Isoamyl Acetate Research Articles

Innovating the Basic Organic Chemistry Experiment: Using the Synthesis of Isoamyl Acetate as an Example

Innovating the Basic Organic Chemistry Experiment: Using the Synthesis of Isoamyl Acetate as an Example

Effect of nano-encapsulated food flavorings on streptozotocin-induced diabetic rats.

Flavors and aromas are widely used in food and pharmaceutical industries to enhance food palatability. However, it is worth noting that they may also have bioactivity. This study aims to examine the potential impact of key flavors and their nanocapsules on health and diseases, such as type 2 diabetes mellitus (T2DM). The 36 nanocapsules of key flavorings were prepared by high shear homogenization (HSH). Seventy-two male Sprague-Dawley rats received a single dosage of streptozotocin (35 mg kg-1 body weight) intraperitoneally. All of the nutritional and biochemical parameters were statistically analyzed. A virtual docking study was conducted. Linalool nanoemulsion results showed the highest encapsulation efficiency (86.76%), while isoamyl acetate nanoparticles showed the lowest (69.99%). According to GC-MS analysis, encapsulation did not affect the flavoring structure with particle size distributions ranging from 277.3 to 628.8 nm. Using TEM, nanoemulsion particles appeared spherical with a desired nanometric diameter size. In the oral glucose tolerance test, flavorings in oil and nanoforms had no discernible hypoglycemia effects in normal rats. The nutritional and biochemical parameters confirmed that both normal and nanoencapsulation forms demonstrated a potential anti-hyperglycemic effect, and enhanced the rat health compared to the raw flavorings. The studied flavorings and their nanocapsules seem to have the potential double effect of a flavor compound as a food palatability enhancer with a potential beneficial effect on type 2 diabetes mellitus without any health drawbacks.

Covalent immobilization of lipase on an ionic liquid-functionalized magnetic Cu-based metal-organic framework with boosted catalytic performance in flavor ester synthesis.

Enzymatic esterification plays an important role in the fields of chemistry and biotechnology. In this study, lipase was immobilized on an ionic liquid (IL)-modified magnetic metal-organic framework (MOF) and used to synthesize isoamyl acetate. The immobilized lipase (PPL-ILs/Fe3O4@MOF) showed 2.1-fold and 1.8-fold higher activity compared to the free and immobilized lipase without ILs (PPL-Fe3O4@MOF), respectively. In addition, the anti-denaturant ability and reusability of the PPL-ILs/Fe3O4@MOF were also higher than those of other samples. The ester yield reached 75.1% when the biocatalyst was used to synthesize isoamyl acetate in hexane. The synthesized supports supplied a good microenvironment for the immobilized lipase through multiple interactions. Results of the structural analysis showed that the conformation state of lipase molecules changed after immobilization. The magnetism of the prepared biocatalyst makes it easy to recycle so that PPL-ILs/Fe3O4@MOF maintained 70.2% of the initial activity after eight cycles. The prepared composite materials exhibited good potential in lipase immobilization with enhanced catalytic ability and stability.

Use of Mixed Cultures for the Production of Grape–Plum Low-Alcohol Fermented Beverages

