Sourdough discard doesn’t need to feel like it is waste – there are actually a few really great ways to incorporate the discard into daily recipes. Once you know what sourdough discard is, and how to fold it in to create everyday sourdough recipes – you’ll stop feeling like you’re literally pouring money down the drain every time you feed your sourdough starter. We’ve got some great tips on how to put less in the bin, and more in back in the pantry for happy tummies in the whole family.

What is sourdough discard?

Sourdough discard is the part of the sourdough starter that you need to remove before feeding the starter with fresh flour and water. It’s basically the extra amount that builds up over time as you complete feeds. 

The discard has the same basic ingredients of just flour and water, but with a much higher acidity profile and probiotic bacteria content. It’s older, unfed, and no longer strong enough on its own to reliably raid a fluffy loaf of sourdough. That’s why we “discard” (or in the best case – reuse!) a portion of a hungry starter and then begin again with a fresh feed of flour and water. 

How is sourdough discard different to active sourdough starters?

Active sourdough starter is at its peak – very bubbly and light, not too acidic, well fed and ready to go into a full sourdough loaf. An active starter is full of energy – there is still some food there within the starter batter, it rises again and again after feeding your starter. An active sourdough starter can lift a whole dough during the bulk fermentation of a final loaf.

Sourdough discard is different. It has gone past the peak of bubbly fermentation, it is overly acidic, it is hungry for new flour and fresh water, and it would not raise the best possible loaf of sourdough if you tried to make a loaf with it. It is low in food, hungry, and although it may still bubble a little bit, it is tired, slow and weak. However, it is perfect for adding the acidity profile to other recipes, and improving textural elements of baked goods like pancakes, waffles and banana bread. It can be a secret ingredient to making these recipes that little bit “extra”. 

Why do I have to discard sourdough starter?

If you tried to continuously feed a sourdough starter without ever discarding a portion before the feeding, two things would happen:

1. The jar would overflow; you would be using far too many ingredients.

2. The starter would become overly acidic and sluggish.

Discarding a portion of starter before each feeding cycle means that you can keep the right amount of starter going in between baking sourdough loaves, and you won’t waste money on ingredients that are “discarded”. Even better, discarding and keeping the ratios of flour and water right for your microbial sourdough starter means that the microbes are happy, strong, and ready to run that next race of baking a fluffy, chewy and crispy sourdough loaf.

Can I skip discarding my sourdough starter?

Regular discarding practice is part of maintaining a healthy and reliable starter. Think of your starter as a pet – you feed your pets (in this case flour and water), you exercise your pets (in this case, warmth and time to bring a starter to its peak bubbling activity), and you let your pets out to the toilet regularly (a tricky analogy, but it’s the right one – discarding a portion of starter is the toileting phase of keeping a sourdough microbial community as a pet).

Skipping the discard step for a few days here and there, if your starter is refrigerated, is ok occasionally. However, if you never discard, the starter will weaken, be overly sour, and will take several feeding cycles to return to a thriving level of activity ready for baking. If you left it too long – your starter will eventually die.

How much starter should I discard before feeding?

Most people follow a simple pattern of feeding and discarding: 

1. Measure out the base starter from the original jar before feeding = 50 g.

2. Feed the new base starter with 50 g flour and 50 g water.

3. The remainder left in the original jar is now the sourdough discard.

Most likely you will develop your own feeding and discarding ratios once you have become accustomed to the routine advice. When you become familiar with how often your bake sourdough, and how many loaves you make at a time, you’ll probably adjust the ratios to suit your family and kitchen needs.

Is sourdough discard the same as sourdough starter?

This is a great question – and the answer is both yes and no. 

Yes: Sourdough discard and starter are the exact same ingredients and microbes.
No: Sourdough discard is more acidic, less active, and won’t be re-fed. 

Basically, sourdough discard is at a different stage in life. It has passed it’s peak, it is hungry and can’t be used to start a sourdough loaf with any great success. This doesn’t mean that it doesn’t have strength as its own ingredient. Sourdough discard is actually a rare treat that can make other recipes just that little bit more special, because of the added acidity and microbial profile.

How long does sourdough discard last in the fridge?

You can collect sourdough discard into a dedicated jar in the fridge and use it when you are ready. Sourdough discard is fine to be used within 7-10 days if it still remains pleasantly sour in aroma and doesn’t show any discolouration or other classic signs of food deterioration. Just remember that the older the sourdough discard is, the more acidic the profile will be.

Can I freeze sourdough discard?

