Flavor Release Research Articles

Understanding and controlling the behaviour of aroma compounds in thermally processed foods

The challenge of designing heat-stable flavourings consists in combining high flavour retention during heating with high release during eating. These demands are conflicting and difficult to comply with because it is the same factors that control aroma retention and release. In this review, the possibilities to meet these demands will be discussed. For optimum use of these possibilities it is necessary to model the highly complex physical and chemical interactions in sufficient detail to allow prediction of flavour formation, retention and release. This allows a considerable reduction in the time needed to formulate heat-stable, high-performance flavourings with low cost-in-use.

Flavor Release of Diacetyl and 2-Heptanone from Skimmed and Full Fat Milk under Mouth Conditions

To gain insight into the process of retronasal olfaction, flavor release from skimmed milk and full fat milk (containing 3.75% fat) was investigated using a model mouth system with a screw plunger. Large differences were determined in the quantity of flavor released using two different methods : with screw plunger movement, which represents “retronasal” flavor release, and without the screw plunger, which represents “orthonasal” flavor release. The screw plunger motion accelerated the release of diacetyl and 2-heptanone in both skimmed and full fat milk. The amount of diacetyl released was not influenced by the fat content of the milk in either case (with or without screw plunger operation), while the amount of 2-heptanone released was lower in full fat milk both with and without screw plunger motion. The influence of fat content on the amount of flavor released was explained by the lipophilicity of the flavor components, and mass transfer also contributed to release of the hydrophilic flavor compound.

Investigation of the retronasal flavour release during the consumption of coffee with additions of milk constituents by ‘Oral Breath Sampling’

The aim of this study was the investigation of the influence of milk proteins (casein and whey proteins) and milk fat on the release of flavour compounds from white coffee beverages in the oral cavity. For this reason a retronasal headspace technique for measurement of the after-flavour was adapted. A ‘Gas Sampler’ equipped with a mouthpiece was used as an ‘Oral Breath Sampler (OBS)’. Analyses were performed by gas chromatography with mass spectrometric detection. It was noticed that the sampling at different hours resulted in different standard deviations. The flavour release is more constant in the morning (Variation coefficient from 3% to 28%; median: 10%) than in the afternoon (7–52%; median: 23%). The relationships between flavour release and some salivary parameters like salivation rate, buffer capability and protein content were also studied. The ‘Oral Breath Sampling’ was considered to be a valuable sampling method for the analysis of the retronasal aroma release from coffee beverages.

Flavour encapsulation and controlled release – a review

SummaryFlavours can be among the most valuable ingredients in any food formula. Even small amounts of some aroma substance can be expensive, and because they are usually delicate and volatile, preserving them is often a top concern of food manufacturers. Encapsulation describes different processes to cover an active compound with a protective wall material and it can be employed to treat flavours so as to impart some degree of protection against evaporation, reaction, or migration in a food. Encapsulation of flavours has been attempted and commercialized using many different methods such as spray drying, spray chilling or spray cooling, extrusion, freeze drying, coacervation and molecular inclusion. The choice of appropriate microencapsulation technique depends upon the end use of the product and the processing conditions involved in the manufacturing product. This overview describes each method cited above in terms of the basic chemical and/or physical principles involved and covers mechanisms of flavour release from food matrices.

Flavor Encapsulation in Yeasts: Limonene Used as a Model System for Characterization of the Release Mechanism

Empty yeast cells are used as a new delivery system for flavor encapsulation. The flavor release mechanism from yeast cells is characterized using a series of analytical techniques, and limonene is used as a model representing a hydrophobic flavor. Furthermore, the thermal stability of the capsules was assessed. The characterization of the cell wall structure gives rise to the development of an empirical model explaining water adsorption as well as the desorption singularities observed on drying. The study of the rate of flavor release as a function of temperature and water uptake in the cell wall clearly demonstrated a particular behavior of the yeast cell wall permeability. Below a water activity around 0.7, no flavor release is permitted whereas release occurs above it. Surface analysis on dry or wet cells using atomic force microscopy is discussed.