This work presents the attempt to develop a production technology for grape–plum low-alcohol beverages and enhance their chemical composition and flavor complexity through the non-Saccharomyces species. Saccharomyces cerevisiae (SC) pure cultures were used as reference beverages. Pure cultures of Lachancea thermotolerans (LT) and co-inoculated Lachancea thermotolerans with Saccharomyces cerevisiae (MIX) were included for grape–plum must fermentation at a pilot scale. The process involves two steps: a primary alcoholic fermentation in stainless steel tanks (F1) and a secondary fermentation in a bottle after dextrose syrup addition (F2). The chemical compositions of all beverages obtained in F1 and F2 were studied. Compared to SC, must inoculated with L. thermotolerans (LT and MIX) required four more days to complete the fermentation of sugars during F1. SC fermentation tended to have slightly higher pH and titratable acidity values and lower concentrations of total phenols. Final levels of aromatic precursor nitrogen and sulfur amino nitrogen were obtained more in SC than in LT and MIX. SC treatment had higher final levels of histidine, phenylalanine, isoleucine, lysine, methionine, threonine, valine, and cysteine. Related to individual amino acids, SC treatment had higher final levels of histidine, phenylalanine, isoleucine, lysine, methionine, threonine, valine, and cysteine. Analysis of the volatile composition showed that, compared with SC, MIX had the highest percentage of higher alcohols (3-methyl-1-butanol and 2-methyl-1-butanol) and acetates (isoamyl acetate and isobutyl acetate) which are associated with fruity and banana aromas. A decreasing trend in volatile fatty acids was observed in LT and MIX compared to SC. LT application, both in pure and mixed culture, significantly modified the values of the percentage of 5 of the 10 ethyl ester compounds analyzed. Finally, the sensory analysis showed that there were no significant differences, even though the non-Saccharomyces had a higher percentage of volatile metabolites. The results have shown that through this process an innovative and high-quality product was obtained: a low-alcohol beverage made from grapes and plums, which could be developed at an industrial level due to the increasing interest of consumers in this type of product.

The critical roles of α-amylase and amyloglucosidase in improving the quality of black waxy corn beverages: Special attentions to the color and flavor

To preserve the nutrients while maximizing the value of black waxy corn, beverage is the most promising manufacturing product. However, the poor stability and bland flavor profile are significant issues limiting its popularization. This study, firstly profiled the anthocyanidins of black waxy corn and the effects of α-amylase and amyloglucosidase treatments on the anthocyanidin levels, color properties, and flavor qualities were systematically studied. A total of 5 anthocyanidins and 11 anthocyanins were identified. The concentration of cyanidin, petunidin, peonidin, pelargonidin, and malvidin in liquefied liquids (YHY) and saccharified liquids (THY) were significantly increased by 55.46% and 56.62% after α-amylase and amyloglucosidase treatments. The enzymatic hydrolysis was found to enrich the volatile profile. The relative odor activity value and multivariate statistical analyses further suggested isoamyl acetate, benzaldehyde, 2-nonenal, 2,4-decadienal, dodecanal, 2-buten-1-one, 3-buten-2-one, and dimethyl trisulfide as key odorants to discriminate black waxy corn beverages produced by α-amylase or amyloglucosidase.

Определение летучих органических примесей в виски методом газовой хромато-масс-спектрометрии

Alcoholic beverages are complex multicomponent objects. Their quality and safety control is a serious analytical task that requires new, more accurate instrumental methods, e.g., chromatography-mass spectrometry. 
 The research involved domestic and foreign whiskey, other alcoholic beverages, and 40% water-alcohol model solutions. The analytical studies were carried out on a Maestro 7820A gas chromatograph GC with an Agilent Technologies 5975 Series MCD mass selective detector, a G4513A autosampler, and a high polarity FFAP capillary column.
 The research revealed the optimal parameters of chromatographic separation and mass spectrometric detection. The relative measurement error remained below 25% in the range of 1.0–10 mg/dm3 and 18% in the range of 10–500 mg/dm3. These modes were used to study the composition of the volatile organic impurities. The largest proportion of the total volatile impurities was 34.84–58.08% isoamylol, 17.31–26.76% acetic acid, and 12.50–21.28% isobutanol. Other chemical compounds were not so abundant: 0.34–0.86% isoamyl acetate, 0.13–0.39% 1-butanol, 0.03–0.06% 1-pentanol, 0.40–11.20% ethyl lactate, 0.16–2.74% ethyl caprylate, 1.40–6.44% furfural, 0.18–14.60% ethyl caprate, 0.74–2.97% ethyl laurate, and 1.75–2.39% 2-phenylethanol. The maximal total content of volatile organic impurities was 2040.30 mg/dm3: it was registered in apple samogon. The minimal total content of volatile organic impurities was 392.16 mg/dm3 in the unaged rum distillate sample.
 The new method proved highly accurate in determining the qualitative and quantitative composition of twelve volatile consumable components in whiskey. The procedure took 17 min; it can be applied to mass concentrations of volatile impurities in such alcoholic beverages as grape-brandy, rum, tequila, brandy, samogon, rum, and various distillates.

