Why Spoiled Milk is Not the Same as Soured Milk

Raw Milk Fresh from the FarmI’m currently spending a couple of weeks with my elderly father. I was asking him about his childhood, when he suddenly mentioned that he knew how to cook. Loyal readers might recall that growing up, I never saw my father make much more than a cup of tea. But it turns out that he knows the recipe for farmer’s cheese: Set out fresh milk for a day or two and let the fat rise to the top. Remove the fat. Let the milk sit for another couple of days. Put it in a cloth and let it drain.

I would love to try this recipe, but I can’t make farmer’s cheese. I only have access to pasteurized milk. My father made cheese from the raw milk he collected from the local farmers that his mother would sell out of their home in pre-war Poland.

Pasteurized milk is also a problem in recipes calling for sour or soured milk, like quick breads and pancakes. In times when refrigeration wasn’t common, milk spoiled quickly and home cooks found uses for milk that was turning sour. They took advantage of the natural bacteria in milk that caused it to ferment. Soured milk adds a tart flavor to baked goods in the same way that many recipes call for wine, vinegar, and sourdough yeast that are also naturally fermented foods.

Nowadays, milk is pasteurized to kill harmful bacteria that can cause illness—the pathogenic bacteria. Pasteurization involves heating the milk to about 72 degrees Celsius for 15 to 20 seconds. The problem is that pasteurization kills the “good” bacteria that made sour milk suitable for cooking or for making cheese. But bacteria is relentless and attacks any food that is not properly preserved, including pasteurized milk. The bacteria are non-pathogenic, but they still destroy food and will eventually cause the milk to spoil.

While spoiled milk won’t kill you, the bacteria have broken down the milk enough that there isn’t much nutrition left in it. It also tastes terrible, and heating it won’t return the fresh flavor. Drinking spoiled milk or spoiled food of any kind is unwise unless you’re literally starving.

If you have a recipe calling for sour milk, put a teaspoon of vinegar in a cup of fresh milk and let it sit for a few minutes.

Tip: Scalding milk, or heating the milk to just below boiling, was a way to stop unpasteurized milk from fermenting. If you come across scalding in a recipe you can skip it.

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  1. I hear you. Sour milk isn’t the same as spoiled milk, but even if the milk is rancid, it won’t get you sick because you’re killing any bacteria by cooking it. I dunno, I follow what my doctor father tells me. If he says its perfectly healthy to eat spoiled milk cooking in things, I’ll believe him.

    • I’m just wondering whether what I read about the milk turning rancid is completely correct. Won’t bacteria from the environment start to grow in the pasteurized milk, just like it would in cooked chicken, for example?

    • I researched a little more and updated the post.

  2. I thought maybe you were getting into the raw milk thing, Hannah. I’m guessing there is some farmer on Long Island who will sell you raw milk. It is becoming more in vogue, partly for health reasons and partly because people like the taste. Raw milk is supposed to be good for some people with Crohn’s, for example.

    You won’t catch me drinking either pasteurized or raw milk. Can’t stand the stuff.

  3. To clarify — you are saying that pasteurized milk does not sour, rather it spoils, because all the good bacteria that would result in souring are killed through pasteurization. Is that correct?

    I love soured milk in stuff like pancakes or corn bread, but I have found that 2 tbsp lemon juice per cup of room temp or warmer milk works better than vinegar.

    Are you saying that farmer’s cheese is drained, soured milk and not spoiled or curdled via any kind of agent? That is very interesting.

    I have made panir cheese (Indian cheese) using just lemon juice to curdle it and then rinse and drain. It was very good, but takes a LOT of milk to make a little cheese.

    Our food coop used to sell raw milk (Philadelphia in the 70’s) and I recall really liking it. But I’m a milk fanatic anyway. Still drink several quarts of whole milk/week.

    I’ve also heard raw milk can be good for some things. I wouldn’t mind getting some, but my husband is dead set against it and anyway it’s illegal in MD.

    • Tanya, yes. I’m going to include your suggestion. The farmer’s cheese recipe is my father’s, I haven’t confirmed it.

