2-phenylethyl Acetate Research Articles

Study on changes of bioactive substances and flavour characteristics during fermentation of jujube vinegar

SummaryJujubes are an excellent source of sugar and nutrients, making them well‐suited for fermentation. Previous research on jujubes has primarily focused on their use in fermented beverages and fruit wines, but their potential for vinegar production has not been sufficiently explored. Therefore, this study produced jujube vinegar from jujube as raw material using microbial fermentation technology, and the changes in bioactive substances and volatile components during different fermentation stages were monitored. Results revealed that the primary organic acids in jujube vinegar were acetic acid, malic acid and lactic acid. The levels of phenolic compounds, such as epicatechin and ferulic acid, increased significantly by 3.5‐fold and 3.2‐fold, respectively, after acetic fermentation, resulting in an improvement in antioxidant activity. In addition, a total of seventy‐three volatile substances were detected in jujube vinegar, with acids accounting for 72.13% of the overall content. Isoamyl alcohol, ethyl phenylacetate, benzaldehyde and 3‐hydroxy‐2‐butanone were also the principal flavour compounds of jujube vinegar, which are the main source of its intense flavour. This study reveals the dynamic law of nutrients and flavour compounds during the fermentation process of jujube vinegar. The findings provide a theoretical reference and practical basis for the production of jujube vinegar.

Four new wines from La Mancha region: Chemical characterization of oenological parameters, phenolic composition and volatile compounds

In this study, Carnelian, Barbera, Negro Amaro, and Limberger wines were obtained across two harvests from foreign red grape varieties cultivated in the La Mancha region. The results show that the general composition of all wines was in concordance with quality red wines from La Mancha region. The spectrophotometric method was employed to determine the main families of phenolic compounds and higher concentrations of these compounds were found in Carnelian wines. Free aroma compounds were isolated using solid-phase extraction (SPE), followed by analysis through gas chromatography-mass spectrometry (GC/MS). The GC-MS analysis of the wines identified 71 volatile compounds in Barbera wines and 58 free aroma compounds in Carnelian, Negro Amaro, and Limberger wines. The volatile compounds with the greatest capacity to introduce modifications in the aroma composition of the studied wines were (Z)-3-hexen-1-ol, 2-phenylethyl acetate, linalool, β-damascenone, phenylethyl alcohol, and butyric acid. This research presents the first comprehensive aromatic characterization of Carnelian, Barbera, Negro Amaro, and Limberger wines from the La Mancha region. The data suggested that these wines have great aromatic potential and can be considered viable alternatives to traditional grape varieties.

Conching of dark chocolate – Processing impacts on aroma-active volatiles and viscosity of plastic masses

The conching process plays a key role in determining the sensory and rheological properties of dark chocolate. To further understand this process, changes in the chocolate mass during plastic conching were investigated on a time-resolved basis with varying conching temperature, shear direction, and with or without the presence of residue from previous trials (pre-charge) on the conche vessel wall. Six selected odorants (acetic acid, benzaldehyde, linalool, 2,3,5,6-tetramethylpyrazine, 2-phenylethanol, 2-phenylethyl acetate) were quantified in fat and particle phases of chocolate masses. Particularly at elevated conching temperature, the odorant concentrations were found to decrease (up to 78.0% in the fat phase). The highest concentrations of desired odorants were determined mostly after conching without pre-charge. During conching, odorants were observed to accumulate increasingly in the fat phase (up to 91.7%) with decreasing odorant polarity. Similarly, it was found that conching temperature and the absence of pre-charge had the highest impact on the rheological properties of the chocolate mass, resulting in lowest and highest complex viscosity, respectively. In conclusion, some positive outcomes of conching, namely the retention of desired odorants and the reduction of viscosity, were inversely related at elevated temperature or in the absence of pre-charge, necessitating compromises to achieve optimal flow properties and flavor. Our results contribute to a deeper understanding of the influence of conching on the quality of dark chocolate by providing insights into the complexity of aroma migration and rheological changes during conching.

