Review and Thermodynamic Modeling with NRTL Model of Vapor–Liquid Equilibria (VLE) of Aroma Compounds Highly Diluted in Ethanol–Water Mixtures at 101.3 kPa

A review of the vapor-liquid equilibrium data of aroma compounds highly diluted in hydroalcoholic mixtures at 101.3 kPa is presented. The study includes 44 aroma compounds present in distilled beverages from seven chemical families: acetals, alcohols, carbonyl compounds, carboxylic acids, esters, furans, and terpenes. The equilibrium data are modeled using the ideal gas hypothesis (with a correction term for dimerization in the case of carboxylic acids) and the NRTL model. A set of binary interaction parameters is generated, and the quality of the representation is evaluated. A classification of the aroma compounds in terms of their relative volatility with respect to ethanol and water is proposed over the whole ethanol composition range in the liquid phase. Finally, a comparison with the representation obtained when using interaction parameters calculated from binary and ternary mixture data at high concentrations is performed in order to evaluate the extrapolation capability of the NRTL model

Vapor-liquid equilibria measurements of bitter orange aroma compounds highly diluted in boiling hydro-alcoholic solutions at 101.3 kPa

In this work, experimental vapor−liquid equilibria (VLE) of water + ethanol + five aroma compound (two monoterpene hydrocarbons, α-pinene and D-limonene, and three oxygenated compounds, linalool, citral, and linalool oxide) mixtures were measured at boiling point at 101.3 kPa for ethanol molar fractions ranging from 0.0140 to 0.8389. The five aroma compounds were selected for their strong contribution to the aroma of the distillate of bitter orange essential oil. First, the thermodynamic consistency of the experimental VLE data was validated. Then the NRTL and Henry's law type models were tested to correlate the experimental data. Good agreement was obtained with both models to predict the phase equilibrium of the oxygenated compounds, and a better agreement was obtained with Henry's law type models for the monoterpene hydrocarbons in this kind of mixture

Vapor–Liquid Equilibrium of Ethyl Lactate Highly Diluted in Ethanol–Water Mixtures at 101.3 kPa. Experimental Measurements and Thermodynamic Modeling Using Semiempirical Models

A thermodynamic study of the vapor–liquid equilibrium for the ternary system ethyl lactate–ethanol–water was performed at 101.3 kPa and infinite dilution regarding ethyl lactate, for boiling temperatures ranging from (352.3 to 370.0) K. The experimental measurements were carried out with a recirculation still and the equilibrium compositions of ethyl lactate were determined by gas chromatography. The volatility of ethyl lactate decreases when the ethanol content in the liquid phase is increased. The investigated system was correctly correlated by the NRTL and UNIQUAC models, with an average absolute relative deviation below 10%. The comparison with the results obtained from interaction parameters fitted to experimental data of the binary systems ethyl lactate–ethanol and ethyl lactate–water at 101.3 kPa, proves that the parameters calculated in this work give a better description of the ethyl lactate volatility, a key parameter in distillation, at low concentrations. These latter parameters are therefore recommended for process simulation and optimization in alcoholic beverages production

Vapour–liquid equilibria of aroma compounds in hydroalcoholic solutions: Measurements with a recirculation method and modelling with the NRTL and COSMO-SAC approaches

International audienceAqueous solutions of aroma compounds are commonly encountered in the food and biofuel industries, and the knowledge of their thermodynamic properties is very important for process design. Here, we report the measurements of the vapour-liquid equilibria of water-ethanol solutions containing 13 aroma compounds (alcohols, aldehydes and esters), for temperatures between 351 and 366 K, and ethanol concentration ranging from 10 to 90% (v/v). The new data were obtained with a recirculation apparatus and are represented with the non-random two liquid (NRTL) activity coefficient model. It is observed that the partition coefficients of the aroma compounds can decrease of several orders of magnitude by increasing the proportion of ethanol. The COSMO-SAC (conductor-like screening model-segment activity coefficient) model provides reasonable predictions of the new data for alcohols and aldehydes, but underestimates the partition coefficients of the long ethyl esters. It is observed that the COSMO-SAC predictions depend a lot on the molecular conformations used to generate the sigma profiles, in agreement with previous studies. The COSMO-SAC predictions can be empirically improved by changing the real space cut-off distance employed in the ab initio calculations. The COSMO-SAC model is then reliable not only at infinite dilution but also over a whole composition range. The model is used to define a limit of validity for the infinite dilution approximatio