A Targeted and an Untargeted Metabolomics Approach to the Volatile Aroma Profile of Young 'Maraština' Wines.

This study investigated the detailed volatile aroma profile of young white wines of Maraština, Vitis Vinifera L., produced by spontaneous fermentation. The wines were produced from 10 vineyards located in two Dalmatian subregions (Northern Dalmatia and Central and Southern Dalmatia). Volatile compounds from the wine samples were isolated by solid-phase extraction (SPE) and analyzed by an untargeted approach using two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC/TOF-MS) and a targeted approach by gas chromatography-tandem mass spectrometry (GC-MS/MS). A comprehensive two-dimensional GC×GC analysis detailed the total volatile metabolites in the wines due to its excellent separation ability. More than 900 compounds were detected after untargeted profiling; 188 of them were identified or tentatively identified. A total of 56 volatile compounds were identified and quantified using GC-MS/MS analysis. The predominant classes in Maraština wines were acids, esters, and alcohols. The key odorants with odor activity values higher than one were β-damascenone, ethyl caprylate, ethyl isovalerate, ethyl 2-methylbutyrate, ethyl caproate, isopentyl acetate, ethyl butyrate, and phenylacetaldehyde. The metabolomics approach can provide a large amount of information and can help to anticipate variation in wines or change winemaking procedures.

Gradually supply of isoamyl alcohol increases the isoamyl acetate production in solid-state fermentation.

Nowadays, isoamyl acetate production is carried out by chemical synthesis with a recent interest in developing biological producing processes, mainly based on microorganisms in submerged fermentation. This work assayed producing isoamyl acetate through solid-state fermentation (SSF), feeding the precursor in the gas phase. Polyurethane foam functioned as the inert support to contain 20ml of a solution of molasses (10%w/v, pH 5.0). The yeast Pichia fermentans was inoculated at 3×107 cells per gram of initial dry weight. The airstream to supply oxygen also served to supply the precursor. Slow supply was obtained using an isoamyl alcohol solution of 5g l-1 in the bubbling columns and an air stream of 50ml min-1. For fast supply, fermentations were aerated using 10g l-1 and 100ml min-1 for isoamyl alcohol solution and air stream, respectively. It demonstrated the feasibility of isoamyl acetate production in SSF. Moreover, the slow supply of the precursor increased isoamyl acetate production up to 390mg l-1, which is 12.5 times higher than that obtained without precursor (32mg l-1). On the other hand, fast supply caused an evident inhibition of the growth and production capacity of the yeast.

Volatile Profiles and Sensory Characteristics of Cabernet Sauvignon Dry Red Wines in the Sub-Regions of the Eastern Foothills of Ningxia Helan Mountain in China.

To elucidate the effects of the different terroir on wine aroma in six sub-regions of Eastern Foothills of Helan Mountain in Ningxia, a premium wine-producing region in China, 71 Cabernet Sauvignon wines were investigated by gas chromatography-mass spectrometry (GC-MS), check-all-that-apply (CATA), and quantitative descriptive analysis (QDA). The bidirectional orthogonal partial least squares-discriminant analysis (O2PLS-DA) results showed that the Cabernet Sauvignon dry red wines from Xixia (XX) and Yongning (YN) had similar volatile profiles due to their geographical proximity and were characterized by higher concentrations of esters, higher alcohols, and volatile phenols because the similar aromatic profiles were detected in their dry red wines. Shizuishan (SZS) and Hongsipu (HSP) wines showed clear differences compared to the wines of the other four sub-regions, being mainly characterized by relatively higher phenolic aldehydes and volatile phenols. The concentrations of methoxypyrazines and norisoprenoids varied mainly depending on the climate diversity of the sub-regions. The highest 3-isobutyl-2-methoxypyrazine (IBMP) concentration was presented in the Helan (HL) wines. The Qingtongxia (QTX) wines have the highest β-damascenone, which might be influenced by the fact that QTX has the lowest effective accumulated temperature and the highest sunshine duration among the five sub-regions. Esters including ethyl octanoate, ethyl decanoate, ethyl butanoate, ethyl hexanoate, and isoamyl acetate were the highest in HL. Additionally, the herbaceous, black berry, and red berry notes in HL and QTX were the most outstanding.

