Spoiled for Choice, Sour by Choice?
May 30, 2012 10:16 PM   Subscribe

Sour Milk, Soured Milk, and Spoiled Milk. Is there an effective chemical difference? To what extents are any and all unsafe to cook and eat?

I am very sensitive to off smells in my food, especially sour milk and bread with even a little wee wafting tinge of mold.

So, I often find myself too early with a large amount of milk I just can't take in coffee or eat over cereal. However, what my nose doesn't smell doesn't bother my mouth a bit, and I would happily commit to really making use of my sour milk in biscuits, breads, cottage cheese, and especially paneer. This makes me feel like a tough old broad, a resourceful good patriot, and like having a nice fermenty beer with my yummy thrift-biscuits.

But is this wrong? The internet disagrees with itself everywhere (even here, previously) I look about the appropriateness of using (what I know as) sour milk, in cooking.

Some say only unpasteurized, non-homogenized milk sours in the way proper to culinary use, and that deliberately soured milk is instead appropriate. Experience tells me this is something of a practical fallacy... souring (or clabbering) milk entails adding vinegar or lemon juice, curdling the milk instantly, no? This is a step I know from cheesemaking. To use this milk would surely have a different effect on a baked good, for example, than simply milk a bit off, unadulterated with acid and unchanged in consistency.

What is the culinary truth? I don't suppose I need to be really worried about using milk that doesn't past MY sniff test, we're not talking chunky milk before time here, because I know I'm very picky and many people would happily auto-lacto-mustachio with milk I would pass over.

I want to know. Spill it. Please provide citations in excess of your or your granny’s practices, and, to calibrate your touchiness, say whether you would or would not, if inclined by appetite, eat a piece of pepperoni pizza which had sat out overnight.

And what about fat content? Any relevance to this?
posted by Ambrosia Voyeur to Food & Drink (9 answers total) 5 users marked this as a favorite
According to the article linked in this FPP, one of the three different things that "buttermilk" has referred to is milk that was beginning to go bad, which before refrigeration was available was frequently what was used to make butter. (Because they tended to have lots of it handy, since milk spoiled relatively quickly.)

This is making me think that it might be an idea to look for information on Google Books in texts from before refrigeration was widely available. Many of the books there are cookbooks and home economics books.
posted by XMLicious at 10:33 PM on May 30, 2012

As you mention above, I've safely used sour/old raw milk, but would not use sour/old pasteurized milk, and instead would curdle it with lemon juice to use for cheese. I don't have good sources to cite for you, other than received wisdom from chef pals, but I'm sure there are good resources somewhere.
posted by judith at 11:22 PM on May 30, 2012

Some lactobacilli are associated with cavities and there are there are some pathogenic bacteria that they sometimes keep company with, but given that there are many foods that are sour due to fermentation and these foods were around for several thousand years prior to germ theory, much less widely available cultures, I think you don't have too much to worry about with milk that you think most people would say is starting to go off.

Many beers (lambics and Guinness stout) deliberately include a lactobacter fermentation as part of the process. The Belgians routinely source their flora by opening a window and waiting until the wort is cool.

If the smell isn't typical of soured milk, I'd give that a miss.

Given that most everything in peperoni pizza is petty much the product of a preservation technique, or something that we store at room temperature anyway (except for the tomato sauce which should have a low pH and be a pretty bad culture medium in that regard) and that your pizza spent some quality time time at 400°, I'd eat that sucker. Some other toppings would worry me more, but most of the traditional ones are pretty stable.
posted by Kid Charlemagne at 11:39 PM on May 30, 2012

"Experience tells me this is something of a practical fallacy... souring (or clabbering) milk entails adding vinegar or lemon juice, curdling the milk instantly, no? "

No, if you have pasteurized milk you can sour it by adding the right bacteria. Buttermilk with live cultures will do it. (Just a little bit is needed.) I usually do this with cream, though. I let the cream sit (covered) at room temperature or overnight and then I put it in the stand mixer and it makes excellent cultured butter.

(It does NOT work with ultra-pasteurized milk/cream, btw.)

A lot of the stuff that would make good soured milk is removed by pasteurization. That's why you replace it by adding the good stuff back in. If you just let normal pasteurized milk sit around, the bad bacteria grows in it. It smells entirely different and I don't think you should eat it.

Soured milk -- the old fashioned kind -- doesn't smell bad, it smells more like sour cream. It is a good smell, slightly yeasty and tangy. You don't generally get that with sour modern milk that's just been left out to spoil.

I wouldn't eat a slice of pizza that had been left out all night but I have eaten a LOT of soured cream that had been left out all night to sour. It's gooooood.

(I've also made cheese by adding vinegar or lemon juice. That's different. That's just making curds, not souring, to my mind. You can sour the milk first, though...)
posted by litlnemo at 1:00 AM on May 31, 2012

If I were in your situation with some less-than-fresh milk, I would make a new bacterial culture in it using a starter from a fermented milk product I already knew I liked (like yogurt).

First re-pasteurize the milk in a pot, cover it, wait for it to cool to about body temperature, and then inoculate it with yogurt or buttermilk. That way the good-tasting bacteria will establish a strong foothold. Let it sit around covered for another 8-12 hours in a warm place, and then taste it. It should be on the way to being delicious. At that point, refrigerate again. It will continue to thicken, but it should taste good and last much long than the milk would otherwise.
posted by overeducated_alligator at 5:03 AM on May 31, 2012

Re: fat content -- as far as I know, fat content won't affect fermentation, but higher-fat dairy products tend to taste less sharply acidic when fermented. Whether sour from added acids like vinegar/lemon juice, or sour from bacteria, it's going to be different in pH from the original milk. So you may have to compensate in baking recipes by increasing baking soda or cream of tartar.
posted by overeducated_alligator at 5:12 AM on May 31, 2012

Many English grannies advise that scones are better with sour milk (that is, slightly gone off).

It had not occurred to me that their advice predated pasteurisation, so there is that.
posted by Helga-woo at 5:49 AM on May 31, 2012

Growing up it was common practice for us to write sour on the side of a gallon of milk that failed the sniff test and put it back it the fridge. And there it would sit until being used as "buttermilk" in recipes. Until today I didn't know there was a difference between spoiled milk and sour milk.

Occasionally the "sour" milk sat long enough to separate. At this point we'd throw it out, but only because we didn't know how to make cheese. I have no doubt that if we'd had the internet back then we would have been making our own paneer.

As for citations I've searched high and low and I couldn't find anything definitive and reputable.

As for calibrating my touchiness: yes I've eaten that pizza.
posted by zinon at 6:37 AM on May 31, 2012

I agree with litlnemo and overeducated_alligator.

And I would eat that pizza.
posted by werkzeuger at 2:21 PM on June 3, 2012

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