Odour pineapples

Ethyl Valerianate.—This ester, C HgCOOC Hj, is an oil with a pineapple odour. Its specific gravity is 0 894, and boiling-point about 133°. 

The sulfur components ethyl S-(+)-2-methylbutanoate and dimethyl trisulfide (with 0.006 and 0.01 pg/L odour thresholds in water, respectively) were reported as impact-flavour compounds in fresh Hawaiian pineapple essence prepared by solvent extraction. The major volatile components were methyl and ethyl esters [59]. 

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. 

OAVs are calculated on the basis of odour threshold values which have been estimated in a medium that predominates in the food, e.g. water, oil or starch. As an example, the OAVs of the odorants of pineapples are listed in Table 16.7. 

The highest OAVs were found for 4-hydroxy-2,5-dimethyl-3(2H)-fura-none, followed by ethyl 2-methylpropanoate, ethyl 2-methylbutanoate, methyl 2-methylbutanoate and ( ,Z)-l,3,5-undecatriene. It is assumed that these odorants contribute strongly to the aroma of pineapples [50]. However, FD factors and OAVs are functions of the odorants concentrations in the extract, and are not psychophysical measures for perceived odour intensity [71,72]. To take this criticism into account, aroma models are prepared on the basis of the results of the quantitative analysis (reviewed in [9]) and in addition omission experiments are performed [9]. 

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. 

Table 16.8 Odour of the model for pineapple as affected by the absence of one compound [50]...

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. 

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 ]. 

Ripe guavas develop such a powerful odour that a whole room can be perfumed by their smell. The taste varies according to its degree of ripeness from sour, green, harsh, over fresh, fruity pineapple and pear like to spicy, cinnamon, creamy, quincelike with some astringent aspects. 

CIC The powerful odour is dominated by 2-isobutyl thiazole and 3-pentanethiol. The green notes are lipid degradation products like (E)-2-hexenal, hexanal and higher unsaturated aldehydes, the pineapple-pear like fruity notes are derived from methyl hexanoate, ethyl-2-hexenoate and hexyl acetate. The spicy cinnamon notes are represented by 3-phenyl propyl acetate, cinnamyl acetate, methyl cinnamate, ethyl cinna-mate and ciimamaldehyde. Gamma-decalactone and 2,5-dimethyl-4-hydroxy-furan-3(2H)-one and 3-hydroxy-2-butanone add the sweet, creamy body. Beta-famesene, citronellol, 2-phenylethanol, beta-ionone add the sweet, floral, quincelike part and methyl benzoate and ethyl benzoate impart a characteristic medicinal, exotic topnote. 

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). 

The relative peak area of esters found in the pea cultivars is shown in Fig. 5. No differences (P > 0.05) were found between the cultivars grown in different locations (Tables 2 4). Ethyl acetate was the most abundant ester in all the pea cultivars studied (Tables 2 4). This compound has an ether and brandy odour and a fruity, sweet taste and has also been reported in soybeans and beans (Burdock, 2002 del Rosario et al., 1984). Hexanoic acid, methyl ester also identified in the peas reportedly has an ether and pineapple odour (Burdock, 2002). 

Flavouring agent with heavy sweet odour resembling apricot/pineapple. Liq. Insol. H2O. d 1.01. Bp 227°. 

An important sulfide is methional (8-37). Methional in beer and wine is formed by the activity of microorganisms. It is partly reduced to the corresponding alcohol methionol (8-13) and reaction with acetyl-CoA yields 3-methylthiopropyl acetate (8-129), which is an important component of various fermented foods. Another ester of acetic acid 3-(methylthio)hexyl acetate is a component that posseses attractive tropical fruity notes on dilution. The less odoriferous (-)-(J )-enantiomer (8-130) is reminiscent of passion fruit, while the (-l-)-(S)-form has a more herbaceous odour. The odour thresholds of these thiols in air are 0.10 ng/1 and 0.03 ng/1, respectively. Both isomers have been found in passion fruit (Passiflora edulis, Passifloraceae), guava Psidium guajava, Myrtaceae) and aromatic white wines. Methyl-3-(methylthio)propionate, or pineapple mercaptan (8-131), has a flavour reminiscent of pineapple. S-Methylthiohexanoate (8-132) is a component of the durian fruit smell. Condensation of methional with ethanol yields (Z)-2-(methylthio)methylbut-2-enal also known as 2-ethylidenemethional (8-133), which is an important component of potato chips aroma. It also occurs in... 

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. 

Isol. from plant sources. Fragrance ingredient. Liq. with pineapple odour, dj 0.900. Fp —93.3°. Bp 119.9°. 

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