Ethyl Pentanoate Research Articles

High yield of ethyl valerate from the esterification of renewable valeric acid catalyzed by amino acid ionic liquids

Ethyl valerate (EV) as a promising fuel additive was produced by esterification of valeric acid with ethanol over Bronsted acidic amino acid ionic liquids. Hammett method and density functional theory (DFT) calculations were preformed to evaluate the acidities of the catalysts. The composition of catalyst, reaction temperature, reaction time, molar ratio of reactants, amount of catalyst, and recycling ability of the catalyst were investigated. Proline bisulfate (ProHSO4) ionic liquid has the highest catalytic activity and the best recyclability under the optimized esterification conditions. A high conversion of valeric acid (>99.9%) was obtained for 7 h at 80 °C, with 100% selectivity of EV. The density, viscosity, melting point, boiling point, elemental analysis and heat of combustion of the EV product were measured. The density of EV is 0.896 g cm−3. The viscosity of EV was 1.7 cP at room temperature. The heating values of EV are 4158.1 kJ mol−1 and 31.9 kJ g−1. EV obtained from esterification has higher energy density than methanol, ethanol, γ-valerolactone, and valeric acid, which illustrates that EV is a promising biofuel candidate.

New generation biofuels: γ-valerolactone into valeric esters in one pot

Ethyl valerate and pentyl valerate, suitable as a gasoline additive and diesel component respectively, can be obtained in a one pot one step reaction from γ-valerolactone, readily available from lignocellulosic biomass. The reaction takes place in ethanol under H2 through nucleophilic addition of the alcohol to the carboxylic group giving hydroxypentanoate, dehydration to pentenoate and hydrogenation to the saturated ester. The bifunctional catalyst used consists of a non noble metal, namely copper, supported on an amorphous weakly acidic material, therefore representing an interesting alternative to Pt–zeolite catalysts. Pentyl valerate can be obtained in one pot with conversions >90% and selectivity up to 83%.

Catalytic conversion of biomass-derived levulinic acid to valerate esters as oxygenated fuels using supported ruthenium catalysts

The development of the catalytic conversion of biomass-based platform molecules into oxygenated fuel molecules is of great significance in order to reduce the dependence on fossil resources and to solve environmental problems. Alkyl valerate esters were proven to have the potential to be renewable additives of gasoline and diesel. In this work, we studied the hydrogenation of levulinic acid (LA) to valerate esters over supported Ru catalysts, and found that the acidity was an important factor for the catalyst performance. A bifunctional catalyst Ru/SBA-SO3H was developed as an active catalyst, and a highest yield of 94% to ethyl valerate (EV) was achieved. The catalyst was characterized by nitrogen adsorption/desorption methods, X-ray power diffraction (XRD), transmission electron spectroscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The effects of reaction conditions were comprehensively investigated and probable reaction pathways were proposed and verified. The conversion of LA to various alkyl valerate esters can also be catalyzed by the bifunctional catalyst. In addition, supported Cu and Ni catalysts were also screened under similar reaction conditions as Ru-based catalysts, and the combination of Ni/SBA-15 and SBA-SO3H exhibited activity for the conversion of LA to EV.

Correlation of volatile and nonvolatile components with the total antioxidant capacity of tartary buckwheat vinegar: Influence of the thermal processing

Shanxi aged tartary buckwheat vinegar differs from other vinegars in that it has a unique thermal processing (6days at 85°C) which is helpful to create its typical flavor and functional properties. The present study evaluated the relationship between some volatile and nonvolatile compounds, the total antioxidant activity of tartary buckwheat vinegar, and the influence of thermal processing on the vinegar. Correlation analysis showed that 1-(2-furanyl)ethanone, isoamyl acetate, ethyl valerate, tetramethyl pyrazine, benzothiazole, browned compound and total polyphenolic content were highly significant while 3-methylbutanoic acid, 3-hydroxy-2-butanone, benzyl methyl ketone, and total flavonoid content were significantly associated with total antioxidant capacity measured by 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and redox potential methods. Principal component analysis allowed tartary buckwheat vinegar separation according to volatile and non-volatile compounds (PC1) and antioxidant capacity (PC3). Comparing with alcoholic and acid fermentation, thermal processing not only contributed to the characteristic aromas of the vinegar, but also retained its antioxidant capacity. The result of this study suggested that aromas from thermal processing of the vinegar may be served as natural antioxidants.

