Dynamic Flavour Release Research Articles

Dynamic flavor release from chewing gum: Mechanisms of release

Dynamic flavor release curves from chewing gum were measured using an Artificial Mouth coupled to the AFFIRM®. A flavor distribution model for chewing gum is proposed, where flavor is present as droplets in both the hydrophilic (water-soluble) and the hydrophobic (water insoluble) parts of the chewing gum and as molecularly dissolved in the hydrophobic part of the gum. During mastication, the flavor droplets in the water-soluble phase are released and responsible for an initial burst release. The flavor droplets captured in the gum-base are pushed towards the interface by mastication and are responsible for the subsequent release. The flavor molecules dissolved in the gum-base, released by diffusion, are only responsible for the release at very long time scales. It was found that the oil-water partition constant is an important parameter to explain the flavor release, where hydrophobic components show slower and longer release, while more hydrophilic components show more burst release.

Influence of mastication rate on dynamic flavour release analysed by combined model mouth/proton transfer reaction–mass spectrometry

The influence of mastication rate on the dynamic release of seven volatile flavour compounds from sunflower oil was evaluated by combined model mouth/proton transfer reaction–mass spectrometry (PTR–MS). Air/oil partition coefficients were measured by static headspace gas chromatography. The dynamic release of the seven volatile flavour compounds from sunflower oil was significantly affected by the compounds’ hydrophobicity and the mastication rate employed in the model mouth. The more hydrophobic compounds were released at a higher rate than their hydrophilic counterparts. Increase in mastication rate increased the maximum concentration measured by 36% on average, and the time to reach this maximum by 35% on average. Mastication affected particularly the release of the hydrophilic compounds. The maximum concentration of the compounds correlated significantly with the compounds’ air/oil partition coefficients. The initial release rates over the first 15 s were affected by the type of compound, but not by the mastication rate. During the course of release, the proportions of the hydrophilic compounds to the overall flavour mixture in air decreased. The contribution of the hydrophobic compounds increased. Higher mastication rates, however, increased the proportions of the hydrophilic compounds and decreased those of the hydrophobic compounds.

In vitro and in vivo volatile flavour analysis of red kidney beans by proton transfer reaction?mass spectrometry

The volatile flavour released from red kidney beans was evaluated in vitro (in a model mouth system) and in vivo (in-nose). The dynamic release of the volatile flavour compounds was analysed by proton transfer reaction–mass spectrometry. The flavour compounds were identified by gas chromatography–mass spectrometry. Four masses ( m/z 33, 45, 59 and 73; mass flavour compound + 1) were predominantly measured in the headspace of the beans and selected for dynamic flavour release studies. Comparison of the four masses, identified compounds and their quantities present showed that the four masses probably correspond to methanol ( m/z 33), 2-methylbutanal ( m/z 45), 2,3-butanedione ( m/z 59) and 2-methylpropanal/2-butanone ( m/z 73). Three mastication rates were employed in in vitro analysis (0, 26 and 52 rpm) and two mastication rates in in vivo analysis (52 rpm and free chewing). In in vitro analysis, dynamic release patterns varied significantly among the compounds and the mastication rates (MANOVA, P <0.05). Increase in mastication rate from 0 to 52 rpm increased the maximum flavour concentrations measured by 50–400%. It also increased the persistence of the flavour compounds. The extent of the mastication effect varied among the compounds and, therefore, altered their proportions. Principal component analysis on the relative in vitro and in vivo data revealed that the normalised in vivo release curves were between those of the in vitro samples. This indicates that in vivo release was satisfactorily simulated by the in vitro technique.

In vitro Study of the Influence of Physiological Parameters on Dynamic In-mouth Flavour Release from Liquids

Influences of shear rate (surface extension), airflow, in-mouth headspace volume, synthetic saliva and human epithelial cells (modelling mucosa) on the initial dynamic flavour release from liquids were analysed. Simulating physiological mouth parameters, initial dynamic flavour release experiments over a time period of 30 s were carried out using a proven mouth model apparatus. Flavour compounds of different chemical classes were dissolved in water or in aqueous starch hydrolysate in concentrations typically present in food ( micro g/l to mg/l). Forced by increasing shear rates the enlargement of the gas-liquid interface (vortex formation) caused an increased release of flavour molecules. The release of less soluble compounds was reduced by increasing shear forces due to an improved dissolution. Increasing volumetric airflow rates resulted generally in higher release rates and in a change of pattern of release kinetics. Maximum flavour release was found at a ratio of 1:1 for in-mouth headspace and liquid volume. Neither addition of saliva alone nor the combination of saliva and mucosa showed significant influence on in-mouth flavour release from liquids in the model mouth.

