Caramel aroma

Cocoa flavor. Some of the over 500 known volatile components of C. f. are already present in raw cocoa, but most are formed after diying and roasting (at 110-130 °C), mainly by Maillard or Strecker reactions from amino acids, peptides, and sugars resulting from anaerobic fermentation. C. f. is not determined by one impact compound but is rather a composition of various aromas caramel-like ( maltol, Furaneol , and 2-hydroxy-3-methy 1-2-cyclopenten-1 -one), flowery ( linalool, 2-phenylethanol, phenylacetaldehyde). 

Caramel color is a dark brown or even black product used for centuries in home cooking to provide color and specific aromas to foods. The first commercial caramel was produced in Europe about 1850. ... 

Although many routes are known for its synthesis, maltol is still isolated mainly from beechwood tar. It is used in aroma compositions with a caramel note and as a taste intensifier, for example, in fruit flavors (particularly in strawberry flavor compositions). 

CeHgOs, Mr 128.13, was found in, e.g., fenugreek, coffee, sake, and flor-sherry. Its aroma characteristic changes from caramel-like at low concentrations to currylike at high concentrations. A method described for its preparation comprises condensation of ethyl propionate with diethyl oxalate and reaction of the intermediately formed diethyl oxalylpropionate with acetaldehyde. Acidic decarboxylation of the ethyl 4,5-dimethyl-2,3-dioxodihydrofuran-4-carboxylate gives the title compound [199]. 

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. 

Pyrroles are found in the volatiles of most heated foods [29], although they have received less attention than some other classes of aroma volatiles. Some pyrroles may contribute desirable aromas, e.g. 2-acetylpyrrole has a caramel-like aroma, and pyrrole-2-carboxaldehyde is sweet and corn-like, but alkylpyrroles and ac-ylpyrroles have been reported to have unfavourable odours [22]. Many more volatile pyrroles have been found in coffee than in other foods [30], and they are common products of amino acid-sugar model systems. Pyrroles are closely related in structure to the furans, and they are probably formed in a related manner from the reaction of a 3-deoxyketose with ammonia or an amino compound followed by dehydration and ring closure (cf Scheme 12.2). 

Chemical modification of simple sugars during drying, baking, or roasting operations can either have a desirable or undesirable effect upon the organoleptic quality of the final product. We have become accustomed to the characteristic roasted or baked flavors of coffee, peanuts, popcorn, and freshly-baked bread. The color and flavor and aroma of caramel make it a useful additive for the food industry. On the other hand, the burnt flavor of overheated dry beans or soy milk reduces marketability of these products. 

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. 

As a rule furan derivatives are considered important aroma constituents from a sensory point of view. They are mainly associated with sweet, fruity, nutty or caramel-like odor-impressions. The furans have no meaty characteristics, but it seems possible that they contribute to the overall odor of broiled and roasted meat. 

As a consequence of bottle aging, carbohydrate conversions can occur, although slowly at cellar temperature, to form the caramel-like 2-furfural aroma for example, in aged Madeira wines. Rapp and Giintert (86MI141) have shown that such carbohydrate decomposition in Riesling wines leads to 2-furfural 9,2-acetylfuran 10, ethyl furan-2-carboxylate 11, 2-formyl pyrrole 12, and 5-hydroxymethylfurfural 13. 

Compared to most white and red wines, Vin Santo wines, and especially the slightly sweet and sweet styles, are characterized primarily by their flavor and taste, rather than their aroma. Accordingly, in addition to sweetness and acidity, the most used descriptors to evaluate Vin Santo in relation to its perception in the mouth are alcoholicity (warm sensation), texture, viscosity, and overall taste persistence. Among the flavor descriptors, those relating to caramelization (like flavors of honey, milk-honey candy, molasses, caramel) are the most used, as these are more suitable to describe the different Vin Santo. It is estimated that these descriptors... 

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). 

An Isolation and concentration scheme should be appropriate for the sample under Investigation. As an example of this, a distillation technique would not be satisfactory for separating caramel aroma compounds such as Maltol, Cyclotene, or Furaneol which possess an enolone structure and do not steam distil. 

With alkaline degradation, the formation of 1,2-enols is also the initial step. This reaction in turn can produce three-carbon compounds which yield a series of intramolecular reactions involving condensation and polymerization. Both acidic and alkaline caramelization produce numerous volatile and nonvolatile compounds that significantly contribute to aroma, taste, and color. 