Experimental and Detailed Kinetic Modeling Study of Ethyl Pentanoate (Ethyl Valerate) Oxidation in a Jet Stirred Reactor and Laminar Burning Velocities in a Spherical Combustion Chamber

To improve our understanding of the combustion characteristics of ethyl pentanoate, a possible second generation biofuel, new experimental data were acquired for its oxidation kinetics in two complementary experiments. In a JSR (jet stirred reactor), concentration profiles of stable species were measured at 10 atm over a range of conditions (equivalence ratios of 0.6, 1, 2, fuel initial concentration of 1000 ppm, and temperatures between 560 to 1160 K). In a spherical combustion chamber, unstretched laminar burning velocities of ethyl pentanoate–air mixtures were measured at different pressures and temperatures and for equivalence ratios in the range 0.7–1.4. The oxidation of ethyl pentanoate was modeled using a new detailed kinetic reaction scheme (2719 reactions, 522 species). The chemical kinetic mechanism proposed here yielded good agreement with the present data. To interpret the results, reactions flux and sensitivity analyses were carried out.

게 향미제의 저장중 품질특성 변화

Crab-like flavorants (CFs) were made from snow crab cooker effluent (SCCE) using response surface methodology (RSM) and reaction flavoring technology (RFT). Type A CF was made from SCCE via RSM, RFT, adding starch syrup, centrifugation, and microfiltration. Type B was made from type A by adding the food additives dimethyl sulfide, ethyl valerate and fish sauce. The stability of the CFs was evaluated in terms of the color values, sensory evaluation, and flavor profiles after storage for 90 days at three different temperatures: 10, 20, and <TEX>$30^{\circ}C$</TEX>. The compounds, ethanol and 3-methyl-1-butanol, were considered key components of off-flavor and a decrease in dimethyl-2-vinylpyrazine affected the occurrence of off-flavor. It may be a microbial metabolite arising from contamination and lab-scale micro-filtration. At the lowest temperature (<TEX>$10^{\circ}C$</TEX>), the decrease in volatile compounds, such as pyrazines, was not as dramatic as at <TEX>$20^{\circ}C$</TEX> and <TEX>$30^{\circ}C$</TEX> and alcohol formation was prevented or delayed. Therefore, it is necessary to store CFs at < <TEX>$10^{\circ}C$</TEX> with suitable sterilization to preserve volatile flavor compounds and prevent off-flavor from occurring.

Correlation and prediction of mixing thermodynamic properties of ester-containing systems: Ester + alkane and ester + ester binary systems and the ternary dodecane + ethyl pentanoate + ethyl ethanoate

Excess thermodynamic properties VmE and HmE, have been measured for the ternary mixture dodecane+ethyl pentanoate+ethyl ethanoate and for the corresponding binaries dodecane+ethyl pentanoate, dodecane+ethyl ethanoate, ethyl pentanoate+ethyl ethanoate at 298.15K. All mixtures show endothermic and expansive effects. Experimental results are correlated with a suitable equation whose final form for the excess ternary quantity ME contains the particular contributions of the three binaries (i–j) and a last term corresponding to the ternary, all of them obtained considering fourth-order interactions. The fit goodness for all mixtures is good and comparable to others equations taken from the literature. In this work the dissolution model for the binaries and ternary is analyzed with a special attention to ester–ester binaries whose behaviour is discussed. The application of the UNIFAC group contribution model to estimate the HmE yields acceptable results for the binaries (with the exception of ester–ester) and for the ternary mixture.

