Baking with yeast

Yeast is a very handy raising agent.  Without it bread would be as dense as bricks.  However, yeast can be very tricky to bake with.  Yeast is a complex organism.  The emphasis with yeast is that it is a living organism.  As such certain factors must be taken into account.

Water:  Yeast like moist environments.  However, as bread is made by mixing flours with liquids this is a fairly easy need to fulfil.

Air:  Yeast need oxygen just like us - this is why it is important to sift the flour before use as this allows for the most aeration of the flour as possible; ensuring the larges air pockets for the yeast.

Food:  Yeast live on sugars.  This is why sugar is added to bread mixtures - too feed the yeast.

Heat:  This is a big factor.  This often where people fail in the baking process.  It is important to keep all ingredients of the bread dough at a temperature between 20-37 degrees Celsius.  This is because yeast's optimal growth happens in this 20-37 temperature range.  It is equally important for the rising process to place the dough in a place where the temperature is 20-37 degrees for an hour prior to baking.

The importance of sifting

Sifting is an important, and often forgotten, element in baking.  Historically, the act of sifting flour came about as a way of removing the lumps from the grinding stones used to mill the flour, insects and insect parts and removing the solid lumps of flour that form when flour was kept in poor, damp conditions.  However, the practise has continued into modern baking for one very good reason - it separates and aerates the flour.  This is  an important step to achieving light and fluffy cakes and muffins.  Aerating the flour allows more space between the flour molecules so the yeast have more space to grow or allows for more air for the reaction that causes baking soda/bicarbonate to create air pockets.  Whether you use yeast or bicarb, sifting clearly helps to create a lighter product.