Flavour Generation in Bioreactors

The application of well defined starter cultures enables the unequivocal determination of the main route of fermentation. The micro-organisms imparted to the food raw materials in the form of concentrated starter cultures quickly overgrow undesired germs in the raw material because of their high initial count and suppress deviating metabolic pathways which may give rise to misfermentations and off-flavours. 

Starter cultures are mainly applied as liquid cultures with about 10 to 10 ° microorganisms per ml. They are also available in a freeze-dried or deep frozen preparation with the advantage of very simple application. 

To a limited extent a starter culture once established can be propagated on site (sour dough, yoghurt cultures, yeast in the brewery). 

Besides the application of a well defined starter culture which has to be tested every time before use, the preconditioning of the food raw material is of critical significance. This preconditioning ranges from simple washing to complete sterilization. Besides, the supplementation of nutrients and the adjustment of a defined pH-value is frequently decisive for the result of a fermentation. 

Apart from these measures, the application of spontaneous and starter culture mediated fermentative generation of flavour active substances does not require any further technical equipment. This fact and the traditional experience with such processes are the reasons for the still considerably high amount of food produced by this technology. In 1990, such products exhibited a value of 23 billion compared to the total amount of 91 billion in the same year for all food products [3], 

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