Milk processing: perfect milk in five automated steps

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Without milk processing, our diet would be different to what we are used to today.

For many of us, milk is an integral component of our daily cuisine and provides an important base for many popular products and dishes. Whether enjoyed as it is from a glass, as the basis for our morning porridge, or as a dollop of cream to add the finishing touch to our favourite cake – in its many diverse forms, milk is an ever-present part of our daily nutrition.

But how is raw milk processed after milking? Which steps does it undergo? Which factors influence the flavour of the milk? And what contribution does automation technology make in this process? We will answer all of these questions in our topical special on milk processing!

Automation24 guides you through the five steps of milk processing. Learn how raw milk is processed with a view to giving it the characteristic flavour and quality that many of us could not do without in our everyday lives.

Step 1: From the farm to the dairy – raw milk collection and transport

Milk's journey ideally begins on a farm where cows live in species-appropriate conditions. This not only promotes their well-being, but also has a positive influence on the quality of the milk.

Milk production on farms typically begins with the regular milking of the cows. To this end, milking machines are attached to the cow's udders up to twice daily. In this way, the milk is suctioned off and fed into the milk storage vessel; generally in hygienic 30inch stainless steel tanks. In this way, an average of 30 litres per day can be acquired from each cow.

As soon as no further milk can be collected, the milking equipment automatically drops off.

This process is completely automated and takes place under sterile conditions, so as to adhere to hygiene standards right from the very beginning.

Finally, the milk is pumped into a tank, whereby a hygienic level sensor monitoring the milk level to prevent overflowing and dry running.

Overnight, the milk is cooled to 4°C to 8°C and is stored until it is collected by a milk truck the next day or two days later, to be transported to the dairy. During this waiting time, temperature sensors or temperature transmitters ensure that the required storage temperature is maintained.

Before the milk is moved on for further processing, a receiving inspection is performed. Here, a sample is taken and tested for various criteria, such as the possible presence of drugs and bacteria residues, and to ensure a normal colour and smell. In addition, the pH value must be checked, which must be at least 6.60.

Only if the sample is in flawless condition will the milk be pumped from the milk truck and make its way into the milk tank in the dairy.

There, it is stored at 4°C to °6C, before moving on to the next process step. Here, the correct temperature is also ensured using temperature sensors or temperature transmitters.

Raw milk consists of 4% fatty cream and low-fat skimmed milkd, which must be separated from one another.

To this end, the raw milk is fed into a separator or centrifuge. Due to the strong spinning force, also known as centrifugal force, the skimmed milk is pushed to the edge of the centrifuge, while the cream or milk fat remains in the centre.

Non-round movements of the separator can be detected and promptly corrected using vibration sensors. This enables the prevention of potential damage and extends the life of the separator.

The cream and the skimmed milk are finally fed out of the centrifuge separately and undergo further processing.

3.1 Adjusting the fat content and the cream content

First, industrial dosing and mixing systems are used to adjust the desired fat content or cream content, so that the milk variety of choice can ultimately be produced.

By producing the correct mixing ratio of cream and skimmed milk, various types of milk can be manufactured, including skimmed milk, semi-skimmed milk or full cream (whole) milk, with the corresponding fat contents, namely 1.5%, 3.5%, or 3.8%.

3.2 Homogenisation of cream and milk

Finallym the skimmed milk and cream are mixed accordingly. However, due to their differing composition, the two components cannot be easily blended together, as skimmed milk consists mostly of water, while cream consists mainly of milk fat. Fat tends to rise to the top. Therefore, a special handling process is required to produce an even mixture.

Here, the process of homogenisation proves helpful. Here both the skimmed milk and the cream are pressed through the very fine nozzles of a so-called homogeniser, at very high pressure, A hygiene-compliant and specialist pressure sensor or pressure transmitter contributes to ensuring that the required pressure is maintained.

This causes the fat globules in the cream to be split sufficiently finely that they distribute evenly in the aqueous skimmed milk, and bind with it. In this way, the milk can no longer cream and a homogeneous liquid is produced. This is a result that is not only more visually appealing, but is also evident in the consistency, the creaminess, and the balanced flavour of the milk.

Therefore, in milk processing, the subsequent heat treatment is vitalin order to kill off remaining germs and bacteria and extend the shelf life of the milk.

Through strong heating, microorganisms are eliminated and enzymes are deactivated, which are responsible for decomposition processes in the milk. At the same time, milk proteins are denatured as a result of the heat treatment. This means that they are sufficiently altered in terms of their structure so that they can be better utilised by the human body.

In order to adhere to the different temperature specifications, here too, temperature sensors, temperature transmitters or temperature controllers are essential. Again, data managers / data loggers offer a means by which to verify maintenance of the correct temperature.

A differentiation is made between two main classic forms of heat treatment (a and b), and two special forms (c and d).