand for vegan and eco-friendly products while providing enhanced nutritional benefits that support potential health claims.

Introducing CCD1 into isolated Rhodotorula strain enhances flavor production and improves cigar fermentation.

The fermentation process plays an important role in enhancing the quality of cigar tobacco leaves. Through fermentation, microbial metabolism can degrade aromatic precursors and macromolecules, which increases the content of aroma compounds and reduces irritancy of tobacco leaves. To further enhance the fermentation effect of cigar tobacco leaves, a Rhodotorula strain (Rh3), capable of producing carotenoids and improving fermentation quality, was isolated from cigar tobacco leaves. Subsequent genetic engineering techniques introduced the carotenoid cleavage dioxygenase 1 (CCD1) gene into the isolated Rh3. The modified Rh3 exhibits a significant increase in carotenoid degradation products compared with the original Rh3 in culture medium (from 0.29μg/mg to 15μg/mg). Subsequent cigar tobacco leaf fermentation experiments revealed that the modified Rh3 produced 65.9% more carotenoid degradation products compared to the control group, outperforming the original strain, which achieved a 41.4% increase. Furthermore, the modified strain preserves its ability to improve the intrinsic chemical composition of cigar tobacco leaves. We show here that modified Rh3 can increase the content of carotenoid degradation products, thereby enhancing the fermentation effect of cigar tobacco leaves. This study presents a beneficial exploration to improve the quality of cigar tobacco leaves for future use and offers a promising strategy for producing flavor compounds from discarded tobacco leaves.

Optimization of preparation process for seasoning derived from the lees of Shaoxing Huangjiu(Chinese yellow rice wine) based on multi round progressive strategy

Huangjiu lees are rich in flavor compounds, but traditional methods of utilizing them remain inefficient. Developing an efficient process for the rapid release and extraction of these flavor compounds from Huangjiu lees to produce lees-flavored seasonings holds significant promise. To tackle this complex process, a multi-round, progressive optimization strategy was devised. First, four separate orthogonal experiments identified the key factors for pre-fermentation, acid hydrolysis, enzyme hydrolysis, and debittering/decolorization, which were determined to be pre-fermentation time, HCl concentration, flavor enzyme concentration, and activated carbon ratio, respectively. Subsequently, response surface methodology was employed to rank the importance of these four factors in influencing the sensory score of the seasonings. The optimal conditions were determined as follows: pre-fermentation time of 7.785 days, HCl concentration of 14.978 %, flavor enzyme concentration of 6.276 %, activated carbon ratio of 7.496 %, with an expected sensory score of 45.117. Finally, the AI-based ANN-PSO method was applied for further refinement, yielding optimized conditions of a pre-fermentation time of 7.417 days, HCl concentration of 12.569 %, flavor enzyme concentration of 6.843 %, activated carbon ratio of 6.946 %, and an improved expected sensory score of 47.838. Verification experiments confirmed the superiority of the latter conditions. This study not only establishes a novel method for the efficient utilization of the abundant flavor resources in Huangjiu lees, which has substantial market potential, but also demonstrates that combining multiple optimization methods in a stepwise, multi-round approach is effective in addressing complex manufacturing processes involving multiple stages and factors.

The dynamic of physicochemical properties, volatile compounds and microbial community during the fermentation of Chinese rice wine with diverse cereals

This study investigates the impact of liquid state fermentation on the key flavor compounds and microbial community structure in Chinese rice wine brewed from five different raw materials: buckwheat, sorghum, japonica rice, glutinous rice, and black rice. Using HS-SPME-GC–MS and HPLC, the volatile compounds were analyzed across various grain liquefaction methods, detecting 82 volatiles, including esters, alcohols, aldehydes, and acids. The concentration of flavor compounds such as esters, amino acids, phenolic acids, and organic acids varied significantly depending on the raw material used. Based on odor activity values, 31 key compounds were identified, including 15 ethyl esters, like ethyl laurate, responsible for the unique and complex aroma of the rice wines. Bitter amino acids, making up over 50 % of the total amino acids, were predominant. Among the varieties, the buckwheat-fermented wine exhibited the highest ester content (27.39 mg/L), nearly double that of other samples, along with elevated amino acids (1.47 mg/mL) and phenolic acids (904.29 mg/L). Black rice ranked second in amino acid content (0.93 mg/mL), while glutinous rice had the highest organic acid content (239.76 mg/mL). Metagenomic sequencing on the fifth day of fermentation revealed significant differences in microbial community structure among the raw materials. Saccharomyces, Aspergillus, Thermomyces, Epicoccus, and Albertella were dominant fungi, while Weissella, Thermoactinomyces, Bacillus, and Saccharopolyspora were dominant bacteria. Sensory analysis showed that buckwheat-fermented rice wine was distinguished by its honey, floral, creamy, and umami attributes, while balancing alcohol, acidity, bitterness, and Qu aroma. The results demonstrate the significant influence of raw material selection and liquefaction method on both flavor profile and microbial diversity in Chinese rice wine.

