Nutrition: Which foods contain proteins and salts?
Purpose/Hypothesis
This project will help you identify proteins and salts, nutrients needed for cell repair and daily maintenance. Proteins, present in every cell, are known as body builders. They help you grow and replace cells. Salts are minerals that your body uses to maintain water balance.
Level of Difficulty
Moderate. This experiment requires the purchase of two chemicals and the supervision of an adult.
Materials Needed
- silver nitrate (a salt-indicator solution, which can be purchased from science supply catalogs)
- Biuret solution (a protein-indicator solution, also available from science supply catalogs)
- glass test tubes or glass cups
- test tube rack
- food from one meal
- water
- goggles
- rubber gloves
Approximate Budget
$20 for the silver nitrate and Biuret solutions, depending on the quantity. The silver nitrate can be purchased as a crystal and dissolved in water.
Timetable
1 hour.
How to Experiment Safely
Ask an adult to help you with this project. Wear goggles or other eye protection and protective gloves when handling silver nitrate. Be careful with the silver nitrate, as it stains the skin.
Step-by-Step Instructions
- Create ¼-teaspoon-size samples of each type of food from your meal.
- Set test tubes in rack.
- For the protein test, put a food sample into a test tube and add 10 drops of Biuret solution.
- Wait 10 minutes. If the blue Biuret solution turns lavender, the sample contains protein. Record the result on a data chart.
- For the salt test, put a food sample into a test tube and fill tube halfway with water. Shake gently. Add 10-20 drops of silver nitrate solution.
- Watch to see if the clear silver nitrate forms a milky white precipitation in the water. If so, salt is present. Record your results.
- Repeat Steps 3 through 6 for each food sample, recording all your results on the data sheet.
Summary of Results
After testing a typical meal, analyze your results. How many samples contained protein or salt? Do you see any pattern? Write a paragraph summarizing your findings.
Troubleshooter's Guide
Here is a problem that may arise during this experiment, a possible cause, and a way to remedy the problem.
Problem: None of my foods tested positive for salt.
Possible cause: Insignificant amounts of salt may be present. Make a test tube sample of salt and water. Add silver nitrate to see if the solution turns white. If not, the silver nitrate may be contaminated.