In vitro and in vivo volatile flavour analysis of red kidney beans by proton transfer reaction–mass spectrometry

The volatile flavour released from red kidney beans was evaluated in vitro (in a model mouth system) and in vivo (in-nose). The dynamic release of the volatile flavour compounds was analysed by proton transfer reaction–mass spectrometry. The flavour compounds were identified by gas chromatography–mass spectrometry. Four masses ( m/z 33, 45, 59 and 73; mass flavour compound + 1) were predominantly measured in the headspace of the beans and selected for dynamic flavour release studies. Comparison of the four masses, identified compounds and their quantities present showed that the four masses probably correspond to methanol ( m/z 33), 2-methylbutanal ( m/z 45), 2,3-butanedione ( m/z 59) and 2-methylpropanal/2-butanone ( m/z 73). Three mastication rates were employed in in vitro analysis (0, 26 and 52 rpm) and two mastication rates in in vivo analysis (52 rpm and free chewing). In in vitro analysis, dynamic release patterns varied significantly among the compounds and the mastication rates (MANOVA, P<0.05). Increase in mastication rate from 0 to 52 rpm increased the maximum flavour concentrations measured by 50–400%. It also increased the persistence of the flavour compounds. The extent of the mastication effect varied among the compounds and, therefore, altered their proportions. Principal component analysis on the relative in vitro and in vivo data revealed that the normalised in vivo release curves were between those of the in vitro samples. This indicates that in vivo release was satisfactorily simulated by the in vitro technique.

Initial dynamic flavour release from sodium chloride solutions

Initial dynamic flavour release from solutions of sodium chloride was theoretically modelled. Predictions were validated by experimental data obtained applying a computerised apparatus for real time measurements. Modelling was based on the convective mass transfer theory, combining physicochemical properties of flavours and sodium chloride solutions, and on parameters of the apparatus. Hydration of dissociated ions and concurrent decrease of ‘free water’ volume, together with solution polarity, were found to be rate limiting for the release process. Predicted and experimental data showed a significant positive correlation between solute concentration and release for each flavour compound used. Nevertheless, reduced volume of ‘free water’ influenced flavour compounds to a different extent, resulting in changing overall release profiles.

Lipid molarity affects liquid/liquid aroma partitioning and its dynamic release from oil/water emulsions.

Initial dynamic flavor release from oil/water emulsions containing different TAG phases was studied using a computerized apparatus and thermodesorption GC. A significant influence of lipid molarity on liquid/liquid partitioning and release of some flavor compounds was found. The release of the least hydrophobic compounds was not affected by any type of lipid. Hydrophobic compounds showed a positive correlation between their release and decreasing molarity of the lipid phase, that is, with increasing number of lipid molecules; only the most hydrophobic compounds did not show such a correlation. A strong linear correlation between low-melting TAG/water partition coefficients and lipid phase molarity was validated by volatile partition data of C6, C11, and C16 alkane/water systems. Lipid phase transition from the liquid to solid state did not affect flavor partitioning and release. Neither experimental nor theoretical octanol/water partition coefficients agreed with experimental TAG/water and alkane/water partition coefficients.

Influence of oil‐in‐water emulsion characteristics on initial dynamic flavour release

AbstractProperties of oil‐in‐water (O/W) emulsions affecting initial dynamic flavour release were studied in real time considering mouth conditions. Aroma molecules from different chemical classes at concentrations typically present in beverages were used. The emulsion droplet diameter showed no significant influence on the dynamic flavour release. No barrier properties of the emulsifier were found, as the flavour release from equilibrated emulsions flavoured via either the oil phase or the aqueous phase showed no significant difference. Emulsifier concentrations above the critical micelle concentration did not influence the release. Even though the chemical composition of the lipids had considerable influence on flavour release, phase transition during equilibration from the liquid to the solid state insignificantly affected the initial dynamic release process. Copyright © 2003 Society of Chemical Industry

Dynamic flavor release from sucrose solutions.

