Partition Of Aroma Compounds Research Articles

Determination of Aroma Compound Partition Coefficients in Aqueous, Polysaccharide, and Dairy Matrices Using the Phase Ratio Variation Method: A Review and Modeling Approach.

The partition of aroma compounds between a matrix and a gas phase describes an individual compound's specific affinity toward the matrix constituents affecting orthonasal sensory perception. The static headspace phase ratio variation (PRV) method has been increasingly applied by various authors to determine the equilibrium partition coefficient K in aqueous, polysaccharide, and dairy matrices. However, reported partition coefficients are difficult to relate and compare due to different experimental conditions, e.g., aroma compound selection, matrix composition, equilibration temperature. Due to its specific advantages, the PRV method is supposed to find more frequent application in the future, this Review aims to summarize, evaluate, compare, and relate the currently available data on PRV-determined partition coefficients. This process was designed to specify the potentials and the limitations as well as the consistency of the PRV method, and to identify open fields of research in aroma compound partitioning in food-related, especially dairy matrices.

Study and modeling of the evolution of gas-liquid partitioning of hydrogen sulfide in model solutions simulating winemaking fermentations.

The knowledge of gas-liquid partitioning of aroma compounds during winemaking fermentation could allow optimization of fermentation management, maximizing concentrations of positive markers of aroma and minimizing formation of molecules, such as hydrogen sulfide (H2S), responsible for defects. In this study, the effect of the main fermentation parameters on the gas-liquid partition coefficients (Ki) of H2S was assessed. The Ki for this highly volatile sulfur compound was measured in water by an original semistatic method developed in this work for the determination of gas-liquid partitioning. This novel method was validated and then used to determine the Ki of H2S in synthetic media simulating must, fermenting musts at various steps of the fermentation process, and wine. Ki values were found to be mainly dependent on the temperature but also varied with the composition of the medium, especially with the glucose concentration. Finally, a model was developed to quantify the gas-liquid partitioning of H2S in synthetic media simulating must to wine. This model allowed a very accurate prediction of the partition coefficient of H2S: the difference between observed and predicted values never exceeded 4%.

Partition of volatile compounds in pea globulin–maltodextrin aqueous two-phase system

This study is based on the assumption that the off-flavour of pea proteins might be decreased using the retention of volatile compounds by a mixture with another biopolymer. The partition of volatile compounds in an aqueous system containing pea protein and maltodextrins was followed under thermodynamic incompatibility conditions. Firstly, the phase diagram of the system was established. Then, the partition of aroma compounds between the phase rich in protein and the phase rich in maltodextrin was measured by SPME–GC–MS. There was a transfer of volatile compounds during phase separation. Variations of pH were also used to vary the retention of volatile compounds by proteins. The concentration of volatile compounds in protein solution at pH 2.4 was higher than at pH 7.2. It was possible to increase the transfer of volatile compounds from the phase rich in protein to the phase rich in maltodextrin using the effect of pH on protein denaturation.

Effect of human saliva and sip volume of coffee brews on the release of key volatile compounds by a retronasal aroma simulator

The influence of human saliva and sip volume on aroma release in coffee brew was studied under mouth-simulated conditions. 24 aroma compounds of coffee brew were monitored and quantified in dynamic headspace of four different coffee brews by SPME–GC–MS in selective ion monitoring (SIM) modality.In the first part of our study, American, Neapolitan, moka and espresso coffee brews showed a different partition of aroma compounds when coffee brew comes into contact with saliva, with respect to the initial amount of volatiles analyzed by the orthonasal way. In addition, every brewing technique seems to imply a different behavior in the aroma release.In the second part, a significant influence of coffee sip volume on aroma headspace was observed. By analyzing the headspace concentration of aroma compounds after retronasal aroma simulation assay, an increase was obtained for some aldehydes assuming 25mL coffee in one sip, while when smaller sips were considered, the aldehyde release decreased and the levels of β-damascenone and 4-vinylguaiacol increased. The different aroma release could not be attributed to direct action of salivary constituents, but rather to the modification of volatile partition into the different phases of coffee brew caused by the presence of saliva. This modification could be mainly related to the chemical properties of volatile compounds and to the non-volatile matrix composition of different coffee brews, which affects the partitioning of volatile compounds and their perception.