Exploring Non-Saccharomyces yeasts from Daqu for beer production

Daqu is an essential component in the solid-state fermentation of Chinese Baijiu, and non-Saccharomyces yeasts from Daqu significantly contribute to the complex flavors in Baijiu. However, the potential of non-Saccharomyces yeasts from Daqu in beer production has remained unexplored. In this study, 80 strains representing 14 non-Saccharomyces yeast species were isolated from various Daqu. These strains were scrutinized for their stress tolerance, flocculation, fermentation performance, and the production of flavor compounds. Subsequently, representative strains were chosen for beer production, and the resulting products from both single- and mixed-strain fermentations underwent sensory evaluation. Toruaspora delbrueckii TD2 exhibited excellent fermentation properties in wort. In compared to US-05, the non-Saccharomyces yeast strains tested significantly increased volatile favor compounds. Notably, the Wickerhamomyces anomalus strain showed a 13.86-fold increase in ethyl acetate production, while the Hanseniaspora osmophila strain displayed a 7-fold increase in phenylethyl acetate production. Co-fermentations of these strains with US-05 did not impact attenuation and ethanol concentration but significantly enhanced aromatic profiles. This study offers valuable insights into the fundamental attributes and brewing potential of non-Saccharomyces yeasts sourced from Daqu, broadening the spectrum of yeast selection for the creation of innovative beers.

Technological usage of ripe banana pulp for the development of a salad dressing

Oxidized banana (OB) is one of the important food wastes which contains a high potential to use in different products such as salad dressing. OB is a good ingredient in salad dressing due to its presence of antioxidants, vitamins, dietary fibers, and starch. the current study aimed to replace OB with non-oxidized banana (T1: 0 % T2: 25 %, T3: 50 %, T4: 75 %, and T5: 100 % OB) in salad dressing formulation and focused on the effects of OB on color, sensory, physical, chemical, rheological properties, microbial growth, and consumer studies. E-nose and volatile compounds analysis by GC-MS was also performed. According to the results, L*, a*, and b* values decreased significantly (P < 0.5) leading to a darker color of the product and effected other color evaluations (Hue, chroma, and ∆E). Viscosity was decreased significantly by the addition of the OB in the dressing formulation while pH did not change between T5 and T1 treatments. All sensory attributes score (9-point hedonic scale) decreased and consumers were given of fact of OB salad dressing has environmental benefits. Steady shear flow measurements, frequency sweep analysis, and the thixotropic loop of the oxidized banana indicated that adding OB to salad dressing negatively affected textural properties. The most effective attributes are, texture, and color discriminating the underlying differences among all 5 treatments according to MANOVA Wilks’ P-values. McNemar’s test was applied to analyze before and after consumers had been given the information about OB environmental benefits indicating that emotional attributes were changed after knowing the fact state as well as the odds ratio predicted purchase intent which increased with an increase in overall liking, pleased, flavor, and satisfied attributes. The acceptability threshold for OB in salad dressing formulation is 50 % OB. Among the identified volatile organic compounds are acetic acid, hexanoic acid, 3-methyl-1-butanol, 2-methylpropyl acetate, ethyl hexanoate, and phenylethyl acetate. The volatile organic compounds identified are 3-methyl-butanoic acid, 2-methyl-butanoic acid, and (E)-2-Decenal. The electronic device could discriminate these aromas, and the results obtained agree with those of the tasting panel and the volatile compounds.

Characterization of volatile compounds and sensory properties of spine grape (Vitis davidii Foex) brandies aged with different toasted wood chips

Aging is an important process for improving wine and brandy quality. In this study, the chemical characterization and sensory properties of spine grape brandies were compared after aging with various species of wood chips, including French oak (FO), American oak (AO), Mongolian oak (MO), Japanese blue oak (JO), chestnut, catalpa, and cherry. The results showed that high color intensity and significant concentrations of tannins and polyphenols were observed in the brandies aged with FO, AO, and chestnut chips. The volatile compounds, such as ethyl decanoate, ethyl 2-methylbutanoate, ethyl octanoate, methyl salicylate, (Z)-2-hexenol, and furfural, contributed to the floral, fruity, and roasted/smoky attributes of the brandies aged with FO, AO, and chestnut chips. The 1-butanol, 1-propanol, phenylethanol, phenylethyl acetate, isoamyl acetate, and linalool contributed to the fruity, honey, and floral attributes of the brandies aged with JO and cherry chips. These findings are extremely useful for the production of differentiated and high-quality spine grape brandies.