Conformational Analysis of Green Apple Flavour: The Gas‐Phase Structure of Ethyl Valerate Validated by Microwave Spectroscopy

We report on the microwave spectrum of ethyl valerate, C(4)H(9)-COO-C(2)H(5), observed by molecular beam Fourier transform microwave spectroscopy (MB-FTMW). Highly accurate rotational and centrifugal distortion constants of the two most abundant conformers were determined. Their structure was investigated by comparison of the experimental rotational constants with those obtained by quantum chemical calculations. MP2/ 6-311++G(d,p) calculations failed to give a proper description of the observed conformers in the supersonic jet. Therefore, also other basis sets were tried using Hartree-Fock, second-order Møller-Plesset (MP2), and B3LYP methods to predict the observed gas-phase structures of the molecule. The quantum chemical results guided the conformer assignment of the rotational constants, obtained from the microwave experiment. One of the two observed conformers has C(s) symmetry, while the most abundant conformer has C(1) symmetry. The main conformer possesses a strong spectrum with high intensities. Additionally, harmonic frequency calculations at different levels of theory where carried out and a low lying vibration of the entire n-butyl group against the rest of the molecule was identified. The symbiotic interplay of microwave gas-phase investigations and quantum chemical calculations becomes evident in our results.

Earthworms Use Odor Cues to Locate and Feed on Microorganisms in Soil

Earthworms are key components of temperate soil ecosystems but key aspects of their ecology remain unexamined. Here we elucidate the role of olfactory cues in earthworm attraction to food sources and document specific chemical cues that attract Eisenia fetida to the soil fungi Geotrichum candidum. Fungi and other microorganisms are major sources of volatile emissions in soil ecosystems as well as primary food sources for earthworms, suggesting the likelihood that earthworms might profitably use olfactory cues to guide foraging behavior. Moreover, previous studies have documented earthworm movement toward microbial food sources. But, the specific olfactory cues responsible for earthworm attraction have not previously been identified. Using olfactometer assays combined with chemical analyses (GC-MS), we documented the attraction of E. fetida individuals to filtrate derived from G. candidum colonies and to two individual compounds tested in isolation: ethyl pentanoate and ethyl hexanoate. Attraction at a distance was observed when barriers prevented the worms from reaching the target stimuli, confirming the role of volatile cues. These findings enhance our understanding of the mechanisms underlying key trophic interactions in soil ecosystems and have potential implications for the extraction and collection of earthworms in vermiculture and other applied activities.

Characterization of odor-active compounds of various cherry wines by gas chromatography–mass spectrometry, gas chromatography–olfactometry and their correlation with sensory attributes

To characterize the aroma of cherry wine, five samples were analyzed by quantitative descriptive sensory analysis, gas chromatography–mass spectrometry (GC–MS) and gas chromatography–olfactometry (GC–O). The aroma of cherry wines was described by 6 sensory terms as fruity, sour, woody, fermentation, cameral and floral. Fifty-one odor-active (OA) compounds were detected by GC–O and quantified by GC–MS, and 45 of them were identified. Twenty-nine OA compounds having more than 50% detection frequency were selected as specific compounds correlated to sensory attributes by partial least squares regression (PLSR). The correlation result showed ethyl 2-methyl propionate, 2,3-butanedione, ethyl butyrate, ethyl pentanoate, 3-methyl-1-butanol, ethyl hexanoate, 3-hydroxy-2-butanone, ethyl lactate, 1-hexanol, (Z)-3-hexen-1-ol, ethyl hydroxyacetate, acetic acid, furfural, 2-ethyl-1-hexanol, benzaldehyde, propanoic acid, butanoic acid, guaiacol, beta-citronellol, hexanoic acid, 2-methoxy-4-methylphenol, 2-ethyl-3-hydroxy-4H-pyran-4-one, ethyl cinnamate, 2-methoxy-4-vinylphenol were typical OA compounds, which covaried with characteristic aroma of cherry wines.