The effects of low-molecular-weight emulsifiers in O/W-emulsions on microviscosity of non-solidified oil in fat globules and the mobility of emulsifiers at the globule surfaces

Electron Spin Resonance spectroscopy (ESR) was used to measure the mobility of the spin probe TEMPO in O/W-emulsions. This allowed determination of temperature-dependent microviscosity of the liquid fraction in lipid globules. Six hydrogenated palm kernel oil (HPKO) based emulsions containing caseinate and different combinations of lactic acid ester of monoglyceride (LACTEM), unsaturated monoglycerides (GMU) or saturated monoglyceride (GMS) were studied. The non-solidified oil in emulsions made with LACTEM+GMU had a high microviscosity, whereas the emulsion made with GMS had a low microviscosity. Also the partitioning of TEMPO between the lipid and aqueous phases was found to be highly temperature dependent, most likely due to the change of solid fat content with temperature. This behaviour may mimic the partitioning of aroma compounds in emulsions. The spin probe 5-doxylstearic acid was used to study the mobility of the components at the lipid globule surfaces. At 5°C all emulsions had a very low surface mobility. At 25°C the mobility of the spin probe was found to be correlated to the surface protein load. Emulsions with GMU had a high protein surface coverage and low mobility of the spin probe on the droplet surfaces. Conversely, in presence of LACTEM and GMS, the protein surface loads decreased and high surface mobilities were observed. Based on these results it is argued that the high macroscopic viscosity and lipid agglomeration of emulsions containing GMU is due to a lipid globule–protein-network where the lipid globules are connected via caseinate.

Modelling of the gas–liquid partitioning of aroma compounds during wine alcoholic fermentation and prediction of aroma losses

A model was elaborated to quantify the gas–liquid partitioning of four of the most important volatile compounds produced during winemaking fermentations, namely isobutanol, ethyl acetate, isoamyl acetate and ethyl hexanoate. Analyses of constant rate fermentations demonstrated that the partitioning was not influenced by the CO2 production rate and was a function of only the must composition and the temperature. The parameters of the model were identified in fermentations run at different temperatures, including anisothermal conditions. The prediction of the partition coefficient (ki) by the model was very accurate for isobutanol, isoamyl acetate and ethyl hexanoate. The technological potential of the model was confirmed by using it to calculate the losses of volatiles in the gas phase during fermentation and comparing them with experimental data. Up to 70% of the produced volatile compounds were lost. The difference between observed losses and losses estimated from predicted ki values never exceeded 3%.

Comprehensive Study of the Evolution of Gas−Liquid Partitioning of Aroma Compounds during Wine Alcoholic Fermentation

Calculating the gas-liquid partitioning of aromatic molecules during winemaking fermentation is essential to minimize the loss of aroma and to optimize the fermentation conditions. In this study, the effect of the main fermentation parameters on the partition coefficients (ki) of higher alcohols (2-methylpropan-1-ol and 3-methyl butan-1-ol) and esters (ethyl acetate, 3-methyl-1-butyl acetate, and 2-ethyl hexanoate) was assessed. The values of ki were first determined in synthetic media simulating must and wine. They varied considerably with both the hydrophobicity of the compound and the composition of the medium. Then, the effect of temperature on ki was quantified. The absence of any effect of gas composition was also established by replacing air with CO2. Finally, the impact of CO2 stripping was assessed by running specific fermentations in which the rate of CO2 production was kept constant by perfusion with assimilable nitrogen. These fermentations showed that in contrast to temperature and must composition, CO2 stripping did not change the gas-liquid partitioning of higher alcohols and esters.

Effects of texture and temperature on the kinetic of aroma release from model dairy custards

The structure of a foodstuff, and its perceived texture, are important characteristics involved in the sensory availability of flavour compounds released during the food consumption. This study identifies the effect of texture on the dynamic release of aroma compounds under simulated oral conditions (temperature and shearing). Two custard desserts, with two levels of texture but the same composition, flavoured with four aroma compounds, were analysed. The rheological behaviour of the custards and the release of aroma compounds (SPME analysis) were simultaneously followed, using a mouth simulator. The custard with the lowest texture level showed the highest kinetic release for all aroma compounds studied. With fast increase of temperature (10–25 °C), the decrease in viscosity of the custards and its impact on flavour release seemed to be less important than the heat transfer inside the products and its effect on partition of aroma compounds.

