Recovery Of Aroma Compounds Research Articles

Liquid-liquid extraction and air stripping in membrane contactor: application to aroma compounds recovery

This work focuses on a non-destructive process for recovering valuable aromatic fractions from odorous industry aqueous effluent. Non-dispersive extraction often selected aroma compound was carried out on very diluted model aqueous solutions, using membrane contactors, in two configurations: liquid-liquid and liquid-gas. Mass transfers from water to n-hexane, from water to miglyol (two solvents widely used in aromatic industry) and from water to air were studied using a cross-flow designed hollow fibre membrane contactor. The influence of physico-chemical properties of the aroma compounds and the influence of the solvent viscosity on mass transfer are discussed. Moreover, a resistance-in-series model has been applied and allowed to predict the mass transfer intensity in agreement with experimental values whatever the separation principle, liquid-liquid or liquid-gas.

Recovery of Valuable Tea Aroma Components by Pervaporation

The present work describes the possibility of using pervaporation to recover the tea aroma compounds from tea aroma condensate generated in the manufacturing of tea or instant tea, as well as directly from tea extract. Eight compounds that make a significant contribution to tea aroma, namely, trans-2-hexenal, linalool, cis-3-hexenol, 3-methylbutanal, 2-methylpropanal, benzyl alcohol, phenylacetaldehyde, and β-ionone, were studied in this work. Permeation studies for all of these compounds with poly(octyl methyl siloxane) (POMS) and poly(dimethylsiloxane) (PDMS) membranes in a batch-type vacuum pervaporation system were carried out, first, in their aqueous solutions (binary mixtures); second, in a model solution containing all of the above-mentioned compounds; and last, with an actual tea extract. In this work, mainly the effect of the feed concentration on the organic flux and separation factor was studied. The permeation studies with the mixture revealed that β-ionone, trans-2-hexenal, linalool, cis-3-hexenol, and 3-methylbutanal offered very good selectivity, whereas phenylacetaldehyde, 2-methylpropanal, and benzyl alcohol gave moderate selectivity. The results indicate that pervaporation is an attractive technology for the recovery of tea aroma compounds from tea aroma condensate as it (i) yields good separation and (ii) operates under mild conditions. However, it should be noted that, because the selectivity offered by pervaporation varies considerably from compound to compound, attempts to concentrate a solution of volatiles to a high degree can result in significant alteration in the profile of the aroma. Thus, the commercial utility of this approach will need to be ascertained on a case-by-case basis.

Recovery of Aroma Compounds from Dilute Model Blueberry Solution by Pervaporation

ABSTRACT Pervaporation (PV) is a membrane‐separation process showing unique capability of separating target compound(s) from dilute systems. Experiments were performed on a bench‐scale flat sheet PV unit with a model solution to evaluate separation factor of 6 constituent aroma compounds (1‐hexanol, 1‐heptanol, trans‐2‐hexenal, ethyl acetate, linalool, and d‐limonene), representing some of typical flavoring ingredients from blueberry juice. The results showed that separation factor was in the range of 70 to 430, depending on molecule size and polarity property of the compounds. Except for 1‐heptanol, all compounds showed no significant coupling effect in the mixture system. The effect of temperature was also examined for a given feed‐flow rate. Keywords: pervaporation, membrane, aroma compounds, blueberry, multicomponent diffusion

Recovery of volatile aroma compounds from black currant juice by vacuum membrane distillation

This study evaluated the recovery of seven characteristic black currant aroma compounds by vacuum membrane distillation (VMD) carried out at low temperatures (10–45 °C) and at varying feed flow rates (100–500 l/h) in a lab scale membrane distillation set up. VMD at feed flow from 100 to 500 l/h at 30 °C gave concentration factors, calculated for each aroma compound as C permeate/ C feed, from ∼4 to 15. The concentration factors increased with decreased juice temperature during VMD; at 10 °C concentration factors of 21–31 were obtained for the highly volatile aroma esters. The recovered levels of the highly volatile aroma compounds ranged from 68 to 83 vol.% with a feed volume reduction of 5 vol.% (10 °C, 400 l/h). The theoretically predicted aroma recovery as a function of the feed volume reduction was in accordance with the experimentally obtained values. VMD thus turned out to be a promising technique for gentle stripping of black currant juice aroma compounds.

