Blackcurrant volatile compounds

Important aroma compounds of black currant berries have been identified mainly by GC-O techniques by Latrasse et al. [119], Mikkelsen and Poll [115] and Varming et al. [7] and those of black currant nectar and juice by Iversen et al. [113]. The most important volatile compounds for black currant berry and juice aroma include esters such as 2-methylbutyl acetate, methyl butanoate, ethyl butanoate and ethyl hexanoate with fruity and sweet notes, nonanal, /I-damascenone and several monoterpenes (a-pinene, 1,8-cineole, linalool, ter-pinen-4-ol and a-terpineol) as well as aliphatic ketones (e.g. l-octen-3-one) and sulfur compounds such as 4-methoxy-2-methyl-butanethiol (Table 7.3, Figs. 7.3, 7.4, 7.6). 4-Methoxy-2-methylbutanethiol has a characteristic catty note and is very important to blackcurrant flavour [119]. 

Wiley (1945) reported for this oxazole the odor of pyridine and a similarity with that of 2,4-dimethylthiazole (M.9). According to Shibamoto (1977), this compound has a nutty and sweet flavor. After the analysis of volatile basic compounds derived from roasted barley, Harding et al. (1978) reported that the inclusion of 2,4-dimethyloxazole to ale resulted in a soapy after taste, presumably at levels above the recognition threshold. At a concentration of 5 ppm it has a green, fruity and blackcurrant flavor (Chemisis, 1987). 

Apart from citrus oils, other essential oils have also been analyzed by means of LC, such as the blackcurrant bud essential oil [100]. The latter was fractionated into hydrocarbons and oxygenated compounds, and the two fractions were submitted for RP-HPLC analysis. Volatile carbonyls consist of some of the most important compounds for the blackcurrant avor and, hence, were analyzed in detail. The carbonyls were converted into 2,4-dinitrophenylhydrazones and the mixture of 2,4-dini-trophenylhydrazones was separated into derivatives of keto acids and monocarbonyl and dicarbonyl compounds. Each fraction was submitted to chromatographic investigation. 

Finally, within the muscat group, the free and glycosidic terpenol profile and concentrations vary greatly with respect to the variety (see also Volume 2, Section 7.2) (Bayonove, 1993). Sulfurous compounds and volatile phenols responsible for diverse aromas (medication, blackcurrant, etc.) most likely vary in the same way (Rapp, 1993). 

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