Lactiplantibacillus plantarum CN2018 enhances the milk fermentation characteristics by improving antioxidant capacity and enhancing the milk flavor profile

Lactiplantibacillus plantarum has been extensively studied for its probiotic properties. Previous studies have demonstrated that L. plantarum CN2018 exhibited antioxidant properties and the potential to inhibit Helicobacter pylori. This research aimed to further investigate the fermentation potential of L. plantarum CN2018 as a co-fermenter in the production of fermented milk, including fermentation characteristics, textural properties, antioxidant capacity, flavor compounds and the metabolic changes. The addition of CN2018 significantly influenced the fermentation characteristics, resulting in a reduction in fermentation time and an increase in the total viable bacterial count (1.41 × 109 CFU/mL). The textural properties of chewiness, gumminess, and adhesiveness improved by 15.29% (p < 0.05), 20.05% (p < 0.001), and 44.87% (p < 0.05), respectively. Additionally, CN2018 enhanced the antioxidant capacity of fermented milk, which SOD activity, T-AOC and DPPH scavenging were increased by 51.78% (p < 0.05), 80.46% (p < 0.05) and 43.58% (p < 0.01), respectively. Key flavor compounds including 1-(4-methylphenyl)-ethanone, phthalic acid, hex-3-yl isobutyl ester, (E)-2-decenal, and phenylethanol were identified, thereby enhancing the flavor profile of the fermented milk. Metabolomic analysis demonstrated that hypoxanthine, a compound associated with oxidative stress, significantly reduced in fermented milk of CN2018. This may be associated with the enhanced antioxidant capacity of fermented milks. These findings indicate that CN2018 can effectively degrade or absorb hypoxanthine in fermented milk. Overall, L. plantarum CN2018 demonstrates considerable potential as an auxiliary fermenter to enhance the nutritional and functional properties of fermented dairy products.

Effects of Thermal Oxidation Interaction via Various Polar Lipid and Myofibrillar Proteins on the Aroma Formation in Large Yellow Croaker

It is a key focus in research on the interaction between different types of lipid and proteins for the aroma formation of fish. The interaction oxidation model of myofibrillar proteins and polar and non-polar lipid in different ratios was constructed to investigate the molecular mechanism of aroma formation of the large yellow croaker. The thermal interaction of lipid and protein was found to generate much more fishy compounds when the ratio of non-polar and polar lipid was 4:1. The aroma intensity reached the highest after thermal interaction at the ratio of non-polar and polar lipid was 1:1. As the proportion of non-polar lipid increased, the concentration of (E,E)-2,4-Heptadienal increased and reached 0.09 μg/g. Triglyceride was the main non-polar lipid that participated in thermal interaction with myofibrillar proteins for the formation of characteristic odorants of fish. As the amount of non-polar lipid increased, lipid oxidation and chain breakage made it easier to convert into volatile flavor compounds under the interaction of myofibrillar proteins. Further, this study provides certain support and influence for the regulation of flavor in fish processing by lipid.

