Odor activity values

Odor activity values The number of times an odorant is present above its threshold as measured in the food matrix... 

Reliable quantitative data are a prerequisite for evaluating the contribution of a single odorant to a positive aroma or off-flavor. They are needed to calculate odor activity values (OAV) that are defined as the ratio of the concentration to the sensory threshold of a given compound in a matrix (Rothe and Thomas, 1963 Acree et al., 1984). These values give guidance in the evaluation of the impact of an odorant to the overall aroma profile. 

Grosch, W. 1994. Determination of potent odorants in foods by aroma extract dilution analysis (AEDA) and calculation of odor activity values (OAVs). Flavour Fragrance J. 9 147-158. 

A first step to approach the situation in the food is a calculation of odor activity values (OAV)... 

Concentrations (pg/kg) and odor activity values (OAV) of selected key odorants in roasted... 

Odor activity values of the six key odorants of Emmentaler cheese [301 ... 

During AEDA, interactions between the odorants are not taken into consideration, since every odorant is evaluated individually. Therefore, it may be possible that odorants are recognized which are possibly masked in the food flavor by more potent odorants. Furthermore, the odor activity values only partially reflect the situation in the food, since OAVs are mostly calculated on the basis of odor thresholds of single odorants in pure solvents. However, in the food system, the threshold values may be influenced by nonvolatile components such as lipids, sugars or proteins. The following examples will indicate that systematic sensory model studies are important further steps in evaluating the contribution of single odorants to the overall food aroma. 

In an alcohol-free beer, the concentrations of the beer odorants were 5 to 10-fold lower than in the pale lager beer [18] suggesting that the former beer is a very appropriate matrix for the determination of odor thresholds. A determination of the odor thresholds in the alcohol-free beer revealed (Table 15) that, compared to water, the odor threshold of all odorants increased, but to a different extent. For instance, the threshold of (E)-B-damascenone increased by a factor of 2500, while that of HDF was enhanced only by a factor of eight. Odor activity values calculated on the basis of the odor thresholds in the alcohol-free beer (Table 15) now confirmed the significant contribution of HDF to the dark beer flavor. 

Comparison of odor activity values of important odorants in pale and dark beer [18]... 

Concentrations and odor activity values of 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDF) in processed foods ... 

One way to quantify the odor impact of a compound is to determine the aroma value or odor activity value (OAV). This is calculated by dividing the concentration of the compound by its perception threshold. Therefore, the odor impact of a compound increases in proportion to its OAV when this value is >1. Thus, compounds exhibiting higher OAV values are more likely to contribute to the aroma of wine and have an important influence on its sensory characteristics. 

The intensity of aroma compounds found by AEDA and CHARM may be determined with further accuracy by subjecting them to odor unit (also called odor activity value) measurement.71,72 This is done by first measuring the odor threshold of a compound while the concentration of this compound in the specimen is determined using internal standards (for instance, isotopic samples in contemporary approach). Dividing the latter concentration with the odor threshold will give the odor unit value, naturally being higher when a compound better contributes to the total aroma. 

Escudero, A., Gogorza, B., Melus, M.A., Ortin, N., Cacho, 1., and Ferreira, V. (2004). Characterization of the aroma of a wine from Maccabeo. Key role played by compounds with low odor activity values. J. Agric. Food Chem., 52, 3516-3524. 

To establish exactly the flavor differences between Scheurebe and Gewurztraminer wines, it is therefore necessary to quantify the levels of recognized odorants and to calculate the odor activity values (OAV s). According to Rothe and Thomas (75) the OAV is defined as ratio of concentration to odor threshold value of the compound. 

Table II. Concentrations and Odor Activity Values (OAV s > 10) of Potent Odorants of Scheurebe and Gewurztraminer Wines...

Table VII. Influence of barrel aging on the concentrations and odor activity values (OAV"s) of potent odorants in Gewiirztraminer wine...

Using odor activity value (ratio of concentration to odor threshold), Forss et al. (23), Urbach et al. (24), and Stark and co-worker (25-27) reported 5-decalactone, 8-octalactone, decanoic acid, dodecanoic acid, skatole, and indole as important contributors to the flavor of butter oil. In addition, the data of Siek et al. (28) indicated that in fresh butter, the levels of butanoic acid, caproic acid, 5-decalactone were above their taste threshold. 

IRMS LC MDGC MS MSA NIF NMR OAV OSV PCA RAS RP SDE SFE SIM SNIF SPME TIC TLC Stable Isotope Ratio Mass Spectrometry Liquid Chromatography MultiDimensional Gas Chromatography Mass Spectrometry Multivariate Sensory Analysis Nasal Impact Frequency Nuclear Magnetic Resonance spectroscopy Odor Activity value Odor Spectrum Value Principal Component Analysis Retronasal Stimulation Reversed Phase Simultaneous steam Distillation Extraction Supercritical Fluid Extraction Selected Ion Monitoring Surface of Nasal Impact Frequency Solid Phase Micro Extraction Total Ion Current Thin Layer Chromatography... 

ODOR ACTIVITY VALUE (OAV) OR ODOR UNIT OR AROMA VALUE OR FLAVOR UNIT... 

On the basis of the odor activity value (OAV) concept, only a limited number of volatile components are sensorially relevant in a given foodstuff (Grosch, 1994). Teranishi et al. (1996) also presented a computer-assisted correlation of chromatographic and sensory data in food aromas. In a bar graph were shown the logarithms of the concentrations and of the odor units of the individual constituents of the aroma. The representation shows clearly the constituents present above the threshold values and therefore the most useful for the aroma. 

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