Old recipe wants sour milk
An old Vermont recipe for Sour Milk Doughnuts calls for sour milk. While it is possible to sour un-pasteurized milk it is my understanding that pasteurized milk doesn't sour, it goes bad.
I don't think buttermilk is what is wanted, or was "sour milk" an expression for buttermilk? Anyway I'd like to hear some thoughtful answers on the subject.
This is exactly what I do, in fact most of the recipes I have that ask for sour milk, give this as part of the method. Sometimes, I do have sour milk in the fridge to use by accident because pasteurized milk will sour.
There are some good references here http://www.answers.com/topic/pasteuri... including a quote from the Food Lover's Companion which says "lactic acid bacteria, which cause milk to sour, are not destroyed by pasteurization."
I wonder if this is the same thing as clabbered milk?! In quite a few of my older Swedish cookbooks, they talk about clabbered milk. The recipe tells to smear the bottom of a glass bowl with sour cream, then add the milk.Let stand with a piece of paper covering the bowl for a few hours. It claims the milk should be thickened and slightly sour as well.
Hope this helps!
Buttermilk in modern times is milk cultured with certain bacteria, originally it was the liquid left after churning milk that had cultured or clabbered naturally into butter. Pasteurized milk will spoil if you attempt to sour it as the natural flora and fauna are no longer present. Maybe give it a try with buttermilk unless you can find some raw milk to experiment with.
The modern-day cultured buttermilk, that you can get at the grocers, is a satisfactory substitute for sour milk. Wish we could get the "real thing", but commercially cultured "buttermilk" works just as well.
I put "buttermilk" in quotes because, unless you know of a dairy farmer who makes churned butter, it is darned near impossible to get the genuine article!