Bio based fuels and fuel additives from lignocellulose feedstock via the production of levulinic acid and furfural

Abstract The demand for biomass-derived fuels and fuel additives, particularly in the transportation sector, has stimulated intense research efforts in the chemistry of levulinic acid and levulinic acid secondary products over the past decade. Additionally, recent technological progress in lignocellulosic feedstock (LCF) chemistry has also increased attention in this regard. As a result, several oxygenating fuel additives with potential applications in both gasoline and diesel fuels have been identified. Some of the chemicals, such as ethyl valerate, appear to be viable alternatives to the currently used branched, short-chain ethers that are derived from side products of petrol refining. Cost-effective applications of lignocellulosic biomass are a crucial aspect of its feasibility. In consideration of the LCF biorefinery concept, the feasibility must also include the chemical pulping of LCF and the comprehensive utilisation of its main constituents cellulose, hemicelluloses, and lignin. The present study focuses on cellulose and hemicelluloses as viable sources for the production of biofuels and biofuel additives. Multifunctional catalysis, including hydrogenation and acid catalysis are the primary instruments used for the conversion of the monomeric carbohydrate building blocks, i.e., mainly C5 sugars, such as xylose and arabinose, and C6 sugars in the form of glucose and their respective secondary products, furfural and levulinic acid. Lignin utilisation is not addressed in this paper.

Brain-state–independent neural representation of peripheral stimulation in rat olfactory bulb

It is critical for normal brains to perceive the external world precisely and accurately under ever-changing operational conditions, yet the mechanisms underlying this fundamental brain function in the sensory systems are poorly understood. To address this issue in the olfactory system, we investigated the responses of olfactory bulbs to odor stimulations under different brain states manipulated by anesthesia levels. Our results revealed that in two brain states, where the spontaneous baseline activities differed about twofold based on the local field potential (LFP) signals, the levels of neural activities reached after the same odor stimulation had no significant difference. This phenomenon was independent of anesthetics (pentobarbital or chloral hydrate), stimulating odorants (ethyl propionate, ethyl butyrate, ethyl valerate, amyl acetate, n-heptanal, or 2-heptanone), odor concentrations, and recording sites (the mitral or granular cell layers) for LFPs in three frequency bands (12-32 Hz, 33-64 Hz, and 65-90 Hz) and for multiunit activities. Furthermore, the activity patterns of the same stimulation under these two brain states were highly similar at both LFP and multiunit levels. These converging results argue the existence of mechanisms in the olfactory bulbs that ensure the delivery of peripheral olfactory information to higher olfactory centers with high fidelity under different brain states.

Covalent immobilization of lipase onto amine functionalized polypropylene membrane and its application in green apple flavor (ethyl valerate) synthesis

In this study, a functionalized hydrophobic polypropylene chloride membrane (PPC) was prepared by the amination of chlorinated polypropylene with hexamethylene diamine (APP). The PPC and APP membranes were characterized using SEM, FTIR and contact angle studies. The aminated polypropylene (APP) membrane was used for covalent immobilization of Candida rugosa lipase via glutaraldehyde coupling. The retained activity of the immobilized lipase was 76%. Kinetic analysis shows that the dependence of lipolytic activity of both free and immobilized lipase on tributyrin substrate concentration can be described by Michaelis–Menten model. The estimated apparent K m values for the free and immobilized lipase were 2.9 and 8.4 mM, respectively. The V max values of free and immobilized enzymes were calculated as 926 and 741 U/mg enzyme, respectively. Optimal temperature was 5 °C higher for immobilized enzyme than that of the free enzyme. Thermal and storage stabilities were found to be increased upon immobilization. Finally, the immobilized lipase was used for the production of green apple flavor (i.e., ethyl valerate) in hexane medium.

Volatile profile of khanom jeen, Thai fermented rice noodles, and the changes during the fermentation process.

This study was carried out to determine the volatile compounds profile of khanom jeen (Thai fermented rice noodles) and the changes in the volatile compound composition during fermentation. Rice samples were collected at each step of the fermenting process. Identification and quantification of volatiles were performed by evaluating dynamic headspace with gas chromatography mass spectrometry. For khanom jeen, a total of 43 compounds were found. Among them, 2-methylpropanoic acid, 3-methylbutanoic acid, diacetyl, ethyl acetate, ethyl valerate, ethyl hexanoate, ethyl heptanoate, heptanal, octanal, nonanal, decanal, and 3-methylbutanal were identified as potent odourants based on their odour activity values. Most of the volatile compounds increased during the first 24–48 h of the rice fermentation process, except for some esters which increased thereafter during the sedimentation step. The concentrations of selected aromatic volatile compounds in khanom jeen were affected by the fermentation steps – particularly 2-methylpropanoic acid and 3methylbutanoic acid, which were not found in the raw material (broken rice). The amount of ethyl acetate in the water elimination process was found to be twice as much as in the first day of rice fermentation. The presence of straightchain aldehydes changed only slightly during rice fermentation. However, the concentration of 3-methylbutanal increased substantially. The results indicated that the aroma of khanom jeen was affected by the fermentation process.

