Search Results (58)

Medium-milled rice is increasingly valued for its health benefits and distinctive aroma, which differs from that of white rice because differences in milling degree modify the content of lipids and other aroma precursors. However, its aroma profile remains underexplored. This study aimed to systematically analyze aroma differences among four Simiao rice cultivars after medium milling (8% degree of milling) and to elucidate the chemical basis underlying consumer preference. Odor sensory evaluation identified Xiangzhuxiang as the cultivar with the highest aroma acceptance. Subsequently, gas chromatography–olfactometry–mass spectrometry and odor activity value analysis characterized the volatile profile, identifying 45 volatile compounds across the four cultivars, including 17 key odor-active components. Multivariate statistical analysis pinpointed the discriminating key odor-active compounds responsible for the superior aroma quality of Xiangzhuxiang. The results showed that (E,E)-2,4-decadienal and indole (VIP > 1.0, FDR-adjusted q < 0.05, FC > 1.2, OAV > 1.0, confirmed by GC-O) significantly increased the aroma scores of Xiangzhuxiang; imparted nutty, fatty, and sweet notes; and thus played a decisive role in shaping its characteristic aroma. Moreover, the moderate levels of hexanal and octanal in Xiangzhuxiang facilitated its characteristic aroma expression. These findings provide a basis for developing premium fragrant Simiao rice cultivars optimized for medium milling. Full article

Flavor enrichment in commercial yogurts commonly relies on exogenous flavoring agents, failing to meet consumer demand for clean-label products with natural ingredients. This study developed a starter culture for malty-aroma yogurt by combining Lactococcus lactis BL-19 with a commercial yogurt starter culture. Evaluation by eleven trained sensory assessors indicated that malty-aroma yogurt exhibited a distinctive sensory profile compared with four commercially available plain yogurts. Time-series flavoromics identified 13 key aroma compounds and revealed the 3 h as the key time node of flavor evolution during fermentation. Furthermore, time-series metabolomics analysis revealed metabolic transitions from nutrient adaptation to active biosynthesis at 3 h, significantly increasing the odor-active values of the key aroma compounds. Moreover, correlation network analyses revealed potential metabolic precursors and metabolic bypass associated with the production of key aroma compounds and highlighted the valine, leucine and isoleucine biosynthesis pathway as central to malty-aroma formation. This study elucidates the evolution of flavor compounds and the underlying bioformation mechanisms of malty-aroma yogurts, offering insights for the precise flavor modulation of fermented dairy products. Full article

Cyanobacterial blooms pose significant threats to aquatic ecosystems and drinking water safety, primarily through the release of diverse secondary metabolites. This study systematically explored the dynamics of secondary metabolites in Microcystis aeruginosa and Anabaena sp. under controlled conditions, focusing on the effects of temperature (10 °C, 25 °C, 35 °C) and growth phases (exponential, stationary, decline). Key parameters measured included cell density, dissolved organic carbon (DOC), microcystins (MC-LR, MC-RR), taste and odor compounds (β-cyclocitral, β-ionone), and disinfection by-product formation potentials (trihalomethanes (THMs) and haloacetic acids (HAAs)). Results revealed striking interspecific differences: M. aeruginosa exhibited significantly higher metabolite production, with peak DOC, extracellular MC-LR, and particulate β-cyclocitral observed in the decline phase at 25–35 °C. In contrast, Anabaena sp. showed an “early accumulation advantage” for THM precursors and “residual release” in the decline phase. Temperature played a critical regulatory role, with 25 °C as the optimal for most metabolites, while 35 °C enhanced extracellular release of dissolved β-cyclocitral in M. aeruginosa. Growth phase dynamics were consistent across species, with stationary and decline phases marked by elevated metabolite concentrations due to intensified synthesis and cell lysis, particularly for HAAs. These findings highlight species-specific metabolic strategies and their environmental drivers, providing critical insights for assessing and managing cyanobacterial bloom risks in aquatic ecosystems. Full article

