Integrierte Vermeidung und Verminderung der Umweltverschmutzung

Chapter 2
neutralised by adding the alkaline solution in a reactive vessel at atmospheric pressure. The
reaction takes place within a temperature range of 80 to 105 °C. In the second step, water
evaporation and nibs roasting are carried out in a FBD.
2.1.4.4 Fermentation (D.4)
2.1.4.4.1 Objective
Fermentation is the controlled action of selected micro-organisms to alter the texture of foods,
to preserve foods by the production of acids or alcohol, or to produce or modify flavours and
aromas. It also preserves products by lowering the pH tolerance limits of many microorganisms.
2.1.4.4.2 Field of application
Fermentation is an important processing step for a number of FDM products. Typical
applications include beer, wine, various dairy products, vegetables, meat and fish.
Alcoholic fermentation is used in beer and winemaking and for the production of spirits, mostly
with cereals, grape musts, sugar juices and molasses as a raw material. Lactic acid fermentation
is used for making yoghurt and other fermented dairy products, fermented meat products such
as certain types of sausages and vegetables, i.e. sauerkraut. In the lactic acid fermentation of
vegetables, the sliced raw material, e.g. green cabbage in the case of sauerkraut production, is
salted and then fermented under anaerobic conditions.
2.1.4.4.3 Description of techniques, methods and equipment
There are two types of fermentation processes, i.e. alcoholic fermentation and lactic acid
fermentation.
The breakdown of simple sugars into alcohol is normally referred to as alcoholic fermentation.
Yeasts, usually Saccharomyces sp, e.g. cerevisae or bayanus, are used to produce ethanol from
carbohydrates and very small amounts of other organic compounds. This conversion can be
represented by the following equation:
C6H12O6 = 2C2H5OH + 2CO2
(Glucose) = (Ethyl alcohol) +
(Carbon dioxide)
This is an anaerobic process, i.e. it does not require the presence of oxygen. The temperature of
fermentation is usually in the range of 8 to 30 ºC. The temperature affects the rate of
fermentation, the efficiency of conversion and the flavour and the aroma of the finished product.
The pH may also be adjusted. This ensures that the fermentation is efficient and produces the
required flavour. The type of yeast species used affects the rate, efficiency, flavour and aroma
and is, therefore carefully selected to give the desired results. Selected strains of yeasts are often
used to optimise the alcohol yield and the production of aromatics as secondary components.
Nitrogen, vitamins and trace elements are usually added as yeast nutrients. Traditionally,
fermentation in beer and winemaking has been carried out in open fermentation vessels. Some
have been replaced by cylindrical closed fermenters, making recovery of CO2 possible.
In lactic acid fermentation, lactose or other sugars are converted into lactic acid and small
amounts of other components. Lactic acid formation is accompanied by a decrease in pH, which
is important for the taste, the aroma and the preservation of the product. There are several
species of bacteria which are able to produce lactic acid. Each species gives its own typical taste
and aroma. Lactic acid fermentation is an anaerobic process. It is sometimes necessary to
remove as much of the oxygen as possible to enhance the fermentation process. Lactic acid
fermentation is carried out at 20 to 40 ºC.
28 January 2006 RHC/EIPPCB/FDM_BREF_FINAL