Mechanistic insights into soy sauce flavor enhancement via Co-culture of Limosilactobacillus fermentum and Zygosaccharomyces rouxii

For years, the intricate interactions between microorganisms in fermented food have played a key role in enhancing flavor. Our previous study highlighted that co-culture of Limosilactobacillus fermentum (L. fermentum) and Zygosaccharomyces rouxii (Z. rouxii) could enhance the flavor improvement capability of Z. rouxii in soy sauce fermentation, but the mechanism has been understudied. In this study, gas chromatography-mass spectrometry (GC-MS), GC-MS combined with derivatization (Der-GC-MS) and metabolite addition experiments were employed to elucidate their interaction. The first reason for the enhanced flavor of co-culture was that L. fermentum itself could produce the caramel-like compounds, such as HDMF and 2-furanmethanol. Another important reason was the commensality interaction between L. fermentum and Z. rouxii, where L. fermentum not only grew vigorously, but also significantly promoted the growth of Z. rouxii, mitigating the inhibitory effects of acetic acid on Z. rouxii. Further validation revealed that the metabolites of L. fermentum could stimulate the reproduction of Z. rouxii and increase the synthesis of aroma compounds such as phenylethyl acetate and ethyl acetate. Notably, glycerin and lactic acid emerged as pivotal metabolites facilitating enhanced aroma production. This study offers valuable insights for advancing flavor regulation techniques in soy sauce production.

Potential of Endophytic Microorganisms in Fermentative Processes Using Agro-Industrial Waste as Substrates

This study investigated the potential of endophytic microorganisms in fermentative processes using agro-industrial residues as substrates. The aim was to explore sustainable biotechnological methods for producing valuable compounds from waste. Endophytic microorganisms were isolated from strawberry, lychee, and tangerine and used in fermentative processes with passion fruit, guava, and pineapple residues. Key methods included isolating and screening potent aroma-producing microorganisms, identifying them using MALDI-TOF MS, and analyzing volatile compounds by GC-MS. The results identified 37 endophytic microorganisms, with Kloeckera apiculata presenting the greatest aromatic potential. Fermentation with agro-industrial residues produced significant volatile compounds, identifying 27, 23, and 22 compounds from passion fruit, pineapple, and guava residues, respectively. The main conclusions highlighted the high production of ethyl acetate and 2-phenylethyl acetate, which contributed to fruity and floral aromas. The novelty of this study lies in the use of endophytic microorganisms isolated from tropical fruits to biotransform agro-industrial waste into high-value aromatic compounds, offering economic and environmental benefits. This research is significant, as it proposes a sustainable approach to valorize waste and produce natural aroma compounds through biotechnological processes.

Regulatory mechanisms of the microbial starter fortification on the community and flavor characteristics in Doubanjiang

Doubanjiang is a special Chinese seasoning paste produced by mixing broad bean paste with chili paste. Besides the antimicrobial substances, such as capsaicin contained in chili, the microbiota and metabolism are directly developed by the stress effect of abiotic factors that periodically change during the fermentation process. The microbial starter is a promising way to improve the quality of Doubanjiang production. In the present study, the regulatory mechanisms of the microbial starters (Tetragenococcus halophilus, Zygosaccharomyces rouxii, and Candida versatilis) were explored by comparing the microbial community, flavor characteristics and their correlation networks between the fortified and control groups. In comparison to the control group, the volatile compound content increased by 30.77%, with notable increases in phenylethyl alcohol, beta-ionone, etc. Conversely, there was a reduction in non-volatile compounds, including reducing sugar, acidity, amino acid nitrogen, and organic acids. The microbial structure underwent a shift, with an increase in the relative abundance of C. versatilis, while Z. rouxii demonstrated no variance and T. halophilus was not detected. The correlations of the specific microbes and certain flavor compounds were modified by the starter (p < 0.05). Notably, the correlation between Enterobacter/Malassezia and 3-furaldehyde was shifted from a negative to a positive conversion. The observed increase in beta-ionone, ethyl phenylacetate, etc., resulted from the synergistic effects, correlated transformations, and reduction of antagonistic interactions. These findings indicate that the starter powerfully regulates the interactions between microbial communities and metabolic networks, thereby provide valuable insights for the improvement of Doubanjiang quality.

