CHARM analysis

Charging, batteries, 3 410 CHARM analysis, 11 519-520 Char Oil Energy Development (COED) process, 6 853... 

Ethyl 2-methylbutanoate, 2-methylbutyl acetate and hexyl acetate contribute most to the characteristic aroma of Fuji apples [49]. In Red Delicious apples, ethyl butanoate, ethyl 2-methylbutanoate, propyl 2-methylbutanoate and hexyl acetate contribute to the characteristic aroma as determined by Charm-Analysis and/or AEDA [50, 51]. In a comparative study of 40 apple cultivars, the highest odour potency or Charm value was found for -damascenone [52]. This compound usually occurs in a glycosidically bound form and is present primarily in processed products owing to hydrolysis of the glycoside bond after crushing fruit cells [53]. -Damascenone has a very low odour threshold with a sweet, fruity, perfumery odour and is not typical of apple aroma in gen-... 

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. 

Gas chromatography/olfactometry (GCO) methods have been developed as screening procedures to detect potent odorants in food extracts. The FD-factors or CHARM values determined in food extracts are not consequently an exact measure for the contribution of a single odorant to the overall food flavor for the following reasons. During GCO the complete amount of every odorant present in the extract is volatilized. However, the amount of an odorant present in the headspace above the food depends on its volatility from the food matrix. Furthermore, by AEDA or CHARM analysis the odorants are ranked according to their odor thresholds in air, whereas in a food the relative contribution of an odorant is strongly affected by its odor threshold in the food matrix. The importance of odor thresholds in aroma research has been recently emphazised by Teranishi et al. [58],... 

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. 

With regard to a glucose-proline system, Roberts and Acree277 have examined the sensory aspects in much more detail by applying Charm analysis (see the Olfactory Threshold section above). Four compounds provided most of the aroma 2-acetyl-3,4,5,6-tetrahydro-l//-pyridine (burnt, caramel 63%), 2-acetyl-1-pyrroline (popcorn 19%), 2-acetyl-l,4,5,6-tetrahydro-l//-pyridine (burnt, caramel 12%), and UDMF (cotton candy 4%). All Maillard systems of interest need to be submitted to similarly detailed analyses. 

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). 

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)... 

Fig. 8E.1 Scheme showing the basics of AEDA and Charm analysis. Different sequential dilutions of the sample extract are analyzed in the GC-O system. In AEDA the judge simply marks the retention times and the odor descriptions. The FD value is R , where p is the p-th dilution of the extract at which the odor was last detected and R is the dilution rate (3 in the figure). In Charm, he/she presses the space bar of the computer during the odor detection, and the outputs are combined to form the Charm chromatogram... 

The knowledge that not all of the volatiles (e.g. more than 800 in roasted coffee) [5] that occur in a food contribute to its aroma was the rationale for changing the methodology of analysis. Since 1984, when the procedure for charm analysis was published [4], techniques have been developed that focus on the identification of compounds contributing to the aroma with higher OAV. 

Separation of the concentrate by GC and localisation of key-odorants by charm analysis or AEDA... 

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. 

Charm analysis constructs chromatographic peaks, the areas of which are proportional to the amount of the odorant in the aroma concentrate [4], The difference between the two methods is that charm analysis measures the dilution value over the entire time the compounds elute, whereas AEDA simply determines the maximum dilution value [8],... 

Charm analysis and AEDA both constitute screening procedures, as the results are not corrected for the losses of odorants during the isolation procedure. Furthermore, in GCO, the odorants are completely volatilised and then evaluated by sniffing, whereas the volatility of the aroma compounds in foods depends on their solubility in the aqueous and/or oily phase as well as their binding to non-volatile food constituents. To elucidate which of the compounds revealed in the dilution experiments contribute with high OAV to the aroma, quantification of the odorants with higher FD factors and calculation of their OAVs are the next steps in the analytical procedure. 

Isolation of Nonvolatile Precursors of /3-Damascenone from Grapes Using Charm Analysis... 

Bioassay for p-damascenone. Figure 2 shows a flowchart of the bioassay for p-damascenone. Sample extracts (0.5 mL) were placed in 5 mL. 1 M citric acid and heated 12 min at 90 C in 16 x 125 mm culture tubes covered with a vented metal cap. Preliminary experiments showed little change in the p-damascenone formed after 8 min. Loss of free p-damascenone due to volatilization was prevented by cooling to room temperature in ice water. Then 0.5 mL methanol plus 1.0 mL Freon-113 was added with mixing. The Freon layer was removed, and a series of three-fold dilutions were made from it. Thus each sample in the series was 1/3 the concentration of the previous. These were stored until charm analysis. 

Charm analysis. Charm is a formal procedure to quantify human response to odor in gas chromatographic effluents, or for that matter, any technique that can deliver... 

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

The CHARM 11 and AEDA analyses based on odor detection thresholds (measurement of the odor potency) have been criticized. The conclusions as to the relative contribution of odorants to a flavor may be limited, the responses for a given compound being dependent on the concentration. The relative intensity of two odorants with the same threshold does not necessarily correspond to their relative concentrations in a mixture (Abbott et al., 1993). For these authors, the contribution of a compound to an odor is probably better determined by CHARM analysis than by AEDA, which does not take into account the duration of the smell. Other methods have been proposed for a better determination of potent odorants. 

Gaffney, B.M., M. Haverkotte, B. Jacobs, and L. Costa, 1996. Charm Analysis of two Citrus sinensis peel oil volatiles. Perf. Flav., 21 1. 

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