To characterize the key odorants and elucidate the flavor profiles of compound fermented beverages after fermentation, single-compound fermented beverages (GW, AW) and a compound fermented beverage (CW) were prepared using Italian Riesling grapes and SirPrize apples as raw materials. The flavor and metabolite profiles were systematically analyzed by integrating flavoromics (comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry, GC × GC–TOF MS) and metabolomics (LC–MS/MS). The results demonstrated that CW exhibited the most favorable acid/reducing sugars (2.18), imparting a drier taste and superior stability. Compounds with relative odor activity values (rOAV) greater than 1—including 3-methyl-1-butyl acetate, ethyl hexanoate, ethyl butanoate, and ethyl octanoate—collectively contributed prominent fruity, floral, and sweet aromas to all three wine types. Ethyl decanoate provided an additional distinctive traditional fruity note specifically to AW, while 1-octen-3-ol contributed a mushroom-like aroma to both GW and CW. Moreover, 3-methylbutanal, 4-ethyl-2-methoxyphenol, and ethyl 3-methylbutanoate added additional significant aroma contributions to CW, imparting floral, clove-like, and fruity notes, respectively. Notably, ethyl hexanoate (fruity aroma) exhibited a remarkably high rOAV of 27.43 in CW, significantly surpassing its levels in the single-substrate fermentations. Lipid metabolism and the phenylpropanoid pathway were significantly activated in CW, facilitating the coordinated synthesis of esters and phenolic compounds. Sensory attribute network analysis further confirmed that CW possessed more pronounced “sweet”, “fruity”, and “floral” characteristics. Correlation analysis revealed significant relationships between volatile organic compounds (VOCs) and total soluble solids (TS), titratable acidity (TA), the TA/TS ratio, and metabolite levels, underscoring the close connections among physicochemical properties, precursor/intermediate metabolites, and flavor formation. Comprehensive analysis of non-volatile metabolites and flavor-associated VOCs revealed variety-specific characteristics and compounding effects, providing valuable insights for enhancing the quality of compound fermented beverages. Full article

Although the aroma profile of Lentinula edodes has been extensively studied in fruiting bodies, the mycelial stage provides a distinct context for elucidating the fundamental metabolic pathways, free from the complexities of organismal development. To elucidate the mechanism underlying aroma differences between L. edodes strain 808 (the control strain) and its mutant strain ww808 (with almost no shiitake aroma), this study employed GC-IMS combined with PCA and OPLS-DA to identify key aroma biomarkers during the mycelial stage. All analyses were performed with three biological replicates. Furthermore, fatty acids composition, key enzyme activities of the LOX pathway, and their gene expression levels were systematically compared. The results indicated significant differences in the content of volatile aroma compounds in the mycelia of the two strains, primarily stemming from fundamental restructuring of gene expression and enzyme activity in the LOX pathway. The LOX gene expression and LOX activity of 808 mycelium were relatively high, facilitating the accumulation of key aroma compounds such as phenylethanal, benzaldehyde, and ethyl acetate, which constitute its distinctive aromatic profile. However, although the mycelium of ww808 possessed richer fatty acid precursor (C18:2), its lower LOX gene expression restricted the flux of this pathway. The significantly increased expression of ADH2, ADH3, and ADH5 genes and higher ADH activity enhanced the conversion capacity of aldehydes to alcohols and ketones. Given the generally higher odor thresholds of alcohols and ketones compared to aldehydes, distinct aroma profiles emerged between the two strains. Pearson correlation analysis further confirmed the significant correlations between the aroma biomarkers, fatty acids, key genes, and enzyme activities. This study revealed the formation mechanism of aroma differences in the mycelia of the two strains from the perspective of metabolic pathways, providing a theoretical foundation and candidate targets for the directed genetic improvement of L. edodes aroma quality. Full article

