milk receival system

How Lactose Free Milk is Made – Lactose 101

This is a guest post by a fellow food technologist (in training), Shriya Kumar. She is currently working towards a Master’s degree at Wageningen University & Research and soon, a career in the food industry.

Before you start reading this post, take a second to think of three people you know who are lactose intolerant. Done? Something tells me that wasn’t difficult. You probably had more than three people’s names pop into your head.  It’s why you can buy lactose-free dairy products nowadays.

But where does lactose come from, why is it associated with dairy and how can you get rid of the lactose? Let’s go back to the basics and see what lactose actually is. Stick around to see whether people with these intolerances have to steer away from dairy altogether. Lactose 101 coming right up!!

What is Lactose?

Lactose is a disaccharide. This means it contains two sugar (or saccharide) units namely : glucose and galactose (both monosaccharides).

glucose molecule


Lactose is naturally found in milk, where it makes up around 4.6% lactose. Products made from milk vary in lactose content based on the processing they went through. Yogurt and Kefir contain around 3-4% lactose respectively. Butter, which mainly consists of fat, has anywhere between 0.5% – 1% lactose. Dried or dehydrated milk derivatives have a higher lactose content on account of being concentrated when water is removed. Milk powder from whole milk can contain between 35.9 – 38.1% lactose whereas condensed milk can have 11.4-16.3%. Cheese contains only around 14% of the total lactose content in milk i.e. 0.64%!!

A lot of the processed foods we consume can also contain lactose. Imparting a sweetness of less than 50% of regular sugar (sucrose), it is a convenient ingredient for food developers to use as a bulking agent or filler in products. Pharmaceutical products, creamy liquor, powdered mixes like instant coffee products, soups or cake mixes are very likely to contain this carbohydrate. Lactose (with its source : milk) will always be declared as a mandatory requirement to meet regulations. Pro tip : Always take a quick look at the label of these products!

 Why are some people lactose intolerant?

To break down our food, our body produces enzymes. Enzymes are highly specialized molecules that can help chemical reactions take place. Enzymes are crucial for digesting our food where they break down larger molecules into smaller ones. Pepsin, amylase, protease, lipase are some examples. Proteases for instance break down proteins, whereas lipase breaks down lipids.

Similarly, we also produce lactase to break down lactose into the two monosaccharides (glucose and galactose), to eventually be absorbed by our body. If lactose isn’t digested (broken down) completely, this may cause a series of symptoms. Common symptoms are abdominal discomfort, flatulence, cramps or dehydration and there is a wide range of severity of these. Some people can comfortably consume small portions of products made with milk (depending on how severe their reaction is) whereas others should avoid all lactose at any cost. Such individuals are lactose intolerant.

home made yogurt in jars
Yogurt contains less lactose than milk, but still quite a bit!

Primary and secondary lactose intolerance

It is usually rare for children below the ages of 6 to be lactose intolerant and only children with congenital lactose intolerance (i.e. no production of lactase genetically) develop this from birth. The chances of developing the intolerance increases as we age. As human beings age, our bodies stop producing lactase and this increases our predisposition to this intolerance, the primary intolerance.

Secondary intolerance occurs when activity of lactase is affected due to intestinal problems/damage (cow milk allergy, Celiac’s disease etc.). This type is not as common.

Some populations or ethnicities are more prone to being lactose intolerant. Europeans are most likely to continue lactase production through their lives whereas people from certain parts of Asia, Mediterranean regions, or Africa can develop intolerance more easily. (LINK)

Can lactose intolerant people consume dairy products?

The question on its own seems pretty rhetorical right? Without giving it a second thought, it could be dismissed as “Of course not”! That is not completely true though.

Nowadays manufacturers can remove lactose from milk which allows consumers intolerant to lactose to drink this milk. But there are more dairy products that do not contain lactose. 

Fermentation, used for making yogurt, for instance, can reduce the lactose content. Yogurt usually has around 30-40 g lactose/kg yogurt, slightly lower than the original 46g lactose/kg milk. This is because, lactic acid bacteria (LAB), the microorganisms that ferment the milk, consume the lactose and convert it to lactic acid. Though the process only breaks down a fraction of the lactose in the milk, this reduction could make it possible for some less-sensitive individuals to consume yogurt. Moreover, bacteria can produce lactase in yogurt (from the bacteria) which can aid the lactose digestion. Techniques like heat treatment can reduce the activity of these enzymes though.

Other fermented milk products like Kefir work in a similar way. An important thing to remember here though, is that while enhanced digestion of lactose does take place after eating fermented milk products, individuals can still have the symptoms.

freshly made paneer from water buffalo milk
Cheese in progress, contains less lactose than milk, but isn’t lactose free!

How lactose free milk is made?

To cater to this lactose intolerant population, there is a wide range of products that contain no/reduced lactose. While non-dairy products are, of course, an option, nowadays, you can also find lactose free milk! It has all the other ingredients of milk but no significant lactose content: win-win!!

Using lactase

The simplest way for manufacturers to remove the lactose is to break it down before people consume it. This is very similar to how your body would have broken down the lactose themselves. To do so, manufacturers simply add the lactase enzyme to milk.

Lactase can be added either before or after the pasteurization or UHT treatment. Of the two techniques, some prefer adding the lactase after the heat treatment to control the Maillard reaction in the milk.

If you have ever tried lactose-free milk and found it to be sweeter than regular milk, it’s because of the free glucose and galactose (which are both significantly sweeter than lactose). The enzymatic reaction breaks the lactose down into its individual monosaccharides.

Physical separation

The other way to produce lactose-free milk is to physically separate it from the milk using filtration. Lactose is quite a small molecule, compared to the other major molecules in milk: proteins and fats. However, it’s bigger than the salt in milk, such as calcium.

