2021-02-28 A Deep(er) Dive Into Starter Maintenance

Let's look at what modest sized bakeries do first. When we visited Boudin Bakery in San Francisco they had a bus tub filled with a very dense starter, probably around 50% hydration, in a walk in cooler. It seemed they would use some of it every day to feed up for the next day's production. When the amount in the tub was sufficiently reduced, or when it lost vitality, they'd feed the starter in the tub until it was where they wanted it to be and then put it back in the walk in. My feeling was they had more than one such tub, so if anything happened to one tub, there were more to fall back upon. Of course, Boudin also has multiple locations, so if one location lost all their starter they could get some from another location. Having a backup is important!

This technique is consistent with what Dr. Sugihara, the researcher who discovered the characteristic microorganisms that make San Francisco sourdough work, did. He used a technique used by the San Francisco Sourdough Bakers in the 1960's and 1970's, maintaining the starter at 50% hydration and almost tripling the amount of starter with each feeding.

From what we have been able to determine a famous French bakery maintains their starters at about 76% hydration, which is quite thick, and feed their starters twice a day, each feeding being a blend of flours and enough to increase the size of the starter about 2 1/2 times.

Many bakeries prefer a more liquid starter, and make up enough each day so they can meet their production needs and have enough to feed for the next day's production. Let's imagine I need 80 kilograms of starter every day this week. If I am feeding the starter a 1:2:2 ratio three times a day, I need to have 3 kilograms at the end of the production cycle to feed up for the next day's bake. To 3.1 kilos of starter, I add 3.1 kilos each of flour and water, giving me 9.3 kilos of starter. 8 hours later, I feed that 9.3 kilos of starter with 9.3 kilos each of flour and water, giving me 27.9 kilos of starter. 8 hours later, I feed the 27.9 kilos of starter another 27.9 kilos of flour and water, giving me 83.7 kilos of starter. We could further fine tune the numbers.

French trained baker, Gerrard Rubaud, fed his starters four times a day, quadrupling the amount of starter with each feeding. He ground the bulk of the flour used to feed the starter with a hand cranked flour mill. He also feels of the starter ever gets below 50F/10C it is ruined and must be discarded. He also starts a fresh starter every 3 or 4 months because his starter becomes too acidic for him to tolerate.

Blaine Marvin, of the Elmore Mountain Bakery, keeps her starters at 100% hydration, feeds her starters twice a day, with each feeding doubling the size of the starter, until the last starter before baking which explodes the amount of starter. Her last feeding increases the starter by a factor of 20. Put another way, the starter before the feeding is 5% of the final starter amount. She feels this helps control the acidity of the starter, as well as increasing the yeast activity. In general, high feeding ratios tend to favor the yeast part of the starter symbiosis.  We talk about this in the Five Percent Solution blog post.

As mentioned, German bakers have done things differently. Instead of back slopping, a typical German baker gets a new pure sourdough culture from a biological laboratory every Friday. It is fed in a large temperature controlled tank with oxygenation and agitation all weekend long. On Monday, the culture has eaten through the nutrients in the tank and is all but dead. However, the starter is very acidic and very flavorful. It is used to acidify and flavor doughs, with baker's yeast added to raise the dough. Rye breads benefit from having an acidic dough, and sourdough acidifies the dough very effectively. The acidic starter is used all week long, and the process starts again on Friday. The German bakers keep their starter very liquid as they want the starter to be pumpable, so they can dispense it from hoses into the mixers. This style of sourdough horrifies many American sourdough hobbyists who don't want to use bakers yeast with sourdough, but the German bakers make excellent bread.  As a result of this practice, the Sourdough Library in Belgium is reluctant to accept starters from Germany as they want naturally occurring starters, not lab created ones.

The German Federal Centre for Cereal, Potato and Lipid Research which was located in Detmolder, Germany, wanted to help sourdough rye bakers and created a number of feeding paradigms to get a starter into shape to make rye bread quickly and efficiently. I've used these techniques to revive wheat starters as well as rye starters. The three stage process involves three carefully thought out feedings, each with precise amounts of flour and water added to a starter at a controlled temperature for a specific time. The final starter is at 94% hydration. With this process you can turn 60 grams of starter into 10,000 grams in three feedings over 2 days. Many rye bakers use the 2 and 3 stage versions of this process which are usually called the Detmolder 2 stage and Detmolder 3 stage processes.  I talked about the Detmolder 3 stage process in a blog post. (Of course I did.)

Recently, some younger German artisan bakers have moved back to the more historic sourdough handling using back slopping, such as is seen in the United States.

If you are curious about these different feeding paradigms, our sourdough feedup spreadsheet will help you use them. Just check our downloads area, or skip straight to the spreadsheet download here.