Sichuan-style black soybean soy sauce is a traditional fermented condiment renowned for its complex and regionally distinctive flavor profile. This study systematically investigated the physicochemical properties, flavor compounds, and microbial succession during six months of natural fermentation to elucidate the mechanisms underlying its unique flavor formation. Results showed that the amino acid nitrogen level increased to a peak of 1.37 g/100 mL before stabilizing at 1.01 g/100 mL, accompanied by a continuous rise in total acidity (0.69–2.75 g/100 mL). A total of 132 volatile compounds were identified, with esters (e.g., hexanoic acid, methyl ester, hexadecanoic acid, and methyl ester), alcohols (e.g., (E)-2-hepten-1-ol and trans-2-undecen-1-ol), and aldehydes (e.g., benzaldehyde and benzeneacetaldehyde) serving as key differentiating components. Nine taste-active (TAV ≥ 1) and 22 odor-active (ROAV ≥ 1) compounds were recognized as major flavor determinants, among which methional (ROAV = 4.77–119.05), 1-octen-3-ol (ROAV = 40.68–149.35), and 4-ethyl-2-methoxyphenol (ROAV = 4.70–36.26) were dominant contributors imparting sauce-like, mushroom-like, and smoky-clove notes, respectively. Microbial succession revealed a transition from Weissella and Aspergillus dominance in the early stage to salt-tolerant Tetragenococcus and aroma-producing yeasts (Kodamaea and Zygosaccharomyces) in later phases. Beyond organic acids and fermentation parameters (e.g., pH and salinity), microbial interactions were identified as critical drivers shaping community assembly and succession. Metabolic pathway analysis revealed a stage-dependent mechanism of flavor formation. During the initial stage (0–2 months), Aspergillus-mediated proteolysis released free amino acids as key taste precursors. In the later stages (3–6 months), Tetragenococcus and aroma-producing yeasts dominated, synthesizing characteristic esters (e.g., benzoic acid and methyl ester, correlated with Tetragenococcus; r = 0.71, p < 0.05), phenolics (e.g., 4-ethyl-2-methoxyphenol, correlated with Wickerhamomyces; r = 0.89, p < 0.05), and sulfur-containing compounds (e.g., methional, correlated with Wickerhamomyces; r = 0.83, p < 0.05). Full article

Ammonia (NH₃) emissions from swine manure pits contribute significantly to odor nuisance, health risks, and secondary PM_2.5 formation. This study assessed the pilot-scale performance of three source-control technologies: surface sealing with surfactant-based foam system (FOAM SYSTEM), swine manure wiping and removing system (WIPING SYSTEM), and belt-conveyor-based solid–liquid separator system (BELT SYSTEM). Each technology targets a different pathway in the ammonia generation process. The FOAM SYSTEM suppresses volatilization by forming a foam barrier at the air–liquid interface. The WIPING SYSTEM reduces precursor contact time by periodically removing feces. The BELT SYSTEM separates feces and urine upon excretion, inhibiting enzymatic ammonia formation. Among the individual systems, the BELT SYSTEM achieved the highest ammonia reduction efficiency of 91.7%, followed by the FOAM SYSTEM (73.6%) and WIPING SYSTEM (64.4%). The combined FOAM SYSTEM + BELT SYSTEM yielded the best performance with an ammonia reduction efficiency of 94.4%, showing modest synergy without operational interference. In contrast, the FOAM SYSTEM + WIPING SYSTEM configuration achieved 71.1%, slightly lower than the FOAM SYSTEM alone, likely due to foam disruption. Environmental sensitivity tests revealed that higher temperatures and alkaline pH elevated NH₃ emissions, whereas systems that maintained near-neutral pH, like the FOAM SYSTEM, demonstrated greater stability. These findings highlight the importance of integrating physical and source-control mechanisms while considering environmental variability for effective on-farm ammonia mitigation. Full article

Spirulina’s (Arthrospira platensis) use in food applications is limited by its dark color and sulfurous odor. This study aimed to develop a preharvest bioprocessing strategy using Saccharomyces cerevisiae co-cultivation to address these limitations. At a yeast/microalgae biomass ratio of 10:1000 with 5 g/L of glucose supplementation, co-cultivation for 24 h induced a rapid color transition from dark blue–green to light green and imparted “floral–fruity” aromas. Major bioactive compounds, including β-carotene, linoleic acid, and γ-linolenic acid, increased significantly, while volatile sulfur compounds were eliminated. Chlorophyll a and carotenoid contents rose by over two fold, reflecting enhanced photosynthetic efficiency. Mechanistic analyses revealed that yeast-derived acetic acid upregulated genes involved in flavor precursor biosynthesis and promoted biomass accumulation. This strategy integrates sensory improvement with nutritional enhancement, providing a sustainable approach for developing spirulina-based functional foods. Full article

