Strawberry furaneol

Fig. 17.6 Stereodifferentiation of Furaneol (J) and mesifuran (2) from strawberries a HPLC chromatogram of strawberry extract mesifuran (fraction ft), Furaneol (fraction/2) b HPLC fractions, analysed by enantioselective capillary GC [23]...

Furanones have been prepared by treatment of y-ketoacids with acetic anhydride. Furanones have also been formed by hydrolysis and dehydrobromination of j8,y-dibromoacids (B-50MI31200). The furan-3(2//)-one system (164) has been prepared by intramolecular cyclization of the diazoketones (163) (74TL3073). Some natural 3(2//)-furanones are known furaneol (166), occurring in strawberries and pineapples, is obtained by acid or base treatment of the dihydroxydiketone (165) (73JOC123). 

Only a few natural 3(2H)-furanones have been found. Furaneol (166) is present in strawberries and pineapples (73JOC123). 

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. 

By applying the concept of odour values (2j[) to this class of compounds only Furaneol and Maltol contribute to coffee flavor. Both constituents are known as important flavor compounds and are used as nature identical flavorings in many foods. Furaneol contributes a fragrant caramel note to coffee and is known as important compound in pinapple and strawberries. The consumption of Furaneol in the USA in these products is respectively 41,800 to 2,650 to 1,100 kg (per year) compared to 2,718 kg of synthesized Furaneol used in nature identical flavoring. Similar figures were presented for Maltol and other coffee compounds by Stofberg and Grundshober (8J. 

Furaneol (= 2,5- Fragaria virginiana (strawberry) (Rosaceae), OR-R (candy cotton, burnt... 

Oxidation. As one step in the synthesis of furaneol (3, a flavor principle of pineapples and strawberries), Buchi et a . wished to effect hydroxylation of 2,5-dimethyl-2,5-dimethoxy-2,5-dihydrofurane (1). They tried oxidation of(1 15.8 mmole) with potassium chlorate (22.8 mmole) and osmium tetroxide (0.3 mmole) in aqueous letrahydro-furane containing sodium bicarbonate at 30° for 63 hr. however, the expected diol... 

Re, L., Maurer, B., Ohloff, G. A simple synthesis of 4-hydroxy-2,5-dimethyl-3(2//)-fiiranone (Furaneol), an important aroma compound of pineapple and strawberry. Helv. Chim. Acta 1973, 26, 1882-1894. 

Furaneol is formed when the sugar rhamnose is heated in the presence of a substance containing an amino group through a Maillard reaction (Fig. 3.62). HMF results from heating of fructose (Fig. 3.63). Both furanones occur in various foods. For example, Furaneol has been identified in pineapple, strawberries and popcorn both Furaneol and HMF have been found in meat broth [21 [. Both furanones are applied as flavour modifiers in foods where maltol and ethyl maltol are used [1[. 

Mosandl [313, 314] has found 8 C-values from -33.6 to -34.9%c for 2,5-dimethyl-4-methoxy-2H-furan-3-one ( mesifuran ) and -23.7 to -26.8%c for 2,5-dimethyl-4-hydroxy-2H-furan-3-one ( furaneol ) from strawberries. This difference, even found in products from the same source, suggests independent biosyntheses. Another natural sample of mesifuran showed a very positive 8 C-value (-18.5%c), which indicates its origin from a CAM-plant (pineapple). However, the recent data by Preston et al. [207] show that furaneol from this provenience can, but must not have quite positive 8 C-values. This and the seeming coincidence of the data for natural and nature-identical mesifurane show that the situation with these compounds is still not quite clear. 

Furaneol is a natural flavour principle, isolated from pineapple and strawberry, and used in the food and... 

Using a model system with water solutions of Furaneol and adding an internal standard to die ether extract it was found that the averse absolute recovery for Furaneol was 19% and for Maltol 32%. With Maltol as internal standard, the method was applied to the analysis of Furaneol in fresh tomatoes and fresh strawberries and gave quantitative data consistent with published data for these products. 

Biichi G. Demole E. and A.F. Thomas A.F. (1973) Synthesis of 2,5-dimethyl-4-hydroxy-2,3-dihydrofuran-3-one (furaneol), a flavor principle of pineapple and strawberry. J. Org. Chem. 38, 123. 

Low concentrations of ethyl-2-and 3-mercapto-propionate, mentioned earlier in this chapter, have a fruity aroma, whereas in larger quantities they have sulfurous smells. Acree et al. (1990) also demonstrated the presence of 2-amino-acetophenone in Vitis labrusca, as well as two furanones (4-hydroxy-2,5-dimethyl-3-furanone, commonly known as furaneol, and 4-methoxy-2,5-dimethyl-3-furanone) reminiscent of strawberries (Rapp et al., 1980). Most of these compounds have also been identified in Vitis vinifera wines, but at lower concentrations (Guedes de Pinho, 1994 Moio and Etievant 1995). 