Recovery of aroma compounds from tomato industry effluent using membrane-based solvent extraction

This work focuses on a non-destructive process for recovering valuable aromatic fractions from an odorous tomato industry aqueous effluent. Non-dispersive solvent extraction of four selected aroma compounds, chosen as key aroma, was, at first, carried out on very diluted model aqueous solutions. Mass transfers from water to n-hexane and from water to Miglyol (two solvents widely used in aromatic industry) were studied using a cross-flow designed hollow fibre membrane contactor. The influence of physico-chemical properties of the aroma compounds studied and the influence of the solvent viscosity on mass transfer are discussed. The results obtained with model solutions have been validated on the industrial process effluent.

Pervaporation as a deodorization process applied to food industry effluents: recovery and valorisation of aroma compounds from cauliflower blanching water

In the food industry, unit operations of stabilisation (such as blanching) produce aqueous effluents generally non-polluting but often odorous. The objective of this study was to apply the pervaporation process to the deodorization of a cauliflower blanching effluent in order to reduce its volatile organic compounds content and to try to recover a valuable food flavouring fraction. A systematic study of pervaporation has been performed on three sulfur compounds identified as typical compounds of the cauliflower odour. Then, the separation performances obtained on an industrial effluent were evaluated through physico-chemical and sensorial analysis. They showed that pervaporation was an efficient process for deodorization and offers a real potential for valorisation of the permeate.

Scale-up of pervaporation for the recovery of natural aroma compounds in the food industry Part 2: optimisation and integration

In this study the integration and optimisation of hydrophobic pervaporation for the recovery of natural aroma compounds in the food industry has been studied. The simulation developed in the first part of this study was applied to the design and scale-up of pervaporation units for the recovery of natural apple juice aroma. Both semi-batch and continuous process configurations were considered and the process conditions were optimised taking the cost of the process into account. For the semi-batch process, the cost per kg concentrated aroma was between 31.30 and 33.60 ▪, depending on the membrane type. When returning the recovered aroma to the apple juice after heat treatment, the cost of aroma recovery per kg concentrate was between 0.31 and 0.34 ▪. In the case of the continuous process, the cost for the apple juice aroma recovery was between 2.19 and 5.38 ▪, while the cost of aroma recovery per kg apple juice was between 0.03 and 0.05 ▪. Upon analysing the optimised processes with a sensitivity analysis of the key cost factors associated with pervaporation, membrane life-time and membrane cost, it was revealed that the membrane life-time is more important than the membrane cost and that the continuous process is more sensitive to changes in membrane life-time and membrane cost. Overall, this study revealed that pervaporation has the potential to become an alternative to conventional processes in recovering and concentrating aroma compounds in the food industry.

Scale-up of pervaporation for the recovery of natural aroma compounds in the food industry. Part 1: simulation and performance

The possibility of using pervaporation for the recovery of natural aroma compounds in the food industry has been widely recognised. The aim of this study was to build a bridge between experimental studies of multi-component systems and potential applications of pervaporation in the food industry. Therefore, a novel process simulation of pervaporation has been developed for multi-component mixtures. By applying this simulation to 10 aroma compounds of relevance in the food industry, the influence of process parameters such as permeate pressure, feed temperature, degree of aroma folding and membrane area, on the performance of pervaporation has been investigated. Based on the results of the simulations, it has been demonstrated that process simulation can play an important role in integrating and optimising pervaporation in the food industry.

Recovery of sulfur aroma compounds using membrane-based solvent extraction

This work focuses on a non-destructive process for recovering valuable aromatic fractions from the food industry’s odorous wastewaters. Non-dispersive solvent extraction of three sulfur aroma compounds, dimethyldisulfide, dimethyltrisulfide and S-methyl thiobutanoate, was carried out from very diluted aqueous solutions representing real effluent. The mass transfer from water to n-hexane was studied using a cross-flow designed hollow fiber membrane contactor. A preliminary study showed high affinity of solutes for n-hexane, with constant partition coefficients at infinite dilution between water and hexane in a 90–560 range. The influence of tube and shell side hydrodynamics on mass transfer was studied, with the aqueous phase on the tube side, and the organic phase on the shell side. The diffusion of solutes from the bulk aqueous phase to the aqueous–organic interface controlled the separation and contributed, under the conditions tested, to more than 97% of the overall mass transfer resistance. A resistance-in-series model overestimated overall mass transfer coefficients. The main explanation is the inaccuracy of the Lévêque correlation used at low Reynolds numbers. The choice of a correlation for predicting mass transfers in the solvent phase did not affect the estimation, since the corresponding mass transfer resistance was negligible. Mass transfer fluxes obtained experimentally by membrane-based solvent extraction were greater for the three aroma compounds than those obtained by pervaporation.