Engineering Living Material for Controlled Fragrance Release Utilizing Kluyveromyces marxianus CBS6556 and Adaptive Hydrogel.

The demand for controllable fragrance materials is substantial owing to their potential to impart enduring scents in a variety of applications. However, the practical application of such materials has been limited by challenges in tunable morphogenesis, structural variability, and adaptability to diverse conditions. In our study, we introduce a hybrid living material that integrates a genetically engineered strain of Kluyveromyces marxianus CBS6556 with an adaptive hydrogel. The engineered K. marxianus achieved temperature stability in 2-phenylethanol (2-PE) and 2-phenylethyl acetate (2-PEAc) production by expressing relevant genes in the 2-PE metabolic pathway using the high-temperature preferential promoter SSE1. The enhanced water retention capacity supports the metabolic activities of the encapsulated yeast cells, ensuring their survival and functionality over an extended period. Fragrance-releasing living material (FLM) is designed to controllably emit fragrance 2-PE by adjusting the microbial concentration within the hydrogel matrix. The FLM exhibits versatile adhesion capabilities, effectively binding to a spectrum of surfaces such as wood, textiles, and glass as well as to natural substrates like leaves. This adaptability enhances the material's applicability across various settings. Furthermore, FLM can be crafted into various forms, including microbeads, fibers, and films. This research opens up new horizons for controlled fragrance release of living materials.

Fermentation Performances and Aroma Contributions of Selected Non-Saccharomyces Yeasts for Cherry Wine Production.

This study evaluates the fermentation performances of non-Saccharomyces strains in fermenting cherry must from Italian cherries unsuitable for selling and not intended to be consumed fresh, and their effects on the chemical composition of the resulting wine. Fermentation trials in 100 and 500 mL of must were carried out to select 21 strains belonging to 11 non-Saccharomyces species. Cherry wines obtained by six select strains were chemically analyzed for fixed and volatile compounds. Quantitative data were statistically analyzed by agglomerative hierarchical clustering, partial least squared discriminant analysis, and principal component analysis. Wines revealed significant differences in their composition. Lactic acid and phenylethyl acetate levels were very high in wines produced by Lachancea and Hanseniaspora, respectively. Compared to S. cerevisiae wine, non-Saccharomyces wines had a lower content of fatty acid ethyl esters 4-vinyl guaiacol and 4-vinyl phenol. The multivariate analysis discriminated between wines, demonstrating the different contributions of each strain to aroma components. Specifically, all wines from non-Saccharomyces strains were kept strictly separate from the control wine. This study provided comprehensive characterization traits for non-conventional strains that enhance the aroma complexity of cherry-based wine. The use of these yeasts in cherry wine production appears promising. Further investigation is required to ascertain their suitability for larger-scale fermentation.

Characterization of aroma and aroma-active compounds of black carrot (Daucus carota L. ssp. sativus var. atrorubens Alef.) pomace by aroma extract dilution analysis

The aim of this study was to characterize the aroma and aroma-active compounds of black carrot pomace, a valuable by-product of black carrot juice industry. Aroma compounds were analyzed using GC-MS-O and extracted via the SAFE technique. The extract samples were determined to represent the odor of black carrot pomace quite well according to the results of the representative test. Accordingly, the aromatic extract scored 77.7 mm for intensity and 87 mm for similarity on a 100 mm unstructured scale. A total of 47 volatile constituents were identified and quantified including terpenes (20), alcohols (11), acids (7), esters (4), ketones (4), and lactone (1). It was observed that terpenes were the major aroma group. The use of aroma extract dilution analysis (AEDA) revealed only 29 of these compounds as aroma-active constituents. Phenylethyl alcohol (FD:512, OAV: 2488, rose) and phenylethyl acetate (FD:256, OAV:280, rose) were the aroma substances providing the strongest rose odor. Following these compounds, acetic acid (vinegar), dimethyl-propanedioic acid (pungent), (E)-β-caryophyllene (salty cheese) and elemicin (spicy) were identified as other strong aroma-actives with FD values of 128 contributing to the characteristic odor of the black carrot pomace samples. The odor activity values (OAVs) ranged from 1 to 2488. The highest OAVs represent the high aromatic active compounds (FD ≥ 128). The distinctive aroma and rich color of black carrot pomace make it a recommended choice for enhancing flavor and adding natural coloring to food products.

