Basics of Sourdough

Understanding sourdough: adapting to the environment


It took me a while to figure out how my environment was a huge factor in my bread outcome and once I understood how temperature, time and humidity affected my bread, it was an epiphany!  

Understanding the science behind sourdough and adapting your procedure to bring about the ideal conditions for your bread fermentation will result in a better end product.  It all goes back to science!  Sourdough fermentation is optimized at temperatures between 70° F - 85° F (21° C- 30° C) for four hours.


Sourdough ferments well between 70° F - 85° F (21° C- 30° C)  Between these temperature ranges, the microbes are very active and during the bulk fermentation less byproduct is released, resulting with a milder flavored bread.  However it is at these temperatures, where the bacteria is breaking down the carb. and releasing the minerals in the flour to make it readily available for our bodies to absorb. So, in essence, making it a healthier bread.

Outside of this temperature range, fermentation still occurs even just above freezing and below 110° F (43° C), but it produces quite a bit of byproduct which gives the dough the characteristic sour taste.  Research has shown that at high temperatures, the bacteria produces lactic acid with a sourness like the taste of yoghurt.  At low temperatures, the bacteria produces acetic acid with a sourness like the taste of vinegar.  

Producing a bread with both the health benefits and the sour notes can be attained by adjusting both temperature and time.

To attain the ideal dough temperatures during bulk fermentation, 2 conditions can be changed.  

Initial dough temperature

Proofing environment

Temperature Range

(Your environment)

Initial Dough Temperature Adjustment

Proofing environment at current room temperature

Proofing by Environment Adjustment


Above 85°F 

(30° C)

Use refrigerated water / put ice cubes in water. (Remove ice!) 

Allow to rest for 20-25 minutes between stretch and folds.

Place in cool room.  Allow to rest for 25-30 minutes


70°F – 75°F
(21°C – 24°C)

Use room temperature water.

(70° F - 85° F or 21° C to 30 ° C)

Allow to rest for 25-30 minutes between stretch and folds.

Leave on counter at room temperature.


Below 60°F 


Combine boiling water with room temperature water.  (Measure temperature of water with thermometer ~85°F  (30° C.)

Allow to rest for 35-40 minutes between stretch and folds.

Place dough in cold oven or microwave oven with light on. Allow to rest for 25-30 minutes


From the above table, you can see that the resting time during bulk fermentation can be adjusted as well depending on the the environment's temperature.  When the temperature is warmer than ideal, the microbes are more active and thus need less time to ferment.  On the other hand, when the temperature is very cold, the microbes are more sluggish and need more time to ferment.


According to some technical guides, optimal humidity levels for sourdough are 60%-80%.  For home bakers, this is very difficult to achieve without a proofing box.  Understanding that humidity is necessary when making bread, always keep the dough covered during bulk fermentation and especially during proofing.  Use an air-tight container during bulk fermentation.  A six quart plastic food container with lid works well.  This can be attained by placing your dough with batton in a plastic bag before placing it in the refrigerator.  The purpose of humidity when making bread is to prevent a "skin" from forming on the outside of the dough.  This "skin" prevents the dough from expanding which makes the dough light rather than dense.

Plastic container for sourdough bulk fermentation.

Plastic container for sourdough bulk fermentation.

Optimizing taste

To optimize taste and health benefits, my sourdough process incorporates both the "ideal" temperature range during the three hour bulk fermentation and then proof my dough in the refrigerator for 48 hours AFTER a one hour proof at a temperature between 70°F – 75°F (21°C – 24°C).  The end result will be fermentation for 4 hours at a temperature between 70°F – 75°F (21°C – 24°C) to reap fermentation's health benefits followed by a slow, cold proof in the refrigerator to optimize the bread's taste with the characteristic sour notes!

If you are not happy with your bread and need assistance with what needs tweaking, please feel free to ask any questions in the comment section below.  I'll be happy to try to assist you.

Sourdough Basics

Good to Know

This sourdough glossary will help you understand some of the terminology used

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Here are some essential utensils and tools for sourdough baking.  These basic

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Baker's percentages and hydration percentages are two math concepts that are helpful

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Getting Started

Many sourdough starter recipes out there are derived from professional bakers who

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Some recipes use the word starter and levain interchangeably.  Both are made

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Sourdough Techniques

How To's

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