Caramel furanone

As for coriander, in the unripe fruits and the vegetative parts of the plant, aliphatic aldehydes predominate in the steam-volatile oil and are responsible for the peculiar aroma. On ripening, the fruits acquire a more pleasant and sweet odour and the major constituent of the volatile oil is the monoterpene alcohol, linalool. Sotolon (also known as sotolone, caramel furanone, sugar lactone and fenugreek lactone) is a lactone and an extremely powerful aroma compound and is the major aroma and flavour component of fenugreek seeds (Mazza et al., 2002). 

A flavor is tried at several different levels and in different mediums until the most characteristic one is selected. This is important because the character of a material is known to change quaUty with concentration and environment. For example, anethole, ben2aldehyde, and citral taste different with and without acid. Gamma-decalactone has different characters at different levels of use. -/ fZ-Butyl phenylacetate with acid is strawberry or fmity without acid it is creamy milk chocolate. 2,5-Dimethyl-4-hydroxy-3-(2Fi)-furanone with acid is strawberry without acid it is caramel or meat. 

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. 

Amongst furans are several compounds of great importance in fragrances and flavours. The rose owes some of its odour to a terpenoid furan, rosefuran, coffee some of its characteristics to furylmethanethiol and related compounds. Compounds like the 3-furanone derivative furaneol (10) are particularly interesting for their odours depend upon concentration— furaneol can seem to resemble pineapple, caramel, burnt toast etc. Furaneol is a dihydrofuran-3-one dihydrofuran-2-ones are obviously lactones and are usually dealt with as such. 

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 7.10 Structures of volatile compounds characterized from toasty caramel aroma released in wine from toasted woods during aging. (1) 3,5-dihydroxy-2-methyl-4H-pyran-4-one (2) 3-hydroxy-2-methyl-4H-pyran-4-one (3) 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one (DDMP) (4) 4-hydroxy-2,5-dimethylfuran-3(2H)-one (furaneol) (5) 2,3-dihydro-5-hydroxy-6-methyl-4H-pyran-4-one (dihydromaltol) (6) 2-hydroxy-3-methyl-2-cyclopenten-l-one (or cyclotene) (Cutzach et al., 1997 ) (7) 3-hydroxy-4,5-dymethyl-2(5H)-furanone (Sotolon Camara et al., 2006a,b,c) (8) 2-furanmethanethiol (furfurylthiol Tominaga et al., 2000). 

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... 

C, no esters and furanones are found, but thiazoles, cyclopen-tenones and other heterocyclic compounds dominate. These data imply that esters and furanones are stable at mild temperatures while the formation of thiazoles, cyclopentenones and other heterocyclic compounds require a higher temperature. Also at 160°C, trithiolanes, thiophenones and 2,4-hexanedione predominate, indicating that formation of such compounds is favored by a medium temperature. Bread, crusty and caramel aromas were found in the 100°C sample, pot-roasted, roasted, meaty and clean aromas were found at 160°C, and roasted, roasted-meat, chemical and off-notes were produced at 200°C. 

Furanones and pyranones are oxygen-containing heterocyclic compounds associated with caramelized flavor notes. Most common flavors of these compounds are caramel-like, sweet, fruity and burnt (40). 2,5-Dimethyl-4-hydroxy-3(2H)-furanone (DMHF) was one... 

Furanones and pyranones constitute a family of compounds that derive from a common a-dicarbonyl intermediate, namely, CHj-CO-CO-(CHOHJn-CHjR (where R-H or OH). Acetylformoin, which has a fruity-caramel aroma, has been isolated from browned instant orange juice (43) and from a sugar model system containing a catalyst (38). It can be formed by dehydration and cyclization of methyl dihydroxy-ethyl reductone (enediol of the methyl dicarbonyl intermediate), but it decomposes easily in air to pungent compounds (44). 

Hydroxy-5-methyl-3(2H)-furanone (norfuraneol) is an important contributor to cooked beef flavour, although it has a caramel-type odour. It can be obtained by heating xylose, ribose, or ribose-phosphate with amine salts. It is thought to be formed by 2,3-enolisation, probably as in Scheme 3.1. 

The typical caramel flavor is the result of a number of sugar fragmentation and dehydration products, including diacetyl, acetic acid, formic acid, and two degradation products reported to have typical caramel flavor by Jurch and Tatum (1970), namely, acetylfor-moin (4-hydroxy-2,3,5-hexane-trione) and 4-hydroxy-2,5-dimethyl-3(2H)-furanone. 

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. 

Hydroxy-2,5-dime- thyl-3(2H)-furanone (Furaneol ) Eructose-1,6-diphosphate Zygosaccharomyces rouxii Caramel, roasty... 

Hydroxy-2,5-dimethyl- 3(2H)-furanone Fructose-1,6-diphosphate, lactaldehyde Aldolase, triosephosphate isomerase Caramel, roasty... 

Group 13 sets the frame for the complex world of furanones. Important fruity and caramelic representatives are Furaneol (Flavis 13.010, FEMA 3174) and the corresponding methoxy derivative mesifuran (Flavis 13.089, FEMA 3664). In addition the linalool oxides and angelica lactone are in this group. 

