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Milk is one of the most important and complete human foodstuffs; rich in proteins and numerous essential nutrients. Quality milk production depends on healthy cows consuming a nutritious food ration and plentiful fresh, clean water.
Although commercially produced milk is processed, it remains entirely natural. And so is modern milk filtration. Today’s professional on-farm milk filtration uses entirely clean technology, based solely upon molecular size – it requires absolutely no additives. This clean technology helps farmers to produce milk of the highest quality and value, and to comply with the increasingly rigorous demands of both public authorities and consumers.
As well as maximising the quality and value of milk, the installation of a good filtration system also protects both milking and cooling equipment from potentially harmful foreign particulates. This means that farmers benefit from filtration in two ways: they save money by maximising the longevity and minimising the maintenance of their milking equipment, and by producing milk of the highest possible quality they can command the best market price.
Although milk is subsequently filtered at the milk plant, effective milk filtration on the farm plays an important role in:
• producing raw milk of the highest quality for the dairy company
• indicating the effectiveness of teat cleaning prior to milking
• identifying udder health problem (e.g.mastitis)
• identifying cow environment problems
• ensuring optimum plate cooler efficiency and hygiene.
Milk tanker in Sweden
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DeLaval milk filter boxes |
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People all over the world consume the milk of many different species of animal, but cows, sheep, goats, and buffalo form the primary sources, forming the basis of commercial milk production across the globe.
The composition of milk differs vastly between species, breeds, and even between individual animal and lactation phases. The factors affected include the types and pro-portion of protein, the fat and sugar content, vitamin and mineral levels, the size of butterfat globules and the curd strength.
Given the differences in milk composition, professional milk filters must be capable of performing well under varied conditions in order to achieve the best possible result.
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Filtration is the process used to separate one substance from another. Depending upon the industry and the substances to be separated, many types of filter system are available, inclu-ding electrostatic precipitators, centrifuges, cyclones, scrubbers and mechanical separators.
In on-farm milk filtration, a mechanical filter is used to separate the raw milk from any solid particles that may become suspended in it, before it reaches the bulk milk tank. This includes material such as dirt, manure, straw, hair, clots and insects – all of which can potentially cause problems for milking equipment and, of course, contaminate the bulk tank milk. But on-farm milk filtration is not a way to fix poor or unhygienic milking procedures. It is a best practice that plays an important role in good, holistic milking management.
It is important to note that although filtration is an effective method of removing dirt and other particles from the raw milk, it does not remove bacteria or other material that may have dissolved in the milk. Milk continues to flow across any sediment trapped in the milk filter and this can dislodge bacteria that may be stuck to the particles, potentially increasing the bacterial count of the bulk milk.
Inspection of the milk filter after milking has finished can provide an excellent guide to the herd’s udder health and to whether the teat preparation regime is adequate. Any signs of mucous or clots on the milk filter indicate clinical mastitis in the herd.
The mechanical filtration method used to filter milk on the farm is also called barrier filtration. This is because the filter provides a porous physical barrier with highly specialised properties that enable the raw milk to be separated from the solids.
The driving force of the filtration process is the difference in pressure between the two sides of the milk filter. When raw milk is pumped across the porous surface of the milk filter, a pressure difference either side of the filter is created. The pressure difference forces those elements that are smaller than the pore size of the milk filter (such as water, fat, proteins etc.) to pass through. Any elements that exceed the pore size of the milk filter (including straw, hair, insects, etc.) are unable to pass through and remain in the milk filter.
The process of forcing milk through the milk filter by using a pump is the most common method in modern milking plants. The milk filter resembles a sleeve, or sock, that fits over a perforated metal support, or cage, within a cylindrical tube. Optimum filtration performance is achieved when milk flows at a low but continuous pressure across the milk filter.
With in-line milk filtering, it is important that the milk is filtered prior to cooling, because milk fat can pass through the filter more easily when the milk is warm. Filtering the milk prior to cooling also ensures that solids do not pass through to the cooling plate, as a build-up of sediment will not only compromise its heat-exchange efficiency, but also contribute to increased bacterial count in the bulk milk.
Milk filters and plate heat exchanger
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As mentioned previously, the role of on-farm milk filtration is to enable farmers to produce milk of the highest possible quality and value, as well as helping to protect the milking and cooling equipment. To ensure these demands are met efficiently, a good milk filter must possess certain physical properties. It is essential that the selected filter is the correct size and capacity to match the demands of the milking equipment and herd size. It must also be manufactured from highly uniform fabric, incorporating:
• high wet strength
• even pore size and distribution
• a strong seam • dimensional stability
• food compliance.
Finally, it is essential to choose a milk filter that complies fully with EU and FDA regulations, as well as USDA requirements.
In order to achieve optimal performance in on-farm filtration, the position of the milk filter is critical. Milk should always be filtered before it reaches the cooling system. Warm milk, within the temperature range of 36°–38°C (98°–100°F), can be filtered very efficiently as the milk fat can pass readily through the milk filter. When milk is cold however, between 0°–5°C (32°–40°F) for example, problems can arise. Milk fat in cold milk can block up
disposable milk filters as it can not pass easily through the filter. This causes the milk flow through the filtering unit to be reduced to an unacceptable level.
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