Marshmallows and Saliva

Your digestive system starts with your mouth. Not only do the teeth chew and break down the food into smaller parts, the saliva itself has various enzymes (amylase and lipase) that start to break down the starches and fats on the molecular level.

A good quick test of whether or not a substance has starch in it is by adding a drop of iodine to it. Iodine normally has a brownish color, but if it is in presence with a starch, it turns a distinctive dark blue/purple.

Try this out. In a clear cup, gather some of your saliva. Mix in some ground up crackers. In another clear cup, gather the equal amount of water. Mix in the same amount of ground up crackers. Wait 5 minutes for the amylase to break down the starches. Add a drop or two of iodine and see what happens. Which cup still has starches to react with the iodine?

What other foods have starches? Test it out with marshmallows, cheeses, rice, potatoes, meat, etc. . . Just make sure to break down the food into smaller chunks and mix with water before adding the iodine.

Activity adapted from http://www.exploratorium.edu/ti/conf/nsta_2006/karen_kalumuck_session/Amylase.pdf