When I first found out I was lactose intolerant and started drinking lactose-free milk, I thought that removing the lactose from the milk is what made it last so much longer than other milk. That is not the case however.
Lactose-free milk lasts longer than other milk because it is pasteurized at a higher temperature which kills more bacteria. This higher temperature pasteurization, either Ultra High Temperature or Ultra pasteurization, is used because lactose-free milk often remain on store shelves longer than regular milk as it doesn’t sell as quickly.
Lactose-Free Long Shelf Life Explained
The shelf life of refrigerated lactose-free milk that is ultra pasteurized is 30-90 days after processing, while the majority of other milk lasts only about 20 days after processing when refrigerated, depending on the method of pasteurization used.
Removing lactose from milk has no impact on the shelf life. The process of making milk lactose-free involves breaking down the complex sugar lactose into simple sugars galactose and glucose, both of which remain in the milk. As nothing is actually removed from the milk, the shelf life is not impacted in this process of breaking down the sugar.
The longer shelf life of lactose free milk is explained by the pasteurization process used, which is either ultra high temperature (UHT) pasteurization or ultra pasteurization, with ultra pasteurization being the more common of the 2 methods. Most other milk products undergo high temperature short time (HTST) pasteurization, which uses a lower temper than ultra pasteurization and UHT pasteurization (More on this in the next section).
However, ultra pasteurization isn’t reserved only for lactose-free milk, and there are other milk products that are ultra pasteurized. The type of pasteurization is determined by the end use of the milk and the pasteurization equipment that dairy producers have.
Lactose-free milk benefits from a longer shelf life because it doesn’t sell as quickly as other milk products. Another reason a longer shelf life may be necessary is that lactose free milk is produced in less locations than other milk and has to traveler for longer periods of time before it reaches stores.
Even though up to 65% of adults experience some sort of lactose intolerance (this percentage varies by country and ethnicity), lactose-free milk still sells at a slower rate that other milk products. This may be because some who are lactose intolerant choose dairy free milks, or no milk, over lactose-free milks, or they find that taking lactase pills relieves enough of the symptoms of lactose consumption that they feel comfortable drinking milk.
The 5 Types of Pasteurization
There are 5 main types of pasteurization used for dairy products, each using different equipment, temperatures, and different lengths of time to pasteurize milk. In general, the higher the temperature used, the more bacteria is destroyed during the process, resulting in products with longer shelf lives.
Vat Pasteurization (Also called batch or low temperature pasteurization)
With vat pasteurization, small batches of milk are held at a temperature of at least 63ºC or 145ºF for 30 minutes and then rapidly cooled. Some brands offer vat pasteurized milk because the flavor is better preserved with this method than other pasteurization methods. Vat pasteurized milk is closest to the taste of raw milk.
However, vat pasteurization is not as common as it used to be because it takes significantly longer than other pasteurization methods. While vat pasteurization takes 30 minutes and can only handle relatively small batches of milk, other pasteurization methods take 15 seconds or less and process much higher volumes of milk.
High Temperature Short Time Pasteurization – HTST (Also called flash pasteurization.)
With HTST pasteurization, a continuous of flow of milk is held at a temperature of at least 72ºC or 161ºF for 15 seconds and then rapidly cooled. This continuous flow allows dairy produces to keep up with the high demand for milk by pasteurizing large volumes very quickly. HTST is the most common method of pasteurization in the US.
Refrigerated HTST pasteurized milk can last about 20 days after processing.
Higher-Heat Shorter Time Pasteurization – HHST
HHST pasteurization requires holding a continuous flow of milk at temperatures ranging from 89ºC or 191ºF to 100ºC or 212ºF for times ranging from 1 second to .001 seconds, with the higher temperatures requiring shorter times. As the name implies, this method uses higher heat and requires shorter time than HTST pasteurization.
Ultra pasteurization (UP)
Ultra pasteurization requires holding milk at a temperature of 138ºC or 280ºF for 2 seconds and then rapidly cooling it. This higher temperature destroys more bacteria than the HTST or HHST pasteurization methods, giving the milk a longer shelf life.
Refrigerated ultra pasteurized milk can last 30 to 90 days after processing.
Ultra High Temperature pasteurization (UTH)
UTH pasteurization uses the same temperature and heat of ultra pasteurization, 138ºC or 280ºF for 2 seconds, but the milk is packaged and sealed in sterile airtight containers, allowing the milk to be considered completely sterile. An example of this is milk being canned instead of being bottled or put in cartons.
Unlike all other pasteurizing methods, UTH pasteurized milk does not need to be refrigerated until it is opened, and has a shelf life of up to 6 months.
Here’s a table of the temperature and time requirements for each of the 5 types of pasteurization.
|Vat Pasteurization||63ºC, 145ºF||30 minutes|
|High temperature short time (HTST)||72ºC, 161ºF||15 seconds|
|Higher-Heat Shorter Time (HHST)||89ºC, 191ºF||1.0 second|
|Higher-Heat Shorter Time (HHST)||90ºC, 194ºF||0.5 seconds|
|Higher-Heat Shorter Time (HHST)||94ºC, 201ºF||0.1 seconds|
|Higher-Heat Shorter Time (HHST)||96ºC, 204ºF||0.05 seconds|
|Higher-Heat Shorter Time (HHST)||100ºC, 212ºF||0.01seconds|
|Ultra Pasteurization (UP) & Ultra High Temperature (UTH)||138ºC, 280ºF||2.0 seconds|
Why is Milk Pasteurized?
Milk is pasteurized in order to kill harmful organisms that cause disease. The Food and Drug Administration (FDA) requires milk products sold across state lines that are intended for human consumption to be pasteurized according to specific standards. Each state regulates the sale of raw (unpasteurized) milk within its own state.
According to the FDA’s website, “Pasteurization kills harmful organisms responsible for such diseases as listeriosis, typhoid fever, tuberculosis, diphtheria, Q fever, and brucellosis.”
The FDA adds that these harmful organisms found in raw milk are more dangerous for those with “weakened immune systems, children, older adults, and pregnant women.”
The FDA regulation prohibiting the sale of raw milk between states lines became effective September 9th, 1987. Laws vary by state as to whether or not raw milk can be sold in stores or only at the farm where it is produced. For example, Alabama prohibits the sale of raw milk, whereas my home state of California allows raw milk to be sold in stores.
An additional benefit of pasteurization is that killing the bacteria in the milk increases the milk’s shelf life. Raw milk has a very short shelf like of 7-10 days compared to the 20-90 days of pasteurized milk, depending on the type of pasteurization.
After adding up processing time, shipping time, how long milk sits on the store’s shelf before it’s purchased, how long milk sits in our fridge before we open it, and how long it takes us to drink the milk after we open it, raw milk with a 10 day shelf life would have a hard time beating pasteurized milk for those who don’t go through cartons of milk quickly.