Differences in the Effect of Bolus Weight on Flavor Release into the Breath between Low-fat and High-fat Products

The maximum intensity of flavor release increased as the weight of food introduced into the mouth (the bolus) was increased for a range of different foods. The relationship was not directly proportional (1:1) but followed a power law function. Low-fat (< or = 1 g/100 g) foods showed a different relationship than high-fat (> or = 5 g/100 g) foods, but all low-fat and all high-fat foods were broadly similar irrespective of food type or flavor molecule chemistry. For low-fat foods the intensity of flavor release increased with increasing bolus weight to a greater extent than high-fat foods. This may be associated with the capacity of fat to selectively adhere to the surfaces of the oral cavity, thereby changing the effective surface area for the release of lipophilic flavors.

Real-Time Flavor Release from French Fries Using Atmospheric Pressure Chemical Ionization−Mass Spectrometry

Flavor release from French fries was measured with atmospheric pressure chemical ionization-mass spectrometry (APCI-MS) using both assessors (in vivo) and a mouth model system (in vitro). Several volatiles measured with APCI were identified with MS-MS. The effect of frying time, salt addition, and an alternative process using superheated steam was determined on I(max) (maximum intensity of compounds) and on t(max) (time of maximum intensity). In vitro a "chewing" frequency of 0.60 Hz caused an increased t(max) for low molecular weight compounds compared to the other frequencies tested. Above 0.93 Hz further increase in the frequency did not affect t(max). Trends observed with in vivo experiments could be verified with in vitro experiments. I(max) correlated well with frying time. Addition of salt resulted in a decreased t(max), suggesting a salting-out effect. The alternative process caused a layer of oil on the surface, and this resulted in a higher t(max), but no effect on I(max) was found. This phenomenon may be critical for the sensory quality and would not have been observed with static volatile measurements, demonstrating the value of flavor release measurements.

Flavour release at gas/matrix interfaces of stirred yoghurt models

Release of strawberry flavour compounds at vapour/matrix interfaces was studied in model food systems simulating a yoghurt with a fruit preparation syrup. The effect of different parameters including physicochemical characteristics of the flavour compound, the structure and composition of the matrix and the temperature (4 and 10°C) on the release of the flavour compounds were investigated. There was an effect of the composition and structure of the matrix upon the partition of the flavour compounds. In the dairy gel, retention of flavour compounds was caused by the physicochemical interactions with the proteins and the solubilisation in dispersed fat. The addition of syrup to the low-fat dairy gel slightly increased the retention of the flavour compounds; this was attributed to physicochemical interactions with pectin and sucrose. In the presence of fat (5%), the flavour compounds were solubilised in the fat and their release was not affected by the composition of the dispersing medium. As expected, temperature affected the release; an increase from 4 to 10 °C resulted in an increase in the overall amount of flavour released.

Correlating instrumental measurements of texture and flavour release with human perception

SummaryAttempts to correlate sensory perception with analytical measurement of the physical or chemical properties of a food are widespread in both industry and academia. Reasons for this are discussed, along with some of the techniques employed. The inter‐relationship between instrumental analysis and sensory evaluation in the development and quality control of food products is emphasized. Three examples are drawn from the field of flavour research, where a combination of instrumental and sensory techniques was used for different purposes. Instrumental measures may be used to predict sensory quality within a known design space, provided this has first been validated with appropriate sensory methodology. It is true, however, that a significant correlation between analytical and sensory data does not necessarily imply that a causal relationship exists between the two.

Influence of the texture of gelatin gels and pectin gels on strawberry flavour release and perception

The release of strawberry flavour compounds from pectin gels and gelatin gels was evaluated by instrumental and sensory analysis. Three gel textures were established based on Young’s modulus of elasticity ( E) for each gel. The E of the low, medium and high rigidity gelatine and pectin gels was 181, 300 and 493 N m −2, respectively. Air/gel partition coefficients were determined by static headspace analysis. In-nose/proton transfer reaction-mass spectrometry analysis produced temporal release profiles. Sensory analysis was conducted to assess perceived odour, thickness, strawberry flavour and sweetness using magnitude estimation. The type of hydrocolloid affected static and in-nose compound concentrations significantly. The pectin gels showed lower air/gel partition coefficients than the gelatin gels, but increased flavour release. Increased gel rigidity resulted in lower air/gel partition coefficients; higher maximum concentrations of volatiles and lower release rates during in-nose analysis; decreased perception of odour, strawberry flavour and sweetness; and higher intensity ratings for thickness in sensory analysis. Consequently, both type of hydrocolloid and rigidity of the sample greatly affected flavour release and perception.