Synthesis of the ‘green apple ester’ ethyl valerate in organic solvents by Candida rugosa lipase immobilized in MBGs in organic solvents: Effects of immobilization and reaction parameters

Ethyl valerate, also known as the green apple flavor is well known for its wide applications in the areas of food, pharmaceuticals and cosmetics industries. Candida rugosa lipase was immobilized in microemulsion based organogels (MBGs) and used for ethyl valerate synthesis in organic solvents. Various immobilization and reaction parameters were scrutinized for enhancement of ester production. Among the immobilization parameters, sodium bis-2-(ethylhexyl) sulfosuccinate (AOT), n-heptane and gelatin were found to be the highest yielding combination. Cyclohexane was found to be the solvent of choice as the reaction medium while pH 7, 40 °C and 1:1.6 ratio of valeric acid to ethanol were the reaction parameters exhibiting highest ester formation. The organogels were highly stable in the solvents and were reused for nine cycles with meager loss of activity. Also, immobilized enzyme was thermostable at 50–70 °C for ten hours. Hence, MBGs verify to be a promising enzyme immobilization system for ester synthesis in organic solvents.

Investigation of Formic Acid Separation from Aqueous Solution by Reactive Extraction: Effects of Extractant and Diluent

This study aims to investigate the extraction of formic acid by a high molecular-weight aliphatic amine, tridodecylamine (TDA), and a phosphorus-bonded, oxygen-containing extractant, tributyl phosphate (TBP), dissolved in five different diluents (ethyl valerate, diethyl adipate, diethyl sebacate, 1-octanol, and heptane) each. The experiments were carried out at 298.15 K. Comparisons of the results were made using the distribution coefficient, loading factor, separation factor, and the percentage of extraction yield. The results demonstrated that combination of TDA and diethyl adipate had the greatest synergistic effects with a distribution value of 6. The maximum value of the extraction efficiency was found to be 87 % with a 1.09 mol·L−1 concentration of TDA in diethyl adipate.

Characterization of aroma-active compounds, sensory properties, and proteolysis in Ezine cheese

Ezine cheese is a white pickled cheese ripened in tinplate containers for at least 8 mo. A mixture of milk from goat, sheep, and cow is used to make Ezine cheese. Ezine cheese has geographical indication status. The purposes of this study were to determine and compare the changes in basic composition, aroma, and sensory characteristics, and proteolytic activity of Ezine cheese stored in tinplate containers and plastic vacuum packages during storage. Aroma-active compounds were determined by thermal desorption gas chromatography olfactometry. To evaluate the proteolytic activity, casein and nitrogen fractions were determined. The results indicated that compounds identified at high intensities were dimethyl sulfide, ethyl butyrate, hexanal, ethyl pentanoate, (Z)-4-heptenal, 1-octen-3-one, acetic acid, butyric acid, and p-cresol. Characteristic descriptive terms were cooked, whey, creamy, animal-like, sour, and salty. The level of proteolysis increased in Ezine cheese during storage. Ezine cheese can be ripened in small-size packaging after 3 mo of storage. Approximately 6 mo is sufficient to produce the characteristic properties of Ezine cheese.

