How Lactose Free Milk Is Made

How Lactose Is Removed from Milk

Lactose-free milk is made by adding the enzyme lactase to regular milk, which breaks lactose into its easily digestible component sugars.
Lactose-free milk is made by adding the enzyme lactase to regular milk, which breaks lactose into its easily digestible component sugars. Colleen Butler / Getty Images

If you avoid regular dairy products because of lactose intolerance, you can turn to lactose-free milk and other dairy products. Have you ever wondered what being lactose intolerant means or how the chemical is removed from milk?

Lactose Intolerance Basics

Lactose intolerance isn't an allergy to milk. What it means is that the body lacks insufficient amounts of the digestive enzyme, lactase, needed to break down lactose or milk sugar. So, if you suffer lactose intolerance and ingest regular milk, the lactose passes through your gastrointestinal tract unaltered. While your body can't digest the lactose, gut bacteria can utilize it, releasing lactic acid and gas as products of the reaction, which lead to bloating and uncomfortable cramping.

Ways Lactose Is Removed from Milk

There are a few different ways to remove lactose from milk. As you'd guess, the more involved the process, the more the milk costs at the store.

  • A common method is to simply add the enzyme lactase to milk, essentially pre-digesting the sugar into glucose and galactose. The resulting milk still contains the enzyme, so the milk is ultra-pasteurized to deactivate the enzyme and extend the shelf life of the milk.
  • Another method is to pass milk over lactase that is bound to a carrier. Using this procedure, the milk still contains the sugars glucose and galactose, but not the enzyme.
  • Membrane fractionation and other ultrafiltration techniques may be used to mechanically separate lactose from milk. These methods completely remove the sugar, better preserving the "normal" flavor of milk.

Why Lactose-Free Milk Tastes Different

If lactase is added to milk, the lactose breaks into glucose and galactose. There isn't more sugar in the milk than before, but it tastes a lot sweeter because taste receptors perceive glucose and galactose as sweeter than lactose.

In addition to tasting sweeter, milk that is ultra-pasteurized tastes different because of the extra heat applied during its preparation.

How To Make Lactose-Free Milk at Home

Lactose-free milk costs a lot more than regular milk because of the additional steps required to make it. However, you can save most of the expense if you turn regular milk into lactose-free milk yourself. The easiest way to do this is to add lactase to the milk. Lactase drops are available at many stores or online from stores, such as Amazon. The amount of lactose removed from the milk depends on how much lactase you add and how long you give the enzyme to react (usually 24 hours for full activity). If you are less-sensitive to the effects of lactose, you don't need to wait as long or you can save more money and add less lactase. Aside from saving money, one advantage to making your own lactose-free milk is that you won't get that "cooked" flavor of ultrapasteurized milk.

Reference: Membrane fractionation processes for removing 90% to 95% of the lactose and sodium from skim milk and for preparing lactose and sodium-reduced skim milk. Morr CV and Brandon SC. J. Food Sci. 2008 Nov: 73(9).