What is Sourdough?
‘Sourdough’ is any bread leavened with naturally occurring wild yeasts and lactobacilli, and without the use of manufactured bakers yeast. It is as simple as flour and water, and making it can be just as simple. Allowing time and providing a warm environment, the yeasts and beneficial bacteria that occur naturally in the flour are able to multiply. The yeasts give off carbon dioxide gas which aerates the dough and causes it to rise. The beneficial bacteria help to develop flavour, nutritional value, digestibility and keeping quality.
Lactic acid bacteria (LAB) are the important microbes in a typical sourdough, and here is a short list of the health benefits of making bread in a way which allows them to fully get to work:
Sourdough LAB can neutralise the bits of gliadin and glutenin protein in wheat flour that are toxic to people with coeliac disease and gluten intolerance.
Sourdough LAB produce beneficial compounds: antioxidants, the cancer-preventive peptide lunasin, and anti-allergenic substances, some of which may help in the treatment of auto-immune diseases.
The long fermentation time of sourdough breads is sufficient to neutralise the phytic acid that commonly ‘locks up’ minerals such as iron, calcium, magnesium and zinc in fast-fermented wholemeal breads.
Sourdough LAB produce organic acids that, under the heat of baking, cause interactions that reduce starch availability and therefore a low glycaemic index (GI). The lowest-GI breads are wholegrain sourdoughs with a compact texture.