Levain is the French word for sourdough bread. In English we use the term leaven to describe any raising agent used in baking. This can include baking soda, shop bought yeast, or a home-grown, living culture known as a sourdough starter. The starter is made by attracting and cultivating wild microorganisms that transform wet dough into loaves of bread (with a bit of heat as well). For thousands of years this was how humans made bread.
Before commercial bicarbonate of soda became widely available in the early 1800s people in Ireland used a variety of wild cultures to raise bread. According to Lennon (2003) these included: a ‘barm” made from by-products of beer brewing; the soured juice of grated potato; “sowans” or “bulls milk” made from the fermented juice of oat husks.
The Bangor Bakehouse starter could contain a number of different microorganisms. This depends largely on what the food source is and how the culture is looked after (more on this next time). One of the more common types is a lactic acid bacteria called Lactobucillus sanfranciscensis (guess where that was first discovered). This little guy usually works in conjunction with a common wild yeast such as, the wonderfully named, Kazachstania exigua.
Scientists are beginning to explore the complex and intricate ways these organisms work together and the benefits they provide to our own health. What must have seemed like magic to our ancestors, or a gift from the gods, is still a bit of a mystery to us today.