Strawberry flavor The strawberry aroma is made up of caramel-like [ impact compounds Furaneol, mesifuran (see Furaneol )], fruity [ fruit esters, 4-decanolide (see alkanolides)], green [( )-2- hexen-l-ols, ( )-2- hexenals, 2-hexenyl acetate (see fruit esters)], and flowery notes ( linalool, methyl anthran-ilate). Particularly important fruit esters are ethyl butanoate and hexanoate as well as the corresponding methyl esters. Free acids such as 2-methylbutanoic acid (C5H,o02, Mr 102.13, CAS [116-53-0]) and trace substances, e.g., dimethyl sulfide and vanillin, round off the aroma. 

Synonyms Alletone Alnose Dimethylhydroxy furanone 2,5-Dimethyl-4-hydroxy-3-furanone 2,5-Dimethyl-4-hydroxy-3-(2H)-furanone Furaneol 3(2H)-Furanone, 2,5-dimethyl-4-hydroxy- Pineapple ketone Strawberry furanone... 

FIGURE 4.10 The biosynthetic pathway for the formation of furaneol and its derivatives in strawberry. (From Roscher, R., R Schreier, W. Schwab, Metabolism of 2,5-dimethyl-4-hydroxy-2H-furan-3-one in detached ripening strawberry fruits, J. Agric. Food Chem., 45(8), p. 3202, 1997. With permission.)... 

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). 

Furaneol and norfuraneol are significant sensorially active substances with low threshold concentrations. They are synthesised and added to numerous aroma compositions with a pleasant sugary, jammy, fruity and caramel flavour reminiscent of cooked strawberries and pineapple, which is where furaneol was identified for the first time (see Section 8.2.11.1.1). 

An important compound is 4-hydroxy-5-methyl-2H-furan-3-one, known as norfuraneol. Norfuraneol occurs in caramel, roasted chicory root and also in meat broth. 4-Hydroxy-2,5-dimethyl-2H-furan-3-one, known as furaneol, strawberry furanone or pineapple furanone, arises in the Maillard reaction from L-rhamnose (Figure 4.39) and in a reaction of methylglyoxal with hydroxyacetone (Figure 4.41). It occurs, for example, in strawberries, pineapple, roasted almonds, popcorn, meat broth and a number of other foods as a racemic mixture. The structure of (+)-(J )-furaneol responsible for the characteristic odour is given in formula 8-160. The odour of furaneol is sugary, jammy and reminiscent of strawberries and, at higher concentrations, caramel (threshold concentration is... 

An example of a furanone with methylated hydroxyl in position C-4 is 4-methoxy-2,5-dimethyl-2H-furan-3-one, also known as mesifurane, which is derived from furaneol. (-F)-(R)-Mesifurane (8-163) has a burnt and caramel-Hke odour, but is more subtle and mellow than the odour of furaneol. Mesifurane accompanies furaneol in fruits (such as pineapple, raspberry, strawberry and grape) and other foods. 2,5-Dimethyl-2H-fiiran-3-one, which does not contain the C-4 hydroxy group occurs as a constituent of bread and coffee flavour its odour resembles bread. 

Nowadays, more than 400 compounds forming the large-fruited strawberry Fragaria ananassa and other hybrids, Rosaceae) flavour are known, yet the importance of many of them is not yet fuhy understood. Besides a number of esters (mainly butanoates) and aldehydes, such as (Z)-hex-3-enal, which generally have green and fruity flavours, 4-hydroxy-2,5-dimethyl-2 f-furan-3-one (furaneol, also known as strawberry or pineapple furanone) and its methyl ether 4-methoxy-2,5-dimethyl-2 f-furan-3-one... 

Pineapple Ananas comosus, Bromeliaceae) aroma consists of about 200 alcohols, esters, lactones, aldehydes, ketones, monoterpenes, sesquiterpenes and other volatiles. About 80% of the total volatile substances are esters. The main components in the green fruit are ethyl acetate, ethyl 3-(methylthio)propionate (8-189) with a distinctive pineapple aroma and ethyl 3-(acetoxy)hexanoate (8-190). The ripe fruit contains, as the main esters, ethyl acetate, (2J ,3i )-butane-2,3-diol diacetate (8-191) and ketone 3-hydroxy-butan-2-one. An important compound for the typical character of pineapple aroma, as in strawberry aroma, is 2,5-dimethyl-4-hydroxy-2//-furan-3-one (furaneol), present as a glycoside, and 2,5-dimethyl-4-methoxy-2H-furan-3-one. 

Table 10 Results Reported in the Literature on the Presence of Furaneol and Its Methylether in Strawberries—Effect of Analytical Conditions...

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