Because of spam, I personally moderate all comments left on my blog. However, because of health issues, I will not be able to do so in the future.

If you have a personal question about LI or any related topic you can send me an email at I will try to respond.

Otherwise, this blog is now a legacy site, meaning that I am not updating it any longer. The basic information about LI is still sound. However, product information and weblinks may be out of date.

In addition, my old website, Planet Lactose, has been taken down because of the age of the information. Unfortunately, that means links to the site on this blog will no longer work.

For quick offline reference, you can purchase Planet Lactose: The Best of the Blog as an ebook on or Almost 100,000 words on LI, allergies, milk products, milk-free products, and the genetics of intolerance, along with large helpings of the weirdness that is the Net.

Wednesday, February 18, 2009

Lactose-Free Milk Lasts Longer

Lactose-free milk is actual real cow's milk, exactly like regular milk in every way. Except one. Maybe two.

First, of course, lactose-free milk is lactose-free. Chemically and nutritionally, that's not a big difference. The lactase enzyme is used to break down - digest - the complex sugar lactose into the simple sugars galactose and glucose. That makes the resulting milk slightly sweeter. It's an oddity of sugar chemistry that both components of lactose are sweeter individually than when combined. Everything else about the milk stays the same.

Like almost all other commercially-available milks in the U.S. lactose-free milk is both homogenized and pasteurized. Homogenization breaks down the fat globules in milk and disperses them so that they don't separate and float up to the top. In the old days, the fat - in the form of cream - could be skimmed off the top of milk. That left the rest of the milk with uneven and constantly changing amounts of fat. People preferred milk with a set and regulated amount of fat, so homogenized milk is standard. Pasteurization is also standard. Indeed, mandated by law. Pasteurization kills the microorganisms that can make you sick from milk, and not lactose intolerant sick but deadly ill sick.

There are a number of types of pasteurization. The McClatchy newspaper syndicate had a column on milk that covers some of these types.

Q: What's the difference between milk that expires in 7 to 10 days and milk like Lactaid that lasts for more than a month?

A: First, remember that the date on the milk isn't an expiration date, it's a sell-by date. The store has to sell it or pull it by that date.

That doesn't mean you can't continue to use the milk. Milk is vulnerable to very slight temperature variations, always a problem in home refrigerators, which may not stay below 40 degrees or where the door may be opened and closed constantly.

But as long as your milk is kept cold in a container that blocks light, it usually will keep past the date.

The difference in the sell-by date on milk products is in how they were pasteurized.

In addition to regular pasteurization, where milk is heated to 161 degrees for 15 seconds to kill bacteria, there is low-heat pasteurization -- 145 to 150 degrees for 30 minutes -- and ultra-heat, in which the milk is heated to as high as 250 degrees for less than a second.

Ultra-high heat is used for many specialty milk products, such as lactose-free milk and even some certified-organic milks, to extend their shelf life.

Those products are usually transported longer distances or kept longer before they're sold.

The simple truth is that lactose-free milk sells in tiny quantities compared to regular milk. And the average consumer of lactose-free milk uses much less than the many families with children that go through gallons of the regular milk every milk. So fewer people buy lactose-free milk less often. That's powerful incentive to make milk that keeps for as long as possible. The ultra-pasteurization process can make tiny changes to the taste of the milk that some people notice, though most don't. There should be absolutely no difference in any nutritional value, though.

Some regular milk also comes ultra-pasteurized, including some other types of specialty milks and also so-called "shelf stable" milk that needs no refrigeration. Ultra-pasteurized milk is also much more common in Europe, which is why many tourists find the taste of milk different there.

You can do anything with ultra-pasteurized milk that you can with regular milk. And in comes in all forms, whole, 2%, 1%, fat free, chocolate, fortified, flavored. It just lasts longer. And that's a good thing.

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Darktangent said...

My lactose free milk says to use withing 7 days of opening, but my regular milk does not. Is there any difference that would make lactose free milk not last as long as regular milk after it is opened?

I usually keep my regular milk until the sell by date, even if it's been open for a couple weeks. I suppose as long as the lactose free milk doesn't smell sour I will keep using it as well.

Unknown said...

Good job using your nose, kid.