Two enzymatic assays, based on release of p-nitroaniline and its spectrophotometric detection at 405 nm, were used to screen lager and ale brewing yeasts for carboxypeptidase and γ-glutamyltranspeptidase activity. Both activities were found in all the investigated yeasts and did not significantly distinguish Saccharomyces cerevisiae from S. pastorianus species. Large between-strain differences were measured for both carboxypeptidase (from 1.61 A/h for BRAS-45 to 41.71 A/h for E-30) and γ-glutamyltranspeptidase (from 1.26 A/h for US-05 to 48.72 A/h for S-33). No correlation was found between either enzymatic activity and the previously published ability of Saccharomyces yeasts to degrade glutathionyl or γ-GluCys- precursors to free polyfunctional thiols. Only for fermentation at lower temperatures does carboxypeptidase activity seem relevant for identifying the most interesting candidates. Measuring transport efficiency and β-lyase activities individually on the three possible intermediates emerges here as more promising for future flavor potential screening. Full article

Current marine mackerel (Scomberomorus niphonius) products predominantly involve low-value-added processing, while high-value-added products like fish floss remain underdeveloped. This study utilized mackerel dorsal muscle treated with flavor protease (FP), papain (PP), and neutral protease (NP) (10 U/g, 30 min), followed by steaming and stir-frying. Combined with sensory evaluation, HS-GC-IMS, and automatic amino acid analysis, the characteristic flavor was evaluated by multi-omics. The results showed that FP and NP significantly enhanced odor by reducing fishy compounds (e.g., hexanal) and increasing pyrazines/furans. PP enhanced taste by elevating umami and sweet amino acids (26.68% and 25.98%, respectively). Correlation analysis revealed the following potential pathways: Val and Leu served as precursors for furan, suppressing 2-methyl-3-(methylthio)furan formation, while Asp, Tyr, Phe, Gly, Cys, and Ile promoted 2,5-dimethylpyrazine and 2-methyl-3-(methylthio)furan generation while inhibiting furan. This study demonstrates that minimal protease addition effectively optimizes dried mackerel floss flavor, providing a novel approach for high-quality marine product development. Full article

The objectives of this study were to investigate the effects of extended and constant ethanol and hexanal exposure on ‘Gala’ apples’ production of aroma compounds after long-term CA storage. ‘Gala’ apples were stored in a CA under 2 kPa O₂ and 98 kPa N2 at 1.0 ± 0.1 °C with a constant ethanol (CA-et) or hexanal (CA-he) concentration maintained at 50 µgL⁻¹ throughout a six-month storage period. A total of 25 volatile compounds (VOCs) were identified. The odor activity value (OAV) results show that nine VOCs were key aroma compounds. Among them, hexyl acetate, 2-methylbutyl acetate, and 1-butanol were the highest. Hexanal increased the production of hexyl acetate, while ethanol increased the production of 2-methylbutyl acetate and ethyl 2-methylbutanoate. Both precursors promoted the production of 1-butanol after two months of storage and 1 day of shelf life. Overall, the impact of the precursors on aroma production was more pronounced after two months than after six months of storage. Different storage atmospheres significantly influenced VOC correlations, suggesting that ethanol and hexanal addition altered aroma biosynthesis pathways in the ‘Gala’ apples. For varieties like ‘Gala’ that rapidly lose their aroma during CA storage, CA-et and CA-he treatments may be beneficial for short-term storage, enhancing key aroma compounds and improving sensory quality. Full article

The development of plant-based meat substitutes is imperative for reducing animal fat intake and promoting dietary diversification. However, the flavor profiles of these products frequently fall short of consumer expectations. This study sought to optimize the production process of meat flavorings for plant-based products using the Taguchi method. The study investigated the effects of sugar type, concentration, and reaction temperature on the Maillard reaction products, sensory characteristics, and volatile organic compounds. The thermal process flavors were obtained from the flavor precursor by heating in a laboratory microwave station at 30 bar for 15 min. The variable factors were the type of sugar (fructose, glucose, xylose), its concentration (25, 50, and 100 mM), and the temperature of the reaction (140, 150, and 160 °C). The study’s findings indicated that temperature emerged as the predominant factor influencing the formation of Maillard reaction products and the sensory characteristics of the flavorings. Specifically, 25 mM xylose-based flavorings prepared at 140 °C demonstrated the most notable meat flavor and the highest level of acceptability. Moreover, the analysis of volatile organic compounds revealed the presence of a diverse array of substances, including aldehydes, ketones, and alcohols, that are characteristic of meat flavor. A heat map of the volatile content was constructed to facilitate a comparison of the samples. The study demonstrates the effectiveness of the Taguchi method in optimizing the production process of meat flavorings for plant-based products and provides valuable insights for the development of more balanced odor profiles. Full article

