Odor furanone

In an attempt to use the chemical constituents of the Quararibea-Matisia complex as an aid in their classification, these simple testing procedures were applied to 20 Central American samples representing either of the two genera. The highly odorous furanones, as well as positive alkaloid tests, were noted in 13 of these samples and absent in seven. The suggestion is that the former represent... 

The potent odorants of Swiss cheese have been evaluated by the methods reported in 6.2.4.2 [51-53]. Table 6.32 shows the identified neutral odorants. Furanones nos. 7 and 8 are of special interest as there are indications that - in addition to sweet tasting calcium and magnesium propionate ]54] - they contribute to the sweet and caramellike note which has been perceived in the flavour profile of emmental ]55], Further experiments revealed that lactic acid bacteria cause the production of furanone no. 7 in Swiss cheese ]56],... 

Although most consumers appreciate the fieriness of chile, capsaicinoids are not perceived through odor or taste receptors but through the nociceptive pain receptors described earlier. The compounds in chile fruit that create the flavor and aroma are produced in the fruit wall. Buttery et al. [90] generated vacuum steam distilled oil from green bell pepper macerate, with well over 40 peaks on subsequent GC/MS analysis. Of these peaks, the major flavor compound associated with bell pepper aroma was 2-methoxy-3-isobutylpyrazine (Fig. 8.1). They also reported several monoterpenoids in abundance, limonene, trans- 3-ocimene, and linalool as well as other aliphatic aldehydes and ketones. The flavor composition of dried red bell pepper powder (sweet paprika) extracted with ether identified 44 key peaks by GC/MS [91]. In these dried samples the key compounds were P-ionone and several furanones. The post-harvest processing and the different fruit maturities as well as possible varietal differences are all causes for the different aromatic profiles. 

Aliphatic sulfur compounds, in particular disulfides such as methyl propyl disulfide, dipropyl disulfide, and especially cis- and /ran -propenyl propenyl disulfide are mainly responsible for the typical odor of onion oil [235]. The presence of 2-hexyl-5-methyl-3(2H)-furanone [33922-66-6] is a characteristic of authenticity [235a]. 

In the case of boiled beef the results of AEDA were compared with those of AECA. Table 16.4 indicates that they agreed except in three cases. The odour potencies of 4-hydroxy-2,5-dimethyl-3(2H)-furanone, 3-mercapto-2-pentanone and methional were more than one dilution step higher in AECA than in AEDA [56]. Most likely, portions of these odorants had been lost during concentration of the extract for AEDA. AECA was also used in studies on the aroma of pepper [55], coffee [57] and Camembert cheese [58]. 

The influence of the sensitivity of the assessors on AEDA has been studied [11], with the result that the differences in the FD factors determined by a group of six panellists amount to not more than two dilution steps (e.g. 64 and 256), implying that the key odorants in a given extract will undoubtedly be detected. However, to avoid falsification of the result by anosmia, AEDA of a sample should be independently performed by at least two assessors. As detailed in [6], odour threshold values of odorants can be determined by AEDA using a sensory internal standard, e.g. ( )-2-decenal. However, as shown in Table 16.6 these odour threshold values may vary by several orders of magnitude [8] owing to different properties of the stationary phases. Consequently, such effects will also influence the results of dilution experiments. Indeed, different FD factors were determined for 2-methyl-3-furanthiol on the stationary phases SE-54 and FFAP 2 and 2 , respectively. In contrast, 5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone showed higher FD factors on FFAP than on SE-54 2 and 2, respectively. Consequently, FD factors should be determined on suitable GC capillaries [8]. However, the best method to overcome the limitations of GC-O and the dilution experiment is a sensory study of aroma models (Sect. 16.6.3). 

The majority of the more than 100 odorants (reviewed in [1]) synthesised for use as internal standards are labelled with deuterium. However, during the quantification procedure some deuterated odorants might undergo deuterium-protium exchange, which would falsify the results. Examples are 4-hydroxy-2,5-dimethyl-3(2H)-furanone (furaneol) [68, 69] and 3-hydroxy-4,5-dimethyl-2(5H)-furanone (sotolon) [70], which are consequently labelled with... 

