How does soaking liver in milk work?
Soaking liver in milk is said to be a common technique that supposedly helps to remove impurities, softens flavour, and tenderises the liver.
I tried it, and the liver turned out alright, but it got me wondering: how does this work? What's the chemistry behind it? Exactly what's happening between the milk and the liver?
Is it the acid in the milk tenderising the liver? That would mean I could soak liver in a marinade based on lemon juice or vinegar? (It doesn't seem like a terrific idea)
Or is there something else involved? I searched around, but nothing I found seemed terribly exact.
My knowledge about the phenomenon itself is limited but I did see it mentioned in "Modernist Cuisine" (Nathan Myhrvold, p. 147)
Many recipes for foie gras, liver, sweetbreads, and other offal include a soaking step before cooking. For kidneys, this step serves a very simple purpose: to remove any trace of the animal's bodily fluids. Recipes often call for soaking foie gras, liver, and sweetbreads in milk. It is often said that milk improves the taste, purges blood, lightens the color, or affects some other property of the meat. We were skeptical, so we tried several experiments. With a mild-flavored organ meat like foie gras, we could taste a difference, but, frankly, in our tests, we prefer the taste of water-soaked to milk-soaked foie gras. With stronger-flavored organ meats, there is even less of a difference than with foie gras. So our suggestion is to simply soak the meat in water.
So, there you have it.