Student’s name
Instructor’s name
Course
Date
Lab Report Testing for Nutrition
Introduction
Organic molecules make up all organisms (the units are attached by hydrogen or carbon atoms). Several processes within the living body depend on materials that supply the body with nutrients and energy. The nutrients derived from the food eaten include proteins, carbohydrates (starch and sugar) and lipids (fats). Simple or reducing sugars would alter the color of Benedict’s solution to yellow-brown-blue-black. The reducing sugars do not change the color of iodine. Proteins would change the color of a Biuret Reagent from light blue to violet or pale pink. Lastly, when the brown paper is rubbed in lipids, the color would appear translucent.
Objectives
The lab describes the structure and the significance of proteins, lipids, and carbohydrates.
It helps the student familiarize with the various chemical examinations for different nutrient molecules.
It also identifies the presence of molecules in everyday foods.
Challenge: identify the substances within the four solutions
Hypothesis: when an unknow solution obtains a positive outcome for sugar tests or starch, lipids, and protein, then this would demonstrate that there are macronutrients present within the solution. This happens since a positive test outcome would highlight particular features that show the macronutrient presence. Still, any result that does not display these features would mean the absence of the nutrients. A test on the protein that produces violet color is a positive outcome. A starch test with black color involves a positive result. A Benedict’s solution with orange color would signify a positive effect. A positive lipid examination outcome would be translucent within the brown paper, causing light to be transmitted through the paper.
Materials
Test tubes, pipettes, distilled water, Benedict’s solution, beaker, hot plate, and a 30%-glucose solution. Also, egg albumen, Biuret solution, parafilm. Filter paper, glass bowl, pencil, petri dish, vegetable oil, tweezers, and Sudan iv stains.
Experimental procedure
The Tests
Lipid Test (positive: translucent upon light shining through)
– Place filter paper on a clean surface, draw circles on the filter paper at two inches labeling water and oil.
– Place a drop for both water and oil in the circles, respectively, allow the paper to dry and put within a petri dish.
– Soak in a Sudan IV solution for 3 minutes, and fill the glass bowl with water
– Rinse the paper for 1 minute and notice the color changes on the circles.
– Give time to observe the color change to translucent = lipids
Sugar Test (positive: Burnt orange)
– Set the sample in a test tube
– place drops of Benedict’s solution to the test tube
– Place test tube within boiling water for 3 minutes
– Record the color changes
Protein test (positive: black)
– In the 2 test tubes put a pipette of albumen solution and add a pipette of water in the second test tube
– Add a Biuret reagent to the test
– Mix , observe color change and record the initial and final colour of the solution
Starch Test (positive: Black)
– Fill beaker with water halfway
– Prepare 2 test tubes and place glucose solution. Add a dropper with Benedict’s solution and mix. A positive reaction control will be noticed.
– Put a pipette of water in the 2 test tube and add Benedict’s solution. There will be a negative control since the water will not react with the benedict’s solution.
– Put three drops of iodine to mix
– Record the color changes
Predictions
Table 1: chemical tests and results
Chemical test
Test for:
Positive reaction color
Negative reaction color
Benedict’s reagent
Glucose
Orange = 3
No change (clear blue)
Lugol’s iodine
Starch
Dark ,pinky blue blade
No change (clear orange)
Biuret reagent
Albumen (protein)
Dark purple
Light purple
Sudan IV
Fat (lipids)
Orange
Red – no change
Tests
Unknown substance1
Unknown substance2
Unknown substance3
Unknown substance3
Starch
+
–
–
–
Lipids
–
–
–
+
Protein
–
–
+
–
Sugar
+
+
–
–
Exercise 2: Pineapple and Coffee tests
Chemical test
Food
Test for
Positive reaction color
Negative reaction color
Benedict’s solution
Pineapple juice
Glucose
Green
No change
Iodine solution
Pineapple juice
Starch
Yellow
No change
Biuret solution
Pineapple juice
Protein
Olive green
Clear
Sudan IV solution
Pineapple juice
lipids
Clear
No change
Pineapple juice has a high glucose presence owing to the color changes to green. This is followed by protein, demonstrating the olive green color, starch with yellow, and small or zero lipids, as shown by the table.
Coffee test
Chemical test
Food
Test for
Positive reaction color
Negative reaction color
Benedict’s solution
Coffee
Glucose
Light blue
No change
Iodine solution
Coffee
Starch
Dark brown
No change
Biuret solution
Coffee
Protein
Blue
No change
Sudan IV solution
Coffee
lipids
red
No change
Coffee has a higher amount of monosaccharide owing to the color having an actual dark brown color. There is also a relatively average amount of glucose in the coffee that leading to the color to turn light blue. Protein follows in the order and a small number of lipids in the coffee substance owing to the color changes to blue and red, respectively.
Conclusion
In the unknown solution1, the substances found were sugar and starch. The solution had sugar since it changed to orange color when Benedict’s test was performed. Unknown solution one also contained carbohydrates because there was a color change from clear to black following the addition of iodine to the specimen. The second unknown solution had glucose since it generated an orange color from Benedict’s test. A protein presence was noted in unknown solution 3 because of color change to violet after Biuret addition. The fourth unknown solution had both lipids and protein. There was protein presence, but the test on protein revealed a negative result since the protein amount within the specimen was not sufficient for detection. The lipids present in the sample was due to the brown paper turning translucent after a rub in of the solution on the paper.