Mechanistic modeling and equilibrium prediction of the reactive extraction of organic acids with amines: a comparative study of two complexation-solvation models using 3-hydroxypropionic acid

International audienceA comprehensive study of equilibrium states involved in the reactive extraction of 3-hydroxypropionic acid (3-HP) by tri-n-octylamine (TOA) in n-decanol is described. Complexation phenomena between 3-HP and TOA were revealed by infrared spectroscopy (FT-IR). This study demonstrated that the main extraction mechanism is the formation of an ion pair involving the dissociated form of 3-HP. Chemical models were then formulated, taking the formation of the ion pair between 3-HP and TOA and the influence of the amount of solvent in the organic phase into account. Two models are proposed: (1) a stoichiometric model where the solvent is seen as a reagent that is involved in the complexation as a synergistic extractant, but with competition for solvation via H-bond interactions with TOA; (2) a model where the solvent is seen as a phase modifier that improves the physicochemical properties of the extractant and that changes the complexation equilibrium. Both models describe the extraction yields in the investigated ranges, with Model (2) being particularly predictive since it provides a mean absolute prediction error of less than 2% in yield units. According to this latter model, the complexation equilibrium coefficient increases with the increase of the n-decanol proportion in the organic phase. Model (2) shows that solvation effects are better described as non-stoichiometric interactions. Therefore, the two mechanistic models accurately represent extraction yields over a wide range of initial conditions and are potentiall

Identification of aroma compounds formed during the distillation of Cognac spirits

International audienceCognac spirit have a complex composition in aroma compounds which contributes to the product’s typical features perceived by the consumer. These compounds have different origins: they could come from grape musts, can be formed during fermentation, or be produced during distillation.The formation of compounds during distillation remains little understood, making this process hard to control regarding the specific aroma generated by heating during distillation. However, the “Charentaise distillation” of Cognac spirit is a traditional process well described in terms of equipment and operation by professionals.All the aroma compounds found in Cognac spirit freshly distilled results from the combination of several factors occurring before or during distillation. Indeed, the wine’s characteristics (acidity, alcohol content, aroma arising from yeast fermentation…), the method and the period of distillation strongly affect the final aroma composition of freshly distilled spirit. This work focus on the distillation process and in particular on aroma specifically produced by reaction during heating, besides aroma enrichment in final product through volatility principle.The “Charentaise distillation” method to obtain Cognac spirit is performed in two phases: the first step consists in heating the wine introduced in the boiler in order to obtain a distillate called “brouillis”. This brouillis is brought back to the boiler for a second distillation (second step) to obtain the spirit that will undergo a slow maturation in an oak barrel. The double distillation takes place under thermal conditions that could promote the generation of aroma compounds. The aim of this study is to identify these aroma compounds formed during distillation and formulate hypothesis regarding the reactions at the origin of their formation.To study the formation of these compounds at large-scale, a pot-still (alembic) with a capacity of 25 hectoliters have been made available, on which temperature sensors and a density meter have been installed. These devices allow a continuous follow-up on the evolution of these parameters. Sampling during distillation have been performed on the distillate and inside the boiler. The analysis on those samples allowed to perform a mass balance and point out several types of aroma compounds whose quantities have strongly increased during the distillation process. These compounds can be distinguished by their chemical family. Thus, two aldehydes: isobutanal (having a flowery odour) and 2-methylbutanal (having a chocolate odour) are mainly formed during distillation, coming certainly from a Strecker degradation. Moreover, two aromatic compounds, from norisoprenoids family: 1,1,6-trimethyldihydronaphtalene and 1-(2,3,6-trimethylphenyl)-3-buten-2-one commonly called TDN and TMPBE respectively are formed as well. TDN possesses notes of hydrocarbons whereas TMPBE has violet notes. Both are certainly present in the wine in their glycosidic form, and this issue will be studied in detail. The whole results suggest that part of aroma compounds found in Cognac spirit is formed during distillation due to chemical reactivity phenomena to be further studied in depth in our work