Recovery of aroma compounds from orange essential oil

The objective of this work was to study the recovery of aroma compounds present in the orange essential oil using experimental data from CUTRALE (a Brazilian Industry of Concentrated Orange Juice). The intention was to reproduce the industrial unit and afterwards to optimize the recovery of aroma compounds from orange essential oil by liquid-liquid extraction. The orange oil deterpenation was simulated using the commercial software PRO/II 4.0 version 1.0. The UNIFAC model was chosen for the calculation of the activity coefficients.

Aroma compounds recovery from mycelial cultures in aqueous two-phase processes

This paper presents the evaluation of the potential use of aqueous two-phase systems (ATPS) for the recovery of 6-pentyl-α-pyrone (6PP) produced by Trichoderma harzianum. The partition behaviour of 6PP and Trichoderma harzianum mycelium (biomass) in polyethylene glycol (PEG)–salt (phosphate and sulphate) and PEG–dextran ATPS was investigated. The influence of defined system parameters (e.g. molecular mass of PEG and dextran, volume ratio, etc.) on the partition behaviour of 6PP and Trichoderma harzianum mycelium was evaluated to select under which conditions 6PP and mycelium partition to opposite phases. In PEG–dextran systems either large extraction phases were required or mycelium and 6PP partitioned to the same phase. ATPS comprising V r=0.23, PEG 8000 6.6% w/w and sulphate 14.0% w/w provided the best conditions to satisfy the process requirement of biomass accumulation into the bottom phase and 6PP concentration in the top phase.

Recovery of aroma compounds from a wine-must fermentation by organophilic pervaporation.

This study investigates the recovery of a wine-must aroma profile, formed by Saccharomyces cerevisiae during a muscatel wine-must fermentation, using organophilic pervaporation. Experiments were carried out along two independent, but organoleptically similar, fermentations. The wine-must samples and the aroma concentrates obtained were characterized organoleptically by a sensory panel and analytically with regard to eight major wine-must components: four alcohols; three esters; and one monoterpenic compound. Pervaporation performance was studied under fermentation conditions, and the permeate concentration, partial fluxes, and enrichment of the respective compounds were determined. The muscatel wine-must aroma profile was recovered purely and faithful to its origin between wine-must densities of 1075 and 1055 g L. At the beginning of the fermentation, too few aromas were present in the must for recovery. Toward the end of the fermentation, high ethanol concentrations in the wine-must caused a dramatic enrichment of two esters in the permeate, whereas other components investigated seemed unaffected. This shift resulted in an unbalanced aroma. In conclusion, it was shown that organophilic pervaporation can be highly suitable for the continuous recovery of very complex and delicate aromatic profiles produced during microbial fermentation. Copyright 1999 John Wiley & Sons, Inc.

Pervaporation of Aroma Compounds: Comparison of Membrane Performances with Vapour-Liquid Equilibria and Engineering Aspects of Process Improvement

The performances of aroma compounds recovery by pervaporation were analysed through an exhaustive review of the literature. Pervaporation is a separation process based on a selective transport through a dense membrane associated with recovery of the permeate from the vapour phase. Thus, the effective selectivity of organophilic membranes was discussed referring to the vapour-liquid equilibria (VLE) of the aroma compounds, which were estimated using thermodynamic data. Firstly, the importance of the nature of the aroma compounds to be extracted in relation with the type of membrane used was emphasized and some chemical groups of molecules were observed to be better separated through the available pervaporation membranes. Secondly, attention was given to the engineering aspects of pervaporation which have to be well-controlled in accordance with industrial aims.

Dairy aroma compounds recovery by pervaporation

Original pervaporation experiments with two dairy aroma compounds diluted in model aqueous solutions through GFT silicalite-filled silicone composite membrane and GKSS PEBA homogeneous membrane (0.1 m 2 effective area) were carried out on a pilot-plant. A systematic approach was done, studying the influence of various operating parameters (feed temperature and permeate pressure). The permeabilities of the membranes were calculated for each permeant, based on the estimation of the driving force as a fugacities difference. The pervaporation membranes tested showed a good selectivity for the extraction of methylthiobutanoate (hydrophobic molecule with cheese fragrance) at high dilution rate. However, these membranes proved to be less selective for the recovery of diacetyl (hydrophilic butter aroma). For this component, the coupling of pervaporation and two-stage condensation improved significantly the selectivity of the whole process. The thermodynamic properties in the liquid feed (real dairy media) as well as in the permeate (vapour-liquid equilibria at low pressure) have to be well known in order to optimize the recovery of the aroma compounds

