[theGeatZhopa]

It's not possible to filter lactose out of the milk. The only possibility to get lactose free milk is to split lactose into glucose and galactose with the enzyme lactase. And that's actually is done: just dump lactase into cow milk. I never drank not sweet lactose free milk.

But, if one is about to make a milk powder, then it is possible to remove the split lactose sugar crystals. But it's not milk anymore..

[masklinn]

You can do it the other way around: instead of filtering lactose out of the milk you filter the solids making a protein and fats concentrate.

This is mostly used as a preprocessing step for cheese production, but by rehydrating you get ultra-filtered milk, which are lactose-free and not sweet.

[theGeatZhopa]

Oh yes.. I haven't thought of this. Oh my. Ultrafiltration by/with osmosis and a semi permeable membrane allows to remove water and small molecules. The same process as dialysis-treatment in kidney failure. To get the sugar and water solubles out of milk, you need to pull a bit of the water from the milk and with it all the stuff that is smaller than the holes in the membrane (filter). And then, you readd plain water or take the ultrafiltrate and do a second stage of filtering with even finer membrane. And readd this to the now concentrated, thick milk. If it's not like the principle of dialysis, then maybe be like lipidapheresis which is a bit different in function. Or a Mix of the two systems :)

So it's possible. Thank for pointing out.

[oidar]

Fairlife brand lactose brand milk claims that they are able to do it.

[lesuorac]

https://patents.google.com/patent/US7829130B2/en via https://www.reddit.com/r/chemistry/comments/1claif5/getting_...

From my understanding they take advantage of lactose being smaller than milk and they just get the milk "stuck" in the filter and then throw out the unfiltered lactose.

[theGeatZhopa]

They remove a part of the lactose first, then add lactase. It's not as sweet anymore then.

[theGeatZhopa]

Yes, they do it with ultrafiltration and as the patent says with nano filtration and, with salt addition to get reversed osmosis. The steps are quite clear described.