Both 4-hydroxy-2,5-dimethyl-3(2H)furanone (HDMF trade name Furaneol Fig. 3.60) and 4-hydroxy-5-methyl-3(2H)-furanone (HMF Fig. 3.60) contribute to flavour at normal usage level they are, however, also enhancers of fruity and creamy odour impressions (see Tab. 3.46). Both furanones have caramel-like odours with HDMF possessing an additional burnt pineapple odour [1, 21]. The odour threshold of Furaneol has been reported to be 0.00004 ppm in water at 20°C [21 ]. 

Cyclopentenolones with a planar vicinal enol-oxo configuration are known to be powerful aroma active substances with distinct caramel notes. By methylation of the enolic function, this flavour impression is changed drastically to a sweet, mildew, and mouldy odour in the case of 2,5-dimethyl-4-methoxy-3-[2H]-furanone (2). This so-called mesifurane as well as pineapple ketone (1) were stereodifferentiated with modified cyclodextrin [103], Although (1) and (2) can be stereoanalyzed without any racemization, both compounds were detected in strawberries, pineapples, grapes and wines as racemates (Fig. 6.43). 

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[. 

The aroma is changed when a brew is prepared from ground coffee. Caramel-like, buttery and phenolic notes become more intense. AEDA shows that this change in the aroma profile is caused by a shift in the concentrations [102]. As detailed in Table 6.52, the polar odorants are preferentially extracted by hot water leading to yields higher than 80% for S-compounds nos. 1 and 4, furanones nos. 13 and 14, vanillin (no. 20) and pentanedione (no. 28). On the other hand, the yield of the character impact odorant of ground coffee, 2-furfurylthiol, is with 19% relatively low. 

Hydroxy-4,5-dimethyl-2(5//)- p-Damascenone furanone (Caramel like) (Sweet, Honey-like)... 

C7H10O3, Mx 142.15, has been identified in, e.g., coffee and melon. The tautomer mixture is a clear slightly yellowish liquid, bpQ02 tpa 82-83 °C, elf 1.137, nf 1.511 with sweet, caramel, fruity, bread-like odor. One commercially applied synthesis is the condensation of 2-pentene nitrile with ethyl lactate followed by oxidation of the intermediate 4-cyano-5-ethyl-2-methyldihydro-3(2/f)-furanone with monoperoxysulfate [189]. 

Using odor units, Tressl (1989) found that some of the compounds that contribute the most are furfurylthiol (Section 5,1.128, sulfury), 4-hydroxy-2,5-dimethyl-3(2//)-furanone (Furaneol", Section 5, 1.100, caramel), 2-isobutyl-3-methoxypyrazine (Section 5,0.77, green), 2- and 3-methylbutanal (Section 5,C.12 and 5,C.13, malty, burnt), guaiacol (Section 5,H.33), and 4-vinylguaiacol (Section 5,H.36, smoky burnt). 

C, and these are known not to be components of essential oil of Pistacia vera, but are the browning reaction products (e.g. furfural, 2-furanmethanol, acetylfuran, 2-furanone, 2,4-dimethyl-furan, furfuiyl acetate and furfuryl alcohol). Most of these components are low in concentration at 200 °C, however show a significant increase at 250 °C. The browning reaction products may be produced either by caramelization or by Maillard reactions during the higher temperatures of 200 and 250 °C. 

The furanones and pyranones are oxygen-containing heterocyclic compounds associated with both caramelized and Maillard flavors [57]. The odor characters most common to this group of compounds would be caramel-like, sweet, fruity, butterscotch, nutty, or burnt. They predominate both in proportion and absolute amount in condensates of carbohydrates that are subjected to browning reactions [47]. 

The caramel character is associated with a planar, contiguous C-alkyl-enol carbonyl group (aUcyl-C=C(OH)-C 0) in the molecule [58]. Maltol (Figure 5.6a) was one of the first compounds in this class to be identified in foods. Ethyl maltol (2-ethyl-3-hydroxy-4(4H)-pyranone) also has a caramel odor but is approximately four to six times stronger in flavor strength than maltol. Furaneol (4-hydroxy-2,5-dimethyl-3(2H)furanone, Figure 5.6b) is the trade name of a compound used extensively in the flavor industry and, like maltol and ethyl maltol, is a flavor enhancer for sweet products. Furaneol itself has a burnt pineapple odor. 

Caramel 25-Dimethyl-4-hydroxy-3(2H)- furanone Caraway d-Carvone... 

The compound 4-hydroxy-2,5-dimethyl-3(2H)-furanone (furaneol, I in Formula 4.67) is the corresponding degradation product from the 6-deoxy-L-mannose (rhamnose) (Formula 4.69). Furaneol can also be formed from hexose phosphates under reducing conditions (cf. 4.2.4.4.6) and from C-3 fragments (cf. Formula 4.47). With a relatively low odor threshold value, furaneol has an intensive caramel-hke odor. It is interesting that furaneol is also biosynthesized in plants, e. g., in strawberries (cf. 18.1.2.6.9) and pineapples (cf. 18.1.2.6.10). 

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