Aroma compound recovery with pervaporation — Temperature effects during pervaporation of a muscat wine

A muscat wine, in which eight aroma compounds had been identified, was pervaporated through a poly(dimethyl siloxane) membrane at four different feed temperatures, 6, 15, 25 and 35 °C. Marked effects were observed in the partial fluxes of aroma compounds as the temperature was increased, a phenomenon which could be described by Arrhenius expressions in the equations used to mathematically describe the pervaporation process. Different aroma compounds were differently affected by the temperature changes, and this resulted in changes in concentrations in the permeate, both total and relative, of the aroma compounds studied and in their aroma values in the permeate. Knowledge of the temperature dependence of different aroma compounds is therefore of great importance in the optimization of the pervaporation process for aroma compound recovery.

Aroma compound recovery with pervaporation - the effect of high ethanol concentrations

A series of pervaporation experiments was performed on (1) ethanol-water solutions, (2) ethanol-water solutions containing aroma compounds with varying ethanol concentration and (3) ethanol-water solutions containing varying concentrations of aroma compounds. The aroma model used consisted of five typical aroma compounds at a total concentration of 96 ppm and the membrane used was a commercial poly(dimethylsiloxane) composite membrane. The results show that the fluxes of ethanol and water have a linear relationship to their concentrations in the feed. Furthermore, the fluxes of the aroma compounds have a simple linear relationship to their concentrations in the feed at a given ethanol concentration. However, in some cases the fluxes of the aroma compounds might be affected by the ethanol concentration in the feed whereas the aroma compounds do not affect the fluxes of ethanol and water.

Aroma compound recovery with pervaporation - feed flow effects

A multi component aroma model, consisting of five organic model components in a dilute water solution, was pervaporated through polydimethylsiloxane membranes using different crossflow velocities and hydraulic diameters. Strong feed flow effects were observed in the laminar flow regime for model compounds with low membrane resistance and high concentrations in the feed. In the turbulent flow regime only small or no feed flow effects were observed. A model based on the resistance-in-series model and Sherwood correlations could describe this phenomenon. The different flux increments with increasing crossflow velocity for the different model compounds could be used as a tool, to some extent, to control the composition of the permeate.

Pervaporation of dilute organic-waters mixtures. A literature review on modelling studies and applications to aroma compound recovery

Pervaporation as a tool for the removal of organic substances from dilute aqueous solutions has been reviewed. During pervaporation the membrane governs the performance of the process. The removal of organics from water is accomplished with membranes made of elastomeric or hydrophobic polymer materials. The performance of these membranes, measured as fluxes and enrichment factors, differs considerably. Total fluxes vary between 24 and 2728 g/m 2-hr while the enrichment factor varies between 0.6 and 372. Modelling of the process involves four successive steps, a mass transfer from the bulk of the feed to the feed-membrane interface, partition of the penetrants between the feed and the membrane, diffusion in the membrane and desorption at the membrane-permeate interface. All these steps are crucial for the overall performance of the process. Several models with different approaches and validities exist for each step. The possible of pervaporation for aroma compound recovery has been verified in a number of studies. These studies indicate that aroma compounds, especially volatile aroma compounds, can be enriched several hundreds of times with pervaporation and that the process could be profitable.

Concentration polarization during the enrichment of aroma compounds from a water solution by pervaporation

Pervaporation has proved to be an interesting technique for the recovery and enrichment of aroma compounds from very dilute solutions. In order to study the mass transfer, a 0·5-ppm solution of butyl butyrate, an important aroma compound present in, for example, apple juice, was pervaporated at different circulation velocities along a PDMS (polydimethylsiloxane) membrane. The permeation of butyl butyrate increased with increasing Reynolds number, demonstrating an influence of concentration polarization. In order to minimize the effect of the polarized layer and to improve the mass transfer, optimization of the feed-circulation velocity is very important.

Adsorbents for the recovery of aroma compounds in fermentation processes

AbstractUsing a model solution of 12 aroma compounds, representative of microbial volatiles, 31 different adsorptive materials were investigated with regard to their solid phase extraction and desorption properties. Well known styrene—divinylbenzene‐based resins and alternative adsorbents including zeolites, β‐cyclodextrin and modified activated carbon were compared. Adsorption/desorption rates in aqueous solution were determined for each adsorbent. Isotherms and adsorption kinetics were determined for the most effective adsorbents.