Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

My sourdough tastes like onions

  1. Mar 7, 2015 #1


    User Avatar
    Gold Member

    A brief introduction: About 6-7 months ago I got really interested in making various types of bread. The one bread that I really wanted to make was sourdough: it is one of the oldest breads in the world, and perhaps one of the most universally loved, described by some as being "the world's best toast". However, many don't make it because it is seen as too tedious having to feed the starter either every day (if left at room temp) or weekly (if left in the fridge).

    My sourdough starter has been going strong for about 200 days now, with regular feedings of equal parts strong, white bread flour, with lukewarm water. I've made just over a dozen 400-800g loaves in total and the results have been slightly different each time.

    The first time I made it was around day 10 or so. This created a bread that had a traditional sourdough taste, the kind that you would taste if you bought it in a shop. Great!

    Around day 50, it tasted even more sour, but still good. There was a much greater depth of flavour. So far, so good.

    It was after 120 days or so it started getting a bit strange. I followed my usual routine -- i.e. waiting a few hours after feeding my starter before using it (doing the "float test"), with no mishaps. Smell and crust were the same as usual. The difference came down to the taste. It had a distinct "caramelised onion" type of flavour, with a hint of the sourness I had previously got. It was a nice taste, but not what I expected at all. Apparently it's to be expected that the sourness of loaves will differ dramatically, but an onion flavour? What is the reason for this? Can this be put down to "the yeast is evolving"? Will the flavour change dramatically over time? Is this a sign that my starter is going bad or isn't being fed properly?

    I should also note that I had previously never cleaned the container it has been in since August. It had developed a flaky crust around the rim, with a yellowy starter-coloured build-up around the sides. A couple of people online said this was normal and that it actually helped your starter thrive, but a few others disagreed. I never noticed any bad smells (only the typical yeasty/fermenting smell before feeding, and sweet/milky smell after feeding), and it doesn't look like any bad yeast has got mixed in with my starter. I have since scrubbed all the build-up out of the container now. Could this has been the reason for the taste?

    I do store my starter in a fridge, but not near to any onions. The recipe I've been using for the past 6 months is here: http://www.bbc.co.uk/food/recipes/how_to_make_sourdough_08213
  2. jcsd
  3. Mar 7, 2015 #2


    Staff: Mentor

    I'm not any kind of expert on this, but if your sourdought starter is starting to smell like onions, the simplest possible explanation is that it's picking up odors from the onions. Just because the two aren't close together doesn't mean much -- the air in a refrigerator circulates all over.
  4. Mar 7, 2015 #3
    I don't know, but a "carmelized onion" bread sounds like it would make a great toasted peanut butter and bacon sandwich.
  5. Mar 8, 2015 #4
    It _may_ have an infection. There are many many many possible vectors for inoculating starters with ...well... all kinds of semi-random stuff. Some people find these new and interesting flavors just part of the adventure.... Probably nothing too harmful, but flavor drift can be an inevitable long term consequence. Maybe it is just time to mix up a new starter..... In purely practical terms, starters _do_ tend to have (highly variable) useful lifespans. It didn't mean you did anything wrong. Handling, air contact, etc can introduce all kinds of things.

    Breadmaking is an art. Sanitation is key. Enjoy yourself.

  6. Mar 8, 2015 #5


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    When you say it smells like onions, do you mean it has some sulfur notes?

    I don't know anything about sourdough but I make hard cider (fermented apple juice), and I've had a sulfury batch or two. In the case of fermenting yeast, it indicates the yeast is stressed due to poor nutrients. Yeast needs more than just sugar in order to thrive. What are you feeding it?
  7. Mar 9, 2015 #6


    User Avatar
    Gold Member

    Thanks for the replies.

    In terms of storage, I have always kept it covered in clingfilm in the fridge. There have been times where I've gone a while without feeding it (8 days or so) and a watery substance has developed over the top. However, after discarding some of it and refeeding, it seems to return to its normal self.

    Feeding-wise, my routine is as follows: first, I take the starter out of the fridge for a few hours until it warms up to room temperature. I discard half the starter and feed it strong white bread flour with an equal amount of lukewarm water. I leave it out at room temperature for about 4 hours for the starter to rise and froth up, before putting it in the fridge again. I repeat this every 5-7 days. I'm not sure about sulfur notes, but it just has a mild onion flavour -- I'm not sure how else to describe it. It's not a bad taste at all but I don't want it to get worse.

    If there was an infection, how would I tell? I've never had any visible mould growing on my starter and it has always smelled pretty much the same. Colour has remained the same, too. Do I need to taste it every so often?

    The recipe I read said flour and water should be enough to keep the yeast alive. On the other hand, I've read about people feeding it all sorts of things like brown sugar and even crushed tablets. I'm not sure about putting that in the starter seeing as I'm going to be eating it too, does anyone have experience in that regard?
  8. Mar 9, 2015 #7
    It doesn't have to have mold. An infection can be actually pretty subtle and can reflect a minor growth of many different things. The flavor drift may be the evidence in itself. This is all a bit speculative, and starters are a bit of an art..... but I'd say that 6 months is a pretty good lifespan for a starter. I would just toss this one and mix up a new batch, unless you are into the idea of a 'lambic' starter :)

    I'll look in some of my books and see what the historically expected lifespans are without too much drift.... but this is a pretty inevitable consequence, even without a significant infection.

  9. Mar 9, 2015 #8
    Mycroft is that you?

    In the CBS TV series Elementary, Mycroft is a restaurateur who owns a gourmet international restaurant chain called Diogenes.
  10. Mar 9, 2015 #9
    Cool reference but not I. You may reasonably infer some of the features tho.... still, go back to the source.

  11. Mar 9, 2015 #10

    Quantum Defect

    User Avatar
    Homework Helper
    Gold Member

    Could be that your bugs have changed. Onion and garlic smells are indicative of the presence of sulfur-containing compounds.


    Some bakers have had problems with thiol (another sulfur compound) producing micro-organisms:


    Food scientists have measured dimethyl sulfide as being a component of sourdough flavor:

    https://books.google.com/books?id=L...#v=onepage&q=sourdough methyl sulfide&f=false

    Wikipedia says that dimethyl sulfide smells like cabbage.

    I suspect that you have/had some bugs that are excreting the offending molecule.
  12. Mar 9, 2015 #11
  13. Mar 10, 2015 #12
    Heh.. just a grouch with a degree in Philosophy :) ....and I love dogs. (and am pretty good at baking).

  14. Mar 11, 2015 #13
    Diogenes probably liked sourdough.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook