I understand that sourdough starter (made from wild yeast) will differ from location to location, based on the different yeast bacteria. How will this change the flavor and type of the starter? What factors will affect the yeast in the wild (e.g. climate, altitude, etc.) and how does this affect one's ability to make a good starter?
Baking – How does sourdough (wild yeast) starter differ from location to location
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Note: This answer goes in a bit more detail than necessary to answer the question. If you truly only care about the hydration, please only read "Water/flour ratio" and "Flavor of the bread". I have added the other information as well since the effects are similar to that of a change in hydration.
I've frequently baked (about once to twice a week) with sourdough for 4 years now. I'm not a professional. The only thing I can take a bit of pride in is that a professional baker who tested a loaf of my sourdough bread told me that it's "fantastic, considering the little possibilities available to control the conditions the sourdough and loaf are exposed to at home". So while far from perfect, I'd consider my sourdough breads and knowledge pretty good.
Most of what I'm writing now was first read on the internet somewhere and confirmed through testing it with my own sourdough culture (I'm still using the same one I started out with).
Apart from the flour you use, there are several factors that affect the taste of the resulting bread:
Temperature
This has, in my experience, the biggest impact on the taste. The following rules apply:
Anything over 40°C is deadly to the microbes in your sourdough.
Lower temperature: More acetic acid, less lactic acid, yeasts develop more slowly.
Higher temperature: More lactic acid, less acetic acid, yeasts develop more quickly.
Lactic acid bacteria prefer temperatures at around 30-35°C
Yeasts like temperatures around 25°C best
Note: Your sourdough can be 1-2°C warmer than the environment due to microbial activity. That can be important to keep in mind.
Water/flour ratio
Most of the time, people use a ratio of 1:1 water/flour for the sourdough and that will give you good results, but you can play around with that ratio to change the taste to your liking:
Lower water content causes more acetic acid production and less developed yeasts
Higher water content will make it easier for the yeasts to grow and increase the lactic acid content
I've found that having more than 1.5 times the amount of water compared to the flour will hardly have any effect on the dough anymore and I'd recommend stirring the dough every couple of hours with that much water.
On single staged sourdough, using less than 0.75 times the water compared to the flour is also not a good idea and you will probably be required to add yeast in the bread dough.
Salt and oil
Adding these, especially salt, to the sourdough already will have a considerable impact on the sourdough taste. A sourdough made with salt in it will taste quite different from one without it. I'm not quite sure about why this is, but it may have something to do with the yeasts growing more slowly (more information below).
Both salt and oil will slow down the growth of the yeasts, but don't have much of an effect on the lactic acid bacteria.
Adding oil mainly affects the mechanical properties of the dough (it will be softer and more ductile). It also helps with the structure of the bread (the air bubbles in the bread will be smaller and more uniformly distributed), especially in the presence of an emulsifyer (lard is both fat and an emulsifyer, so it works well in this regard). For this reason, it doesn't make much sense to add it to the sourdough already.
Of course, if the fat isn't tasteless, it will also add to the taste of the bread (I love using natural olive oil in my wheat breads).
Flavor of the bread
Sourdough actually has some pretty complicated chemistry that I know little about. However, here are some effects that I do know:
Lactic acid will give your bread a mild, sour taste. This works very well for wheat breads.
Acetic acid gives you a stronger, more sour taste (very noticable while eating). This works great for rye breads
The amount of yeast in your sourdough also has a big impact on the smell and taste of the bread. Yeast is beneficial to the bread not only for it's leavening properties. Apart from CO2, it also produces ethanol, which will esterify the lactic acid to ethyl lactate over time, which in turn has a strong flavor.
Okay I think that's it. I hope this helps you.
If you've truly gone anaerobic and the smell is off, you are growing things other than the intended cultures...
As a rule, I simply feed mine flour and water. No sugar. The cultures can get along fine with the flour. (I did read in a reputable baking book about adding leftover water from boiling potatoes, for the starches, but I haven't had a chance to try.)
If the smell is off, I would dump and start over in a more breathable container. Your entire goal is to grow the sourdough cultures and let them flourish in their happy environment. And as you've smelled, there is a distinctive scent of happy sourdough. Now if the smell has changed, you lost your scented sourdough and are now growing something else.
I've kept sourdough for over a decade, and it's from a culture that is 84 years old. But if it smells funny (or gets brightly colored mold), he's going down the sink faster than dishwater. It's just the nature of the beast.
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Best Answer
You're right, sourdough starters are different everywhere, based on what yeasts and bacteria are prevalent in that specific location. Certainly climate and altitude affect the living things that float around, so in turn those variables affect starters. I don't know about the poles or the peaks of Denali or Everest, but you can make a perfectly good starter everywhere else, they will have their own character everywhere you go. Even a distance of a few miles can drastically change the flavor and behavior of your starter. Some places have less or slower to grow natural yeast, so starters can take longer in some places to be ready, but it will happen eventually.
Some places, San Fransisco for instance, are well known for their local starters. You can buy San Fransisco sourdough starter online, but your bread will only taste like San Fransisco Sourdough for a few days or a couple of weeks. If you keep that starter alive, it won't take long before it takes on local yeast and bacteria and creates bread that tastes like the sourdough made by everyone else in the neighborhood.
The bottom line is that without speaking to another maker of sourdough in your immediate area, you can't really predict how fast your starter will grow, how often it will need to be "fed" or what your bread will taste like. Allow for some variance due to location, but standard recipes and techniques will work just about everywhere. Once you've made a few loaves, you'll get to know your local yeast!