Wild yeast are single-celled fungi that exist all around us. They feed on carbohydrates, and as they do so they release carbon dioxide, B vitamins, and alcohol. Because they release carbon dioxide, yeast can leaven bread, and because they convert carbohydrates to alcohol, brewers use yeast to make beer and wine, too. This is the fermentation process.
Although the beneficial wild yeast in the sourdough tend to be lost during the baking process, the fibre and plant compounds, called polyphenols, become more bio-available. These act as an important fuel source for our gut microbes, which makes sourdough bread a gut-friendly choice
Fermentation of food grains also improves bioavailability of minerals. Phytic acid is present in cereals bonded with iron, zinc, calcium and proteins. This bonding makes it difficult for the body to utilise the minerals in flour. The enzymatic degradation of phytic acid requires an optimum pH which can be provided by natural fermentation. Such a degradation of phytic acid can increase the amount of soluble iron, zinc and calcium absorbed by the gut. (Gupta, Gangolya and Singh 2015)
The fermentation process and higher fibre content makes sourdough a useful option for those with blood sugar management issues. This is because, unlike many commercially produced breads, sourdough has less of an impact on blood sugar levels. This especially true of rye sourdough.
Typically, diets high in fibre are associated with a lower risk of heart disease. Sourdough appears to offer additional benefits thanks to the fermentation process; these benefits appear enhanced when wholegrain rye flour is used. All Heritage Bakehouse sourdough has whole rye in it.
Traditional sourdough undergoes a slow fermentation process, . This process starts the breakdown of protein (including gluten), making sourdough easier to digest.