Yeast is an organism capable of reproducing itself which when added to bread makes it rise. Given moisture, food and 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. Brewers 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.
When bread is made using a cultured starter as the raising agent it is referred to as a sourdough loaf. The simplest sourdough starter is made by retaining a piece of bread dough from the last baking. If you want to avoid commercially manufactured yeast you can make your own Sourdough Starter using potatoes and rye flour.
Metric Ingredients Imperial
100g Old Potatoes 4oz
100g Rye Flour 4oz
2tsp Sugar 2tsp
½ tsp Salt ½ tsp
- Boil the un-peeled potatoes.
- Mash them into the cooking water.
- Add remaining ingredients.
- Cover with a cloth and leave for 3 days.
- Use instead of yeast in your bread recipe.
For further information about sourdough, visit www.howstuffworks.com
The easiest yeast to use is Quick Yeast, which is a fine granulated powder that can be mixed straight into the flour. Use 3 teaspoon 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.
Original Dry Yeast
Is a dehydrated form of compressed yeast with the appearance of small 1.22mm spherical granules. It has a long shelf life, provided it is kept airtight. It is activated in the same way as fresh yeast by whisking into a sugar and water solution at about 43ºc (110ºF). The mixture will be frothy and ready to use after 15 minutes. Use 1oz (25g) dried active 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 monoclacium 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 into self raising flour. The raising agents used at Doves Farm are sodium bicarbonate and monoclacium phosphate.
Make your own baking powder or self-raising flour:
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.
Cream of Tartar (Tartaric Acid E334)
Cream of tartar is a fast acting acid that can be combined with bicarbonate of soda to make your own raising agent.
Ammonium Bicarbonate (E503)
This alkali is sometimes know as 'vol' because it disappears during baking. It is often one of the raising agents used in biscuit manufacture where the carbon dioxide and ammonia combine to raise the biscuit dough. As a processing aid the law does not require ammonium bicarbonate to be declared on the ingredient label, however we will always tell you if we add it to a Doves Farm product.
Make your own Baking Powder & Self-Raising Flour
Place 3 teaspoons of bicarbonate of soda with 4 teaspoons of cream of tartar in a jam jar and shake well. Use as required where a recipe call for baking powder.
To make self-raising flour, add 1tsp of baking power to 200g / 8oz plain flour.