An investigation on molecular partition of aroma compounds in fruit matrix and brine medium of fermented table olives

Abstract Aroma is considered as a quality index of olive products. Fermented olives aroma compounds are present both in the fruit matrix and in brine medium. The partition of aroma compounds between fruit matrix and brine medium is deeply different for the two and depends on several factors such as carbon chain length and/or branching, number of polar groups, sodium salt concentration, temperature, etc. In this work, an investigation on volatile compounds quali-quantitative partition in fruit matrix and in brine medium of Greek-style Carolea and Nocellara del Belice table olives has been assessed. Volatile compounds have been extracted by using headspace method for olive fruit and by solvent extraction and distillation for brine medium. Twenty-three volatile compounds in fruit matrix and fifteen aroma molecules in brine medium have been identified by Gas Chromatography and GC/Mass Spectrometry. Results showed that most volatile organic compounds had a major affinity for the fruit matrix depending both on the chemical characteristics of the molecules (chain length and branching, polar or no polar groups, etc.) and on the “salting out” effect due to high NaCl concentration of the brine, which brought aroma compounds to hydrophobic phase of the olive fruit. Industrial relevance The study could be potentially helpful to develop analytical methods in order to estimate the quail-quantitative composition during the fermentation process. So that it would be possible to implement automatic analytical procedures in the currently used plants for the industrial production for table olives. Furthermore, this study allow us to identify off-flavours formed by anomalous fermentation process, in order to reveal them (both in the fruit and in the brine) in premature times (just in small traces), so to obtain the fermentation process recovery.

Monitoring air/liquid partition of mastic gum oil volatiles in model alcoholic beverage emulsions: Effect of emulsion composition and oil droplet size

The purpose of this work was to study the impact of the structure and composition of hydroalcoholic emulsions on the air–liquid partition of aroma compounds of the essential oil of Pistacia lentiscus var. chia, commonly known as mastic gum oil (mainly consists of terpenes). Oil-in-water emulsions ( φ = 0.17), containing 15% (v/v) ethanol, stabilized by three different emulsifiers (sodium caseinate, whey protein isolate and Tween 40), were prepared by using two different lipid phases (sunflower oil and anhydrous butter fat). The homogenization conditions were varied to obtain emulsions with different volume–surface mean diameters. The partition of the volatile compounds between air phase and emulsions at three different temperatures (25, 37 and 50 °C) was monitored by applying the Headspace Solid Phase Microextraction technique, followed by gas chromatography–mass spectrometry (GC–MS) analysis. In general, the results obtained showed that sodium caseinate was the most effective in retaining mastic aroma compounds, while WPI was the least effective. This could partly be explained by the different structure of the two proteins which, when adsorbed at the interface, form a membrane that acts as a barrier and influences the partition of the aroma compounds between the air and the liquid. At the same time interactions of aroma compounds with the two proteins in the bulk phase may also play a role. The retention of the aroma compounds depended on the oil droplet size only in the case of sodium caseinate containing emulsions at 37 and 50 °C. This behaviour could be due to the substantial increase in the thickness of the adsorbed casein layer when moving from a fine sized emulsion to one with a much larger size as well as to differences in the ratio of free to adsorbed emulsifier. The composition of the lipid phase also appeared to have a significant impact on the concentration of volatile compounds in the headspace of mastic gum oil containing emulsions stabilized by proteins. This was lower in the case of butter fat probably due to differences in composition with regard to fatty acid degree of saturation as well as to volatile absorption by the liquid lipid at 40 °C and subsequent entrapment in the semisolid fat at 25 °C.

