Natural aroma chemicals for use in foods and beverages - Natural Food Additives, Ingredients and Flavourings - page 218

Table 10.2 Structure of materials derived from yeast fermentation and their boiling points

Name Boiling point Structure

DMS 37

[10.1]

Ethanol 78

[10.29]

Isoamyl alcohol 130

[10.30]

2,3-Dimethylpyrazine 156

[10.31]

2-Ethyl-3,5-dimethylpyrazine 181

[10.32]

beta-Damascenone 274

[10.33]

as de facto waste from brewing/fermentation. If the process was carried out in
order to produce (say) the natural pyrazines, the cost would add several zeros to
the current market price.

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10.6.2 Microbial methods
Again, as with brewing, the origins of this lie in prehistory, for example, the use
of 'moulds' ( Penicillium spp.) to modify the fl avour of cheese is the technology
behind all 'blue' cheeses such as Stilton, Roquefort and Gorgonzola. This indicates
that there are three uses of microbial systems: (i) an in situ modifi cation of the
fl avours of foods; (ii) the more recent development of the use of microorganisms
to produce aroma chemicals for isolation; and (iii) their use as 'natural reagents'
to carry out specifi c chemical reactions. This is an area of great activity. There are
a number of excellent reviews (Longo and Sanroman 2006; Schrader 2007;
Brenna et al. 2010) and hence only a few examples, those concerning the
production of natural aroma chemicals, are given here.
Amino acids are interesting precursors, in some ways, of course, paralleling
their roles in secondary metabolism. Fermentation of phenylalanine [10.34]