Effect of ultrasonic pretreatment with synergistic microbial fermentation on tenderness and flavor of air-dried duck under low nitrite process

The tenderness and flavor of meat products are critical factors influencing consumers' purchasing decisions. This study investigated the effects of ultrasonic pretreatment with synergistic microbial strain fermentation on tenderness and flavor of air-dried duck under low nitrite process. The results demonstrated that ultrasonic pretreatment combined with microbial strain fermentation improved water retention and tenderness of duck meat by disrupting the muscle microstructure, increasing muscle fiber spacing, and facilitating water migration and distribution. This primarily concerns the cavitation and mechanical effects of ultrasound and the role of lactic acid bacteria and yeasts in muscle protein hydrolysis. A total of 34 and 55 volatile flavor compounds were detected by HS-SPME-GC–MS and GC-IMS, respectively. The results indicated that acetaldehyde (stimulating, fruity, green apple), ethyl acetate (sweet, fruity, pineapple), and 3-hydroxy-2-butanone (sweet, creamy) were responsible for the improved flavor during this process, which was primarily related to the increased activity of neutral lipase (0.38 U/g protein), acidic lipase (0.48 U/g protein), and phospholipase (0.09 U/g protein). This study provides valuable insights into the synergistic effects of ultrasonic pretreatment and microbial co-fermentation, offering a theoretical basis for optimizing air-dried duck production and enhancing flavor quality.

The formation pathway of flavor compounds in steamed Antarctic krill (Euphausia superba) based on untargeted metabolomics

The formation pathway of flavor compounds in steamed Antarctic krill (Euphausia superba) based on untargeted metabolomics

Effect of pre-acidification induction on the physicochemical features, myofibrillar protein microstructure, and headspace volatiles of ready-to-cook goose meat

This study examined the impact of pre-acidification induction on the quality attributes and flavor retention of ready-to-cook (RTC) goose meat products. The results demonstrated that pre-acidification could influence the eating qualities of RTC goose meat by effectively regulating the physicochemical properties of goose myofibrillar proteins (MP) including solubility and water-holding capacity. Elevated carbonyl content indicated an enhanced gel-forming capacity in RTC goose meat during storage, coupled with reduced total sulfhydryl content from enhanced protonation pretreatment and augmented lipid oxidation. Structural characterization of MP via sodium dodecyl sulfate–polyacrylamide gel electrophoresis, circular dichroism spectroscopy, and intrinsic fluorescence revealed the formation of a dense protein matrix under highly acidic conditions. Furthermore, the headspace concentration of aldehydes increased by 3.23 times upon enhancing the pre-acidification intensity, resulting in the production of esters and acidic flavor compounds with favorable aromas. Correlation analysis demonstrated the dependence of headspace concentrations of volatile constituents on the acidification-enhanced surface hydrophobicity of MP, attributed to the modified binding sites of proteins after pre-acidification. Current results have indicated both the positive and negative influence of pre-acidulation induction on the eating quality of goose meat products, suggesting the necessity of introducing extra processes to modulate the quality of prefabricated products.

The potential correlations between cell-free extracts from Rhodobacter sphaeroides grown under low-oxygen conditions and volatile organic compounds in Chinese-style sausage

Limited research has explored the use of Rhodobacter sphaeroides cell-free extracts (RCFE) in meat processing. To examine the potential application of RCFE in improving the flavor quality of Chinese-style sausage, in this study, we investigated the effects and mechanisms of RCFE grown under low-oxygen conditions on the flavor development of Chinese-style sausage, using GC–MS and 4D label-free proteomics. The GC–MS analysis detected 60 volatile organic compounds, with significant increases in acids, esters, and alcohols following the addition of RCFE (p < 0.01). Fifteen differential flavor compounds were identified as potential biomarkers to distinguish sausages. From a total of 2689 proteins, 364 differentially expressed proteins were identified (p < 0.05, |Log2FC| > 1, and VIP > 1,) in RCFE grown under low- and high-oxygen conditions. KEGG pathway analysis suggested that the RCFE grown under low-oxygen conditions may enhance alcohol and acid levels by upregulating the expression of related enzymes, which subsequently increases ester levels in the sausage.

Comparing effects of tangerine-peel (Citrus reticulata Blanco) age and concentration on deep-fried rabbit meat: Impact on heterocyclic aromatic amines, amino acids, and flavor compound formation

Many nutritional experts recommend rabbit meat as a high-protein source. However, the high temperatures used to prepare deep-fried rabbit meat (DFRM) typically produce numerous heterocyclic aromatic amines (HAAs), a class of substances with carcinogenic risks. In this study, we chromatographically evaluate changes in the volatile compounds, amino acids, and HAAs in DFRM while employing tangerine peel (TP) as an additive. A total of 35 volatile organic compounds are detected in the TP, which increase the concentrations of sweet and umami amino acids in the DFRM. Remarkably, the TP substantially inhibits the IQ-type HAAs, particularly MeIQ, MeIQx, 4,8-DiMeIQx, and PhIP, which are produced during deep frying. Correlation analyses reveal that the histidine, aldehydes, and alcohols are strongly and positively correlated (P < 0.001) with the MeIQ, MeIQx, 4,8-DiMeIQx, and PhIP production. This study offers innovative and natural approaches for reducing HAA formation during the frying of rabbit meat.

