April 20, 2025, 9:14 am | Read time: 4 minutes
Lactose-free milk is an important alternative for many people, but how is it actually produced? There are two methods to remove or convert the milk sugar. One of these methods even alters the taste. But what exactly is lactose, and what role does it play in the body?
Lactose-free milk contains almost no milk sugar. But how exactly is it removed from the milk? There are two common methods: either the lactose is split using an enzyme or almost completely removed through special filtration. But before that, it’s worth looking at what lactose actually is and what functions it serves.
Overview
What Is Lactose and What Role Does It Play?
Milk sugar (lactose) is a carbohydrate naturally found in milk. It is a disaccharide, composed of glucose and galactose. Both types of sugar are important energy sources and perform various functions in the body.
The name “lactose” comes from the Latin word for milk (“lactis”). In nature, lactose is found exclusively in the milk of mammals, including human breast milk. All common types of milk, such as cow’s milk, goat’s milk, or sheep’s milk, contain roughly the same amount of lactose. This also applies to products made from them, like sheep cheese or goat cheese. Only a few mammals, such as kangaroos and sea lions, have almost lactose-free breast milk.1
During digestion, the enzyme lactase breaks down milk sugar into its components. The mucosal cells of the small intestine produce this enzyme. If the body does not produce enough lactase, it cannot fully process lactose—a condition known as lactose intolerance. As a result, the undigested lactose reaches the large intestine, where bacteria ferment it. This process causes typical symptoms like bloating and abdominal pain. People with lactose intolerance should adjust their diet accordingly.2
How Is Milk Made Lactose-Free?
Enzymatic Splitting by Lactase
A common method for removing lactose is enzymatic splitting. Here, the enzyme “lactase” is added to the milk. “The lactase splits the lactose into two types of sugar, galactose and glucose,” explains Torsten Sach from the Milk Industry Association. Since these sugars have a higher sweetness, lactose-free milk tastes sweeter than regular milk. Typically, after adding lactase, it is deactivated by heating the milk, which also ultra-pasteurizes or pasteurizes it. Subsequently, other dairy products like cream, yogurt, quark, mozzarella, or fresh cheese are made from the lactose-free milk. The enzyme lactase comes from molds (Aspergillus) or yeasts (Kluyveromyces), which can also be genetically modified.3
The EU regulation stipulates that the composition of consumer milk—such as skim milk, low-fat milk, and whole milk—must remain unchanged. However, it allows the addition of lactase, provided national regulations do not prohibit it. Therefore, manufacturers can continue to sell milk made lactose-free by this method as “whole milk.”
Ultrafiltration to Remove Lactose
In the second method, lactose is almost completely removed through ultrafiltration. “But some lactose is left in, otherwise this milk would taste bitter,” explains Sach. “Lactase is then added again to give the milk a certain sweetness.”
Manufacturers must use clear labeling: If they make milk lactose-free through ultrafiltration, they can no longer label it as skim milk, low-fat milk, or whole milk. Instead, only the designation “lactose-free milk” is allowed.
How Is Lactose Removed from Milk?
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Differences for Consumers? Hardly Noticeable!
For everyday use, it doesn’t matter to consumers which method was used to produce lactose-free milk. “Only someone who tastes such things daily would notice,” says Sach. Both variants are equally suitable for cooking and baking.
For manufacturers, however, ultrafiltration offers an economic advantage: The removed lactose can be reused as a valuable raw material, such as a filler for tablets in the pharmaceutical industry.
Taste-wise, lactose-free milk offers an interesting feature: Its sweeter taste can be used as a natural sugar substitute. “If you usually drink coffee with sugar, you can also use lactose-free milk, and you’ll get a sweetening effect,” says Sach.
*With material from dpa