Prediction Prediction of the Insecticidal Potency of Biduri Plants (Calotropis gigantea) using the PASS online web resource

Calotropis gigantea, a wild plant thriving in arid environments, has been traditionally used for medicinal purposes by communities near Baluran National Park (BNP). The latex of C. gigantea is used as a crab poison due to its ability to cause fatal damage and separation of body parts, possibly related to chitin disruption in insects. This study explores the potential insecticidal properties of secondary metabolites in C. gigantea using Prediction of Activity Spectra for Substance (PASS) Online. Out of 68 identified secondary metabolites, six show significant insecticidal potential, namely Profenophos, Ethion, Alpha-Citral, 1-Phenylethyl acetate, (E)-dec-3-en-2-one, and Benzaldehyde. Notably, Profenophos, Ethion, Alpha-Citral, and Benzaldehyde exhibit toxic properties effective against insects, with enzyme inhibitory activity affecting nerve signaling and immune systems, suggesting potential for bio-insecticide development.

Examination of internal metabolome and VOCs profile of brewery yeast and their mutants producing beer with improved aroma

Volatile organic compounds (VOCs) are metabolites pivotal in determining the aroma of various products. A well-known VOC producer of industrial importance is Saccharomyces cerevisiae, partially responsible for flavor of beers and wines. We identified VOCs in beers produced by yeast strains characterized by improved aroma obtained in UV-induced mutagenesis. We observed significant increase in concentration of compounds in strains: 1214uv16 (2-phenylethyl acetate, 2- phenylethanol), 1214uv31 (2-ethyl henxan-1-ol), 1214uv33 (ethyl decanoate, caryophyllene). We observed decrease in production of 2-phenyethyl acetate in strain 1214uv33. Analysis of intracellular metabolites based on 1H NMR revealed that intracellular phenylalanine concentration was not changed in strains producing more phenylalanine related VOCs (1214uv16 and 1214uv33), so regulation of this pathway seems to be more sophisticated than is currently assumed. Metabolome analysis surprisingly showed the presence of 3-hydroxyisobutyrate, a product of valine degradation, which is considered to be absent in S. cerevisiae. Our results show that our knowledge of yeast metabolism including VOC production has gaps regarding synthesis pathways for individual metabolites and regulation mechanisms. Detailed analysis of 1214uv16 and 1214uv33 may enhance our knowledge of the regulatory mechanisms of VOC synthesis in yeast, and analysis of strain 1214uv31 may reveal the pathway of 2-ethyl henxan-1-ol biosynthesis.

Study on the Kinetic Model of Mixed Fermentation by Adding Glutathione-Enriched Inactive Dry Yeast

In order to investigate the impact of glutathione-enriched inactive dry yeast (g-IDY) on the co-fermentation process of Torulaspora delbrueckii and Saccharomyces cerevisiae, different contents of g-IDY (0, 20, 40, and 100 mg/L) were added to the simulated liquid for fermentation. The yeast quantity, reducing sugar content, and ethanol volume fraction in the fermentation system were determined every 24 h. Nonlinear fitting of the measured values was carried out using classical Logistic, SGompertz, Boltzmann, and DoseResp models. Additionally, the aroma components of the wine were analyzed by GC-MS. The results indicate that the Logistic model performs best in terms of yeast growth kinetics, whereas the DoseResp and Boltzmann models exhibit the same fitting performance for reducing sugar consumption, both superior to the Logistic model, and the Boltzmann model shows the best-fitting performance for ethanol production. All optimal models have fitting coefficients (R2 values) above 0.99, demonstrating that different contents of g-IDY can effectively complete fermentation. Furthermore, all three fitting models can effectively describe the fermentation process using g-IDY. The use of g-IDY can increase the content of ethyl phenylacetate and phenylethanol, which can be employed to enhance the aroma of wine.