Optimizing Huangjiu Fermentation for Enhanced Aroma: Insights into Saccharomyces cerevisiae jiangnan1# Strain

Higher alcohols (HAs) and acetate esters (AEs) are crucial volatile flavor compounds in Chinese huangjiu. The imbalance between HAs and AEs leads to poor flavor quality, lack of drinking comfort and headaches after drinking. By comparing the metabolic profiles and gene expression of Saccharomyces cerevisiae jiangnan1# with control strain (85#), 12.38% reduction in HA levels during unilateral fermentation was identified, especially a significant 47.32% drop in 2-phenethyl alcohol, without affecting AEs levels (P > 0.05). Bilateral fermentation strategies further optimized HA reduction by 8.33% and increased AEs significantly. Transcriptome data highlighted the down-regulation of key enzymes ARO9 and ARO10 in the Ehrlich pathway, linked to reduced HA synthesis, and the up-regulation of ALDH and acetyl-CoA synthase, promoting AE accumulation. The results showed that jiangnan1# strain-specific fermentation characteristics, particularly the regulation of key metabolic pathways, are the primary drivers of differences in HAs and AEs in huangjiu fermentation. These findings are instrumental in developing targeted metabolic strategies for enhancing the aroma profile of huangjiu, emphasizing the role of microbial modulation in food fermentation processes.

Metatranscriptomic insights into the mechanism of 'Multiple Qu' utilization in Jian-flavor Baijiu fermentation

The unique process of “Multiple-qu fermentation” (MF) is essential for the formation of the Jian-flavor Baijiu, but the mechanisms behind its aroma development remain not fully understood. This study compared the effects of “Single-qu fermentation”(SF) and MF on Baijiu production to elucidate the microbial and metabolic interactions responsible for its distinct aroma. Firstly, significant differences were observed in the microbial communities of the two types of Daqu. Medium-temperature Daqu (MT-Daqu) had higher relative abundances of Bacillus, Thermoactinomyces, Thermoascus, and yeasts like Picha and Saccharomycopsis. In contrast, high-temperature Daqu (HT-Daqu) was dominated by thermophilic genera such as Kroppenstedtia, and Thermomyces. In MF, the addition of HT-Daqu promoted an increase in Acetilactobacillus, while simultaneously leading to a decline in Lactobacillus and Kazachstania. Metatranscriptomic analysis revealed that Acetilactobacillus, Lactobacillus, Kazachstania, and Saccharomyces were the primary transcriptionally active genera in Baijiu fermentation. In SF, elevated transcription levels of Lactobacillus promoted the synthesis of ethyl lactate, reaching a concentration of 19.32 µg/L, compared to 7.33 µg/L in MF. Conversely, in MF, elevated transcription levels of Acetilactobacillus, Saccharomyces, and Kazachstania enhanced the synthesis of acetate esters and medium-chain fatty acid (MCFA) ethyl esters, reaching 28.50 µg/L and 195.84 µg/L, compared to 15.77 µg/L and 148.73 µg/L in SF. These differences in microbial communities and transcriptional activity directly shape the synthesis of key flavor compounds, thereby enhancing the distinct sensory characteristics of Jian-flavor Baijiu. This study provides new insights into the microbial and metabolic dynamics driving MF’s role in Jian-flavor Baijiu.

