food science

• Gluten formation - happens when you're kneading dough. The gluten in the flour stretches and creates long protein strands. When the dough is cooked, the strands harden and the bread stays stretched.
• Fermentation is an anaerobic process: glucose → ethanol + carbon dioxide. Yeast provides the enzymes required for fermentation. The temperature has to be warm but not too warm.
• Shortening – fat coats the particles of flour and stops it absorbing water, so only a small amount should be used. The gluten in the flour cannot form long strands. This stops the dough from stretching and products have a crumbly/ firm texture. Used when making short crust pastry.
• Chemical raising agents-

  • Bicarbonate of soda is an alkali raising agent that breaks down when it's heated. Carbon dioxide bubbles form and, when they expand, cause a mixture to rise.
  • Baking powder contains both bicarbonate of soda and an acidic substance called cream of tartar. Heating baking powder sparks a neutralisation reaction.
  • Self-raising flours are made up of baking powder and plain flour.
• biological raising agents-

  • Yeast is a microorganism that's used to help bread dough rise.
  • Yeast releases carbon dioxide and alcohol through the process of fermentation.
  • We usually have to prove doughs that contain yeast. This involves letting them stand in a warm environment to let fermentation happen.
  • During the proving process, the carbon dioxide that's released gets trapped and the dough rises.
  • When the dough is baked, the high heat kills the yeast and ends the fermentation process. Baking causes the carbon dioxide in the dough to expand (and the bread to rise) and the alcohol to evaporate.
• raising agents( steam)-

  • When very liquidy mixtures (e.g. Yorkshire puddings) are cooked in hot ovens, water escapes as steam. The rising steam helps to raise the mixture.
  • The mixture bakes and solidifies as water escapes.
  • Any cold air that gets added (e.g. from opening the oven door) will sink the mixture.
• mechanical processes-

  • We can fold air into doughs and mixtures by:
  • Literally folding pastry doughs into layers. Air gets trapped between folds.
  • Using the folding technique for mixtures. This involves using a spatula or spoon to cut through the mixture and pour it over itself to trap air.
  • Sieving ingredients like flour traps air between individual particles.
  • Creaming adds air.
  • Rubbing fat into flour introduces air between individual flour particles.
• • Beating adds air to mixtures very rapidly. Beating involves mixing ingredients with a spoon or fork.
  • If a whisk is used, we call this process whisking.
• setting mixtures- removal of heat :

  • Technique - gelation. This involves using a starch to set a mixture when it's chilled.
  • Example food product - custard.
• setting mixtures- use protein:

  • Technique - set a mixture containing eggs by heating. The denatured and/or coagulated protein in the eggs causes the mixture to set.