How to Pasteurize Milk: 10 Steps (with Images)

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How to Pasteurize Milk: 10 Steps (with Images)
How to Pasteurize Milk: 10 Steps (with Images)

Pasteurization is a procedure that delays the proliferation of bacteria in food (usually liquid) by heating the item to a certain temperature followed by its cooling. Milk sold in most supermarkets must be pasteurized according to specific regulations set by the government. Drinking unpasteurized milk carries a high risk of bacterial diseases that are particularly dangerous for younger children, the elderly and people with weakened immune systems. If you milk your own cows or goats, learn to pasteurize your milk at home to prevent the growth of bacteria and prolong the shelf life of the milk.


Part 1 of 2: Organizing the materials

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Step 1. Prepare a double boiler.

Fill a large pot with approximately 3 to 4 inches of water. Put another pan a little smaller in this water. Ideally, they don't touch each other. This way of preparing the bain-marie reduces the risk of burning taste.

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Step 2. Place a clean thermometer on top of the pan

It's good to keep track of the temperature constantly, so a floating dairy thermometer or a chocolate thermometer that can be clipped to the edge of the pan are good options. Wash the item in hot soapy water first and then rinse it. The ideal is to disinfect it with cotton wool soaked in alcohol and then rinse it again.

If you cannot fix the thermometer in the pan or let it float, you will need to insert it manually frequently during the pasteurization process. Do everything near a sink so that you can clean and disinfect the object every time you take the temperature

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Step 3. Prepare an ice bath

The faster the milk is cooled after pasteurization, the safer the result of the process and the better the taste. Fill the sink or large bowl with ice water and ice to start.

  • An old-fashioned ice cream maker is very effective. Fill the outer compartment with ice and rock salt as usual.
  • Please read all instructions below before arranging materials. After reading, you may decide to use the longer pasteurization process, in which you have to keep the ice in the freezer for another half hour.

Part 2 of 2: Pasteurizing

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Step 1. Pour the milk into the inner pot

Pass the milk through a sieve if it has not yet been sieved after milking.

For small home batches, it is easier to pasteurize a maximum of 4 liters at a time

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Step 2. Stir while heating

Place the bain-marie over medium heat. Always stir to help even out the temperature and keep the milk from boiling.

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Step 3. Monitor the temperature closely

The part of the thermometer that takes the reading must not touch the sides or the bottom of the pan or the measurement will not take place. As the milk approaches the temperature mentioned below, always stir and move the milk from the bottom of the pan to eliminate hot and cold spots. There are two ways to pasteurize milk and both are safe and approved by sanitary standards:

high temperature, shorter time

Faster, with less interference on taste and color.

1. Allow the temperature to reach 70°C.

2. Keep this temperature or higher for approximately 15 seconds.

3. Remove from heat immediately. Low temperature, long process

Recommended for cheese production to avoid accidental overheating.

1. Reach a temperature of 60°C.

2. Keep the milk at or above this temperature for 30 minutes. Reset the count if the temperature drops below 60°C.

3. Remove from heat.

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Step 4. Cool the milk quickly in the ice bath

The faster the milk is cooled, the better the taste. Put it in the ice bath and stir it frequently to help release the heat. After a few minutes, replace some of the water that has been heated with cold water or ice. Repeat this procedure whenever the water heats up - the more often the better. The milk is ready as soon as it reaches a temperature of 4.5 ºC, which can take 40 minutes in an ice bath or 20 minutes in an ice cream maker.

If the milk does not reach a temperature of 4.5 °C within four hours, it is likely that it has been contaminated again. Pasteurize it again and cool it more quickly

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Step 5. Clean and disinfect containers

Wash milk bottles thoroughly with hot soapy water before using them. For best results, sterilize heat resistant bottles after washing them by soaking them in hot water (minimum 75°C) for 30 to 60 seconds.

Allow jars to air dry. Using a napkin can reintroduce bacteria

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Step 6. Store them in the refrigerator

Pasteurization only eliminates 90 to 99% of the bacteria in milk. You still have to refrigerate it to prevent bacterial colonies from proliferating and reaching unsafe levels. Seal the jars very well and keep them out of light.

Pasteurized milk without any additional processing usually lasts for seven to ten days if it is pasteurized soon after milking. It spoils quickly if stored above 5°C, if a new contaminant is introduced (eg contact with a dirty spoon), or if it has not been stored correctly before pasteurization

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Step 7. Update the techniques

If you have your own animal husbandry and need to pasteurize a large amount of milk, consider purchasing a machine designed for pasteurization. The machine can pasteurize large quantities and can better preserve the flavor of the milk. Machines that work at low temperatures for longer are cheaper and simpler, but those that work at high temperatures (in a shorter period of time) are faster and generally change the taste less.

  • Milk still needs to be cooled quickly for pasteurization to work. Remember to transfer the milk to an ice bath if your machine does not include this step.
  • Machines that work at high temperatures tend to break down (denature) less proteins as long as the heating does not exceed 77, 5 ºC. This gives more consistent results if milk is used to make cheese.


  • After pasteurization, the liquid separates into milk and cream. The milk that is sold in supermarkets is not separated, as it undergoes a further treatment called homogenization.
  • If the milk takes a long time to reach 4, 5 ºC in the ice bath, it is possible to transfer it to the refrigerator after it reaches 26, 5 º C..
  • Pasteurization does not affect most nutrients in milk. It may reduce the amount of vitamin K, B12 and thiamine a little. It can greatly reduce vitamin C, but milk is not a significant source of this vitamin.
  • Calibrate the thermometer frequently to make sure the measurement is accurate. To do this, use it to measure the temperature of boiling water in a pot. If you are at sea level, an accurate thermometer should read 100°C. If you get a different result, make a note of the result and add or subtract that number on subsequent readings to get the actual temperature.
  • Some dairy farmers sometimes perform an alkaline phosphatase test to confirm that the product has been properly pasteurized.
  • Because of the high amount of fat in buffalo milk, increase the pasteurization temperature by 3 degrees.


  • Do not let the thermometer reader touch the bottom of the pan, as this will give a false result.
  • The infrared (contactless) thermometer may be inaccurate for this purpose, as it only measures surface temperature. If you are thinking of using one of these, bring the milk from the bottom of the pan to the surface first to get the most accurate result.

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