Vapour partition of aroma compounds in strawberry flavoured custard cream and effect of fat content

Gas–matrix partition coefficients ( k) of volatile compounds of a strawberry flavour added to a complex model system (custard dessert, COST action 921 recipe) were determined. The influence of fat content on the volatility of the strawberry aroma compounds was investigated using full fat milk- (FFM) and skimmed milk- (SM) custards. For the purpose of this study, the phase ratio variation (PRV) method was used because of its easy application for a mixture of volatiles without requiring any calibration. From the 15 aroma compounds present in the flavouring mixture, seven were volatile enough to be detected and concentrated enough to allow the calculation of k values. Gas–matrix partition coefficients were compared to gas–water partition coefficients. For some aroma compounds (ethyl hexanoate, ethyl butanoate, and hexanal) a significantly lower k value was observed in FFM-custard than in water, indicating a retention effect caused by the matrix. As expected, the fat content and the hydrophobicity of the volatile compounds were of great importance to explain the differences between partition coefficients in SM custards and in FFM custards: for SM-custard, a higher release in the vapour phase was observed than for FFM-custard; the more hydrophobic the aroma compound, the higher the effect. Moreover, ethyl butanoate and hexanal were less retained in SM-custard than in water. This may be attributed to a salting-out effect due to sucrose. The results of this study indicate the importance of the interactions between volatiles and non-volatile compounds as well as of the chemical and physical properties of the aroma compounds in affecting the composition of the gas phase at equilibrium with a complex matrix. More than that, they provided a basis for the studies developed within COST action 921 with the flavoured custard model system.

Emulsification enhances the retention of esters and aldehydes to a greater extent than changes in the droplet size distribution of the emulsion

The physicochemical and organoleptic properties of an emulsion depend on the way the constituents interact with one another to form emulsion droplets, interfacial region and continuous phase. The objective of this work was to evaluate the respective impact of both the emulsification and the modification of the properties of an emulsion, such as the droplet size distribution, on the partition of aroma compounds. The emulsions were prepared with sodium caseinate and the low melting point fraction of anhydrous milk fat ( Φ = 0.3). Their volume-surface mean droplet size ranged from 1.8 to 0.3 μm. Results showed that the measured partition coefficients of ethyl pentanoate, isoamyl acetate, hexanal and t-2-hexenal were lower than the calculated ones from values measured separately over continuous and dispersed phases. The droplet size distribution had no significant impact on the partition coefficient of the three esters whereas, for a volume-surface mean diameter below 0.5 μm, the partition coefficients of the two aldehydes were drastically reduced. The greater retention is not related to the sodium caseinate remaining in the continuous phase of the emulsion. The formation of an interfacial area seems to govern the partition of aroma compounds in emulsions.

Effect of Wine Constituents on Aroma Compound Sorption by Oak Wood in a Model System

The effect of differences in wine matrix on the sorption of aroma compounds (2-phenylethanol, homologous series of ethyl esters, and benzaldehyde) onto oak wood was studied in a model system. Wine components studied included glycerol, ethanol, yeast macromolecules, and aroma compounds. Aroma compounds were sorbed without any interactive effects of co-sorbents, except for 2-phenylethanol and benzaldehyde, which were sorbed in larger amounts from a mixture than when they were the sole volatile solute. The behavior of aroma compounds was not significantly changed by the addition of glycerol. However, as a result of solubility, a decrease of sorption was observed with increasing ethanol concentration from 10 to 15%. Yeast macromolecules also significantly affected the partitioning of aroma compounds between wine model and oak wood. For more hydrophobic aroma compounds, the effect may be the opposite according their origin.

Partition and release of 21 aroma compounds during storage of a pectin gel system.

The increasing popularity of low-fat products increases the need for a better understanding of how flavor release is affected by partial substitution of fat with hydrocolloids. Partitioning and release of aroma compounds from four pectin gels with different compositions were studied with static headspace and with a model mouth. Air/product partition coefficients determine the potential extent of aroma release, and mass transfer determines the rate at which aroma compounds are released to the vapor phase. This study showed that the gel network had large effects on the partition of aroma compounds between the gel and vapor phase. The specific properties of the aroma compounds were also of importance for the air/gel partition. Storage of the four gels showed that one of the weaker gels was influencing the concentration of aroma compounds in the headspace, probably caused by formation of a denser network over time.