Confinement of Sustainable Carbon Dots Results in Long Afterglow Emitters and Photocatalyst for Radical Photopolymerization.

Sustainable carbon dots based on cellulose, particularly carboxymethyl cellulose carbon dots (CMCCDs), were confined in an inorganic network resulting in CMCCDs@SiO2. This resulted in a material exhibiting long afterglow covering a time frame of several seconds also under air. Temperature-dependent emission spectra gave information on thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) while photocurrent experiments provided a deeper understanding of charge availability in the dark period, and therefore, its availability on the photocatalyst surface. The photo-ATRP initiator, ethyl α-bromophenylacetate (EBPA), quenched the emission from the millisecond to the nanosecond time frame indicating participation of the triplet state in photoinduced electron transfer (PET). Both free radical and controlled radical polymerization based on photo-ATRP protocol worked successfully. Metal-free photo-ATRP resulted in chain extendable macroinitiators based on a reductive mechanism with either MMA or in combination with styrene. Addition of 9 ppm Cu2+ resulted in Mw/Mn of 1.4 while an increase to 72 ppm improved uniformity of the polymers; that is Mw/Mn=1.03. Complementary experiments with kerria laca carbon dots confined materials, namely KCDs@SiO2, provided similar results. Deposition of Cu2+ (9 ppm) on the photocatalyst surface explains better uniformity of the polymers formed in the ATRP protocol.

Der Einschluss von nachhaltigen Kohlenstoffpunkten führt zu langnachleuchtenden Emittern und zu Photokatalysatoren für die radikalische Photopolymerisation

AbstractNachhaltige Kohlenstoffpunkte auf der Basis von Cellulose, insbesondere Carboxymethylcellulose basierende Kohlenstoffpunkte (CMCCDs), wurden in ein anorganisches Netzwerk eingeschlossen, was zur Bildung von CMCCDs@SiO2 führte. Das resultierende Material zeigte ein lange anhaltendes Nachleuchten, welches ein Zeitfenster von mehreren Sekunden auch in Gegenwart von Luft umfasste. Temperaturabhängige Emissionsspektren gaben eine Information über die thermisch aktivierte verzögerte Fluoreszenz (TADF) und eine Phosphoreszenz bei Raumtemperatur (RTP), während Experimente zur photoinduzierten Generierung von Ladungsträgern zu einem tieferen Verständnis der Verfügbarkeit von Ladungen in der Dunkelphase führten und daher zu ihrer Verfügbarkeit an der Katalysatoroberfläche. Der photo‐ATRP Initiator α‐Bromphenylethylacetat (EBPA) bewirkte eine Löschung der Emission, was zu einer Verkürzung des Zeitfensters für die Emission vom Millisekundenbereich in den Nanosekundenbereich führte und auf eine Beteiligung des Triplettzustandes an dem photoinduzierten Elektronentransfer (PET) hinweist. Sowohl die freie radikalische Polymerisation als auch die kontrollierte auf einem photo‐ATRP Protokoll basierende radikalische Polymerisation von MMA oder in Kombination mit Styren funktionierten erfolgreich. Die metallfreie photo‐ATRP führte basierend auf einem reduktiven Mechanismus zu einem kettenverlängerbaren Makroinitiator. Die Zugabe von 9 ppm Cu2+ führte zu einem Verhältnis Mw/Mn von 1.4 obwohl eine Erhöhung auf 72 ppm die Einheitlichkeit der Polymere verbesserte, was einem Mw/Mn=1.03 entspricht. Ergänzende Experimente mit in kerria laca eingeschlossenen Kohlenstoffpunkten, insbesondere KCDs@SiO2, führten zu ähnlichen Ergebnissen. Die Abscheidung von Cu2+ (9 ppm) an der Photokatalysatoroberfläche erklärt die bessere Dispersität der Polymere, welche mittels der ATRP gebildet wurden.

