What Should Sourdough Starter Smell Like?
A few times in the past few days I've been asked what sourdough starter should smell like. And I've blown the question off. "I cover that in the sourdough starter primer!" I say. Only.... I haven't.
Yeah, I mention smell in passing here and there. But never in any detail. At least not much past it smells "nice", "awful" or "like acetone (cheap fingernail polish remover)." Of course, two of the hardest things to share in words are smells and tastes. We're better at telling others how things look. Which is why wine, tea and even coffee lovers come up with such strange and tortured descriptions. Here's a description from a coffee ad. "For the loyal supporters who love their company but are nostalgic for taste notes reminiscent of Catfish Hunter or Charlie Parker: dark, oily, stanky, musty, full-bodied, peppery, meaty, and seasoned." Really? What does that even mean? Oddly enough, my fingers weren't on the right home spots on the keyboard and "really" came out as "freaky".)
Still, never let it be said I don't go the extra mile, or sniff, for Sourdoughhome fans!
There are a few categories to consider. Starter as it being created, before it stabilizes. Starter that has matured, when it is healthy and active. The neglected bottle of starter at the back of your fridge or - worse yet - on a countertop.
To recap what we discussed in the sourdough starter primer, flour has a wide range of bacteria and yeast on it. When you mix water with the flour, they become more active. They eat, they reproduce, they fight for dominance in a very Darwinian battle. There is a succession of bacteria and yeast in a starter over the first week. I discuss this in the Breadblog2012. We have found the same sorts of bacteria are in the succession for sauerkraut as with sourdough.
First there are coliform bacteria. They increase the acidity of the starter. At some point, the coliform bacteria can no longer tolerate the acidity they have created. (Among living organisms, only teen-aged human males can live in any concentration of their own waste.)
This sets the stage for the next round of organisms, the Leuconostoc bacteria. Many times these stages are over in hours or a day. Which causes the starter to become very frothy. However, Leuconostoc bacteria aren't in it for the long haul. They don't have the strength to raise dough. I get a fair number of emails that comment, "My starter was frothy in just a day! But it wouldn't raise bread!" If you use the starter at this point, you'll be disappointed. Which is why I suggest waiting to use a starter until it is at least a week old and it can consistently double - or more - in size between feedings. Again, the Leuconostoc bacteria makes the starter more acidic, until they can no longer survive in the acidity they created.
That acidity sets the stage for lactobacillus bacteria, which are the characteristic bacteria in sourdough. Some people use pineapple juice or orange juice to skip the earlier stages of the sourdough starter development and get right to lactobacillus bacteria. While I don't think that is a bad idea, I've also never found it to be necessary. In any case, the lactobacillus bacteria make the starter more acidic, but with proper starter care the acidity remains in a range the lactobacillus bacteria can tolerate. The acids that the lactobacillus bacteria are primarily the mild lactic acid and stronger acetic acid. The acidity that the bacteria creates kills off competing bacteria, and creates an environment few yeast can survive. This is the last stage of sourdough starters, a symbiosis of lactobacillus bacteria and acid tolerant yeast.
At one time it was believed there were something like three strains of bacteria and five strains of yeast that could create a stable sourdough starter. Now, scientists have identified 40 or 50 strains of each that can work. While interesting, this isn't of great importance to the practical baker, after all, it's not like we can - or have a real reason to - identify the strains in our starters. As long as our starter can make good bread, we really don't need to know what's in the starter.
OK, now, let's talk about smells! (You thought I'd gotten lost in another five paragraph digression, didn't you?) The smells that are produced at each stage depend on the kind of flour you are using and the "critters" who are working on the flour. The first stages can be unpleasant. Think dirty sweat socks. Or worse. However, in the early stages just observe and keep feeding the starter. Bubbles and smells are signs that something is happening in your sourdough starter, and that's a good thing.
When your starter reaches the last stage and stabilizes it will develop its own characteristic smells. However, despite the name "sourdough", a healthy sourdough starter usually has a fresh yeasty smell with, perhaps, a bit of an astringent note to it.
The idea of using a fresh starter bothers some people. They seem to think that that you get sourdough bread by adding a strongly flavored sourdough starter to dough in much the same way that adding chocolate chips to cookies makes them chocolate chip cookies. Using a fresh smelling starter just doesn't make sense to them.
The difference is that when you open the bag of chocolate chips, they are as chocolaty as they are ever going to be.
However, the flavors and aromas of sourdough bread are developed through fermentation of the dough, and the flavors and aromas depend on the skill of the baker and what the baker is trying to do. I and the professional bakers I know use a fresh and active starter so that it will be able to survive a long fermentation and still raise the bread dough. Sourdough breads can range from having very mild sour tastes to very assertive sour tastes. Different people prefer different tastes, and different breads call for different levels of sourness.
I make a cinnamon raisin bread with sourdough. The sourdough flavor is very subtle, and many people don't know it's there. However, the bread has an uncommon depth of flavor, and it lasts longer than most breads because of the sourdough.
If you don't feed your starter for a while you'll notice other aromas creep in. When yeast eats sugars and starches, they produce carbon dioxide and alcohol. So, you'll notice more of an alcohol smell. If you still don't feed your starter for a longer period of time, the starter will develop some serious funky smells. What sort of smells? It depends on the critters in your starter, the kind of flour you are using, the temperature of the starter and how long it's been since you last fed the starter. However, I've had starters that were in serious trouble develop pronounced acetone aromas. Acetone is the main ingredient in cheap fingernail polish remover. If you smell that, it's probably time to start a new starter.
Refined white wheat flours, such as all-purpose flour, bread flour, high gluten flour lead to milder aromas in the starter. Whole grains, such as whole wheat flour and rye flours tend to produce more pronounced and sharper smells in your starter. Switching from white flour to whole grain flour will change the smell of the starter in just a few days. And if you switch back to white flours, the smells of the starter will subside in another few days.
A friend tells me that his rye flour has aromas in it like over-ripe apples. Some people who make starter the way Gerard Rubaud does report apple and nutty aromas. I wish I could say something more definite like, "A fresh starter smells of the flour used to make it, and will have a fresh aroma with hints of woodruff, sage and chalk. An older starter will smell strongly of gym socks." However, I can't do that. Sourdough starters can, and do, have different smells. So, smell your starter and learn how it smells when it's fresh and when it's tired. A few bakers tell me they learn more about their starter by tasting it than by smelling it, so give it a taste too! Over time you will learn how your starter should smell and taste!
Except for one starter, all of my starters have smelled pleasant and clean. That exception was a commercial dried starter that I had purchased at a health food store. When it was active it smelled (sorry, this is going to be gross) like a wino's vomit. (Don't ask how I know about that. It's not that interesting a story. It involves an emergency stop at a convenience store on the wrong side of the tracks.)
I called the vendor and they said the smell was to be expected. Would you be surprised if I told you that something that smelled like that made bad bread? You shouldn't be surprised. My family refused to eat a second bite. I finished off a slice wondering, is it supposed to taste like this? As computer types say, garbage in, garbage out.