Surface Modification of Magnetic ZIF-90 Nanoparticles Improves the Microenvironment of Immobilized Lipase and Its Application in Esterification.

Interactions of enzymes with supports significantly affect the activity and stability of immobilized enzymes. Herein, amino-functionalized ionic liquid (IL)-grafted magnetic zeolitic imidazolate framework-90 (MZIF-90) was prepared and used to immobilize porcine pancreatic lipase (PPL). The nanocomposites were fully characterized; meanwhile, the interactions between ILs and ZIF-90 were calculated based on density functional theory. The prepared biocatalyst (PPL-ILs/MZIF-90) had a lipase loading of 178.3 mg/g and hydrolysis activity up to 287.5 U/g. When the biocatalyst was used to synthesize isoamyl acetate, the reaction media, molar ratio of alcohol/acid, temperature, and reaction time were optimized. Under the optimized reaction conditions (in hexane, alcohol/acid = 3:1, under 45 °C, reacted for 9 h), the ester yield reached 85.5%. The results of the stability test showed that PPL-ILs/MZIF-90 retained 88.7% of the initial activity after storing for 35 days and 92.5% of the initial activity after reusing for seven cycles for synthesizing isoamyl acetate. Moreover, the secondary structure analysis showed that the synthesized supports protected the active conformation of immobilized lipase, which lead to the enhanced catalytic performance. Additionally, the biocatalyst can be easily separated with a magnet, which facilitated the reusability. This study provides insights regarding the application of metal organic framework composites in the field of enzyme catalysis.

The aromatic profile of wine distillates from Ugni blanc grape musts is influenced by the nitrogen nutrition (organic vs. inorganic) of Saccharomyces cerevisiae

Although the impact of nitrogen nutrition on the production of fermentative aromas in oenological fermentation is well known today, one may wonder whether the effects studied are the same when winemaking takes place at high turbidities, specifically for the production of wines intended for cognac distillation. To that effect, a fermentation robot was used to analyze 30 different fermentation conditions at two turbidity levels with several factors tested: (i) initial addition of nitrogen either organic (with a mixture of amino acids - MixAA) or inorganic with di-ammonium phosphate (DAP) at different concentrations, (ii) variation of the ratio of inorganic/organic nitrogen (MixAA and DAP) and (iii) addition of different single amino acids (alanine, arginine, aspartic acid and glutamic acid). A metabolomic analysis was carried out on all resulting wines to have a global vision of the impact of nitrogen on more than sixty aromatic molecules of various families. Then, at the end of the alcoholic fermentation, the wines were micro-distilled. A first interesting observation was that the aroma profiles of both wines and distillates were close, indicating that the concentration factor is rather similar for the different aromas studied. Secondly, the fermentation kinetics and aroma results have shown that the nitrogen concentration effect prevailed over the nature of nitrogen. Although the lipid concentration was in excess, an interaction between the assimilable nitrogen and lipid contents was still observed in wines or in micro-distillates. Alanine is involved in the synthesis of acetaldehyde, isobutanol, isoamyl alcohol and isoamyl acetate. Finally, it was demonstrated that modifying the ratio of assimilable nitrogen in musts is not an interesting technological response to improve the aromatic profile of wines and brandies. Indeed, unbalance the physiological ratio of the must by adding a single source of assimilable nitrogen (organic or inorganic) has been shown to deregulate the synthesis of most of the fermentation aromas produced by the yeast. Wine metabolomic analysis confirmed the results that had been observed in micro-distillates but also in the other aromatic families, especially on terpenes. The contribution of solid particles, but also yeast biosynthesis (via sterol management in must) to wine terpenes is discussed. Indeed, the synthesis of terpenes in this oenological context seems to be favored, especially since the concentration of assimilable nitrogen (in addition to the lipid content) favor their accumulation in the medium. A non-negligible vintage effect on the terpene profile was also demonstrated with variations in their distribution depending on the years.Thus, the present study focuses on the metabolism of wine yeasts under different environmental conditions (nitrogen and lipid content) and on the impact of distillation on the fate of flavor compounds. The results highlight once again the complexity of metabolic fluxes and of the impact of nitrogen source (nature and amount) and of lipids. Furthermore, this study demonstrates that beyond the varietal origin of terpenes, the part resulting from the de novo synthesis by the yeast during the fermentation cannot be neglected in the context of cognac winemaking with high levels of turbidity.

