Before jumping into using heat to get our starters and levains fermenting, we’ll take a look at cold.
If you are not using your starter on a daily basis, leave it in the fridge. Anyone who has participated in one of our Sourdough Classes in our Bread School will have looked at, smelled and tasted some 20 year-old sourdough starters: a wholemeal rye sourdough starter and a strong white flour starter which have been left in the fridge without being refreshed for 5 months. As a result of being left this long, both starters have separated into different layers: the top layer is very strong vinegar, the second layer is a blackish layer of sediment and then there’s a layer of thick fermented flour at the bottom. When we taste a tiny sample of the rye starter, balsamic vinegar immediately comes to mind.
These starters are absolutely fine. Within a week of refreshments, they will be bubbling up and be ready to produce beautiful loaves. One note of caution, if you taste your starter and it tastes disgusting (!), as if it has gone off and is rotten, throw it out.
We will do a deeper dive into storing and refreshing sourdough starters and levains with different inoculation rates on another deep dive. At this stage, I just want to bring some attention to storing your starter in the fridge when not in use. If it is strong and healthy, it will be fine. There is no need to be overfeeding, discarding and wasting unneeded starter. It will take a few refreshments to get it lively again but a wholemeal rye starter can usually be left in the fridge for a week then taken out and refreshed to build your levain 10-14 hrs before you wish to bake and should be hitting those ‘sweet spots’ right on time.
A starter made from strong white flour should last about 5 days in the fridge and can be refreshed once before using. Once the starters are out of the fridge and warm up, they will begin to ferment.
To achieve a nice soft open crumb in our sourdough breads, it’s much easier if our levains are in their ‘sweet spots’ (as described in our free ebook ‘The Sourdough Starter Cycle’, available when you join our online baking community).
Most home bakers and some professional bakers (including myself), don’t have proving chambers where we can control the air/room temperature for the fermentation of our starter/levain. We work with whatever the room temperature is. So for us to achieve the correct temperature for our levain to ferment, we vary the temperature of the water we use to refresh it with.
To develop a good understanding of why and how to get your levain into the ‘sweet spots’ refer to our ‘Sourdough Starter Cycle’ ebook.
Here’s a little guide to approximate water temperatures for refreshing our starters and building our levains, for various room temperatures. Cooler water will lead to a longer fermentation time, warmer water a shorter fermentation time. Compared to strong white flour, rye flour can tolerate and require a longer fermentation time at a higher temperature.