4 Reasons Why Your Sourdough Smells and Tastes Bitter

Take a bite of your sourdough bread without any additional butter, cheese or oil. It should taste salty, sour and sweet; bitterness should not be a prominent flavor in sourdough breads.

Sourdough bread tastes bitter when its ingredients have gone rancid; vegetable oil, butter, whole grain flour, seeds and nuts that is found in sourdough bread contains fats and oil turns rancid and bitter over time.

It is quite easy to determine if any of the ingredients have gone rancid and there are some simple strategies you can use in your baking to help keep your ingredients fresh.

1. Rancid Fats and Oil in Sourdough Bread

Some sourdough formulas calls for some type of oil or butter to be added into the dough for baking. The most common reason why your sourdough bread tastes bitter is that the fats (oil and butter)  used in the bake has gone rancid; rancid fats and oil leaves a very unpleasant bitter taste when eaten.

It is best to avoid eating bitter tasting bread as the rancid fats and oils in the bread is harmful to your liver and is potentially carcinogenic; not to mention it taste pretty bad.

Oil and fats turn rancid from over exposure to air, light, and heat. Prevent your oil and fats from turning rancid by storing it in a cool, and dark place, and avoid mixing different types of oils if possible.

We can tell if fats and oil have gone rancid by smelling it; rancid fats and oil smells off, it smells like crayons. If you are still unsure, you can heat up the fats and oil in a pan and take another whiff.

2. Rancid Flour in Sourdough Bread

Even when your sourdough formula does not call for any additional oil or butter in the mix, it can still go rancid because the flour used in sourdough bread contains fats and oils as well.

Whole grain flour in particular is more susceptible to rancidity as compared to white flour because whole grain flour contains the germ of the grain while white flour does not.

The germ of the kernel is the embryonic heart. It comprises only 2.5-3.5% of the kernel but it is packed with vitamins, minerals and fats. Due to the high proportion of fat, the germ tends to turn rancid, and hence whole grain flour which contains the germ is more prone to rancidity.

If you bake using flour from Europe, you will notice that it is characterized by its ash content which indicates how much of the grain is milled into flour; a higher ash content tells us that more of the bran and germ of the grain is used, and hence flour with a higher ash content is more prone to being rancid. Whole grain flour has an ash content of about 1.4% while white flour has an ash content of about 0.5%.

The best way to determine if your flour has gone bad is to smell it. Normally flour should smell odorless or sometimes slightly nutty but when flour has turn rancid, it will smell stale, sour or musty.

Refrigeration of whole grain flour delays rancidity and the baker should also rotate his stock to reduce using flour that is too old.

3. Rancid Seeds and Grains in Sourdough Bread

The addition of seeds, nuts and grains is a great way to add vitamins, minerals and great flavor to your sourdough bread, but because these seeds, nuts and grains contain a high proportion of oil, they can also go rancid and produce a bitter tasting bread.

Stale and rancid seeds, nuts and grains smells and taste similarly to stale fats and oil; take a small bite to check if they have gone bad, before using them in your bake.

There are a few ways to delay rancidity of your seeds, nuts and grains, and hence prolong its shelf life.

  • Whenever possible, buy whole and raw seeds,nuts and grains; chopped and toasted variants has their oils exposed to the air which can turn rancid quite quickly.
  • Store your seeds, nuts and grains in air-tight containers as over exposure to air expedites rancidity.
  • Refrigerate your seeds, nuts and grains as the cold temperature slows down the chemical reactions that causes rancidity.
  • Check the manufacturing date and buy the freshes seeds, nuts and grains that you can find.
  • Buy your seeds, nuts and grains in small batches rather than bulk to prevent using old ingredients that may have gone rancid.

4. Burnt crust and toppings (grains and seeds)

When the bread is baked at too high of a temperature for too long, the crust and toppings can get burnt and contribute to a bitter tasting loaf.

Typical oven parameters during sourdough baking are in the range of 230 Celcius to 240 Celcius for about 25 minutes to 40 minutes. If you are baking at higher than 240 Celcius at more than 40 mins, it could be a reason why your crust and toppings have burnt; lower the temperature and/or baking time.

Whenever the sourdough formula calls for added sugars, fats and oil that could be introduced in the form of honey, milk, oil and butter, it is more prone to getting burnt; monitor the loaf in the oven closely. When it is darkening too much too quickly, lower the temperature by 5-10 Celcius for the rest of the bake.

Seeds, nuts and grains are typically soaked or toasted before adding it into the mix. However, if the seeds, nuts and grains are used to cover the outer surface of the loaf, it should not be toasted prior to loading the loaf into the oven. If you toast it before coating, it will get roasted again once in the oven, get burnt and produce a bitter taste.


Sourdough bread that taste bitter is most commonly caused by the rancid fats and oils of the ingredients used in the bake. When the formula calls for any vegetable oil, butter, whole grain flour, seeds, nuts and grains to be used, the loaf is more susceptible to rancidity.

Smell your ingredients before using it to determine if it has indeed gone rancid; rancidity smells like crayons, it smells off and stale.

Check the manufacturing and expiry date before buying your ingredients, store your ingredients in a cold and dry environment, buy in small quantities and rotate your stock to ensure that the ingredients used in the bake is the freshest possible.

When your loaf is burnt, it also contributes to a bitter taste. When using any sugar or oil in the bread, monitor the loaf in the oven closely, and lower temperature by 5-10C if it starts to take on too much coloration.

Avoid toasting seeds, nuts and grains that are use to coat the outside of your loaf as it will easily get burnt when loaded into the oven.


Hey there! I'm Sam, your go-to pal for all things sourdough. I've been baking and kneading for 10 fun-filled years, and I can't wait to share the joy of turning simple ingredients into heavenly sourdough bread with you. Grab your apron and let's dive into this amazing world of sourdough bread together on this blog.

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