Variations in volatile organic compounds in Zhenyuan Daocai samples at different storage durations evaluated using E-nose, E-tongue, gas chromatography, and spectrometry

In this study, the changes in volatile organic compounds (VOCs) in Zhenyuan Daocai at different storage durations were determined using electronic tongue (E-tongue), electronic nose (E-nose), and other methods. Gas chromatography-ion mobility spectrometry (GC-IMS) identified 81 VOCs in Zhenyuan Daocai, which originated either from the raw materials or developed during processing and storage. Isothiocyanates were the characteristic VOCs in the raw materials of Zhenyuan Daocai, imparting a mustard flavor, heptanal, nonanal, 1-hydroxy-2-propanone, and 2-pentylfuran were the compounds obtained after processing, imparting orange, sweet, and nutty flavors. The characteristic VOCs observed in Daocai after one year of storage were (E, E) −2,4-hexadienal, ethyl acetate, and isoamyl acetate, which contributed to the floral and fruity odors. The characteristic VOCs in Daocai after four years of storage were furfural, 2-methyl-3-furanthiol, and methyl butyrate, which contributed to the almond, roasted meat, fried coffee, and apple flavors.

Influence Evaluation of Enzyme Treatments on Aroma Profile of White Wines

Improving aroma profile represents one of the principal goals in winemaking. This paper focuses to evaluate the influence of enzymes applied before alcoholic fermentation of Fetească regală and Sauvignon blanc wines, even if most studies analyze their use in different winemaking stages. Fetească regală wines are described by higher proportions (1.07–4.28%) of ethyl octanoate (exotic fruits), 3-methylbutyl acetate (pear, banana), hexanoic acid (creamy, phenolic, exotic fruits), propan-2-yl acetate (ripe fruits, banana), and ethyl decanoate (floral, fruity, woody), while Sauvignon blanc wines are distinguished by significant proportions (2.77–42.15%) of 3-methylbutan-1-ol (exotic fruits), acetic acid (vegetal, sour), 1-phenylethanol (floral, honey), and diethyl butanedioate (fruity, floral). Variables as 3-methylbutyl acetate-ethyl decanoate, ethyl decanoate-hexanoic acid (r > 0.8) showed proportional levels in Fetească regală wines. In Sauvignon blanc samples, positive correlations were observed for 2-ethyl hydroxypropanoate-diethyl butanedioate or 2,3-butanediol-ethyl 4-hydroxybutanoate (r > 0.7). Data confirmed a significant influence of enzymes on wine’s aroma profile (p < 0.05). The higher proportions of the most volatile compounds were obtained in samples treated with pectinases, for both varieties. In correlation with the sensory analysis, these variants showed the lowest intensity for negative descriptors such as phenolic sensation, the mineral or bitter taste, demonstrating that pectinases can give more acceptable results regarding the sensory perception compared to β-glycosidases.

Characterization of a new Saccharomyces cerevisiae isolated from banana stems and its mutant with l-leucine accumulation for awamori brewing.

We isolated a new strain of the yeast Saccharomyces cerevisiae, 35a14, from banana stems in Okinawa. This strain did not belong to any industrial yeast groups in a phylogenetic tree and produced high levels of alcohol. Furthermore, awamori, an Okinawa's traditional distilled alcoholic beverage, brewed with an l-leucine overproducing mutant derived from 35a14 showed a high concentration of isoamyl acetate.

