Flavor dilution

Figure 3. Flavor dilution (FD) chromatogram of the neutral/basic odorants in a pale lager beer. The numbering follows Figure 2. RI retention index on a silicone SE-54 GC stationary phase [adapted from ref. 18],...

Many aroma compounds have been identified in crackers but which ones are the most important has still not been established. Further studies of these extracts should involve the use of odor assays to sort out to aroma important compounds in crackers from the unimportant aroma compounds present. For example, the method used by Shieberle Grosch (33) to describe the odor-active components in bread in terms of their flavor dilution values and the technique called charm analysis (43, 44) both concentrate chemical investigations at retention indices with odor activity. 

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. 

Ferreira, V, Ardanuy, M., Lopez, R., and Cacho, J.F. (1998a). Relationship between flavor dilution values and odor unit values in hydroalcoholic solutions Role of volatihty and a practical rule for its estimation. J. Agric. Food Chem., 46, 4341-4346. 

Recently, AEDA and SHA-0 yielded 41 and 45 odor active compounds for Scheurebe and Gewurztraminer wines, respectively (P). Ethyl 2-methylbutyrate, ethyl isobutyrate, 2-phenylethanol, 3-methylbutanol, 3-hydroxy-4,5-dimethyl-2(5H)-furanone, 3-ethylphenol and one unknown compound, named wine lactone, showed high flavor dilution (FD)- factors (Table I) in Gewurztraminer and Scheurebe wines. 4-Mercapto-4-methylpentan-2-one belongs to the most potent odorants only in the variety Scheurebe whereas cis-rose oxide was perceived only in Gewurztraminer (Table I). 4-Mercapto-4-methylpentan-2-one was identified for the first time in Sauvignon blanc wines (JO). The unknown compound with coconut, woody and sweet odor quality, which has not yet been detected in wine or a food, was identified as 3a,4,5,7a-tetrahydro-3,6-dimethylbenzofuran-2(3H)-one (wine lactone) (JJ). 

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. 

Compound Flavor Dilution (FD) Factor Odor Description... 

FD factor (Flavor dilution factor) The ratio of concentration of a compound in the initial concentration to that in the most diluted concentration in which the odor could be detected by GCO. 

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)... 

Numbers correspond to those in Tables HI and IV. Odor quality as perceived during GCO. Retention indices calculated from GCO data, FFAP = Stabilwax DA column. Average logs flavor dilution (FD) factor (n = 2), neutral/basic fraction determined on DB-5MS and acidic fraction determined on Stabilwax DA column. Con ound tentatively identified based on con arison of odor property and retention indices with reference conq)ound. 2,5-dimethyl-4-hydroxy-3(2 -furanone. 3-hydroxy-4,5-dimethyl-2(5/0 ft iione. 3-methoxy-4-hydroxybenzaldehyde... 

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. 

FIGURE 17.4 FD (flavor dilution) factors of flavor components of green tea drinks due to the heating process. 

Kumazawa, K. and Masuda, H. 2002. Identification of potent odorants in different green tea varieties using flavor dilution technique. J. Agric. Food Chem. 50 5660-63. 

The flavor dilution (FD) factors, 2 , were obtained using the aroma extract dilution method developed by Grosch and co-workers 20. 21). The extract was diluted stepwise with dichloromethane in the volume ratio of 1 1 until odorous compounds were no longer detected by GC sniffing. 

Diode Array Detection Flavor Dilution factor... 

In an earlier study we conducted AEDA for the determination of the predominant aroma-active components of C. sativum (1), in which we determined that a nonpolar DB-5 column gave superior results during AEDA to a polar DB-WAX column. Therefore, in the present study a DB-5 column was used for AEDA and for the determination of flavor dilution (FD)-factors. For... 

Another powerful technique known as aroma extract dilution analysis is used to determine the most significant odor and flavor compounds in a complex mixture in a food product. This method determines the odor activity of volatile compounds in an extract eluted from a high-resolution capillary GC-SP column (see Table 11.9). The odor activity or impact of a compound is expressed as the flavor dilution factor (FD), which is the ratio of its concentration in the initial extract to its concentration in the most dilute extract in which the odor can be detected by GC-SP. However, the information from this technique may be of limited practical value, because it ignores the significant effect of food matrices on flavor and odor perception of mixtures of flavor and odor compounds. Advanced instrumental techniques have been developed for flavor analysis during food consumption. These techniques permitting direct mass spectrometry at atmospheric pressure are discussed in Chapter 6. 

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