94-4 |
The alcohol fermentation process as a source of natural flavour materials |
I. L. GATFIELD, J. M. Hilmer, and H. J. Bertram. Corporate Research, Haarmann & Reimer GmbH, PO Box 1253, Holzminden, 37601, Germany When molasses are used as a source of fermentable sugar, the amino acids naturally present undergo reductive deamination thereby forming a mixture of alcohols known collectively as fusel oil. The major alcohols formed are isoamyl alcohol, 2-methylbutanol, n-propanol and also phenylethanol, all of which are important natural raw materials for the flavour industry. For the producers of potable alcohol, fusel oil normally must be removed during the distillation process. Fusel oil can be separated via fractional distillation into its individual components which can be easily converted into the corresponding acids through fermentation. This process will be presented in detail and illustrated by the conversion of 2-methylbutanol into 2-methylbutyric acid, which itself is an important flavour compound. The intermediate in this oxidative conversion is the corresponding aldehyde which can be obtained preparatively by suitably adjusting the fermentation conditions. The aldehydes of all the fusel alcohols are also important flavour compounds. Enzymatic esterification of the so-produced acids with individual fusel alcohols gives rise to a multitude of natural, flavour-active esters. This ability of lipases to synthesize esters, which is a well established industrial process, will be discussed in greater detail. Further interesting flavour-active aliphatic alcohols are present in fusel oil and can be obtained pure via physical processes. Other flavour compounds of importance which are not produced during the fermentation but originate directly from the carbohydrates present in the molasses include furfural, 2-methylfurfural, maltol, cyclotene and especially alkylpyrazines all of which contribute significantly to the caramel, burnt sugar notes typical of molasses and are also to be found in fusel oils.
Session 94, Challenges of converting carbohydrates into flavors by fermentation
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