Activity 2.2.1 Food Testing - PowerPoint Presentation

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Activity 2.2.1 Food Testing

By:

Mahi

Introduction

Anna had high amounts of glucose in her blood at the time of her death. Most likely, she had eaten a large meal before her death. Since glucose levels are related to the food we consume, exploring Anna’s stomach contents at the time of her death, may reveal some information of about her meal and provide some evidence regarding the conditions surrounding her mysterious death. Eating a balanced diet consisting of; carbohydrates (simple sugars), proteins (crucial to help build tissue, etc.), and lipids (known as fats). Scientists analyze these chemical components by using chemical indicators, which is a substance that changes to indicates the presence of a particular compound or type of compound. They may change colors or bubble up. In this activity, you will use chemical indicators to test for compounds in starch, protein, lipids, and sugar.

Equipment needed

Starch solution, 5% corn starch or other starch soluble in water

Protein solution, 5% albumin in water

Sugar solution, 5% glucose in water

Lipid solution, cooking oil

Anna Garcia simulated stomach contents

Project 2.2.1 Autopsy Report resource sheet

Project 2.2.1 Anna Garcia Food Diary resource sheet

3 small samples of food

200 mL of distilled water in a beaker

8 transfer pipettes

Hot plate with beaker containing distilled water (to make a hot water bath)

12 test tubes

Test tube rack

Test tube holder

Test tube brush

1 beaker, 250 mL

1 beaker, 500mL

1 graduated cylinder, 10mL

Equipment needed continued

2 stirring rods

Safety goggles

Gloves

Laboratory apron

Laboratory journal

PBS Course File

Benedict’s solution

Lugol’s Iodine stain

Biuret stain

Brown paper, multiple pieces, approximately 2 to 3 cm square

Test #1: Glucose

Benedict’s solution is the indicator used for this process. It turns blue to green or yellow/orange to red, when simple sugars are present.

To test this process:

Put on goggles and make sure the goggles are completely covering your eyes.

Place 1 mL of Benedict’s Solution in two test tubes labeled #1 and #2.

Add 1 mL of distilled water to test tube #1. Stir.

Add 1 mL of Anna's Stomach Contents to test tube #2. Stir.

Using test tube holders,put each of the test tubes in hot water for 3 minutes.

Observe and record in your data table the colors of each test tube

.

If it turns any color listed above, glucose is present.

Test #2: Starch

Lugol’s Iodine is used as an indicator for starch. If the stomach content being tested is positive, it will turn dark purple or black.

To test this process:

Put on goggles.

Place 3 drops of Iodine in two test tubes labeled #1 and #2.

Add 1 mL. of distilled water in the test tube labeled #1 and stir.

Place a 1 mL. of Anna’s stomach contents in test tube labeled #2.

Observe and record the results from both tests. If starch in present in Anna’s stomach contents, the solution will turn any of the colors listed above.

Test #3: Protein

Biuret Solution is a protein indicator. If proteins are present, the color changes to violet or purple. The shade of the color depends on the type and concentration of the protein. It can range from a light violet to a deep purple.

To test this process:

Put on goggles.

Put 3 drops of Biuret solution in 2 test tubes that are labeled #1 and #2.

Place 1 mL. of distilled water in one test tube and stir.

Put 1 mL. of stomach content in the other test tube.

Observe and record the results from each test.

Test #4: Lipids

Brown paper will be used to test lipids. If there is an oily film left behind, then there is lipid present. Fats and lipids leave marks on brown paper.

To test this process:

Add 1 or 2 drops of distilled water on a piece of brown paper.

Place 1 or 2 drops of stomach content on another area.

Let them dry, then record results.

Examples for Glucose test

Example for Starch test

Example for Protein test

Example for Lipid test

Testing food samples

Now, you test three different foods and use the same stomach contents. Record data and test all foods for all the tests. Summarize information and add information to Anna’s last meal in the Autopsy Report that goes along with this activity. Examples:

Lipid and

protein test on yogurt

Glucose test

Conclusion

Anna had an unbalanced diet consisting of carbohydrates, proteins, and lipids. Too much sugar in the body can cause high levels of blood glucose levels. Since carbohydrates basically help create glucose, eating a lot of it, will cause high levels of glucose. Although, eating a lot of fiber filled foods can help with digestive system and can slow the absorption of sugar in the body when eaten together with sugar in the same food. Starches and lipids have the same thing in common; they both are macronutrients that supply the calories you need for energy. Too much of them, can cause high blood sugar levels and worsen diabetes. Anna ate very healthy and nutritious food the first day mixed in with some unhealthy food and on the second day, she had decided to go back to her original eating habits. Her unbalanced diet can lead to death because it can cause diabetes (which Anna has) which then can lead to malnutrition, cardiovascular diseases, osteoarthritis, and obesity. They can all kill someone. Her unbalanced diet could’ve caused her heart arteries to clog and stop pumping blood and working correctly. In this activity, we learned that food react to certain indicators. This should have also helped you figure out some more problems that could’ve happened to Anna. In conclusion, the unbalanced diet and her diabetes may have caused her untimely death.