Uncovering the flavor differences between black rice wine and glutinous rice wine by GC-MS, GC-IMS, HPLC, and electronic sensory analysis

The black rice bran component (BRBC) is the main difference between black rice and glutinous rice, but its influence on the flavor of rice wines brewed from them is ambiguous. To address this, the flavor profiles and compounds of four rice wines — brewed from glutinous rice (B), glutinous rice with BRBC (added), polished black rice (without BRBC), and whole black rice (HH) — were analyzed using e-nose, GC-MS and GC-IMS. The e-nose revealed significant aroma profile differences between B and HH, with 47 and 49 volatile compounds detected by GC-MS and GC-IMS, respectively. Orthogonal partial least-squares discrimination and fold change analysis highlighted the significant impact of BRBC on the aroma differences between HH and B. Chemometrics and odor activity values identified isoamyl acetate, ethyl caprylate, (E)-2-octenal, phenylethyl acetate, ethyl caproate, 2,4-heptadienal, and 1-octen-3-ol as key contributors to the fresh and fruity aroma in B, while ethyl butanoate, ethyl isoiautyrate, benzene acetaldehyde, (E)-2-octen-1-ol, guaiacol, and heptanal were predominant in HH, contributing to its rich and complex aroma. The e-tongue indicated significant taste distinctions between HH and B, potentially due to the influence of the black rice bran component on the regulation of organic acid and free amino acid content. This study provides new insights into the regulation of rice wine flavor through raw materials.

Lactone Enolates of Isochroman-3-ones and 2-Coumaranones: Quantification of Their Nucleophilicity in DMSO and Conjugate Additions to Chalcones.

Owing to stereoelectronic effects, lactones often deviate in reactivity from their open-chain ester analogues as demonstrated by the CH acidity (in DMSO) of 3-isochromanone (pKa = 18.8) and 2-coumaranone (pKa = 13.5), which is higher than that of ethyl phenylacetate (pKa = 22.6). We have now characterized the reactivity of the lactone enolates derived from 3-isochromanone and 2-coumaranone by following the kinetics of their Michael reactions with p-quinone methides and arylidenemalonates (reference electrophiles) in DMSO at 20 °C. Evaluation of the experimentally determined second-order rate constants k2 by the Mayr-Patz equation, lg k2 = sN(N + E), furnished the nucleophilicity parameters N (and sN) of the lactone enolates. By localizing their position on the Mayr nucleophilicity scale, the scope of their electrophilic reaction partners becomes predictable, and we demonstrate a novel catalytic methodology for a series of carbon-carbon bond-forming reactions of lactone enolates with chalcones under phase transfer conditions in toluene.

The Impact of Microbial Activity on the Chemical Composition and Aroma Profile of Traditional Sparkling Wines

Traditional sparkling wines are produced in a two-step sequence of alcoholic fermentations, followed by extended aging which is an influential factor for the final aroma profile. Traditionally, the second fermentation and aging are conducted in bottles over a minimum of 18 months, resulting in an aroma profile which is shaped by oxidative secondary metabolites like aldehydes, acids and fatty acid esters. In this study, a total of 29 traditional commercial sparkling wines from the categories Champagne, Cava, California Champagne, and others (Prosecco and Cremant) were analyzed. The objective was to determine the impact of microbial activity on the stylistic characteristics of traditional sparkling wines and allow winemakers to reproduce the specific fermentation conditions. The results indicate that malolactic fermentation plays an important role in Champagne and some Cavas, but not in the other sparkling wine categories. The metabolic activity of lactic acid bacteria results in an altered acid profile, amino acid utilization, and aroma production. While primary fermentation esters like phenylethyl acetate and isoamyl acetate are significantly reduced in Champagne and Cava, aroma compounds from secondary microbial activity like ethyl lactate and 2-acetyl-1-pyrroline are increased. This underlines the importance of diverse microbial activity of the characteristic style of traditional sparkling wines.