Increase the Content of Ester Compounds in Blueberry Wine Fermentation with the Ester-Producing Yeast: Candida glabrata, Pichia anomala, and Wickerhamomyces anomalus.

The co-fermentation of Saccharomyces cerevisiae and ester-producing yeasts is considered to be an effective way to improve the flavor and quality of fruit wine. In this study, three kinds of ester-producing yeasts (Candida glabrata NCUF308.1, Pichia anomala NCUF306.1, and Wickerhamomyces anomalus NCUF307.1) and S. cerevisiae NCUF309.2 were used to simulate blueberry wine co-fermentation at different ratios. The results showed that, compared with S. cerevisiae NCUF309.2 fermentation (S), the population of S. cerevisiae NCUF309.2 in co-fermentation samples decreased to varying degrees, and the content of ethanol also decreased. The results also showed that the co-fermentation of C. glabrata NCUF308.1 and S. cerevisiae NCUF309.2 at the ratio of 1:1 (CS1), co-fermentation of P. anomala NCUF306.1 and S. cerevisiae NCUF309.2 at the ratio of 5:1 (PS5), and co-fermentation of W. anomalus NCUF307.1 and S. cerevisiae NCUF309.2 at the ratio of 5:1 (WS5) could significantly increase the content of ester compounds (p < 0.05), which was 3.29, 4.75, and 3.04 times that of the S sample, respectively. Among them, the sample of CS1 was characterized by phenethyl acetate and isoamyl acetate, while the samples of CS5 and PS5 were characterized by propyl octanoate and ethyl decanoate, and the sample of WS5 was characterized by 3-methylbutyl hexanoate. However, the contents of odor active compounds were higher in the CS1 sample. Therefore, the samples of CS1 had the potential to create the distinctive flavor of blueberry wine.

Volatile Organic Compounds from a Lichen-Associated Bacterium, Paenibacillus etheri, Interact with Plant-Parasitic Cyst Nematodes.

Healthy food is one of the major challenges to develop in this century. Plant-parasitic nematodes cause significant damage to many crops worldwide and till now, the use of chemical nematicides is the main means to control their populations. These chemical products must be replaced by more environmental-friendly control methods. Biocontrol methods seem to be one promising option, and the number of biopesticides derived from living organisms has increased in the last decades. To develop new plant protection products, we have decided to combine our skills in natural products chemistry and nematology and to focus on the lichen microecosystem as underexploited ecological niches of microorganisms. We present herein the potential of lichen-associated bacterial suspensions from Paenibacillus etheri as nematicides against the beet cyst nematode Heterodera schachtii and the potato cyst nematode Globodera pallida, in particular the effects of volatile organic compounds (VOCs) produced by the bacteria. A solid phase micro-extraction method associated to gas chromatography-mass spectrometry analysis of 14 day cultures was used to analyze these VOCs in order to identify the main produced compounds (isoamyl acetate and 2-phenylethyl acetate) and to evaluate them on the nematodes.

Biomonitoring of pesticides in urine by using isoamyl acetate as a sustainable extraction solvent

The protection of the health and safety of workers in the agricultural sector requires the assessment of human exposure to pesticides through biomonitoring programs. In doing this, the health and safety of laboratory analysts should be also protected through the use of analytical procedures as safe as possible. According to Green Analytical Chemistry and Green Sample Preparation principles, the use of miniaturized extraction techniques such as dispersive liquid-liquid microextraction (DLLME) should be encouraged, with the aim of limiting the consumption of chemicals (solvents and reagents) and energy, as well as the production of wastes. Moreover, safer and more environmentally friendly alternatives to petroleum-derived solvents must be found. In this regard, the effort of researchers is focused on the development/identification of sustainable solvents, some of which have been ranked according to their disposal, environmental, safety, and health features.Here, we introduce the alternative use of isoamyl acetate (“banana oil”) as sustainable extraction solvent. Compared with the trendy class of eutectic solvents (ESs), isoamyl acetate is advantageous because it is already in the liquid state, which fasters operations, and because it can be evaporated to dryness and reconstituted in a solvent compatible with the mobile chromatographic phase, which is not an option for ESs. The applicability of isoamyl acetate has been here evaluated for the first time to extract 12 pesticides of different polarities from urine matrix, by using a DLLME approach. The HPLC/MS validated method has proven to possess the sensitivity, precision and accuracy required to reliable bioanalytical methods. Its cheapness, simplicity and quickness make it an ideal sustainable choice for the screening of large numbers of samples in health monitoring programs involving people occupationally-exposed to pesticides.