To create lactose free milk manufacturers therefore first need to remove the proteins and fats. That way, they won’t block the pores of a filter in a later step. This is done by using filters through which water, salt and lactose can travel easily, but fat and proteins cannot. These can be micro- or ultra-filters. Alternatively, centrifugation can also be used to separate a large part of the fat on forehand.

Next, filters with even smaller pore sizes are used, called nano-filters. These let the minerals pass through, but keep back the lactose. By then reconstituting the water + minerals (the filtrate) with larger proteins and fat to the right concentration makes lactose free milk.

The lactose that is separated is a useful ingredient and can be used in dry mixes, liquors, confectionary etc,

A combination of the two techniques i.e. enzymatic breakdown and membrane separation can also be employed to improve the efficiency of lactose removal. Of course, if you want to use the lactose for another application, you are limited to filtration only.

Lactose-free is not 100% free

Commercially available lactose free products can still contain around 0.01% lactose since lactose removal is not 100% efficient. With the wide spectrum of sensitivity to lactose, some people with very high sensitivity may still experience symptoms even after consuming products with only traces of the sugar being present in them. Such people would indeed be required to completely avoid any dairy products, even lactose-free ones.

calf looking at you
This is where your milk comes from!

Choosing products

The next time one of the people you know with a lactose intolerance comes by to eat, consider whether you know the severity of their intolerance. If you don’t, products that don’t contain any lactose are your safest best. (If you want to make pancakes, consider using oat milk?!)

However, if your friends are only moderately intolerant (and they’ve confirmed so), you can now impress them by serving lactose-free milk and being able to explain, just actually how it’s made!


GEA, Membrane filtration in the dairy industry, link

Harju, M. & Kallioinen, Harri & Tossavainen, Olli. (2012). Lactose hydrolysis and other conversions in dairy products: Technological aspects. International Dairy Journal – INT DAIRY J. 22. doi: 10.1016/j.idairyj.2011.09.011.

Lactose intolerance – Andrea S. Wiley

Lomer, M.C.E., Parkes, G.C. and Sanderson, J.D. (2008), Review article: lactose intolerance in clinical practice – myths and realities. Alimentary Pharmacology & Therapeutics, 27: 93-103. doi:10.1111/j.1365-2036.2007.03557.x

Louwagie, V. S. (2019). Lactose intolerance. Journal of the American Academy of Physician Assistants, 32(11), 49–50. doi: 10.1097/01.JAA.0000586344.04372.e6.

Middleton, J., 8 surprising sources of lactose, link

Nutra Ingredients, Fermented milk for lactose intolerance, 2-June, 2003, link

Chapter 3 Lactose content of milk and milk products, The American Journal of Clinical Nutrition, Volume 48, Issue 4, October 1988, Pages 1099–1104,

Jonas A. Ohlsson, Monika Johansson, Henrik Hansson, Agnes Abrahamson, Liisa Byberg, Annika Smedman, Helena Lindmark-Månsson, Åse Lundh, Lactose, glucose and galactose content in milk, fermented milk and lactose-free milk products, International Dairy Journal, Volume 73, 2017, Pages 151-154, ISSN 0958-6946,, link

Rusynyk, R. A., & Still, C. D. (2001). Lactose intolerance. Journal of the American Osteopathic Association, 101(4 supplement 1), 10S.

Dennis A Savaiano, Lactose digestion from yogurt: mechanism and relevance, The American Journal of Clinical Nutrition, Volume 99, Issue 5, May 2014, Pages 1251S–1255S,

D A Savaiano, A AbouElAnouar, D E Smith, M D Levitt, Lactose malabsorption from yogurt, pasteurized yogurt, sweet acidophilus milk, and cultured milk in lactase-deficient individuals, The American Journal of Clinical Nutrition, Volume 40, Issue 6, December 1984, Pages 1219–1223,

Segurel, L, Bon, C., 2017, Annu. Rev. Genom. Hum. Genet. 18:297-319, link ; graph visualizing lactose intolerance spread globally

Karl F. Tiefenbacher, Chapter Three – Technology of Main Ingredients—Sweeteners and Lipids, Editor(s): Karl F. Tiefenbacher, Wafer and Waffle, Academic Press, 2017, Pages 123-225, ISBN 9780128094389,, link

Wiley A. S. (2020). Lactose intolerance. Evolution, medicine, and public health2020(1), 47–48. link

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  1. Very detailed study of lactose intolerance in people. Very useful for lactose intolerant people to decide on how to select their choice of food products

  2. Thanks for putting together this very well researched and very well written/ explained article for average people out there looking for answers. Our doctors failed to diagnose and fix a decade old issue of stomach ace, bloating and acid reflex. They did test for Celiac disease among several other things but not Lactose intolerance, which we noticed recently might be the culprit (the problem went away by accidentally removing milk for two weeks from our diets!). Your blog is a rare find, a gem, in the heap of digital information and disinformation we live in these days.

  3. Does lactose free milk still contain lactic acid ? And does it containCaudovirales Bacteriophages?

    • Hi Dianne,

      Fresh milk generally does not contain any lactic acid, this is only formed after some time due to the conversion of lactose into lactic acid by lactic acid bacteria. Since the lactose is generally removed from fresh milk, I’d assume it doesn’t contain any lactic acid, though can’t say it will never be formed during storage.

      I do not know enough about Caudovirales Bacteriophages to say whether those are present. That said, it’s good to know that lactose removal itself does not remove microorganisms. Whether or not microorganisms are present depends more on whether the milk has been pasteurized/sterilized.

      Hope that helps!

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