Science Lesson: Investigating Starches and Fats

Starches and Fats

Starch is a polysaccharide carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. Starch is produced by all green plants as an energy store. It is the most important carbohydrate in the human diet and is contained in such staple foods as potatoes, wheat, maize (corn), rice, and cassava.

Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water. Chemically, fats are generally glycerol and fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure and composition.

Science Experiment

A food science investigation of starches and fats.

Purpose:

Observe the presence of starches and fats in different foods.
Distinguish between foods that contains starch and a food that contains fats.
Define the terms starches and fats.
Classify foods as starches or fats.

Materials (for each group):

• Cookie sheet
• Eye dropper
• Tincture of Iodine
• Typing paper
• Brown paper bag
• Bread
• Crackers
• Sugar
• Cooking oil
• Peanut butter
• Safety goggles

Student Group Procedures:

1. Place samples of bread, crackers and sugar on a cookie sheet.
2. Place a drop of iodine on each of the samples.
3. Observe the samples and explain what happens.
4. The existence of fats is tested by placing a sample of cooking oil, peanut butter and bread on a brown paper bag.

Science Lesson Findings

Starches and fats are observed in samples of different foods. The bread and crackers will turn a dark blue purple illustrating the presence of starch. In contrast, the sugar sample turned brown indicating the absence of starch.

Additionally, fats are tested by the saturation of the brown paper bag by cooking oil and peanut butter. The bread sample shows that fats are not present.