A couple weeks ago I tried making a danish rye bread using Magnus Nilsson's recipe from "The Nordic Cook Book."

The recipe basically calls for a preferment of rye, yeast and buttermilk which you let sit for 72 hours before adding the rest of the rye flour, buttermilk and rye kernels and waiting another 24 hours.

The problem is that by the end of those 96 hours, my concoction was so foul smelling that I can't imagine it turned out correctly. It was the usual rye scent with a strong hint of vomit, and I didn't even try to bake it.

  1. What should the dough smell like after four days of fermentation? How can I tell if it's gone wrong?

  2. For this type of recipe that requires buttermilk or cultured milk, is it possible that the milk+lemon juice substitute simply doesn't work? You need the actual bacteria from real cultured milk?

  3. If my dough did go bad, was it just a matter of bad luck in getting the wrong bacteria, or was there something I could have done?

  • I presume it sits in the fridge, but is that the case? Either way it might well need the lactic acid bacteria, but especially at room temp
    – Chris H
    Apr 27, 2021 at 19:56
  • 1
    One would suppose that buttermilk with a living bacteria culture would not spoil as quickly as regular milk (or even slightly acidified milk with lemon). These kinds of fermented dairy products were originally made to preserve milk (among other reasons). The idea is that the specifically cultured bacteria will out-compete the bacteria that normally cause milk to spoil. I've never left buttermilk out at room temperature for four days - but I do presently have a bottle of buttermilk in my refrigerator for about a month and it still tastes fine.
    – Juhasz
    Apr 27, 2021 at 22:19
  • I can't tell from your question, did you use real buttermilk, or did you substitute milk+lemon juice?
    – csk
    Apr 28, 2021 at 2:46
  • I used the milk+lemon juice substitute, and it sat out at room temperature. I'm starting to think that was the problem.
    – Rekov
    Apr 28, 2021 at 5:52
  • Have you made sourdough before? I can imagine that the smell of a(good!) sourdough culture can be perceived as vomit-like if you don't know it, even if that's how it should be, and this could be a similar concoction. Apr 28, 2021 at 10:11

1 Answer 1


I definitely think buttermilk is required. If you don't want to invest in a whole jug, you might be able to find some plain kefir instead, or even yogurt will work in a pinch.

Sourdough starters (like the preferment like here) contain a combination of yeast and bacteria. It will definitely have a sour and somewhat funky smell, but generally speaking we've evolved to recognize good funk smells from "I'm not going to eat that" smells. It's not perfect, but it's helpful.

Yeast and bacteria are naturally present.... Everywhere basically. We get yeast infections on our skin and in embarrassing places because they are literally everywhere. Ever had dandruff? That's a yeast thing too. But there are lots of varieties of yeast. Beer and wine yeasts have been cultivated to produce/tolerate different amounts of alcohol for example. So even though yeast is everywhere, you added bread yeast to your preferment because you wanted that one. you didn't want some weirdo yeast chilling under your fingernails or something.

The thing with the milk and lemon juice substitute for buttermilk is that it only mimics the acidity and sweet-sour flavor for baking. But the bacterial profile is not the same. It could be anything! Some bacteria naturally present in milk produce iodine, which is bitter. For all I love my ferments, I can't predict whether my milk will become a delicious mesophilic buttermilk or a jug of bitter sadness if I let it spoil naturally..... But that's kind of what you did here.

Your milk and lemon juice both contained bacteria in small amounts to start, and nobody knows what they were. After several days, those bacteria multiplied by a lot, and your nose told you that whatever they were, they did NOT make something delicious. I think you were right to toss it.

So, while you might not have to use buttermilk, I would definitely use some kind of cultured dairy. Buttermilk or kefir would be best because those are room temperature mesophilic ferments. Yogurt will work in a pinch, but they're typically predominantly thermophilic cultures, meaning they flourish in a warmer environment.

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