Raising Agents - PowerPoint PPT Presentation

1 / 8
About This Presentation
Title:

Raising Agents

Description:

Raising Agents Raising Agents are gases which are introduced into a food mixture : During the mixing process In a substance which is added to the mixture – PowerPoint PPT presentation

Number of Views:89
Avg rating:3.0/5.0
Slides: 9
Provided by: Dorot83
Category:

less

Transcript and Presenter's Notes

Title: Raising Agents


1
Raising Agents 
  • Raising Agents are gases which are introduced
    into a food mixture
  • During the mixing process
  • In a substance which is added to the mixture
  • The gas is incorporated or released when
    ingredients are combined.
  • On heating (baking), the minute bubbles of gas
    enclosed in the mixture expand, causing the
    mixture to rise.
  •  
  •  

2
  • The three most common raising agents are steam,
    air and carbon dioxide.
  •  
  • They are frequently used in combination with each
    other
  • e.g. in a creamed cake mixture -
  • Steam from liquid (egg/milk/water)
  • Air beaten in (creaming butter sugar)
  • Carbon dioxide from chemical raising agents in
    baking powder or self raising flour.

3
Steam
  • Some food products have steam as the main raising
    agent. These products must contain a high
    proportion of liquid, e.g. Choux pastry, batter
    used for Yorkshire puddings.
  • For steam to make the mixture rise, two
    conditions are needed
  • A large proportion of liquid (Milk/Water)
  • A high baking temperature of 200oC or above
  •  
  • During baking
  • Liquid reaches boiling point
  • Steam forces its way up through the mixture,
    stretching the mixture and making it rise.
  • The steam escapes and is replaced by air, the
    mixture bakes and sets into the risen shape.
  • Sometimes steam is trapped inside. It condenses
    on cooling and then the product collapses. This
    often happens in Yorkshire puddings.
  •  

4
Air
  • Mechanical action incorporates air into mixtures,
    it is the main raising agent in some food
    products, e.g. whisked sponge cakes and soufflé
  •  
  • Air can be mechanically introduced into mixtures
    by
  • Sieving flour air is trapped between fine
    particles
  • Rubbing fat into flour air is trapped between
    breadcrumbs
  • Creaming fat and sugar air is beaten in, to
    form an air and fat foam.
  • Whisking eggs/sugar or egg whites air is
    whisked ino the egg to form a high volume foam
  • Beating batter air is beaten in, but steam is
    the main raising agent.
  • Rolling and folding pastry air is trapped
    between the layers
  •  

5
Carbon Dioxide
  • This is produced in two ways
  • Biologically from yeast cells during the
    fermentation process
  • Chemically from the action of bicarbonate of soda
    with an acid
  •  

6
Biological Raising Agents
  • Yeasts are micro organisms, during the
    fermentation process, the yeast cells feed on
    sugar and reproduce to produce carbon dioxide.
  •  
  • Certain factors affect the action of yeast -
  • Temperature optimum temperature range is 25oC
    35oC
  • Above 60oC the fermentation process is
    destroyed
  • Below 25oC the reaction is slowed down
  • Fresh yeast can be frozen without killing
    it and it becomes active again once defrosted.
  •  
  • Moisture This is provided from milk/water/egg
  •  
  • Food During fermentation of yeast, the cells
    need to be fed on sugar to produce carbon
    dioxide. There is also a small amount of sugar in
    the flour
  •  

7
Chemical Raising Agents
  • Carbon dioxide is produced from chemical
    reactions. This can be made to happen in many
    recipes by the addition of a chemical raising
    agent.
  •  
  • Chemical raising agents must be measured
    accurately, they
  • Are used in small quantities
  • Are easy to use and often already combined e.g.
    self raising flour
  • Will produce controlled amounts of carbon dioxide
  • to aerate mixtures evenly.
  •  
  • Three types of chemical raising agent are -
  • Bicarbonate of Soda known as sodium
    bicarbonate
  • Bicarbonate of Soda Acid (alkali acid)
  • Baking Power or baking powder in self raising
    flour

8
  • Bicarbonate of Soda -
  • Simplest type of chemical raising agent. When
    heated in a mixture, it produces sodium carbonate
    (soda) steam and carbon dioxide.
  • The carbon dioxide and steam aerate the mixture.
    The soda leaves a dark yellow colour and gives a
    sharp alkaline taste to the mixture.
  • Used in recipes which have other strong flavoured
    ingredients e.g. chocolate cake gingerbread
  •  
  • Bicarbonate of Soda plus Acid
  • The bicarbonate of soda reacts with the acid to
    produce carbon dioxide. The acid helps to
    neutralise and prevent the taste and colour
    residue left when bicarbonate of soda is used on
    its own.
  •  
  • A traditional source of acid is sour milk. This
    is still used in some mixtures, an other sources
    of acid is Cream of Tartar (Tartaric Acid), when
    combined with bicarbonate of soda this releases
    the carbon dioxide slowly, leaving a tasteless
    salt behind. The ratio used is 2 parts Tartar to
    1 part bicarbonate of soda.
  •  
  • Baking Powder
  • Commercial mixture of bicarbonate and acid
    substances ready mixed in the correct
    proportions. A buffer is added in the form of
    cornflower or rice flour to absorb any moisture
    and prevent the reaction taking place in the
    storage container.
  •  
  • Baking powder is added to plain flour to produce
    self raising flour.
Write a Comment
User Comments (0)
About PowerShow.com