It's been 20 years since separation processes involving membranes have been used to treat many different types of foodstuff solutions. These processes show many features that fit this market very well:
- High flexibility, the possibility to work with membranes with different pore size or different construction features
- Low energy consumption
- Hygiene and good microbiological control
- Limited thermal and mechanical stress
This technology has been used in many different fields, including:
- >Wine clarifications, grape musts, fruit juice, etc.
- Protein and lactose recovery from whey
- Bacteria removal and milk standardization
- Brine purification/decoloration
- Sugary solutions purification/concentration
Brine Treatments
The different kinds of brines treated with membranes usually are:
- Cheese salting brine
- Vegetable conservants brine
- Ham cooking stock brine
The type of membrane is chosen according to the specific goals of the case. Varying the porosity of the membrane it's possible to intervene selectively on the pollutants: the attached "Filtration Spectrum" chart shows these possibilities.
Microfiltration removes mainly macropollutants, like colloids and bacteria, whereas if we enter the ultrafiltration field we can remove proteins too from the solution. It is therefore possible to manage the process depending on specific needs.
It's also possible to choose the configuration of the membrane element (e.g. materials, size of the openings) to better suit the working/washing conditions and the different features of the solution.
Plant configuration for dairy brines
The solution adopted is to use the brine until polluted, before purifying it with fossil flour filters (floating solids removal) and boiling it (bacteria dejection).Since these purification systems have low efficiency, it's common to dump the worn out brine and use a fresh one.
This comes with many disadvantages, the main one being that when purification is done with simple filtration and boiling, it's only partly efficient and the consequent replacement of the brine presents the great inconvenience of unloading a big amount of highly polluting brine. For the single chloride load, one part of brine can pollute to a value which surpasses legal limits, one hundred parts of water. In the case of biological depuration plants, a sudden release of a large quantity of brine can kill most of the bacterial flora as a result of an osmotic shock.
Boiling large amounts of water also implies a high energy consumption.
Another disadvantage is the discontinuity of the process. The quality of the brine is very good at the beginning of the cycle but tends to decrease to extremely low levels towards the end. For this reason, it is difficult to obtain a consistent quality on the produced cheese.
A better alternative to this is the use of membrane separation technology with microfiltration and ultrafiltration plants that make use of spiral wound elements. Attached is a description of this technology with examples of the available membranes and the plant layout. The brine is recirculated through the micro/ultrafiltration plant and the purified fraction is taken back to the pool. A small polluted fraction is continuously sent to the purification system.
Operating in the steady state allows continuity and consistency in the quality of the product as the composition of the brine remains constant in time. The small bled flow does not compromise the functioning of the purification system. It is important to note that the entire process is at cold temperatures and therefore the energy consumption is significantly low.
The choice of the membrane depends on numerous factors including: the type of brine, the presence of proteins, etc… The treatment can be optimized according to the type of cheese (aged, fresh, etc..).
The plant runs non-stop with the exception of cleaning and sanitizing periods, which are scheduled on a daily or twice-daily basis for the duration of approximately and hour.
Conclusion
The treatment of brine in the dairy industry is concrete and economically attractive prospective, especially in the modern sanitary and industrial processes.
Every process is targeted to specific needs and has specific peculiarities that need to be addressed according to the application in order to ensure maximum efficiency and optimization of the process.
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