The key steps involved in making milk safe to drink
As one of the largest food processing sectors in Australia, dairy provides plenty of employment opportunities in Australia. Over 64,000 Australians are currently employed in the dairy industry. Dairy also makes up a large part of Australia’s export market. Up to 35 per cent of Australia’s dairy products are exported overseas. But before any dairy product makes it to your fridge, it must go through a stringent pasteurisation process.
What is pasteurisation and why is it done?
Pasteurisation is one of the main food processing steps that makes milk safe for human consumption. This process involves heating milk at a high temperature. In Australia, one of the most common methods of pasteurisation is High Temperature Short Time Pasteurisation (HTST). Milk must be heated to a alest a temperature of 72°C for 15 seconds before being cooled down immediately.
HTST ensures that milk is heated uniformly to the required temperature and is designed to kill heat resistant pathogens called Coxiella and Burnetii. These are both commonly found in raw milk before it’s treated. For this pasteurisation to be carried out properly, a dairy processing plant must be equipped with a continuous pasteurisation system.
HTST also helps to improve milk’s shelf life. Enzymes that would usually contribute to spoiling milk are also destroyed. So the quality and shelf life of milk is drastically increased after a proper pasteurisation process has been undertaken. After the milk is pasteurised it should be safe to consume for a period between 16-21 days. For consumer safety, dairy manufacturers will often reduce the number of days to help push the products off the shelves.
The key steps involved in pasteurisation
1. Chilling
While this is technically not a step of pasteurisation, it is a necessary process before pasteurisation can begin. After the milk is extracted from a cow’s udder, its temperature must be reduced immediately to prevent bacterial growth. Farmers typically ensure that milk is cooled and stored to a temperature of 2° C to 5° C.
2. Pre-heating
After milk is transported to a dairy processing plant it goes through a process of heating. The milk is heated to a temperature of 40° C with a regenerative heating system. This system uses the heat of the already pasteurised milk to heat the incoming milk coming from the chilled milk vat. At the same time, the counter flow of the cool milk helps to cool down the pasteurised milk. This process saves energy both to heat the incoming milk and cooling the pasturised milk.
3. Clarification
The clarification process is used to remove all foreign matter from the milk. Solid particles are removed in the past this was generally done running the milk through tubular metallic filters. The most dairy factories these days a clarifier is then used to remove all sediments and soil from the milk. The clarifiers use centrifugal force where the milk enters a machine which is spinning at high speed, this separates the heavy solid particles to the outer edge of the clarifier where it is discharged to waste and the clean milk passed through the machine.
Most dairy processing plants use separators which also act as clarifiers they are designed to separate the skim milk from the cream again they use centrifugal force the milk enters a set of spinning plates which forces the heavy skim milk to the outside of the machine and the lighter cream is forced to the inside as the milk is pumped into the separator, the separator has valves on the exit for both skim milk and cream which control the amount exiting the separator and by adjusting these values the fat percentage of the cream and skim milk can be controlled.
4. Standardisation
The standardisation process will ensure milk is produced to the same consistent quality. This process is the addition of cream back to the skim milk that is produced by the separator. The amount of butterfat reminding depends on what’s being produced. Milk types such as high fat milk require more cream to be added back to the skim than say a low fat milk where less of the cream will be added, skim milk will have no cream added back to the skim milk. Some of the smaller factories who use clarifiers will standaise their milk by adding skim milk to the whole milk to lower the butterfat percentage to the required amount
5. Homogenisation
Homogenisation is a process which breaks down the milk fat globules within the milk. Fat globules are broken down into tiny droplets to prevent cream separation in the milk. The end result is milk fat that remains uniformly distributed throughout the milk.
6. Heating section
The most important part of the pasteurisation process is the heating section. The milk’s temperature is heated to 72° C to effectively kill harmful bacteria. Hot water which has been heated by steam is used to achieve this temperature while milk is being moved in a countercurrent motion. At the end of the heating section the milk enters the holding tube
7. Holding section
At the start of this process, milk flows through holding tubes at a flow rate that ensures they stay in the tubes for at least 16 seconds. This ensures that the target harmful bacteria are killed. If any milk reaches the end of the holding tube below the target temperature of 72 C it will automatically be diverted back to the holding tank at the start of the pasteuriser. When milk makes it to the end of the holding tubes it flows to a regeneration section where it is cooled down to approximately 30° C, using the cooling action of the cold incoming milk in the regeneration section
8. Cooling/chilling section
After the initial cooling stage, pasteurised milk is moved to the cooling section. Here the milk is cooled and chilled to a temperature of 4° C. This chilled milk is then pumped into packaging machines for packaging and storage in a cold room.
Learn more about dairy production from NFI
Here at NFI, we specialise in providing workplace training for some of the nation’s biggest food processing sectors including dairy. For years we’ve closely monitored the dairy industry and updated our courses to adapt with growing workplace training needs.
When your staff train with us, they’re receiving training that ensures they become effective risk managers in the workplace. So whenever they spot something that might jeopardise workplace safety, they know exactly what to do in order to rectify the situation. This training helps to drastically reduce workplace incidents and improve the safety of your staff.
When it comes to training staff in the dairy industry we ensure they have the most up-to-date knowledge of pasteurising procedures for dairy milk. This ensures your staff understand how important each step is and how important their role is within a dairy processing plant.
So if you’re looking to improve safety and operating standards in the workplace, put your staff first with an NFI workplace based training course. Contact NFI today and discover how new training can help improve your team’s knowledge of the industry they work in.