Polyurethane materials, widely used in indoor environments, occasionally exhibit unpleasant odors. An important source of polyurethane odorants is polyether polyols. Previous studies identified odorous 2-ethyldimethyl-1,3,6-trioxocanes in polyurethane materials and polyols but did not investigate the odor activity of the individual isomers. In the present work, an isomer mixture of the precursor dipropylene glycol was fractionated through preparative high-performance liquid chromatography. After the conversion to the corresponding trioxocanes, gas chromatography-olfactometry analyses revealed that just one positional isomer, namely 2-ethyl-4,7-dimethyl-1,3,6-trioxocane, was odor active. Moreover, we observed clear differences in the odor threshold concentrations among its stereoisomers. Only two out of eight isomers displayed an odor, both with an earthy smell and one being approximately 60 times more potent than the other. These insights contribute to a better understanding of polyurethane odor on a molecular level and provide a basis for effective odor control. Full article

The optimum processing conditions for green laver chips were determined using response surface methodology (RSM) to improve taste and reduce off-flavors by applying reaction flavor and air-frying techniques. The optimum composition (w/w) for the chips included 20% green laver, 20% hairtail surimi, and 60% flour. Additional ingredients included distilled water (90 mL) with GDL (3 g), NaHCO₃ (2 g), salt (1 g), sugar (12 g), roasted soybean powder (1.5 g), and reaction flavor solution (RFS, 10 mL). The mixture was kneaded, shaped, dried at 50 °C for 2 h, and air-fried at 195 °C for 80 sec. The resulting green laver chips showed overall acceptance and brittleness values of 7.00 ± 0.74 and 5.89 ± 0.59 N, respectively, with absolute residual errors of 8.43% and 7.07%. The optimum reaction flavor precursors for green laver chips were determined to be threonine (1.0 g%), proline (1.0 g%), glycine (1.4 g%), methionine (0.05 g%), and glucose (2 g%). Flavor analysis revealed that green laver chips with reaction flavor (GLCR) contained 13 alkylpyrazines with corn-like and nutty odors, and 2-acetylpyrrole, which contributed a popcorn-like odor. In contrast, green laver chips without reaction flavor (GLC) predominantly contained straight-chain aldehydes with undesirable odors. The heating process in the air fryer appeared to reduce the aldehyde content and promote pyrazine formation, significantly enhancing GLCR’s flavor. Full article

Volatile Organic Compounds (VOCs) are not only essential precursors for the formation of ozone and PM_2.5, but also hazardous to human health and responsible for unpleasant odors. The pharmaceutical industry has become an important industrial source of VOCs due to China’s large emissions and complex emission chains. In total, 245 VOCs samples were collected and analyzed from 11 typical pharmaceutical companies in Zibo City of the North China Plain, in order to investigate the VOCs emission characteristics and odor impacts. The emission factor for the pharmaceutical industry was 7.97 ± 8.21 g/kg pharmaceuticals, while the main emission links were chimney emissions, equipment sealing leakage, and so on. Finally, considering both purifying efficiency and economic benefits, the multistage absorption (AB) method is most effective for VOCs concentrations below 100 mg/m³, while UV photo-oxygenation combined with adsorption (UVA) is more suitable for concentrations below 300 mg/m³. The Regenerative Thermal Oxidizer (RTO), Catalytic Oxidizer (CO), and Condensation + Adsorption (CA) technologies demonstrated greater stability and efficiency, particularly in the treatment of complex organic pollutants, highlighting their advantages in both VOCs and odor removal at higher concentrations. Full article