Types of Raising Agents
Yeast is an organism capable of reproducing itself which, when added to bread, makes it rise. Given moisture, food, warmth, and time, yeast will grow, producing carbon dioxide gas to rise bread dough and creating the cellular structure of breadcrumb.
Before the commercial production of leavening compounds, bakers relied on their knowledge and bakery skills to make the best bread they could with the ingredients available. Good quality yeast would produce good quality doughs and bread, so across the centuries bakers sought to protect and control their source of yeast as it was their livelihood.
From early times, brewing and baking were often linked. Brewer's ferments and by-products would typically be added to ground grains or flour to make a barm that would be used to leaven bread. Dried barm or a piece of remaining unbaked dough could be moistened, reworked and added as a starter to each new baking. Today, sourdough starters are used in a similar way.
The easiest yeast to use is Quick Yeast, which is a fine granulated powder that can be mixed straight into the flour. Use 3 teaspoons of quick yeast to 1.5kg of flour.
Compressed cakes of crumbly fresh yeast will keep for about two weeks in a refrigerator. Discard fresh yeast if it has gone brown and hard. To activate fresh yeast it is creamed into a sugar and water solution at about 35ºC (95ºF). After 15-20 minutes the mixture will be frothy and ready to add to your flour. Use 50g (2oz) fresh yeast for 1.5kg of flour.
It is the chemical combination of an acid and an alkali in baking powder that produces carbon dioxide gas which can raise baked goods. Commercial baking powders sometimes contain an inert filler such as wheat or rice starch so check the ingredients label if you are on a special diet, or make your own baking powder.
Historically baking powder is a nineteenth-century invention. A famous chemist, Justus Von Liebig, explored the relationships of organic chemistry to agriculture and plant physiology. He was interested in obtaining maximum plant yield and to control processing of grain without wastage. Instead of using yeast he tried to raise bread with sodium bicarbonate and hydrochloric acid, with uncontrollable, dramatic and sometimes explosive results.
He eventually found the combination of sodium bicarbonate and monocalcium phosphate, when mixed with water, would release carbon dioxide at a controlled rate for successful baking. This is still the basic formula for many modern baking powders.
Self Raising Flour
The correct proportions of the raising agents, acid and alkali, are already added to self raising flour. The raising agents used at Doves Farm are sodium bicarbonate and monocalcium phosphate.
Sodium Bicarbonate (E300)
Sodium Bicarbonate, sometimes called Bicarbonate of Soda, is an alkali and can be used on its own as a raising agent if the dough or batter is sufficiently acidic to allow a reaction that creates carbon dioxide. Lemon juice, yoghurt molasses and sour cream are acidic enough to react with Sodium Bicarbonate but may impart a distinctive strong taste to your baking.