Irrewarra Sourdough Website At Irrewarra Sourdough we make bread with real flavour and texture using traditional bread-making techniques. Our breads are 100% authentic sourdough. That means they are made using as a leaven, a culture of wild yeasts and bacteria which naturally occur in the air and flour. Our culture was created by allowing these natural yeasts and bacteria to multiply in a mixture of flour and water which is then used each time we bake. This method is the original bread-making process used before baker’s yeast was developed. in Lifestyle > Food and Beverage > Foodwith breadfoodgeelongirrewarralifestylemelbournesourdoughyeast Note: "White Oval Loaf or Casalinga" is really rather wonderful.