Effect of Fermentation Strategy on the Quality and Aroma Characteristics of Yellow Peach Wines

To obtain high-quality yellow peach wines of varying characteristics, different fermentation strategies, including various pre-fermentative treatments, were applied. This study aimed to determine the effect of different fermentation strategies on the physicochemical properties, monomer phenol content, in vitro antioxidant activity, and volatile compounds of yellow peach wine. The results showed that peach wine P12, fermented with pulp, had higher total phenolic content (TPC), total flavonoid content (TFC), monomer phenol and volatile compound content, and antioxidant activity. Ten monomeric phenols were detected in peach wines, and the content of catechin was the highest. Juice fermentation wine, J12, had a strong floral aroma, and some volatile compounds were released during fermentation when water was added to the pulp, and low alcohol content did not reduce the variety of volatile compounds. The main aroma and common characteristics of the fermented yellow peach wine were dominated by esters, with a relative odor activity value (ROAV) ≥ 1, namely, isoamyl acetate, ethyl hexanoate, and ethyl octanoate. Our results demonstrated that the application of the described fermentation strategies significantly affected the quality and volatile compound content of yellow peach wines. This might assist in the development of a highly diverse yellow peach wine flavor.

Dynamic changes of quality and flavor characterization of Zhejiang rosy vinegar during fermentation and aging based on untargeted metabolomics

Zhejiang Rosy Vinegar (ZRV) is a traditional condiment in Southeast China. This study aimed to track the physicochemical, microbiological, sensory changes, and metabolomic profiles of ZRV during fermentation and aging. The increase of acidity and decrease of reducing sugar were associated with the dominant growth of Lactobacillus and Acetobacter. The total 35 volatile compounds were identified in ZRV, mainly containing alcohols, esters, acids, aldehydes, ketones acids, phenols and nitrogen-containing. Compared to phenethyl acetate with sweet aroma in fresh vinegar, the compound with high odor activity values was isoamyl acetate with fruity aromas in aged vinegar. Furthermore, 1309 types of non-volatile components were identified, and histidine metabolism and arginine biosynthesis were revealed as main pathways during fermenting and aging. Concurrently, various bioactive substances in ZRV were identified. This study enriched the knowledge on the components and flavor of ZRV, and assist to improve the production quality of vinegar.

Decoding the Fine Flavor Properties of Dark Chocolates.

Fine flavor properties of chocolates such as fruity, floral, and cocoa-like were decoded on a molecular level for the first time. The molecular compositions of six chocolates made out of liquors that were referenced with specific sensory attributes were analyzed. After the screening for odor-active molecules by aroma extract dilution analysis, selected compounds were quantitated with the overall aim to decode the distinct fine flavor attributes on a molecular level. Acidic and fruity flavor notes were associated with high dose over threshold factors (DoT factors) of acetic acid and fruity smelling esters such as ethyl 2-methylbutanaote, ethyl 3-methylbutanoate, and 3-methylbutyl acetate, respectively. Cocoa-like and roasty flavor notes were associated with high DoT factors for 2-methylbutanal, 3-methylbutanal, 4-hydroxy-2,5-dimethylfuran-3(2H)-one, and dimethyltrisulfane. The floral and astringent flavors were linked to high DoT factors of (-)-epicatechin, procyanidin B2, procyanidin C1, and 2-phenylethan-1-ol.