Integrierte Vermeidung und Verminderung der Umweltverschmutzung

Chapter 2
2.1.4 Product processing technology (D)
2.1.4.1 Soaking (D.1)
2.1.4.1.1 Objective
The objective of soaking, e.g. of vegetable seeds, such as lentils, is to moisten and soften the
seeds to reduce the cooking time or to aid in seed coat removal. In the malting process, the
objective of soaking is the uptake of water to activate the germination process in the kernel.
2.1.4.1.2 Field of application
Soaking is predominantly applied in the processing of vegetable seeds. It is also applied with
grain, where the grain is soaked in the malting process prior to germination. This is often called
steeping.
2.1.4.1.3 Description of techniques, methods and equipment
Soaking is performed by putting the vegetable seeds in water for a specified time. The time
needed varies, depending on the seed variety and species and with the length of storage and
storage conditions. Traditionally, dry beans are soaked for 8 to 16 hours in cold water with
appropriate hardness. High temperature soaking accelerates hydration. To steep the grain, the
grain is immersed in water at about 16 ºC, ranging from 10 to 25 ºC, depending on the
equipment, the process parameters, the raw material and the finished malt to be obtained.
During steeping, the moisture content increases from 12 to 15 % to anywhere between
30 to 50 %, depending again on the above conditions. During steeping, the water in the steep
tanks is changed one to three times. Alternate wet and dry stages are applied. During the wet
stage, the grain is aerated continuously or at intervals. During the dry stage, the grain can be
aerated or the CO2 can be extracted. The steeping process takes one to three days. Figure 2.2
shows an example of a steeping procedure.
Figure 2.2: An example of the steeping procedure
[87, Ullmann, 2001]
26 January 2006 RHC/EIPPCB/FDM_BREF_FINAL