Pasteurization is the process of slowing down the growth of bacteria in food (usually a liquid) by heating the food to a certain temperature, then cooling it. Unpasteurized milk has a high risk of causing bacterial infections when consumed. If you're milking your own cows or goats, knowing how to pasteurize milk at home will prevent bacterial growth and make the milk last longer.
Step
Part 1 of 2: Getting Ready
Step 1. Prepare a double boiler
Pour water into a large saucepan to a height of about 7.5 to 10 cm. Place the smaller pot in the water. Ideally, the bottoms of the two pans should not touch each other. This technique reduces the chances of the milk having a scorched or burnt taste.
Step 2. Put a clean thermometer in the pot at the top
You should always monitor the temperature of the milk. Floating thermometers or clip thermometers are most effective for this purpose. Wash the thermometer in warm soapy water first, then rinse thoroughly. The best way to sterilize a thermometer is to rub it with a disposable alcohol swab, then rinse it again.
If the thermometer won't float or is clamped to the edge of the pan, you'll need to dip it in the milk frequently during the pasteurization process. Try to work near a sink so that you clean and sterilize the thermometer after using it to take temperature
Step 3. Prepare the ice water bath
The sooner you cool the milk after pasteurization, the safer and better it will taste. Fill a sink or large basin with cold water or ice cubes so you're ready to start the process.
- Old fashioned ice cream machines are very effective for this purpose. Fill the outer compartment with ice cubes and coarse salt as usual.
- Read all the instructions below before you prepare the ice water bath. After reading, you can opt for a longer pasteurization process, in which case you will need to keep the ice in the freezer for another half hour.
Part 2 of 2: Pasteurizing
Step 1. Pour raw milk into a small saucepan
If you haven't strained the milk since you expressed it, pour the milk through a sieve.
If you want to pasteurize at home, it's best to limit it to 4 liters of milk at a time
Step 2. Heat the milk while stirring
Place the double boiler on the stove over medium or high heat. Stir the milk frequently to help homogenize the temperature and prevent the milk from scorching.
Step 3. Watch the temperature carefully
Make sure the thermometer does not touch the wall or bottom of the pan when taking measurements, as the results will not be accurate. When the milk approaches the temperatures mentioned below, stir constantly and remove the milk from the bottom of the pan to reduce the hot and cold parts. There are two techniques for pasteurizing milk, both safe and approved by the US Department of Health:
Short Time High Temperature (HTST)
Faster processing with minimal effect on taste and color.
1. Heat the milk to 72 C.
2. Keep the milk at that temperature or higher for 15 seconds.
3. Remove the milk from the stove immediately. Long Time Low Temperature (LTLT)
It is recommended for cheese making and avoiding accidentally overheating of milk.
1. Heat the milk to 63 C.
2. Keep the milk at that temperature or higher for 30 minutes. Rerun the timer if the temperature drops below 63 C.
3. Remove the milk from the stove.
Step 4. Cool the milk quickly in an iced water bath
The faster the milk cools, the better it will taste. Place the milk in an iced water bath and stir frequently to help release the heat. After a few minutes, replace the warm water with cold or ice water again. Repeat this step each time the water gets warm. The more often you replace it, the better. Milk is ready to be consumed once it reaches a temperature of 4 C. This process can take up to 40 minutes with an ice water bath, or 20 minutes with an ice cream maker.
If the milk has not reached 4 C after 4 hours, it can be assumed that the milk has been contaminated. Pasteurize again and cool faster
Step 5. Wash and sterilize the container
Wash the milk container thoroughly with hot water and soap before use. For best results, sterilize heat-resistant containers after washing by immersing them in hot water (at least 77 C) for 30-60 seconds.
Let the container dry on its own. The washcloth can allow bacteria to move back into the container
Step 6. Store in the refrigerator
Pasteurization only kills 90 to 99% of the bacteria in milk. You will still need to store milk in the refrigerator to prevent the bacterial population from growing to dangerous levels. Close the container tightly and away from light.
Unprocessed pasteurized milk can last 7-10 days if pasteurized immediately after milking. Milk will spoil more quickly if it is stored in a place where the temperature is above 7 C, if it is exposed to new contamination (eg contact with a dirty spoon), or if raw milk is not stored properly before the pasteurization process
Step 7. Use special equipment
If you raise your own livestock and need to pasteurize large amounts of milk, consider purchasing a dedicated milk pasteurizer. The machine is able to pasteurize large amounts of milk and can retain the taste of milk better. LTLT (long-time low-temperature) machines are the most affordable and easy-to-use, but HTST (short-time high-temperature) machines are faster and usually don't affect the taste of the milk.
- Milk must be kept refrigerated quickly for the pasteurization process to work. Don't forget to cool the milk in a cold water bath if the pasteurizer doesn't do this.
- The HTST machine tends to break down (denature) less protein as long as the temperature does not exceed 77 C. This gives more consistent results when milk is used to make cheese.
Tips
- After pasteurization, the milk will still separate into milk and cream. Commercial milk does not separate the two because of a separate process called homogenization.
- If the milk takes too long to reach 4 C in the iced water bath, you can transfer the milk to the refrigerator once it reaches 27 C.
- Pasteurization has no effect on most of the nutrients in milk. This process can slightly reduce vitamin K, B12, and thiamine levels. Pasteurization can reduce vitamin C levels significantly, but milk is generally not considered a source of the vitamin.
- Calibrate the thermometer frequently to ensure accuracy. To do this, use a thermometer to measure the temperature of the boiling water. If your location is at sea level, an accurate thermometer will show a measurement of 100 C. If you get different results, remember to add or subtract future measurements to get the actual temperature.
- Dairy manufacturers sometimes perform a phosphatase test to ensure that milk has been pasteurized properly.
- Due to the high fat content in buffalo milk, increase the pasteurization temperature by 3 C.
Warning
- Try not to keep the thermometer from touching the bottom of the pan as this will give inaccurate results.
- Infrared (non-contact) thermometers may give incorrect measurement results for this process because they only measure surface temperature. If you want to use it, stir the milk from the bottom up first for a more accurate measurement.