The initial dynamic flavor release from sucrose solutions was modeled. Modeling was based on the theoretical hydration behavior of sucrose, theoretical physicochemical data of flavor volatiles, and process parameters of a headspace apparatus used for model validation. The rate-limiting factor determining the initial flavor release was the hydration of sucrose, which in turn depends on the molarity of sucrose in the solution and, therefore, on the actual amount of nonbound water. Improved solubility of the more hydrophilic compounds due to their orientation toward the hydration shells of the sugar molecules was considered. The viscosity of nonassociated water forming the microregion for mass transfer of volatiles was considered instead of the bulk solution viscosity. Experimental validation of the model by real-time measurements of dynamic flavor release using foodlike flavor concentrations confirmed the above theory. Increasing sucrose concentrations resulted predominantly in increased flavor release, and bulk solution viscosity showed no effect.

Dynamic flavour release from Miglyol/water emulsions: modelling and validation

The initial dynamic flavour release from Miglyol/water emulsions was modelled. Modelling was merely based on theoretical physicochemical data of flavour volatiles and process parameters of a headspace apparatus used for model validation. The rate-limiting factor, determining initial flavour release, was the dynamic partitioning from the aqueous phase into the gas phase. This was experimentally confirmed by real time measurements of dynamic flavour release. Improved predictions of the model were obtained when theoretical octanol/water partition coefficients were replaced by measured Miglyol/water partition coefficients.

Modeling dynamic flavor release from water.

A mathematical model derived from the convective mass transfer theory was developed to predict dynamic flavor release from water. A specific mass transfer correlation including a new term for volatile permeability was applied. The model was entirely based on physicochemical constants of flavor compounds and on some parameters of an apparatus used for validation. The model predicted a linear pattern of release kinetics during the first 30 s and large differences of absolute release for individual compounds. Both calculated and experimentally determined release profiles of a test mixture of flavors showed good agreement.

Computerized apparatus for measuring dynamic flavor release from liquid food matrices.

A fully computer-controlled apparatus was designed. It combines a glass reactor with a temperature-controlled hood, in which headspace volatiles are captured. Flavored liquids can be introduced into the reactor and exposed to conditions of temperature, air flow, shear rate, and saliva flow as they occur in the mouth. As the reactor is completely filled before measurements are started, creation of headspace just before sampling start prevents untimely flavor release resulting in real time data. In the first 30 s of flavor release the concentrations of the volatiles can be measured up to four times by on-line sampling of the dynamic headspace, followed by off-line trapping of the samples on corresponding Tenax traps and analysis using GC-TDS-FID. Flavor compounds from different chemical classes were dissolved in water to achieve concentrations typically present in food (micrograms to milligrams per liter). Most of the compounds showed constant release rates, and the summed quantities of each volatile of three 10 s time intervals correlated linearly with time. The entire method of measurement including sample preparation, release, sampling, trapping, thermodesorption, and GC analysis showed good sensitivity [nanograms (10 s)(-1)] and reproducibility (mean coefficient of variation = 7.2%).

Modelling Flavour Release through Quantitative Structure Property Relationships (QSPR)

The use of QSPR to explain the partition behaviour of flavour compounds in different matrices and to predict dynamic flavour release from certain food systems is described. QSPR has been applied in the pharmaceutical and environmental areas to predict properties like the efficacy of drugs (with different substitutions) or behaviours like the accumulation of pollutants in fish, despite the fact that the exact mechanisms are unknown. QSPR relies on the fact that the physicochemical properties of the molecules are responsible for their behaviour and properties in these systems. The models are relatively easy to produce but there are limitations associated with their use outside the defined experimental conditions. The background to modelling flavour partition and release is given, along with examples of relevant QSPR models.