In the case of pineapples, the 12 odorants listed in Table 16.7 were dissolved in water in concentrations equal to those determined in the fruit [50]. Then the odour profile of this aroma model was evaluated by a sensory panel in comparison to fresh pineapple juice. The result was a high agreement in the two odour profiles. Fresh, fruity and pineapple-like odour notes scored almost the same intensities in the model as in the juice. Only the sweet aroma note was more intense in the model than in the original sample [50]. In further experiments, the contributions of the six odorants showing the highest OAV (Table 16.7) were evaluated by means of omission tests [9]. The results presented in Table 16.8 show that the omission of 4-hydroxy-2,5-dimethyl-3(2H)-furanone, ethyl 2-methylbutanoate or ethyl 2-methylpropanoate changed the odour so clearly that more than half of the assessors were able to perceive an odour difference between the reduced and the complete aroma model. Therefore, it was concluded that these compounds are the character-impact odorants of fresh pineapple juice. 

A number of solvents have been used to extract volatiles for aroma analysis but the optimum choice depends on a compromise. Table Gl.1.2 lists the most common solvents used to extract odorants from foods. Although pentane and ethyl acetate are flammable, they have a very low toxicity, represent extremes in polarity, and a sequential extraction using these two solvents will remove most of the volatile odorants from aqueous samples (see Basic Protocol 2) however, if the desire is to do a simpler one-step extraction, then a solvent should be chosen with a polarity that will extract the volatiles of interest. For example, maltol is not extracted well with pentane, and 4-hydroxy-2,5-dimethyl-3(2H)-furanone, the smell of strawberry, is almost insoluble therefore, the choice of the optimum solvent depends on the analyte and may require some testing to find. 

As shown in Table 6, odor thresholds in air are generally much lower than those in an oil. But, the most important point is that the ratios oil/air differ significantly between odorants. For example, compared with 4-hydroxy-2,5-dimethyI-3(2H)-furanone (HDF) the odor threshold of 2,3-butandione is fifteen-fold higher in air, but is eleven-fold lower in oil (Table 6). This implies that compared with HDF the flavor contribution of 2,3-butandione to a fat-rich product might be under-estimated on the basis of FD-factors. 

In Figure 7, the labelled internal standards used for the quantification of eight selected key sesame odorants identified on the basis of AEDA results [46, 52] are shown. Most of them were labelled with deuterium since their preparation was relatively inexpensive. In the case of 4-hydroxy-2,5-dimethyl-3(2H)-furanone, the labelling had to be performed via the more expensive carbon-13 labelled intermediates [68], since the deuterated standard underwent significant protium-deuterium exchanges (unpublished data). 

Influence of additions of 4-hydroxy-2,5-dimethyI-3(2H)-furanone on the odor of a pale lager beer [181 ... 

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

Herz and Chang (21) examined several furan compounds which had a wide variety of aromas, but none of them were meaty, Furans that do not contain sulfur are usually fruity, nutty, and caramel-like in odor. The furanones described above have burnt pineapple and roasted chicory odors, but these contribute to overall flavor impression of meat and important N and S meat flavor compounds might be formed from them during cooking. 

Figure 1. Reaction of 4-hydroxy-5-methyl-3(2H)-furanone with hydrogen sulfide to form mercaptofurans and mercaptothiophenes having beef-like odors (31).

From the wine aromas of Pollux, Castor, and Riesling grapes, Rapp et al. and Schreier and Paroschy have isolated an undesirable strawberry aroma by GC-MS (80V13, 81MI112). This lactone was characterized as 2,5-dimethyl-4-hydroxy-2,3-dihydro-3-furanone 8 ("furaneol") having an odor threshold of 50-100 ppb. 

In addition to GC-MS, recent studies have focused on the identification and quantitative analysis of impact odorants in botrytized wines using gas chromatography-olfactometry (GC-O) analysis. Sarrazin et al. (2007a) investigated numerous botrytized and nonbotry-tized Sautemes wines. They could identify several key odorants that were responsible for the sensory differences between the wines, notably 3-mercaptohexan-l-ol, various furanons, ethyl-hexanoate, methional, phenylethanol, phenylacetaldehyde, sotolon, p-damascenone, and 2-methyl-3-furanthiol. 

