Tuesday, August 15, 2006

What is the Chemistry of Cooking?

Cakes, cookies and pies--who does not love these yummy baked goods? Have you ever seen these goodies being made or actually participated in making/baking any of these? There is lot of chemistry involved in our cooking.

If you had watched anyone bake a cake, you might have noticed them add a pinch of baking soda or baking powder with the flour. These chemicals help in leavening the flour (leaven: to make light/loose). The principle behind the use of baking soda depends on acid-base reactions that eventually release carbon dioxide gas to help the flour rise.

Acid-base reactions are chemical reactions between an acid and a base. Chemists define acids as substances that can accept electrons and bases as substances that can donate electrons. Acids are commonly found in our day to day life and they can be dilute or concentrated. Citric acid is an acid found in common substances such as lemon juice and orange juice. Acetic acid is found in vinegar. These are dilute acids, whereas concentrated acids are not generally kept around home as they can be quite dangerous.

Bases, on the other hand, behave chemically opposite to acids. Many household cleaners are basic or alkaline. When bases and acids react usually the exchange of electrons also releases heat. Most acids and bases react to form salts (minerals) and water. For example, the reaction between hydrochloric acid and baking sodium hydroxide (a base) would form water and common salt.

The main chemical in baking soda, sodium bicarbonate, contains carbon dioxide in bound chemical form. When it reacts with an acid, it releases carbon dioxide gas and water. This is why most cake recipes call for a small amount of vinegar or orange juice. The acid in these liquids reacts with the baking soda to quickly produce carbon dioxide gas that can bubble through the flour mixture, making it rise in the process.

There are also several other acid-base reactions that can occur even inside the body. The stomach contains acid that helps break down bonds in the food. It also reacts with alkaline matter in the food. If someone has acidity problems, the antidote is to eat/drink something alkaline to neutralize the acidity.

For more information on acid-base reactions in our body, see http://www.scienceclarified.com/everyday/Real-Life-Chemistry-Vol-2/Acid-Base-Reactions.html

Little Lion Experiment 1:

Items needed:

  • Vase or wide-mouthed clear jar
  • 1/4 cup vinegar or lemon juice
  • 3 teaspoon baking soda
  • Food coloring


  1. Fill the vase/jar with clean water.
  2. Add 3-4 drops of food coloring.
  3. Add vinegar then add baking soda slowly into the beaker.
  4. Drop in rice, buttons, pasta - and watch them rise and fall.

Experiment source: http://www.armhammer.com/myfamily/kids/magic_beans.asp

Little Lion Experiment 2: Writing With Invisible Ink

These are instructions for making non-toxic invisible ink using baking soda (sodium bicarbonate).

Items required:

  • Baking soda (not baking powder)
  • Paper
  • Q-tips
  • 2 paintbrushes (at least 1)
  • Small cup
  • Cranberry juice or purple grape juice.


  1. Mix equal parts water and baking soda to make a paste. We recommend starting with a small amount (about 2-3 table spoons) first. Sometimes you can dilute it more.
  2. Use the q-tip or paintbrush to write a message onto white paper, using the baking soda solution as 'ink'.
  3. Allow the ink to dry.
  4. To read the message paint over the paper using another brush with purple grape juice. The message will appear in a different color.
Source: http://chemistry.about.com/cs/howtos/ht/invisibleink2.htm