THE BAKING INDUSTRY
Yeast's are found in the air around us. They are found on the skin of fruits - they particularly like grapes. They like the sugar in the grapes and do not need oxygen to live. They like temperatures between 20 and 40 degrees C.
YEAST is one of the raising agents that can be used to make products rise and give them a light taste. If you want yeast to work it has to grow or 'bud'. This means that the yeast cells divides into two and keeps on growing. It cannot do this without help and this help comes in the form of
IT HAS TO BE WARM LIQUID
If you want to kill the yeast - so that it does not start to grow, all you need to do is to have the water or milk, very very hot. The yeast will not do anything at all - just make the liquid look sandy in colour. Your know when the yeast is working - it is very frothy on the top of the liquid - rather like the foam on a glass of beer.
FOAM ON THE TOP = ACTIVATED YEAST!!
Yeast is sold in two forms fresh or dried
The dried yeast look like micro-brown seeds, all the same size and colour. The fresh yeast look like a chunk of light brown fudge and breaks very easily into pieces.
Both yeast's will melt in the warm liquid and then start to bud.
Chemical raising agents
Chemical raising agents - these are powders which need some form of liquid and heat to produce carbon dioxide which then means the product rises.
You have to be very careful AND MEASURE CAREFULLY. This is one time when the 'bung it all in method' does not work!!
BICARBONATE OF SODA
This has a nasty taste if you tried some on your tongue. It needs to be in a recipe which has strong flavours to disguise the taste - like gingerbread, chocolate cake or other spiced cakes.
CREAM OF TARTAR
This is added to the bicarb. Tartar is an acid and this helps takes away the bitter taste.
Instead of using cream of tartar you can add an acid to the bicarbonate of soda - such things as sour milk or vinegar. This is used in scone making.
This is already made up in the factory where it is made. It is a mixture of bicarb and an acid. The makers add cornflower or rice flour to the baking powder to keep it inactive before use.
The chemical raising agents stay 'asleep' so long as they are kept away from liquid either alkaline or acid. The drums they are sold in usually have tight fitting lids to stop moisture getting in.
NON CHEMICAL RAISING AGENTS -
These are AIR and STEAM
You can combine air into a mixture by any of the following -Sieving the flour Creaming the fat and sugar
STEAM MAKING THE PRODUCT RISE
This happens when the product which contains water is heated to a high temperature and steam is formed. This wants to get out of the product and so forces its way out through the mixture and stretches the cake or bread (whatever) leaving the product light and fluffy and risen
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