Apple aroma formation

The major advantage of the seunpling technique developed, was that some trace chemicals could be trapped tind described for the first time as Black Truffle aroma constituents. In particular, some compounds, important flavor contributors, generally appearing in small concentrations, such as benzaldehyde, propanal, ethyl acetate, anisole or dimethyl disulfide - previously identified in Shiitake mushrooms (9) - could be characterized. This was also the case for three aromatic compounds, toluene, xylene and ethyl benzene, well known as raw vegetable constituents (1 ). In addition, two aliphatic esters, isopropyl and sec-butyl formates, and one cyclic sulfur compound (2-formyl thiophene) previously reported respectively in plums and apples (W) and in coffee and bread products (n) were identified. 

Ethyl butyrate is responsible for the sweet aroma of pineapples. Other common esters include methyl butyrate, found in apples, and ethyl formate, an artificial rum flavor. Several perfumes use esters to impart a pleasant smell. For example, oil of jasmine contains benzyl acetate, a molecule found in the jasmine flower. 

Volatile flavor compounds may be formed from lipids via several different pathways. The primary pathways include a- and P-oxidation, and oxidation via lipoxygenase enzymes [8,9]. Some of the earliest work in this area was on the development of banana aroma by Tressl and Drawert [10]. Recent work showing pathways for the formation of several key volatiles derived from apple lipids are illustrated in Figure 4.2. They demonstrated the conversion of labeled acetate to acetate esters and labeled butanoate to butanoate esters by postchmacteric banana slices. They have further shown the conversion of hexanoic acid to hexanol by these tissues. 

Rettinger, K., K. Volker, H.G. Schmarr, F. Dettmar, U. Hener, A. Mossandl, Chirospe-cific analysis of 2-alkyl-branched alcohols, acids, and esters chirality evaluation of 2-methylbutanotes from apples and pineapples, Photochem. Anal., 2(4), p. 184, 1991. Drawert, F., Biochemical formation of aroma components, in Aroma Research, H. Maarse, P.J. Groenen, Eds., Pudoc, Wageningen, 1975, p. 245. 

Kieronczyk, A., Skeie, S., I angsrud, T., and Yvon, M. (2003) Cooperation between Lactococcus lactis and nonstarter lactobadlU in the formation of cheese aroma from amino acids. Appl Environ Microbiol 69, 734-739. 

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