Effect of Xanthan on Flavor Release from Thickened Viscous Food Model Systems

The influence of xanthan concentration (0, 0.02, 0.1, 0.4, and 0.8% w/w) and bulk viscosity on the release of 20 aroma compounds of different chemical classes (5 aldehydes, 4 esters, 5 ketones, 3 alcohols, and 3 terpenes) was evaluated in xanthan-thickened food model systems having different viscosities. Interactions between flavor compounds and xanthan were assessed by measuring air-liquid partition coefficients, K, of aroma compounds in pure water and in the xanthan solutions by static headspace gas chromatography. Mass transfer of aroma compounds was estimated by dynamic headspace gas chromatography. Notably, limonene and some of the esters and aldehydes exhibited decreased K values in the presence of xanthan, indicating that the release of these volatile aroma compounds was reduced due to interaction with the xanthan matrix. The degree of interaction depended on the physicochemical characteristics of the aroma compounds. A similar tendency was observed at nonequilibrium with the decreases in release rates being most pronounced for limonene, followed by the esters and aldehydes, with no effect for ketones and an apparent "salting out" effect for alcohols. The reduction in flavor release by xanthan was thus dependent on the physicochemical properties of the aroma compounds and was apparently a result of the aroma-xanthan interactions and not influenced by the viscosity of the system itself.

Aroma Release and Delivery Following the Consumption of Beverages

Processes controlling aroma release and delivery during and after the consumption of a beverage were studied using real-time physiological and aroma release measurements. The key processes were as follows. During swallowing, a portion of the buccal gas phase was transferred first to the throat and then to the nasal passages via the tidal breath flow. This mechanism accounted for the sharp pulse of aroma seen at the beginning of the swallow breath and on subsequent swallows. The persistence effect was due to liquid-air partition from beverage coated on the throat and was dependent on the concentration of volatile compounds in the beverage. Lipid in the beverage caused a decrease in the intensity of volatile compounds on the breath, but the presence of a thickening agent had no effect on persistence.

Influence of amylose-flavor complexation on build-up and breakdown of starch structures in aqueous food model systems

Starch, in particular the linear amylose, is able to form inclusion complexes with a wide variety of flavor compounds. Build-up and breakdown of starch/flavor structures in aqueous food model systems were followed with iodometric titration, oscillatory measurements, light microscopy and differential scanning calorimetry (DSC). Amylose-flavor complexation promotes gelation and spherulitic crystallization in simple starch dispersions as well as in complex food systems including milk proteins and sugars. Crystalline starch/flavor spherulites and amylose-flavor complexes are very slowly attacked by α-amylase in mouth while fast breakdown of amylose-flavor complexes becomes possible in the gastrointestinal tract. It is concluded that starch/flavor interactions influence the sensory properties of starch based food systems in particular texture quality and flavor release. Amylose-flavor complexation might be an encapsulation principle for food where a controlled flavor release is desired.

In vivo monitoring of strawberry flavour release from model custards: effect of texture and oral processing

The interaction of oral processing protocols and food texture on in vivo flavour release was evaluated by nose-space analysis. Nose-space analysis was carried out by proton transfer reaction mass spectrometry, and strawberry-flavoured custards were prepared with 0.1% (w/w) and 1.0% (w/w) carboxymethyl cellulose to modify the texture. Two oral processing protocols were adopted during the study; a free-chewing protocol and an imposed protocol. Twenty-one subjects participated in the study. Significant effects on in-nose flavour release were observed for the type of compound, the custard's texture, the oral processing protocol and the subjects. When people were allowed to eat as they normally do, individuals could be divided into three groups on the basis of swallowing time: first group, swallowing time 6 s; intermediate group, t ( s w a l l o w ) varying (4-6 s). Within each group, different effects of the texture of the custards on in-nose flavour concentrations were observed, indicating that individual behaviour plays a considerable role in determining texture effects on flavour perception.

