Aroma Extract Dilution Analysis AEDA

An aliquot of the extract which was used for the first GC-O experiment is diluted with the solvent, usually as a series of 1+1 or 1+2 dilutions and each dilution is analysed by GC-O. This means that in each GC run the assessor records the retention time of each odour along with a descriptor of that odour. This procedure is continued until no odorants are perceivable. The highest dilution at which a compound can be smelled is defined as its flavour dilution (ED) factor. The ED factor is a relative measure, and is proportional to the OAV of the compound in air. 

Dilution analyses rank the odorants present in an extract according to their relative OAV the identification experiments are then focused on the odorants showing high FD factors. 

It has been reported [28] that there may be a cross-adaptation between two odorants, causing a gap during sniffing of the dilution series. To avoid this phenomenon, AEDA should be performed within 2 days [11], e.g. GC-O of the concentrated extract and of the first dilutions 1 4, 1 16, 1 64, 1 256 and 1 1024 on the fist day, and the dilutions 1 2, 1 8, 1 32, 1 128 and 1 512 on the second day. 

Some authors do not dilute the concentrated extract but dilute the sample before SPME and GC-O. Studies on soy sauce [9] and wine [29] are examples. 

As an example of AEDA, Fig. 16.2 shows a plot of the FD factors of the odorants of parsley versus their retention indices this plot is termed an FD chromatogram. As usual in dilution analyses, the result in Fig. 16.2 is not corrected for losses of odorants during the isolation and GC procedures therefore, not only the odorants showing the highest FD factors (nos. 1, 2, 7 and 13 in Fig. 16.2) were identified but also all of the 14 odorants appearing in the FD-factor range of 4-512. The result is presented in the legend to Fig. 16.2. 

These limitations are eliminated by the stepwise dilution of the volatile fraction with solvent, followed by the gas chromatographic/olfactometric analysis of each dilution. The process is continued until no more aroma substance can be detected by GC olfactometry. In this way, a dilution factor 2 (n = number of 1 -b 1 dilutions) is determined for each aroma substance that appears in the gas chromatogram. It is designated as the flavor dilution factor (FD factor) and indicates the number of parts of solvent required to dilute the aroma extract until the aroma value is reduced to one. 

Another more elaborate variant of the dilution analysis requires, in addition, that the duration of each odor impression is recorded by a computer and CHARM values are calculated (CHARM acronym for combined hedonic response measurement), which are proportional to aroma values. The result of an AEDA can be represented as a diagram The FD factor is plotted against the retention time in the form of the retention index (RI) and the diagram is called a FD chromatogram. 

The FD chromatograms of the volatile compounds of white bread and French fries are presented in Fig. 5.4 and 5.8, respectively. 

The identification experiments concentrate on those aroma substances which appear in the FD chromatogram with higher FD factors. To detect all the important aroma substances, the range of FD factors taken into account must not be too narrowly set at the lower end because 

In the case of French fries (Fig. 5.8), 19 aroma substances appearing in the FD-factor range 2 -2 were identified (cf. legend of Fig. 5.8). Based on the high FD factors, the first approximation indicates that methional, 2-ethyl-3,5-dimethylpyrazine, 2,3-diethyl-5-methylp)razine and (E,E)-2,4-decadienal substantially contribute to the aroma of French fries. 

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Aroma compounds, 11 517 Aroma extract dilution analysis (AEDA), 11 519-520... 

Twenty-nine odour-active compounds were detected by using aroma extract dilution analysis (AEDA) [60]. The results of AEDA together with GC-MS analysis showed ethyl 2-methylbutanoate (described as fruity flavour), followed by methyl 2-methylbutanoate and 3-methylbutanoate (fruity, apple-like), 4-hydroxy-2,5-dimethyl-3(2H)-furanone (sweet, pineapple-like, caramel-like), d-decalactone (sweet, coconut-like), l-( ,Z)-3,5-undecatriene (fresh, pineapple-like), and a unknown compound (fruity, pineapple-like) as the most odour-active compounds. 