Home bakers have historically had similar methods for propagating and maintaining a starter. Many pioneers put their starter into their barrel of flour which tended to maintain a fairly uniform temperature. This is similar to the Desem starter process.

Again, as with modest sized bakeries, larger homes and homesteads maintained fairly large amounts of starter because they were baking often. Biscuits, pancakes, or waffles in the morning, bread or rolls for lunch, and more bread for dinner. Sourdough was also used to leaven cakes.  When used and fed regularly by a skilled baker, starters remained healthy.

And that brings us to the modern home. Family sizes are smaller than historically, and often several people don't want to eat bread at all. Baking daily is just not an option in all but the most fresh bread obsessive family. Bread lasts longer than just a day.  For most families, baking every day means giving away or selling bread or freezing it. If you freeze it, you are only delaying the problem as you will run out of freezer space in short order.

And that brings to the starting point of this post. What do you do with your starter?

When I got into sourdough in the late 1990's, many people felt you had to feed your starter regularly to keep it happy. Like twice a day. If you double the size of the starter each time you feed it, which is a very small feeding ratio, you have a problem in very short order. Starting with a teaspoon of starter, doubling twice a day leads to a swimming pool full in 10 days. And two swimming pools full with the next feeding - and a very irate neighbor. Something has to be done to keep the amount of starter manageable. And that something is to discard half the starter before each feeding. So, instead of accumulating a swimming pool of starter (which is one heck of a waste of flour), you discard 50 to 100 grams of starter twice a day. Which is a much smaller waste of flour, like 50 to 100 grams a day.

We use the word "discard" rather loosely here. The discarded starter has food value. It has flour in it, as well as a lot of microorganisms. It behooves us to do SOMETHING with the discarded starter!  Discarded starter is quite acidic, so it can be used to raise quickbreads.  It can be used to make pasta - pasta made with sourdough discard lasts longer than pasta without.  A number of web sites have recipes to use sourdough discard, we're one of them.  Google can help you find more recipes for sourdough discard.  We like a number of these recipes enough that we often make excess starter just to make these recipes! I tend to think of the discarded starter as starter I've set aside for other uses.

Still, the discard half before feeding approach above is very useful for helping a starter mature. As you use a starter it gains in flavor and power for some time. Depending on who you talk to, 30 days and 90 days are common numbers. So, if you have a new starter, work it for a while at room temperature. Your bread will thank you.

However, there are better ways of handling sourdough starters if you want to limit how much discard you create. Refrigeration is the first step. When your starter is healthy (by which I mean, at least doubling in size between feedings), feed it one more time and put it into the fridge. I call this a storage starter. Dr. Sugihara found starters which were freshly fed survived freezing better than ones that had matured. I find the same is true of refrigerated starters. Some people want to see that their starter will rise before they refrigerate it. My view is, if it has been consistently rising after feeding, it will rise again. Interestingly enough, your starter will rise in the fridge. Slowly.

When you are getting near a bake day, look at your recipes to see how much starter you will need. Take enough starter out of the fridge so you can feed it up over three days to get the amount of starter you need. This insures the starter you use will be healthy. An old systems analyst mantra has it that "it takes a consistent process to create a consistent product". The consistent process starts with a consistent starter.  Pro-tip - the spreadsheet mentioned above will help you calculate how to create the amount of starter you need.

If you are baking commercially, consistency is very important. If you tell people this is your Colorado High Mountain Whole Wheat Bread, your regular customers will have an expectation of what the bread will be, and will let you know if it doesn't measure up. At home, having a good loaf of bread is often good enough even if it isn't just the same as last time. If you are in the "good enough is good enough" camp, you can use a storage starter fresh from the fridge if it's been there less than a week.  I won't be very judgy.

When you run low on storage starter in the fridge, or when you think your storage starter isn't as healthy as it was, you can pull some out, feed it up, and put it into a fresh jar. The old jar can be kept as a backup, until the next time you feed up your storage starter.

If you are making a storage starter at 100%, or higher, hydration, you may find it throws off hooch and loses vitality fairly quickly. I like to re-feed such a storage starter once a month or so. A hooch layer is a good hint that your starter is weakening, as is the starter taking longer to revive than usual.

And that brings us to my last technique for dealing with storage starters. Instead of storing it at 100% hydration, I store it at 50% hydration. When I use it, I feed up a few grams of it to the amount I need for a bake, so the fact it isn't at the same hydration as my usual starters just doesn't matter as the original storage starter hydration is overwhelmed in the feeding process. I've had these starters in the fridge for a year with no problems. If you check out our spreadsheets, you'll see there are spreadsheets that make feeding specific amounts of starter easy.