Composition of the essential oil of fruits and roots ofFerulago isaurica Peşmen andF. syriaca Boiss. (Umbelliferae) from Turkey

COST Action 921on Food Marrices - Stuctural Organization from Nano- to Marcro Scale and Impact on Flavour Release and Perception -- APR 01-02, 2004 -- Brussels, BELGIUM

COST action 921: food matrices: structural organization from nano- to macro scale and impact on flavour release and perception

COST action 921: food matrices: structural organization from nano- to macro scale and impact on flavour release and perception

Influence of emulsion and powder size on the stability of encapsulated d-limonene by spray drying

The microencapsulation of d-limonene by spray drying was investigated with respect to the effects of emulsion droplet size, powder particle size, as well as to the effects of various kinds of matrices (gum arabic, maltodextrin, and modified starch) on its stability. It was realized by studying release characteristics and oxidative stability during storage. The release and the oxidation decreased deeply with an increase in powder and emulsion particle size for gum arabic and maltodextrin materials. Further, the distributions of emulsion size in the powder showed an increase in the fraction of large emulsion droplets and changed to a bimodal distribution. However, the modified starch HI-CAP 100 showed a higher stability of encapsulated d-limonene than the others. The influence of powder and emulsion size on its encapsulated flavor as well as the change in the emulsion size during storage could not be observed. Industrial Relevance Spray drying is a common and useful unit operation for microencapsulation of food ingredients. Data on emulsion droplet size and on powder size on product stability provide conflicting results which makes a systematic study regarding these factors highly relevant. The data suggest that an optimal size of flavour powder should be selected for high retention during spray drying, stability during storage and for the ability to control release of flavour.

Molecular encapsulation of flavours as helical inclusion complexes of amylose

Abstract The formation of helical inclusion compounds of amylose with different typical flavour compounds was optimised. Maximal guest molecule contents between 5.7 and 10.4 wt% in the complex were obtained. This corresponds to segments of 8–16 anhydroglucose units in the amylose helix per included guest molecule. Contents of this order of magnitude approach the maximum content of guest molecules possible in the core of the amylose helix. A method for determining the association constants for complexing using headspace gas chromatography was applied. Constants ranging from K=29–1080 l/mol were obtained. The association constant with the same guest molecule is strongly dependent on the origin and the chain length of the amylose. Flavours with low boiling points such as hexanal (b.p. 128 °C) form complexes which are completely stable under freeze-drying conditions and show long-term stability. Flavour release was only observed at high temperatures (80 °C). On addition of water, guest molecules are quickly released but with water activities of aw=0.3—as found in normal dry food—the complexes are stable at room temperature. Complexes with two or more guest molecules show a remarkable influence on complexing ability induced by the co-inclusion compounds. The overall content of guest molecules is lower compared to that obtained with individual flavour compounds.

Flavor Release Measurement from Gum Model System

Flavor release from a mint-flavored chewing gum model system was measured by atmospheric pressure chemical ionization mass spectroscopy (APCI-MS) and sensory time-intensity (TI). A data analysis method for handling the individual curves from both methods is presented. The APCI-MS data are ratio-scaled using the signal from acetone in the breath of subjects. Next, APCI-MS and sensory TI curves are smoothed by low-pass filtering. Principal component analysis of the individual curves is used to display graphically the product differentiation by APCI-MS or TI signals. It is shown that differences in gum composition can be measured by both instrumental and sensory techniques, providing comparable information. The peppermint oil level (0.5-2% w/w) in the gum influenced both the retronasal concentration and the perceived peppermint flavor. The sweeteners' (sorbitol or xylitol) effect is less apparent. Sensory adaptation and sensitivity differences of human perception versus APCI-MS detection might explain the divergence between the two dynamic measurement methods.

Swelling and erosion affecting flavor release from glassy particles in water

AbstractA model of flavor release from encapsulated flavor particles immersed in water has been developed that correlates well with experimental data. Flavor release from particles was determined by measuring both the quantities released from the particle to water and from water to air in the headspace. The model presented here predicts a very different release with time from the encapsulated flavor if the particle develops a hydrogel at the surface (swelling) compared to gradual erosion. Controlled heating showed more retention of flavor when the particle swells compared to a more rapid flavor release under conditions of particle erosion. © 2004 American Institute of Chemical Engineers AIChE J, 50: 3257–3270, 2004