However, a single GC-O run only is usually insufficient to distinguish between the potent odorants that most likely contribute strongly to an aroma and those odorants that are only components of the background aroma. Therefore, to improve the results, two methods, combined hedonic aroma response measurements (CHARM) analysis [4] and aroma extract dilution analysis (AEDA) [5, 6] have been developed. As discussed in Sect. 16.4 in both methods serial dilutions of food extract are analysed by GC-O. 

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. 

At a meeting in Germany in 1983, the idea of using repeated sniffs of sequentially diluted samples, now generally called dilution analysis, was proposed (Acree and Barnard, 1984). This led to the publication of CharmAnalysis in 1984 and Aroma Extract Dilution Analysis (AEDA) in 1987, both of which were based on the idea of quantifying potency by dilution to threshold. Potency here is similar to the concept of titer or the amount of dilution necessary to... 

In order to evaluate the best temperature and time of baking process, Silva et al. (2008) used an expert panel to analyze seven descriptors, including dried fruit, nutty, baked, oak, mushroom, and brown sugar. The optimal temperature and time of baking process respecting the specificity of Madeira winemaking are considered 45 °C for 4 months. On the basis of aroma extract dilution analysis (AEDA), several Maillard byproducts, such as Sotolon, 2-furfural, 5-methyl-2-furfural, 5-ethoxy-methyl-2-furfural, methional, and phenylacetaldehyde, were identified in both Malvasia and Sercial wines under study which may explain the baked, brown sugar, and nutty odor descriptors. 

The volatiles of fresh leaves, buds, flowers and fruits were isolated by solvent extraction and analysed by capillary gas chromatography-mass spectrometry. Their odour quality was characterized by gas chromatography-olfactometry—mass spectrometry (HRGC-O-MS) and aroma extract dilution analysis (AEDA). In fresh bay leaves, 1,8-cineole was the major component, together with a-terpinyl acetate, sabinene, a-pinene, P-pinene, P-elemene, a-terpineol, linalool and eugenol. Besides 1,8-cineole and the pinenes, the main components in the flowers were a-eudesmol, P-elemene and P-caryophyllene, in the fruits (EJ-P-ocimene and biclyclogermacrene, and... 

These methods were developed to quantify and visualize the intensity of aroma as a chromatogram. A specific system named combined hedonic and response measurement (CHARM) was initially developed. Later on, aroma extract dilution analysis (AEDA) (Figure 3), a new method using a conventional GC-O system, was proposed. They share the same strategy aroma extract is diluted to a certain extent and then GC—O methodology is applied. In an AEDA procedure, if such a maximum extent of a dilution that allows the detection of a certain component is times diluted from the original sample, this component is referred to have a flavor dilution (FD) factor of . CHARM value corresponds to FD factor in a CHARM procedure. These values represent the contribution of the volatile the larger these values are, the more important they are considered as key components. 

Based on determination of threshold concentration Aroma Extract Dilution Analysis (AEDA) (Schieberle and Grosch 1987 Ullrich and Grosch 1987), and Charm analysis (Acree et al. 1984)... 

Fang, Y, and Qian, M. (2005). Aroma compounds in Oregon Pinot Noir wine determined by aroma extract dilution analysis (AEDA). Flav. Frag. J., 20, 22-29. 

By using aroma extract dilution analysis (AEDA) of the volatile fractions of fresh and stored butter oil, Widder et al. (29) determined diacetyl, butanoic acid, 8-octalactone, skatole, 8-decalactone, cw-6-dodeceno-8-decalactone, l-octen-3-one, and l-hexen-3-one as potent contributors to the flavor of butter oil. The concentration of l-octen-3-one, trani-2-nonenal, and i-l,5-octadien-3-one increased during the storage of the butter oil at room temperature. 

