Subject flavour compounds

SPME can also be used to extract target analytes from food and drug samples. Thus, it has been employed for the extraction of caffeine from coffee and tea [225], and for that of volatile impurities in drugs. Headspace SPME has also been tested for flavour analysis in foods. Thus, the SPME/GC/TOF-MS tandem was successfully used for the rapid analysis of volatile flavour compounds in apple fruit. The sample (300-450 g of apple) was subjected to static headspace sampling for 4 6 h in order to allow the volatiles... 

Esterification reactions, a common route to natural flavour compounds, have also been the subject of investigation. Nakamura et al. [35, 36] compared rates... 

Grape compounds which can enter the yeast cell either by diffusion of the undissociated lipophilic molecule or by carrier-mediated transport of the charged molecule across the cell membrane are potentially subject to biochemical transformations by enzymatic functions. A variety of biotransformation reactions of grape compounds that have flavour significance are known. One of the earlier studied biotransformations in yeast relates to the formation of volatile phenols from phenolic acids (Thurston and Tubb 1981). Grapes contain hydroxycinnamic acids, which are non-oxidatively decarboxylated by phenyl acryl decarboxylase to the vinyl phenols (Chatonnet et al. 1993 Clausen et al. 1994). 

If multi-compound mixtures are present, it is necessary to introduce the bottom product into a further continuous unit. Mixtures with n components require n-1 separation columns. This technology is used for processes on a large industrial scale. In the flavour industry, mixtures with three or more components are first separated into two to three fractions and then subjected to a discontinuous separation process. The after-run may be separated from its high-boiling constituents by thin-film evaporators. 

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