Salivary Amylase and Starch Digestion

Project Overview: Believe it or not, digestion doesn't start in your stomach. It starts the second food hits your tongue. Your saliva is packed with an enzyme called amylase, whose entire job is to break starch down into sugar before it even reaches your stomach. This project lets you literally watch digestion begin, using a simple color-changing test.

Materials Required: 

1. 1 slice of plain white bread

2. Iodine solution (from a pharmacy or first-aid kit)

3. 2 small clear cups

4. Water

5. A spoon

6. A dropper (optional)

Instructions: 

1. Tear the bread slice into two roughly equal pieces. Place one piece in a cup with a small splash of water and set it aside, untouched. This is your control.

2. Chew the second piece of bread thoroughly for about a minute, letting your saliva mix in well, then spit the mixture into the second cup.

3. Add a few drops of iodine solution to the control cup (untouched bread and water). 

4. Observe the color; iodine turns blue-black in the presence of starch.

5. Add a few drops of iodine solution to the chewed bread mixture in the second cup.

6. Compare the two cups. The control should turn dark blue-black (starch is still present). The chewed sample should show a much lighter color or little to no color change, which shows that salivary amylase had already broken the starch into simpler sugars before the iodine could react with it.

Congratulations, you just proved that digestion starts in your mouth.

Fun Fact: The lighter color in your chewed sample means the starch is already gone; your own saliva broke it down into sugar in less time than it took you to read these instructions.