Absolutely you can freeze sourdough discard, and this is a great kitchen hack to reduce waste to be honest. By freezing sourdough discard, you are making the most of what you pay for in sourdough feeding ingredients. One of our favourite tips is to freeze sourdough discard into large cubes in a silicone ice tray. Just pop one or two out before baking chocolate cake, banana bread or pancakes and you’re winning in all the right ways.

We have a couple of simple tips to make sure freezing sourdough discard goes as smoothly as possible:

1. Use a dedicated silicone ice cube tray for sourdough discard only.

2. Collect cubes into containers labelled with the month of freezing.

3. Use within 6 months of freezing for the best results.

How do I know if my sourdough discard has gone bad?

At Symbiota, we are all about encouraging you to feel confident to trust your instincts, particularly your eyes, nose and tastebuds. Follow these basic guidelines, and you’ll get it right every time.

SAFE:

Looks to be a healthy and acceptable batter, even if a layer of water is on top.

Pleasantly sour aroma.

Tastes sharply acidic.

UNSAFE:

Looks unhealthy, streaky, discoloured or slimy.

Acrid, cheesy or generally unpleasant aroma in any way.

Don’t taste it if your senses identify any of the above unsafe indications.

If you are in any doubt – throw it out. Thoroughly clean any containers used for discard to that point, the start collecting fresh discard again.

Can I collect sourdough discard over multiple days in one jar?

Most definitely, and this is the best and most economical way to do so. A great practice is to select a specific day of the week to spend some quality time with your sourdough, and your sourdough discard. 

Let’s say you’ve picked yourself a Sourdough Sunday, this would be a good guideline to follow:

Weekdays:

Feed your sourdough starter as per your family needs. 

Collect the sourdough discard into a dedicated and sealed jar in the fridge.

Stir the sourdough discard jar every 2-3 days to avoid over-separation.

Sourdough Sunday:

Pop last week’s frozen discard cubes into a labelled container and refreeze.

Pour this week’s sourdough discard into the empty ice cubes and freeze.

Possibly make some pancakes or waffles if your Sunday feels like a baking day!

Does sourdough discard need to be at room temperature before using in a discard recipe?

Most recipes that use sourdough discard are very forgiving of using chilled ingredients, such as pancakes and banana bread recipes that will usually call for chilled milk to be used. 

However, frozen sourdough discard cubes will need to be defrosted before use. The one exception would be the addition of sourdough discard to a pie crust or pastry recipe, where keeping the dough as cold as possible is essential.

If you do have the time to allow the discard to come to room temperature, that’s always a good thing for most recipes. The most important tip we can give is to make sure that you stir the discard well before adding it to any recipe, so that there is no separation of the discard, and the acidity profile is evenly spread throughout the discard batter.

What recipes can I make with sourdough discard?

Sourdough discard is a practical and often special touch ingredient level up moment for several everyday home kitchen recipes. Because it is part flour, part water, and contains live probiotic leavening microbes, it is perfect for any recipes that want a little fluff or extra crispiness. 

Our best recommendations are to incorporate sourdough starter into these favourite recipes:

• Pancakes
• Pikelets
• Crackers
• Pizza Dough
• Banana Bread
• Waffles
• Flatbreads (roti, naan, etc)
• Wraps
• Cake and muffin batters
• Because the sourdough discard has already developed a deep acidic flavour profile, it is a great secret ingredient to make simple recipes taste that little bit extra special and complex in flavour.

Can I use sourdough discard instead of active sourdough starter for bread?

We don’t recommend using sourdough discard in place of active sourdough starter to make a loaf of bread. This is because it is hungry, past the peak of activity that is best for making bread, often too acidic, and often too tired to cope with the bulk fermentation needs of raising a full loaf of healthy sourdough. It’s simply too tired to get the job done right. 

If you only have sourdough discard available, we recommend completing at least 2 fresh feeding cycles before attempting to bake a traditional slow-fermented sourdough loaf. This means that you will have to wait 2-3 days before being able to start the slow-fermentation process of making sourdough.

Do sourdough discard recipes still have probiotic benefits?

This is where knowing the science and research results matters to how you feed yourself and your family. 

Sourdough discard that is at room temperature or chilled in the fridge will contains live probiotic bacteria and wild yeasts. These are the microbes that work to ferment flour and gluten into bread by changing the acidity and structure of bread dough. This process of slow fermentation will improve the nutrients available from flour, and the final flavour of the bread.

When you add heat by baking bread or a recipe that includes sourdough discard, the high temperatures will kill the live probiotic microbes. That means that cooked recipes (like sourdough bread, sourdough pancakes and sourdough crackers) cannot deliver live probiotic bacteria to your gut.

