To say "sourdough" is a bit like describing the beginning of everything in one word. Lactic fermentation is the fundament of the most exquisite breads and sweet doughs. Needless to say, dry yeast is beneath the consideration of a serious foodie. Fresh yeast in the form of a starter dough offers decidedly better results in terms of flavour and aesthetics. Unfortunately, the technique is not easy to master, but by following a few elementary rules and showing a little patience, we will obtain a certain amount of starter that can, under perfect conditions, be preserved for decades.
But how to make sourdough starter? Introductions first: the starter dough is a mix of flour, water and a host of yeasts and bacteria (lactobacilli) unleash the process of lactic fermentation and act as a rising agent. During this process, acidic substances are produced and a large amount of carbon dioxide is released, which is precisely what makes bread rise. The more carbon dioxide, the larger our dough will swell. So three ingredients are needed to make a sourdough starter paste: water, flour and the mix of yeasts and bacteria. We use 100 millilitres of water for every 200 grams of flour. Water is best if bottled, with very little chlorine, but otherwise we can leave it out in a bowl overnight for the chlorine to evaporate. Organic flour is preferred, either 100% or partially wholewheat. This is because the third ingredient, the yeasts, is actually found in the flour itself, so the more natural it is, the more flavourful yeasts it will contain.
Sourdough yeast cultures can be bought as mixes, ready for use, but if we are looking to make a natural starter, we might as well begin from scratch. Seeing that yeasts and lactobacilli are present everywhere, why not take advantage to ferment them? There is nothing unhealthy about cultivating bacteria here. They are absolutely innocuous, yet extremely useful organisms. The first step is to mix the flour with tepid water, which creates a favourable environment for the development of the yeasts. Mix to obtain a smooth and fully amalgamated ball. Carve a cross over the starter, and place it in a flour-dusted glass bowl. A clean jar is fine too. Cover with a damp cloth and seal with plastic wrap. The starter now needs to rest for at least 48 hours at temperatures between 20 and 25 degrees centigrade. The temperature for fermentation is very important. Some bread makers like to position some over-ripe fruit close to the bowl to encourage the starter to ferment. This is a good suggestion, as long as there is a good quantity of such fruit nearby – say at least one kilo. In any case, fermentation will commence even without it, and if the process is slow, we will simply wait for a few hours more. When ready, the starter will be puffy. Remove 200 grams and put the remaining 100 back into the bowl, cover, and put it in the refrigerator for future use. (I usually throw it away, seeing I don't want the fridge filling up with starters.)
Add 200 more grams of the same type of flour, plus 100 millilitres of lukewarm water to the reserved 200 grams of starter. Mix until smooth, and proceed as before, placing the mixture in a clean bowl, or the first one thoroughly washed. Allow to rest for two days, then repeat this operation for three or four weeks. The result will be a sticky mass with an acidic smell: the sourdough. The starter can now be refrigerated and used at will. If we want to conserve it for years, we must repeat the refreshing process once per week. To do so, remove the starter from the cold to sit at room temperature for at least ten hours before refreshing.
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