Effects of air flow‐rate on flavour release from liquid emulsions in the mouth

The penetration theory of interfacial mass transfer was used to model dynamic flavour release from liquid emulsions in the mouth. The gas phase was efficiently stirred by the introduction of gas flows (10–200 mL min−1) through the headspace, which also simulated breathing and the transport of flavour molecules from the oral cavity to the olfactory epithelium. The model was used to predict the time‐dependent release profiles of two volatiles, one hydrophilic (diacetyl) and the other hydrophobic (heptan‐2‐one), as a function of the oil volume fraction. Expressions for the maximum flavour intensity and time to reach the maximum flavour intensity were obtained. In general the initial rates of release were faster for emulsions of lower oil content. The maximum flavour intensity was found to be linearly proportional to the initial flavour concentration, whereas the time to reach the maximum flavour intensity was independent of the initial flavour concentration.

Comparison of Dynamic Flavour Release from Hard Cheeses and Analysis of Headspace Volatiles from the Mouth with Flavour Perception during Consumption

Comparison of Dynamic Flavour Release from Hard Cheeses and Analysis of Headspace Volatiles from the Mouth with Flavour Perception during Consumption

Comparison of Dynamic Flavour Release from Hard Cheeses and Analysis of Headspace Volatiles from the Mouth with Flavour Perception during Consumption

Flavour compounds are released at different times and with differing rates during cheese consumption. This aspect of flavour has received little attention, although it is likely to be of great importance in the perception of hard cheese flavour. Full-fat and reduced-fat hard cheeses were analysed by standard buccal headspace methodology and by conventional descriptive sensory analysis. Cheeses were further analysed by 'time-concentration' buccal headspace methodology and sensory time-intensity analysis. Conventional data distinguished between individual cheeses and between fat contents. Time-course data confirmed the results of conventional analysis, but also allowed the examination of release behaviour and changes in flavour perception with time. Partial least squares regression was successful in predicting some sensory attributes from standard buccal extracts. Time-course studies improved predictive ability.

Effects of Sucrose, Guar Gum, and Carboxymethylcellulose on the Release of Volatile Flavor Compounds under Dynamic Conditions

The effect of viscosity and thickener type (sucrose, guar gum, and carboxymethylcellulose) on dynamic flavor release was tested with model flavor solutions at two equiviscous levels. Dynamic flavor release was measured under simulated mouth conditions in an apparatus at 37 °C, with a shear rate of 100 s-1. The volatilized flavors were swept in a flow of helium gas into a mass spectrometer for selected ion monitoring chemical ionization. A plot of time versus ion abundance was recorded for each data set. The highly volatile compounds showed a large decrease in maximum ion abundance (Imax) as viscosity increased. Carboxymethylcellulose, guar gum, and sucrose solutions with a viscosity of 160 mPa s showed 36, 44, and 86% decreases compared to water, respectively, for the release of α-pinene. Similarly, 1,8-cineole decreased 32, 40, and 70% and ethyl 2-methylbutyrate decreased 58, 63, and 94%, respectively. The less volatile compounds methyl anthranilate, vanillin, and maltol showed less of an effect. Thickened solutions of similar viscosity did not show the same flavor release, indicating that both viscosity and binding of flavors with the food matrix affect flavor release. Keywords: Viscosity; mass transfer; diffusion; volatility; flavor release; mouth; shear; Stokes−Einstein; thickeners; binding; hydrocolloid

Novel Vessel for the Measurement of Dynamic Flavor Release in Real Time from Liquid Foods

A glass vessel that will measure the dynamic flavor release of aroma volatiles from model liquid foods in real time has been built. The sample is maintained at 37 °C and stirred at constant torque. Volatiles released into the headspace are continuously swept by a constant carrier gas flow into a quadrupole mass spectrometer via a jet separator. The mass spectrometer is operated in the chemical ionization mode, and single ion monitoring of the major ion associated with each volatile allows real time detection. The apparatus was used to measure the effect of alcohol content on the dynamic flavor release of four volatile compounds from four different water/ethanol mixtures. Keywords: Flavor release; mass spectrometry; chemical ionization; ethanol; volatiles

A Suggested Instrumental Technique for Studying Dynamic Flavor Release from Food Products

ABSTRACTAn instrumental technique is outlined which can be used to study the dynamic volatile flavor release from various food systems. A mass spectrometer coupled with a specially designed apparatus is utilized. The apparatus provides the capability to study several aspects of the in‐mouth environment including thermal, work input, and salivation effects. Monitoring of the headspace concentration is essentially continuous. The technique yields accurate reproducible results and should be applicable to a wide range of food systems.