Nice to meet you!
Bob is a sourdough starter and although Bob might not look like much, inside that jar is a microscopic community of billions of wild yeast and bacteria living in harmony. But how did Bob come to existence?
For those of you that are new to sourdough, Bob was created through natural fermentation, using flour and water and one of the most important ingredients: time. In essence, a sourdough starter is simple. Mix the same ratios of flour and water together and leave to ferment over 24 hours. Then repeat the process again, adding flour and water to your original slurry. After about 5 days of doing this, you will start to see bubbles forming on the surface and your sourdough starter will start to increase in size between feeding. But why and how does this happen?
Fermentation - Quick overview
All around us in the air are natural yeast spores and bacteria. When you you mix flour and water together, you are providing a home for these wild yeast spores and bacteria to live. They are living organisms and need moisture, food and warmth to survive. This is provided by the flour and water mixture that you make. Once they arrive at their new home, they are able to convert the starch in the flour into simple sugars through the use of enzymes. (We will go into these in more detail in a separate blog in the future!) These simple sugars are then used as an energy source for the yeast and bacteria to function and reproduce.
Like any living thing, they create waste products. In the case of yeast, the main waste products are alcohol and CO2. In terms of the bacteria, the waste products here are CO2, alcohol and acid. It is these waste products that make the sourdough starter rise and provide flavour and aroma.
So there are a couple of different categories of bacteria found mainly in sourdough. These are "Homolactic" and "Heterolactic." Homolactic bacteria one produce one waste product, which is acid (hence the name). Heterolactic produces a number of different waste products including CO2, alcohol and acid. There are of course many different types of bacteria that fall into these categories, and depending where you are in the world depends what type of bacteria you will have in your sourdough starter. This is important, because this means that each sourdough starter is going to be unique in terms of the culture of bacteria and wild yeasts in it, and that means each one will have a unique flavour. No bread will be exactly the same.
So why do I have to keep refreshing it?
If you think of your starter as a living thing, it needs to have a supply of food to keep it alive. By refreshing it, you are adding more starch which can be broken down into simple sugars by the enzymes produced by the yeast and bacteria. If you don't feed your sourdough starter, what will happen? Well enzymes continue to work until they are denatured. So that means that the enzymes will continue to convert the starch into simple sugars until there is none left. Once this happens, the yeast and bacteria have no food source, so will stop functioning and die. There are also other areas to consider in this, as starters that have been left for significant time can become very acidic, which can also affect fermentation in some cases. However, sourdoughs that have been maintained for longer periods of time can and do build up a tolerance to more acidic conditions.
What if I store it in the fridge?
It is very normal for sourdough starters to be kept in the fridge. Like we said at the beginning, both yeast and bacteria need food, moisture and warmth. By keeping your sourdough in the fridge, you are removing the "warmth" part of the equation. It will still ferment but at a much slower rate, which means you don't need to refresh it as often because it uses the food source up much more slowly. However, it is also important that if you plan to bake with your sourdough starter, bringing it out of the fridge and refreshing it before use will help improve your final bread.
We are looking forward to seeing the bread that Bob makes, and always amazed, even now, how sourdough works and natural fermentation! We hope that you found the above quick overview useful! We welcome any comments or questions and also bare in mind that this is a very brief quick overview. There is much more information that you can find out about sourdoughs, and everyone has different methods and processes. If you are intrigued and want to create your very own unique version of Bob, then have a go. We have some useful step by step instructions to make your sourdough starter here - Bread 101 Sourdough Starter
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