Isobaric vapour-liquid equilibrium of α-terpineol highly diluted in hydroalcoholic mixtures at 101.3 kPa: Experimental measurements and thermodynamic modeling

International audienceTerpenes are important varietal compounds responsible for the characteristic aromas of alcoholic beverages. Reliable vapor-liquid equilibrium (VLE) data for this class of aroma compounds in hydroalcoholic media is essential to understand their behavior during distillation and thus achieve a desired quality in the distilled products. In this work, experimental measurements for the VLE of α-terpineol highly diluted in ethanol-water mixtures were carried out in a recirculation ebulliometer operating at 101.3 kPa for boiling temperatures from (354.99 to 369.93) K. Equilibrium compositions were determined by gas chromatography for α-terpineol and by density measurements for ethanol. Results show that α-terpineol is expressively more volatile in the dilute region (x Et 0.15 α-terpineol can be 10 times richer in the liquid phase. The experimental data were correlated by semi-empirical models NRTL and UNIQUAC and compared with predictions by UNIFAC. The data regressed with the NRTL model showed the best agreement with the experimental data. The binary interaction parameters fitted by the model are suitable to be used in the design and simulation of distillation processes for the production of alcoholic beverages

Evolution of volatile compounds during the distillation of cognac spirit

International audienceCognac wine spirit has a complex composition in volatile compounds which contributes to its organoleptic profile. This work focused on the batch distillation process and, in particular, on volatile compounds specifically produced by chemical reactions during the distillation of Cognac wine spirit, traditionally conducted in two steps with charentais pot stills. The aim of this study was to characterize these volatile compounds formed during distillation. Sampling has been performed on the distillates and inside the boiler during a typical Cognac distillation. The analysis of these samples allowed us to perform a mass balance and to point out several types of volatile compounds whose quantities strongly increased during the distillation process. These compounds were distinguished by their chemical family. It has been found that the first distillation step was decisive for the formation of volatile compounds. Moreover, 2 esters, 3 aldehydes, 12 norisoprenoids, and 3 terpenes were shown to be generated during the process. These results suggest that some volatile compounds found in Cognac spirit are formed during distillation due to chemical reactions induced by high temperature. These findings give important indications to professional distillers in order to enhance the product's quality

Organic phase screening for in‐stream reactive extraction of bio‐based 3‐hydroxypropionic acid: biocompatibility and extraction performances

International audienceBACKGROUND: 3-Hydroxypropionic acid (3-HP) production through glycerol bioconversion by Lactobacillus reuteri suffers from low yields and productivities due to product inhibition. Reactive extraction assisted by a Hollow Fibre Membrane Contactor (HFMC) is a promising strategy for process intensification. However, the use of this integrated system is hindered by the extraction phase toxicity towards the microorganism. This study describes a solvent selection strategy based on extraction performance (extraction yield and viscosity, related to mass transfer), and a low solvent toxicity, in order to find an extraction phase composition that allows continuous in stream extraction of 3-HP.RESULTS: Inert diluent addition to a trioctylamine (TOA)-decanol mixture decreased its toxicity and viscosity but decreased extraction yield. The linear and ramified long-chain alcohols tested showed that increasing the number of carbon atoms decreased extraction performance as well as toxicity. Ramified alcohols showed the lowest extraction performance. Didodecylmethylamine (DDMA) gave higher extraction yield and lower solvent toxicity than TOA. Flow cytometry with dual staining for cell membrane integrity and enzymatic activity proved to give concordant and complementary information with cells bioconversion ability, being an adequate and quick method for solvent toxicity assessment. The selected organic phase consisted of 20% DDMA, 47% dodecanol and 33% dodecane by volume, and can be used for in stream extraction of 3-HP produced by L. reuteri. CONCLUSIONS: The integrated selection criteria proposed in this study - extraction yield, solvent viscosity and toxicity - provide key information for choosing an organic phase with the best trade-off between extraction performance and biocompatibility

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