Furans are the most abundant products of the Maillard reaction and they account for the caramel-like odor of heated carbohydrates (8). Some sugar degradation compounds, such as maltol, isomaltol, 4-hydroxy-5-methyl-3(2H)-furanone, 2,5-dimethyl-4-hydroxy-3(2H)-furanone, and 2-hydroxy-3-methyl-2-cyclopentene-l-one (cyclotene), have odors usually described predominantly... 

Hodge et al. (45) discussed mechanisms for formation of methyl furanones and related substances from Amadori compounds. They have been produced by heating D-ribose and D-ribose phosphate with ammonia (46 47). Hicks and Feather (48) demonstrated that the Amadori compound 1-benzylamino-l-deoxy-D-threo-pentulose dehydrates to 4-hy-droxy-5-methyl-3(2H)-furanone and it has also been identified as a degradation product of L-ascorbic acid. This compound is believed to be formed from ribose-5-phosphate, and gained prominence when it was isolated from beef by Tonsbeck et al. (49). It became more apparent as a precursor of meat flavor when Van den Ouweland and Peer (50) reacted it and its thio analog with HaS to produce a number of sulfur compounds, some of which had meaty odors. 

Dimethy1-U-hydroxy-3 (2H)-Furanone Odor of roasted chicory roots (102). 

Another group of compounds that have been related to the aroma of heated foods is the furanones. Teranishi (1971) summarized the findings on several of the furanones (see Figure 7-23). The 4-hydroxy-2,5-dimethyl-3-dihydrofuranone (1) has a caramel or burnt pineapple odor. The 4-hydroxy-5-methyl-3-dihydrofuranone (2) has a roasted chicory root odor. Both compounds may contribute to beef broth flavor. The 2,5-dimethyl-3-dihydrofuranone (3) has the odor of freshly baked bread. Isomaltol (4) and maltol (5) are products of the caramelization and pyrolysis of carbohydrates. 

In a disclosure regarding the use of alicyclic carboxylic acid oxycarbonylmethyl esters and their use as odorants and perfumes, a composition was described in which two furan compounds were components <2005W02005108534>. 4,5-Dimethyl-3-hydroxy-2(577)-furanone 80 and 3a,6,6,9a-tetramethyldodecahydronaphtho[2,l- ]-furan 18 were present in <2% in the described perfume. In another fragrance-related application, compound 18 was a component of a perfume composition which was added to a shampoo formulation designed to enhance permeation as well as provide desired fragrant effects <2002JPP2002241238>. The fused tricyclic furan 18 was incorporated as 20% of the perfume mixture of which that was a component of the shampoo in 0.7%. 

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). 

The volatiles of fresh pineapple (Ananas comosus [L] Merr.) crown, pulp and intact fmit were studied by capillary gas chromatography and capillary gas chromatography-mass spectrometry. The fnjit was sampled using dynamic headspace sampling and vacuum steam distillation-extraction. Analyses showed that the crown contains Cg aldehydes and alcohols while the pulp and intact fruit are characterized by a diverse assortment of esters, h rocarbons, alcohols and carbonyl compounds. Odor unit values, calculated from odor threshold and concentration data, indicate that the following compounds are important contributors to fresh pineapple aroma 2,5-dimethyl-4-hydroxy-3(2H)-furanone, methyl 2-methybutanoate, ethyl 2-methylbutanoate, ethyl acetate, ethyl hexanoate, ethyl butanoate, ethyl 2-methylpropanoate, methyl hexanoate and methyl butanoate. 

Compared to emmental cheese, the aroma of gruyere cheese is more intensely sweaty and less caramel-like [55]. The composition of the key odorants reflects these differences as the concentrations of the caramel-like smelling furanones are lower and that of methylbutyric acid is higher [57, 58[. 

Omission experiments [101] confirmed earlier assumptions 77037 that 2-furfurylthiol (no. 3) is the outstanding odorant among the aroma compounds of coffee. In addition, it was shown that 4-vinylguaiacol (no. 19), pyrazines nos. 8-10, furanones nos. 13-16 and carbonyl compounds nos. 22-26 had the greatest impact on the coffee aroma. 

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