Fermentation is central to the bread making process. It arises from the development of natural “wild yeasts” in the dough (sourdough starters), the addition of commercially developed baker’s yeast or a combination of both. Fermentation is crucial to the flavour development and crumb structure of the final product. A good understanding of how the mechanism of fermentation works will help you make superior restaurant quality bread in the comfort of your own home.
What causes bread to rise?
The first step to bread baking requires us to knead flour and water together (Autolyse). The water hydrates the wheat protein (gluten) present in the flour and kneading encourages the formation of an elastic network of strands within. These strands are stretched open during the first rise. Carbon dioxide and ethanol are released by “wild yeasts” that break down the sugars (glucose and maltose) present in dough. The carbon dioxide gets trapped within these gluten strands which causes the dough to inflate and “rise”.
Sourdough breads are made using natural starters comprising of live cultures. These starters are made by mixing flour, water and in some instances honey. The natural “wild yeasts” present in the atmosphere begin acting on it, thus creating a sourdough starter. Making bread with a natural starter involves maintaining a balance between the actions of the bacterias and yeasts. Where it becomes tricky is that the bacteria acts best at 30’c whereas yeasts act best between 20-26’c. Low temperatures cause sourdough breads to taste overtly sour. Further, kneading, hydration, temperature and ingredients all affect the fermentation process.
Fresh Baker’s Yeast
Fresh Baker’s Yeast (sacchoromyces cerevisiae), is used to speed up and aid the natural alcoholic fermentation process in bread baking. It produces carbon dioxide that causes the formation of air bubbles in the bread, as well as various other chemicals that add a distinct aroma and flavour to the bread. It can be used in combination with a natural sourdough starter to balance out over-acidic natural starters, and fine-tune fermentation time.
What is better?
Whether you’re using a natural starter, commercial yeast or a combination of both, it is essential that you watch your dough and be cognisant of the room temperature, humidity levels and quality of ingredients you have used. The fermentation timing mentioned in recipes can vary and so it is helpful to keep a watchful eye on your dough to ensure it doesn’t overproof.