A research review conducted in 2021 at the University of Putra Malaysia looked specifically into the microbiome benefits from sourdough fermentation. The review paper confirmed what we know to be true - that while probiotic bacteria are active during fermentation and change the nutrients in the dough, they do not survive typical baking temperatures. 

At the same time, the key fermentation changes to nutrients – such as breaking down certain proteins and increasing nutrient bioavailability – remain in the baked recipe and is exactly why sourdough has such a great reputation as being a better health choice over commercial fast-fermented breads and other recipes.

There are little hacks to make sure that you can get some live probiotics at the same time as eating a recipe that contains sourdough discard. For example, you can:

• Load up a sourdough discard cracker with avocado and sauerkraut or kimchi.
• Serve sourdough discard pancakes with a side of live yoghurt or kefir.
• Have a glass of Water Kefir or Kombucha with your meal.

That way, you can get the benefits of a nutrient dense baked recipe and a live probiotic boost from a fresh ferment topping or side.

Can I substitute sourdough discard for flour and liquid in any recipe?

Because of the high acid profile of sourdough discard, a straight swap into any recipe won’t work most times – there would be too great of a change in flavour simply by the addition of the acidity.

But, with a little consideration and experience, the measured addition of sourdough discard to recipes that contain flour can often produce a superior result. A simple rule to consider as you learn how to incorporate sourdough discard into your favourite recipes is to think about:

• Sourdough discard = flour + water in equal weight.
• Think about the final flavour of the recipe before deciding how much to substitute.
• Substitute more discard into a recipe for higher acidity complexity or crispiness.
• Substitute less discard into a recipe for lower acidity complexity or crispiness.
• Check the end of our blog for more specific guidance on how much sourdough discard to incorporate into the more popular and well-known home recipes.

What’s the difference between using fresh sourdough discard vs old sourdough discard in recipes?

Fresh Discard (3-4 days old):

Mild flavour, more leavening activity, softer acidity, gentle tang.

Good for pancakes, waffles and cakes.

Older Discard (7-10 days old):

Strong flavour, less leavening activity, higher acidity, pronounced tang.

Good for crackers, pizza dough and savoury recipes.

Sourdough discard that has aged beyond 10 days in the fridge will often be too sharp in acidity for baking. It would be better to compost this aged sourdough discard and start from fresh. If you find you are losing discard to age in the fridge, consider starting a freezing cycle for the excess sourdough discard that you are collecting. 

Can I make a new sourdough starter from discard?

Most definitely, you can bring a sourdough discard back into an active sourdough starter with patience and care. It will take at least 2 cycles of fresh feeding to bring a sourdough discard back to peak activity. 

The simplest approach:

1. Measure 50 g of sourdough discard.
2. Feed with 50 g of flour and 50 g water.
3. Transfer into a clean jar, cover, and allow to ferment at room temperature.
4. Repeat the feeding cycle within 24 hours, regardless of the level of bubbles evident.
5. After the second feeding cycle, start to watch for high activity and peak bubbling.
6. Repeat daily feeding until you have attained a healthy and vibrant starter that reliably doubles in size within 24 hours.

Over just a few days, you will have transformed an old, tired, sourdough discard back into a young and thriving sourdough starter. If only it was as easy as this for us all!

Can I give sourdough discard to someone else to start their own starter?

Absolutely this is possible – following good practice as we described above – then any jar of sourdough discard is simply a jar of tired sourdough starter that needs a little food, warmth, time and care to come back to life. Just make sure that you give your friend clear instructions on good quality ingredients that your sourdough discard is used to, and some guidance as above as to when the discard would be sufficiently recovered to use in a loaf of bread.

Is sourdough discard good for the garden and compost?

Composting sourdough discard is a great way to keep the benefits of the microbes back into the natural environment and away from sewage systems and landfills. The general amounts of sourdough discarded from a home kitchen is safe for home compost bins and can be a valuable addition to your compost microbial communities. 

You can also spread a thin amount of sourdough discard directly onto garden soil but avoid large clumps in a single spot. A large clump can form a barrier layer that is too thick to break down quickly.

How do I reduce waste when maintaining my sourdough starter?

There are a few easy habits to get into your kitchen routines that will make sourdough less wasteful at home:

• Keep a small starter
• Create a frozen sourdough discard routine
• Plan for sourdough discard recipes
• Share sourdough starter/discard with other people

Symbiota favourite recipe ideas for using sourdough discard:

There are several places where you can easily pop sourdough discard into your regular kitchen recipes. We’ve put together a table to use as a starting point, to get you going in the right direction, and gain some valuable experience. As you learn and try new additions, you’ll become adept at incorporating and substituting sourdough discard into all kinds of delicious homemade recipes.