Industrial membrane filtration plants were
introduced to the dairy industry in the beginning of the 1970's. The basis
for using membrane filtration in the dairy industry is that dry matter
components in milk and whey particles consist of different sizes. By
selecting filters/membranes of differrent pore sizes and applying pressure on
the product to be filtered, it is possible to divide the milk and whey in
different fractions. What passes the filter/membrane = permeate and what does
not pass = retentate.
| Particles |
Diameter |
| Fatglobules (and bacterias) |
500-10,000 nm |
| Casein particles |
10-300 nm |
| Whey Protein |
3-6 nm |
| Lactose |
Approx. 1 nm |
| Salts |
0,4-1 nm |
| Water |
Approx. 0,3 nm |
What is membrane filtration used for?
Today, membrane filtration is used in the Food & Dairy
industry and likewise in other process plants delivered by the GEA Group.
There are four kinds of membrane filtration:
-
Reverse Osmosis is used to remove water
from a product to increase the solids content,
evaporator condensate is
often 'polished' by reverse osmosis, so that it can be used elsewhere in the
dairy.
-
Nanofiltration is mainly used to
remove the monovalent ions from whey. A partly demineralization and water
removal is obtained.
-
Ultrafiltration is typically used
for whey, where the whey proteins are separated to form a product with 35, 60
or 80 % WPC. If ultra filtration is applied to skim milk, Milk Protein
Concentrate is obtained. The protein fractions are typically evaporated in
multi-effect
evaporators with
either TVR or MVR recompression to save steam, before
spray
drying.
-
Microfiltration is a low pressure
membrane process for separating colloidal and suspended particles in the range
of 0.05-10 microns and as such used for bacteria removal.