2019-07-07 - Another look at the delicate matter....
Or, Everything you know is STILL wrong!
Somehow last week I never clarified what the delicate matter we discussed then, and continue to discuss this week, is. Many people have strong ideas about what is in their sourdough starters, and many really don't like looking at other information. And broaching the new information can be a rather delicate matter.
Last week we looked at a number of things and wrapped up with a look at two sourdough starters. Rob Dunn Labs had done a careful analysis of hundreds of sourdough starters. Two were of special interest because they were the same starter, only one had been given away 20 years earlier to a friend. The table comparing the two starters is here. You may want to look at the table.
Last week I suggested I was still thinking about what the tests of the two starters meant. And I have some thoughts. It is always suspect when new information confirms ones previous notions. Is this due to a confirmation bias? I hope not, but I am open to other interpretations, so please email your thoughts.
It is amazing is how similar the two starters are. 94.26% of the yeast in David's starter are the same as 99.37% of the yeast in his friend's starter. 99.62 and 99.65% are the same bacteria. Not really a big difference. This suggests, as many researchers have said, that well maintained sourdough starters are very stable.
All this leads to the time honored question, "When I moved from San Francisco to Boise, my starter changed and it just hasn't been the same since! What happened?"
Looking at the two starters, and looking at Dr. Michael Gänzle's comments about starters in his care being unchanged for 50 years, it seems that the makeup of the starter probably didn't change, but - what did? What the starter was fed changed. And that can make a lot of difference. As I've noted here and here, hunters prize acorn fed boars as the acorns give the boar's meat a wonderful flavor. Many nursing mothers report that when they eat some foods their babies refuse to nurse. One mother I talked to found if she consumed cow's milk, her baby developed rashes that went away when she switched to drinking goat's milk or non-dairy milk (to be clear, the mother drank the various milks, the baby suffered for it). French farmers feed geese different foods to change the flavor of the goose livers to make different flavors of pate. A simpler, and faster, example - if you you usually feed your starter white flour, switch to whole wheat for a few feedings - the flavor change will be immediate and dramatic! When you switch your starter back to white flour it will return to its usual flavor and activity, though it will take a while longer than the first change.
In none of those examples did the organism change. The boar is still a boar. The human mother is still a human mother. The goose is still a goose, and your starter is still your starter. For better or worse, when you moved from San Francisco to Boise a lot changed. Your water is different and has a different assortment of minerals. Your flour is different - even if the brand is the same, the wheat was almost certainly raised in different fields and milled in different mills - terroir matters, even with commodity wheat. Your starter will change. But it will still work.
All this presupposes a well cared for starter. Sadly, at times we aren't all that good at maintaining our starters. (Well, maybe you aren't, but I'm perfect! If you don't believe me, just ask me while I'm starting a new starter because the old one died of neglect.) Our starters are a more or less homeostatic culture when they are well maintained. The sourdough bacteria produce a lot of acidity and at least 50 antibacterial compounds to protect their turf. That works well until you forget to feed the silly thing for a week or three.
When the regular reductions in acidity through dilution and infusions of food stop, the yeast and bacteria in the culture change to survive in the new environment. It isn't clear to me whether some of the dominant bacteria learn a new trick and figure out how to eat protein, or some bacteria that are low in the list of active agents suddenly find them selves in a more beneficial situation. Either way, protein eating bacteria have a evolutionary advantage and take over the starter. For quite some time, acetone was produced by fermentation using various strains of Clostridium bacteria, so producing acetone by fermentation is hardly unheard of. In this case, the bacteria which can not eat protein are disadvantaged compared to the bacteria which can eat protein. Protein is present in the flour, as well as the yeast and other bacteria in the starter and in the dough. The newly dominant bacteria changes everything in the starter!
This change in the starter causes problems, as when this is happening dough becomes very soft and insanely elastic. The dough and bread have off flavors. While most starter issues can be resolved by feeding the starter correctly, this issue seems resistant to the usual cure. I've had starters that looked, smelled and behaved as though they were rehabilitated until another feeding was missed and then they reverted to their evil protein eating ways. I found that it was easiest to discard such a starter, sterilize everything the starter had touched, and start a new starter. This is one reason why it is a good idea to keep a backup starter in the refrigerator, freezer, or in a dried state.
Interestingly enough, even short term disruptions can cause problems. In a recent class on making bread from freshly milled flour, the instructor had fed enough sourdough starter for the students but found she hadn't made enough to use for her demonstrations. In order to have some starter, she used a starter that hadn't been fed for three days. Many people tell you if you have a starter that hasn't been fed for a few days, it's OK to just use it - it'll perk up! In this case, we found that the instructors loaves did not rise as well as identical loaves made with fresh and active starter and the same wheat. More interesting, when the loaves were baked in the same oven, at the same temperature, and for the same amount of time the loaves with the tired starter were considerably darker than the loaves made with a fresher starter. All of which reminds us that it takes a consistent process to make a consistent product, and that even short term issues can change how a starter behaves.
This gets back to my recurring notion that it takes a consistent process to create a consistent product. Empirically I've found that I need to feed a starter twice a day until it will double in size between feedings before I can trust it to raise my bread and give me the flavors I want. Your mileage may vary - tell me about it!
Until next time, may your dough always rise, keep its shape and not burn, no matter what you've done to your starter this time.