Release of Strawberry Aroma Compounds by Different Starch-Aroma Systems

In the food industry, the addition of flavours is used to reinforce the aroma profile of different goods. However, interactions between starch and aroma compounds can occur, and this can impact upon aroma release and perception. In the present study, we have investigated the influence of starch type on aroma release from starch-aroma systems. The food model system used was composed of an aqueous starch dispersion (1 g dry starch/100 g dispersion) and 10 aroma compounds (ethyl butanoate, ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, ethyl pentanoate, methyl hexanoate, ethyl hexanoate, methyl ethyl propanoate, hexyl acetate, 3-hexenol, and phenyl methyl acetate). Different commercially available starches were used: Amilogels P, K, PDP, G, MVK, HP, OK and HPW, and carrageenan (Amilogel CAR) and guar gum (Amilogel GG). Aroma release from these starch-aroma systems into the gas phase above food (headspace) were monitored by GC-MS analysis with a solid-phase micro-extraction technique. The smell of the starch-aroma system was also evaluated sensorially by a trained panel. The release of aroma compounds from the different starch-aroma systems was statistically significant (&lt;I&gt;P&lt;/I&gt; &lt; 0.0001) for all of the aroma compounds, with the exception of ethyl pentanoate. A correlation between the concentration of individual aroma compounds in the headspace and the sensory evaluation (smell) was seen. Starch-aroma systems comprising corn starch (Amilogel G), physically modified starches that are soluble in cold water (Amilogels K, PDP), and hydroxypropyl distarch phosphate (Amilogels HP) had sensorially superior smells compared to the other types of starches tested. At the same time, the headspace GC-MS analyses showed ethyl butanoate, ethyl 2-methylbutanoate, ethyl 3-methylbutanoate and ethyl pentanoate to be at the highest concentrations, which are all typical aroma compounds of strawberry fruit, and which also have low perception thresholds. Dextrin-roasted starch, guar gum and carrageenan provided the lowest sensory scores, although in contrast, they more strongly retained these aroma compounds.

Biosynthesis of ethyl caproate and other short ethyl esters catalyzed by cutinase in organic solvent

The main objective of this work was to study the enzymatic synthesis of short chain ethyl esters, a group of relevant aroma molecules, by Fusarium solani pisi cutinase in an organic solvent media (iso-octane), and to assess the influence of different parameters on the reaction yield. Cutinase displayed high initial esterification rates in iso-octane, which amounted to 1.15 μmol min −1 mg −1 for ethyl butyrate (C 4 acid chain) and 1.06 μmol min −1 mg −1 for ethyl valerate (C 5 acid chain). High product yields, 84% for ethyl butyrate and 96% for ethyl valerate, were observed after 6 h of reaction, for an initial equimolar concentration of substrates (0.1 M). The highest product yield (97%) was observed for ethyl caproate (C 6) synthesis, a compound which is a part of natural apple and pineapple flavour, for an alcohol:acid molar ratio of 2 (0.2 M ethanol concentration). Cutinase affinity for short chain length carboxylic acids (C 4–C 6) in ester synthesis in iso-octane confirmed previous observations in reversed micellar system.

Production of aroma esters by immobilized Candida rugosa and porcine pancreatic lipase into calcium alginate gel

Candida rugosa lipase (CRL) and porcine pancreatic lipase (PPL) were immobilized into calcium alginate (Ca-Alg) gel beads by means of entrapment and were used to produce three industrially important flavour esters, namely isoamyl acetate (banana flavour), ethyl valerate (green apple flavour) and butyl acetate (pineapple flavour). Immobilization conditions were optimized in terms of sodium alginate (Na-Alg) and CaCl 2 concentrations by determination of the entrapped enzyme amount as well as by esterification of 4-nitrophenol and acetic acid. The best results were obtained at 2.5% Na-Alg and 2.5 M CaCl 2 for CRL while at 2.5% Na-Alg and 2.0 M CaCl 2 for PPL. On carrying out flavour syntheses in solvent-free medium and also in hexane medium, higher ester yields were obtained in hexane medium for all esters and both types of lipases. Ester esterification efficiency increased in parallel with both enzyme concentrations at immobilization medium and the immobilized lipase amount in esterification medium. Maximum ester production was observed between 40 and 50 °C for CRL and PPL. Besides, the effect of substrate concentrations on ester conversion was remarkable. The best ester yield was obtained for isoamyl acetate when immobilized PPL was used.