Ofcourse, the number of components increase with rising temperature. Examples are carbocyclic compounds. Most of them are cycloalkenones and hydroxycycloalkenones. One reason for this fact is their isomerization. As we could demonstrate (12) cyclotene forms at 180° C 3 isomeric compounds and additionally 3 methylcyclopentanones or-pen-tenones via elimination of one molecule of water (Figure 2). Hydroxy-cyclopentenones and-hexenonesare well known to be important aroma compounds in caramel flavours (13,14). 

Cystine and other sulfur-containing amino acids are recognized as important precursors of food flavors, especially meat flavors (3, 11-12). DMHF, a cyclic-a-dicarbonyl, possesses a sweet, caramel and fruity aroma (13). It is found in many food sources (14-17) and is used extensively in many flavor applications (18-19). DMHF can be formed from sugar via either sugar enolization (caramelization) by a Maillard reaction then cyclization (20). 

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. 

Coffee flavor is a complex mixture of compounds belonging to many classes in distinct concentration ratios. Flament (2 ) listed 1 7 typical constituents of coffee aroma with buttery, woody, green, earthy caramel, burnt, smoky, roasted and sulfury notes, aroma and flavor qualities. 

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). 

Methylcyclopentenolone has a strong caramel-like, maple-like or licorice-like aroma (31j, and was found in browned, dehydrated orange juice at the 1 ppm level (43). Its synergistic flavor effect with other compounds, such as 5-methyl-2-furfural and N-ethylpyrrole- 2-carboxyaldehyde, was reported (43). Although it is present at levels five times below its threshold value, it still impacts on the heat-abused flavor of dehydrated orange juice. This ketone probably results from amine-assisted sugar degradation (45). 

FINAL Red-brown Dark brown Aldol condens. Polymerization Strecker degrad. COj evolution Sulfites do not decolorize Acidic fluorescence Reducing pvr. in acids Caramel, roasted aromas Colloids, melanins form... 

Many of the differences between batter, microwave, and conventionally baked cake are also observed in Figure 1. As might be expected, several compounds typically associated with browning notes were present in the conventional cake. Significantly fewer were observed in the microwave cake and batter samples. Peak 2 at 3.2 minutes, identified as isopentenal, was observed in all three samples and noted to have a caramel, tootsie roll-like aroma. However, the relative abundance of isopentenal appeared to vary dramatically between the three samples with batter having the least and conventional cake the most. 

Likewise, furfural (peak 16, 8.1 minutes) was observed in both microwave and conventionally baked cake, but at a significantly higher level in the latter. Methyl pyrazine (peak 15, 7.8 minutes), furan methanol (peak 17, 9.0 minutes), and acetyl furan (peak 22, 10.9 minutes), were present in the conventional cake samples as were two unidentified compounds (peaks 3 and 9, 3.3 and 5.0 minutes) observed to have buttery, caramel-like aromas. Several other minor peaks were also observed only in the conventional cake. It should be noted that a few nutty, brown, and potato type smells were detected in areas of the conventional cake chromatogram where no peaks were integrated. These aromas suggest the presence of other Maillard compounds in the extract at levels too low for instrumental detection. 

In general, microwave cake appeared to lack many of the nutty, brown, and caramel-type aromas observed in the conventional cake and was in fact more similar to the batter. Table 2 summarizes the predominant aranas noted from each extract in decreasing order. The predominant aromas in both batter and microwave cake were green vegetable notes. Brown, caramel, and potato notes were observed less frequently. The conventional cake profile contained more brown, caramel notes followed by butter, cucumber, potato, and finally, green vegetable aromas. 

For caramel aroma, aliphatic amino acids were required for meaty, sulfur-containing ones for nutty, amides or hydroxy ones for meaty and vegetable, sulfur-containing and aromatic ones for fragrant, aromatic ones for roasted vegetable, aromatic, sulfur-containing, acid, aliphatic and basic or amide ones for baked potato, sulfur-containing ones and for baked, secondary ones. In each case, additional amino acids were or were not present in the mixtures heated. 

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. 

Pyrazines. In the thirties, the attention on pyrazines was focused on its industrial role in dyes, photographic emulsions and chemotherapy. Its importance in life processes was indicated in its derivative, vitamin B2 (riboflavin, 6,7-dimethyl-9-(l -D-ribityl isoalloxazine). Later,in the midsixties, it was identified in foods and its contributions to the unique flavor and aroma of raw and processed foods attracted the attention of flavor chemists Pyrazine derivatives contribute to the roasting, toasting, nutty, chocolaty, coffee, earthy, caramel, maple-like, bread-like, and bell pepper notes in foods. The reader is referred to the reviews on Krems and Spoerri (88) on the chemistry of pyrazines, and the review of pyrazines in foods by Maga and Sizer (89, 90) Table XVI summaries sensory description and threshold of selected pyrazines. 

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