Aroma extract dilution analysis, odor

Blank I, Grosch W, Evaluation of potent odorants in dill seed and dill herb Anethum graveolens L.) by aroma extract dilution analysis,Sci 56 63-67, 1991. 

Nishimura, O. Identification of the characteristic odorants in fresh rhizomes of ginger (Zingiber officinale Roscoe) using aroma extract dilution analysis and modified multidimensional gas chromatography-mass spectroscopy. J Agr Food Chem 1995 43(11) 2941-2945. 

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. 

Fig. 16.2 Flavour dilution (FD) chromatogram obtained by application of aroma extract dilution analysis on an extract prepared from parsley leaves. The odorants were identified as 1 methyl 2-methylbutanoate, 2 myrcene, 3 l-octen-3-one, 4 (2)-l,5-octadien-3-one, 5 2-isopropyl-3-me-thoxypyrazine, 6p-mentha-l,3,8-triene, 71inalool, 8 2-sec-butyl-3-methoxypyrazine, 9 (.Z)-6-dece-nal, 10 / -citronellol, 11 ( , )-2,4-decadienal, 12 / -ionone, 13 myristicin, 14 unknown. RI retention index. [30, 31]...

Grosch, W. 1993. Detection of potent odorants in foods by aroma extract dilution analysis. Trends Food Sci. Technol. 4 68-73. 

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 composition of the volatile fraction of bread depends on the bread ingredients, the conditions of dough fermentation and the baking process. This fraction contributes significantly to the desirable flavors of the crust and the crumb. For this reason, the volatile fraction of different bread types has been studied by several authors. Within the more than 280 compounds that have been identified in the volatile fraction of wheat bread, only a relative small number are responsible for the different notes in the aroma profiles of the crust and the crumb. These compounds can be considered as character impact compounds. Approaches to find out the relevant aroma compounds in bread flavors using model systems and the odor unit concept are emphasized in this review. A new technique denominated "aroma extract dilution analysis" was developed based on the odor unit concept and GC-effluent sniffing. It allows the assessment of the relative importance of the aroma compounds of an extract. The application of this technique to extracts of the crust of both wheat and rye breads and to the crumb of wheat bread is discussed. 

The aroma extract dilution analysis of concentrates prepared from the crusts of wheat and rye breads revealed fourty-three odorants in rye and thirty-two in wheat extracts (37). 

If more exact data are desired, the results obtained by aroma extract dilution analysis must be complemented by quantitative measurements. Quantification of odorants is a difficult task, since the concentration of the odorants showing high FD-factors can be extraordinarily low. 

The aroma extract dilution analysis was applied to extracts obtained from the crumb of wheat bread. Twenty nine odorants were detected and the flavor compounds responsible for the odor notes identified (Schieberle, P. Grosch, W. in preparation). The 12 aroma compounds having the highest FD-factors are presented in Table IV. 

Table IV. Important Odorants (FD 32) of Wheat Bread Crumb Results of an Aroma Extract Dilution Analysis and Identification Experiments (Schieberle, P Grosch, W. in preparation)...

Crust volatiles were isolated immediately after baking by extraction with dichloromethane and sublimation in vacuo ( ). Application of aroma extract dilution analysis 6) to the acid-free crust extract led to the detection of 31 odorants. After separation and enrichment, these compounds were identified by comparison of the MS/EI, MS/Cl and retention data on two columns of different polarity to reference compounds. Aroma quality was also assessed. The results of the identification experiments (Table I) revealed that 2(E)-none-nal (No. 1), followed by 2(E),4(E)-decadienal (No. 2) and 3-methyl-butanal (No. 3) showed the highest FD-factors in the crust of the chemically leavened bread. Additionally l-octen-3-one, 2(Z)-nonenal, 2(E),4(E)-nonadienal and an unknown compound with a metallic odor contributed high FD-factors to the overall flavor (For a discussion of FD-factors, see Chapter by Schieberle and Grosch, this book). 

Odor-active components in cheese flavor, many of which are derived from milk lipids, can be detected using GC-olfactometry (GC-O). GC-0 is defined as a collection of techniques that combine olfactometry, or the use of the human nose, as a detector to assess odor activity in a defined air stream post-separation using a GC (Friedich and Acree, 1988). The data generated by GC-0 are evaluated primarily by aroma extract dilution analysis or Charm analysis. Both involve evaluating the odor activity of individual compounds by sniffing the GC outlet of a series of dilutions of the original aroma extract and therefore both methods are based on the odor detection threshold of compounds. The key odourants in dairy products and in various types of cheese have been reviewed by Friedich and Acree (1988) and Curioni and Bosset (2002). 

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. 

Perhaps the most important compounds identified in the roasted sesame oils are 2-furfurylthiol and guaiacol. Using aroma extract dilution analysis method, these two compounds have been characterized by Schieberle (92) to be the most odor-active compounds in roasted sesame seeds. 2-Furfurylthiol, having an intense coffee-like odor, increased from 16 ppb in roasted oil processed at 160°C for 30 min to 158 ppb in the oil processed at 200°C for 30 min (Table 12). Guaiacol has a burnt and smoky odor with an extremely low-odor threshold of 0.02 ppt in... 

Cemy, C., Grosch, W. Evaluation of potent odorants in roasted beef by aroma extract dilution analysis. Z. Lebensm. Unters. Forsch. 1992, 194. 322-325. 

Schnermann, P, Schieberle, P. Evaluation of key odorants in milk chocolate and cocoa mass by aroma extract dilution analysis. J. Agric. Food Chem. 1997,45, 867-872. 

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. 

Guth, H., Grosch, W. (1993) Identification of potent odorants in static headspace samples of green and black tea powders on the basis of aroma extract dilution analysis (AEDA). Flavour Fragrance J. 8, 173-178... 

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)... 

Table n. Predominant Odorants Detected by Aroma Extract Dilution Analysis of Rice Bran Hydrolyzed... 

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. 

---