Volatile Flavor Compounds of Gamma Irradiated Cucumis sativus L. (Cucumber) Seeds by Simultaneous Distillation Extraction and Gas Chromatography-Mass Spectrometry Analysis

Volatile Flavor Compounds of Gamma Irradiated Cucumis sativus L. (Cucumber) Seeds by Simultaneous Distillation Extraction and Gas Chromatography-Mass Spectrometry Analysis

Investigating the triple-frequency ultrasound-assisted fermented rice lees: Impact on physicochemical, structural, morphological, and metabolic properties

This study examined the effect of triple-frequency ultrasound treatment (TFUT)-assisted lactic acid bacteria (LAB-L. plantarum and L. helveticus fermentation for 24-h and 48-h) on the chemical, structural, morphological, metabolic, and sensory properties of rice lees (RL). Ultrasonicated-assisted RL fermented with L. helveticus (URLH-48) had the greatest total phenolic contents (TPC) (112.1 mg GAE/m), total flavonoid contents (TFC) (163.62 mg RE/mL), and proanthocyanidin contents (PAC) (728.34 mg/mL) compared to RL (control) and other treatments. Furthermore, URLH-48 demonstrated an increase in the concentrations of quinic acid (486.96 mg/L) and gallic acid (201.42 mg/L), as determined by HPLC-UV analysis. Additionally, FTIR spectral analyses demonstrated that TFUT-assisted fermented RL exhibited a greater degree of flexibility and mobility in its secondary structures compared to RL (control). The amino acid’s profile of RL was significantly increased as LAB degraded the RL proteins, and the function of TFUT facilitates bacterial activity. Moreover, SEM observation provides convincing evidence that TFUT improves and speeds up the breakdown of proteins’ structures, resulting in irregular and dense structures. Correlation and molecular docking research suggest that TFUT has different impacts on specific RL and fermented RL characteristics. The analyses conducted using GC–MS and E-nose indicated the generation of highly volatile flavor compounds through fermentation. The sensory evaluation results show an increase in liking following fermentation and TFUT-assisted fermentation, which is attributed to the production of flavor compounds. Consequently, the combined use of TFUT-assisted fermentation markedly improves the polyphenolic composition, antioxidant capacity, flavor profile, micromorphology, and overall quality of RL, which may enhance their functionality and broaden their applications in the food industry.

A novel aggregation-induced emission-featured hyperbranched poly(amido amine)s stabilized copper nanoclusters‑cerium (III) sensor for detection of thiol flavor compounds in processed meat

Thiol flavor compounds are a class of flavoring ingredients that contribute significantly to food flavor. However, rapid discrimination of multiple thiol-flavor compounds remain a challenge. In this study, a ratiometric fluorescent sensor (TPE-ssHPA@Cu NCs-Ce3+) with dual-channel fluorescence features was developed using tetraphenylethene-embedded hyperbranched poly(amidoamine) as a template to stabilize the copper nanocluster‑cerium ions. The sensor was explored for the specific discrimination of six typical thiol flavor compounds, each producing diverse fluorescent fingerprints that were further identified using pattern recognition methods. The sensor achieved a rapid response in identifying thiol flavor compounds and multicomponent mixtures, with detection limits of 0.32–3.13 μM. Furthermore, it was successfully applied to differentiate between the different types and cooking times of meat broths.

Fermentation-linked conversion of dimethylpyrazines in moutai-flavor liquor: Insight from HPLC-FLD analysis

Moutai-flavor Baijiu (MFB), is renowned worldwide for its mysterious brewing process and its sauce-like flavor. Dimethylpyrazines (DMPs) are functional flavor compounds that make significant contributions to the aroma of MFB. To investigate the variation rule of DMPs during the brewing process of MFB, and to gain insights into the link between of DMPs and Moutai-flavor, we developed a simple, rapid, and effective HPLC-FLD method. The detection limits and quantification limits of our proposed method ranged from 0.008 to 0.035 mg/L, with an RSD of precision of less than 2 %. And the average recoveries ranged from 98 % to 100.48 %. The results showed that DMPs initially increased, reaching peak in 6th round with a concentration up to 14.997±0.414 mg/L, and then decreased during fermentation. In the aging stage, DMPs displayed a gradual upward trend, peaking at 10.052±0.252 mg/L after 7 years, before experiencing a minor decline at 9 years. These conversion behaviors are closely related to microbial metabolic activity and the Maillard reaction. We found high content of DMPs from the 4th-6th rounds (A round of fermentation takes a month) and the aged 7 years Baijiu have been described with strong sauce aroma and superior quality. This study provides a technical for focusing further investigating the unique flavor of Baijiu, revealing the conversion behavior of DMPs during the brewing process and their potential causes.

Changes of volatile flavored compounds during lactic acid fermentation in cereal-based products

Changes of volatile flavored compounds during lactic acid fermentation in cereal-based products