Table 5 shows the sensory evaluation by Schieberle et al. (30) of the different kinds of butter, namely, Irish sour cream (ISC), cultured butter (CB), sour cream (SC), sweet cream (SwC), and farmer sour cream (ESC). It revealed ISC butter and ESC butter with the highest overall odor intensities. Table 5 shows that 19 odor-active compounds were detected by aroma extract dilution analysis (AEDA) in a distillate of the ISC butter. The highest flavor dilution (ED) factors have been found for 5-decalactone, skatole, i-6-dodeceno-y-lactone, and diacetyl followed by trany-2-nonenal, cw,c -3,6-nonadienal, c/i-2-nonenal, and l-octen-3-one. 

After the preparation of an aroma concentrate as detailed in [11], dilution experiments are performed (Table 6.23). As reviewed by Acree [8] and Grosch [11], two techniques - charm analysis and aroma extract dilution analysis (AEDA) - are used to screen the potent, medium and lower volatile odorants on which the identification experiments are then focused. In both procedures, an extract obtained from the food is diluted, and each dilution is analysed by GCO. This procedure is performed until no odorants are perceivable by GCO. 

Matsui, T, Guth, H., Grosch, W. (1998) A comparative study of potent odorants in peanut, hazelnut, and pumpkin seed oils on the basis of aroma extract dilution analysis (AEDA) and gas chromatography-olfactometry of headspace samples (GCOH). Fett/I.ipid 100. 51-56... 

Although more than 280 compounds have been identified in the volatile fiction of wheat bread, only a small number is responsible for the flavor notes in the crust and the crumb. Schieberle and Grosch (73) used aroma extract dilution analysis (AEDA) to select 32 odorants in wheat. Among the odorants, 2-acetyl-pyrroline (roasly, bread crust-like) was the most potent aroma, followed by E-2-nonenal (green, tallowy), 3-methylbutanal (malty, nutty), diacetyl (buttery) and Z-2-nonenal (green, fiitty). 

Gas chromatography-olfactometry (GCO) has been used extensively for the identification of characteristic aroma conq)onents of foods (9,10). Aroma extract dilution analysis (AEDA) is a GCO technique in which serial dilutions (e.g. 1 3) of an aroma extract are evaluated by GCO. In AEDA, the highest dilution at which an odorant is last detected during GCO, so-called flavor dilution (FD) factor, is used as a measure of its odor potency (P). One potential drawback to AEDA is that the technique is limited to the analysis of components of intermediate and low volatility. To overcome this limitation, AEDA results have been con5>lemented by results of GCO of decreasing dynamic headspace (DHS) and decreasing static headspace (GCO-H) san5)les (70,77)... 

To correlate differences in the aromas of different samples, first, the most-odor active compounds in the samples treated without HHP have to be identified. The subsequent application of a comparative Aroma Extract Dilution Analysis (AEDA) is a very useful tool to screen and compare odor activities of the same odorants in two different samples. To gain first insights into the influence of HHP on aroma formation in Maillard type reactions, the key odorants formed at 100°C in proline/glucose mixtures treated under HHP or at normal pressure were compared. Labeling experiments were then performed to elucidate the influence of HHP on formation of transient intermediates and an pathways leading to selected key odorants. 

It is well known that the aroma extract dilution analysis (AEDA) is a nsefnl method for the recognition of the odor quality and odor intensity of each component." Especially the AEDA is a useful method for the identification of trace amonnts of the component that significantly affects the flavor of tea drinks. The odor intensity of the flavor component is expressed by the flavor dilution (ED) factor, that is, the ratio of the concentration of the flavor component in the initial extract to its concentration in the most dilnte extract in which odor was detected by gas chromatography-olfactometry (GC-0). Therefore, hereafter, from the viewpoint of sensory evalnation, the change in the flavor of tea drink dnring heat processing by AEDA will be mainly discnssed. Furthermore, in order to inhibit flavor deterioration of tea drink, the stndy of flavor precnrsor in a variety of foods, including tea drinks, will be proposed. 

DILUTION ANALYSIS CHARM ANALYSIS AND AROMA EXTRACT DILUTION ANALYSIS (AEDA)... 

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