  4. You wrote: “Soured milk adds a tart flavor to baked goods in the same way that many recipes call for wine, vinegar, and sourdough yeast that are also naturally fermented foods.”

    Modern recipes will often use buttermilk (in Israel, “rivyon”) to achieve the flavor + rising benefits, eg., for traditional American biscuits.

  5. Aviva_Hadas says

    Yes, raw milk is illegal in MD, but you can get it in Penna. if you want it. My father was in a coop in the 80’s & we got raw milk – I hated it. The eggs & veggies on the otherhand, those were wonderful.

    Thanks for the tip on scalding, that technique has kept me from one or two recipes…

    • You’re welcome, A_H.
      Debbie, don’t know about it. Sounds like something to avoid, but I guess it’s good to avoid wasting food. I wonder if it is sold at a discount (ha).

  6. Someone recently told me that if there’s a printed code on the bottom of a carton of milk in Israel, it means the milk was close to spoilage and returned to the manufacturer to be re-pasturized and reissued. It sounds very strange. Have you heard anything like that?

  7. That business about the manufacturer re-pasteurizing spoiled milk sounds utterly disgusting. IMHO there are few things more revolting than spoiled milk.

  8. BookishIma says

    All the supermarket milk where I live right now is ultra-pasteurized, so I’ve been considering trying out raw milk. It’s a whole story to get it, though. If there was lightly pasteurized organic stuff at the super I wouldn’t bother, but… Does anyone know about getting raw milk in Israel?

  9. Orthonomics says

    Thanks for this information. A lot of frugal digests talk about using milk that has gone sour. I can’t stomach milk that tastes a bit off. I’m not much of a milk person, so I try to plan enough things with milk so our weekly gallon doesn’t end up down the drain.

  10. We (especially I) are huge milk drinkers. We go through about 2 gallons/week. I buy at Trader Joe’s (cheapest prices around) and freeze.

    An important thing to keep in mind when you freeze those large plastic gallon jugs is to first drain 1 cup off the top and keep the top loose. If you don’t, when the milk expands from freezing it will split the seams of the bottle. Then when you defrost it, the bottle will leak.

  11. Orthonomics says

    Good to know. Thanks Hannah and TDR.

  12. We LOVE raw milk (mine is pictured in the photo). I often leave the milk out on the counter for a day or two to sour before making cheese. I also let the cream sour before I make butter as I like the cultured butter better than sweet butter.

    Here in Ohio raw milk is illegal as well, but we purchased shares in a farm. It’s legal to drink raw milk if it’s from you own cow. So we bought a cow and we pay a farmer to take care of it for us. We pick up milk at the farm every week. It’s so much better than store-bought milk for sure.

    If you are considering drinking raw milk, I’d highly suggest only getting it from a reputable farm that pastured their cows. The cows on our farm live happy cow lives, grazing on the fields and getting lots of fresh air and sunshine. The milk has a different flavor in each season depending on the grass or hay they’re eating, it’s quite wonderful to experience this.

  13. Hannah, this article about milk is very helpful and informative!

    I caught a minor typo though in this line:

    `Pasteurization involves heats the milk to about 72 degrees Celsius for 15 to 20 seconds.´

    `heating´ would be the correction

    Thank you for sharing your knowledge! Very much appreciated! 🙂

  14. Liz Undp says

    Interesting post and comments. I’ve always made “farmer cheese” when milk spoils (I have some going right now, as the fridge has died!). I keep the milk out till it thickens and separates, drain through a cheesecloth-lined cheesecloth, squeezing occasionally, until it’s dry, and then flavor with chopped herbs, mashed garlic and a little olive oil. And I’ve lived to tell the tale….

    • Hi Liz, I am glad that it worked for you. A lot of people say that they work with milk that is only slightly spoiled. Sorry about your fridge.

  15. THANK YOU so much for your information!! It made total sense after you explained that pasturizing it IS killing the bacteria that makes it healthy if and when it does go bad. Just so good to know!!