In my recipe for Æblekage: a classic Danish desert I mentioned that the apple cut-offs from making the apple sauce used in the desert could be employed to make a sourdough mother culture (or levain as it is also called) from scratch.

This recipe explains how. You need organic apples which have not been treated with insecticides. They should not be washed before being peeled. The method is based on the assumption that you need peeled and cored apples for something else.

1. Put the apple peel and cores in a clean jar and add unchlorinated water to cover (in most areas tap water will do fine). Losely put on a lid - you basically want air to be able to escape and nothing to enter. Put the jar in a dust-free place away from plants, flowers, fruits and other potential sources of cross-contamination, at room temperature for a week.

2. After a week (on day 7) the contents of the glass should smell slightly of alcohol and some bubbles should be evident (photo 1). You have basically made a natural weak cider at this stage, as well as allowed natural yeasts to develop. Use a sieve to remove the apple peel and cores from the liquid, catching the liquing in a clean bowl. Rinse out the jar, then add 90g of the liquid to it, followed by 75g of flour of your choice (e.g. rye, light rye, stoneground wheat or strong Canadian wheat, all available from Shipton Mill). Mix well. The mixture should be fairly liquid. If it gets too dry mix in a bit more of the liquid but with starters it is convenient to stick as close to 100% hydration (50/50 flour and water) as practical because it makes calculations easier when you later calculate water and flour quantities to make dough. Put the lid back on and put the jar back where you kept it the first week, away from potential sources of contamination (photo 2). Retain the remaining apple liquid in a lidded jar or in a bowl sealed with clingfilm.

3. The following day (day 8), if everything has gone well, you should have a nice and bubbly culture, alive and healthy (photo 3). Feed it with 75g of flour and 75g of the apple liquid (or if you don't have more of it, with lukewarm water).

4. On day 9 you should have a bubbling fully developed sourdough mother with a pleasant, slightly acidic, aroma with notes of apple, smelling a bit like a mild yoghurt if you have used wheat flour, slightly stronger if you have used rye. Add another 25g of flour and another 25g of cold water to feed the culture, and move the jar either into a fridge or to a cold room, e.g. an unheated basement. A temperature around 10°C is ideal. Feed the culture every day for the first few days, then weekly with 50g of flour and 50g of water. Regularity is important for taste consistency, and cleanliness is paramount if you wish to maintain a particular taste over a long period of time, as is temperature control. A sourdoug's taste is basically determined by the mix of yeasts and lactic acid bacteria that constitute the culture. The longer you keep your sourdough culture alive the more it will develop its own particular character, partly influenced by the bacteria growing on your own skin, especially if you don't use gloves when feeding.

I mentioned above that using a mother culture at 100% hydration is convenient. However, as a rule of thumb, a slightly wetter mix (e.g. 125% hydration) develops more acidity, so a different taste.

A sourdugh mother can sometimes go bad, either right from the start if you don't happen to catch a viable bacteria mix, or later for various reasons, mainly under-feeding. If it turns black, mouldy and/or develops a really bad aroma a risk of toxicity exists and the safe bet is to start over. In order to reduce the risk of invasion by unwanted organisms, after feeding you can tighten the lid on the jar, turn it sideways and slowly rotate it so that all sides of the jar as well as the lid, get washed with the acidic culture, thus killing off unwanted intruders.

The day before you want to use it for baking, you just follow the procedure for making a starter below. In case you don't bake often the jar will evetually fill up and you will have to either discard some of the contents (each time you feed for example), or you can dry it, grind it into a powder and use it as a tangy seasoning (if you proof bread in a banneton you can dust the banneton with it).

Using your mother culture for making a sourdough starter: to make a starter for some bread add 100g flour and 100g water at 25-30°C to 25g of the mother culture in a jar or bowl (scale quantities as required). If done in the evening and kept at room temperature overnight it is ready to use the next morning. It will have increased in volume and bubble happily away. You can use any starter with different types of flour. Rye starter give a slightly more tangy result than wheat-based starters.

I have based this description on the use of some apple sauce bi-products that would normally be thrown out without a second thought but you can do similar things with loads of different starting ingredients. Here in the gastronomy laboratory at Gastro-Cooking we have a range of experimental bakery-oriented cultures and other fermentation projects, some of them several years old.

Of course, if you don't wish to go through this whole process you can always just buy a mother culture from one of the organic artisan specialists growing them.