The purpose of this experiment is to detect what kind of macromolecules are present in these three types of milk by using the Benedict’s solution, Lugol’s solution, and Sudan IV solution. Also, using the nutrition facts labels to identify which substance is skim milk, whole milk, and soy milk.
Using the Benedict’s solution to detect for the presence of simple sugar. If the unknown A, B, C milk samples turn from bright blue to orange color during the Benedict’s test, then these samples are positive control and the carbohydrates are present in them. When the solution remains the same, it means the solution is negative control and does not have sugar.
The presence of starch can be detected by using the Lugol’s iodine solution. If the unknown A, B, C milk samples turn to a dark blue color during the Lugol’s test, then these samples are positive control and also contain starch in them. But if the solutions turn to yellowish brown, it means these solutions are negative control
In order to identify the presence of lipids in these samples, we use the Sudan IV solution. If the unknown A, B, C milk samples turn from clear to dark pink color during the Sudan IV test, then the samples are containing lipids in them. But when the solutions do not change color, it means lipids are not present in these solutions.
– Sudan IV stain – Six test tubes
– Benedict’s solution – Corks for test tubes
– Lugol’s solution – Test tube rack
– Water (H2O, distilled or deionized) – Test tube clamp
– Filter paper – Wash bottle
– Petri dish – Milk bottle
– Water bath – Milk (whole, skim,soy)
– Vegetable oil – Pipettes
In the first experiment for lipid detection, the materials used included are a piece of filter paper, a pipette, a petri dish, the forceps and Sudan IV solution. The experiment started by labeling a piece of filter paper with my initials with the following A, B, C, oil, and H2O. I placed two drops of each unknown milk sample, vegetable oil, and H2O next to the labels on my filter paper and allow to air-dry. After these samples were dried, I placed the filter paper in a petri dish containing Sudan IV solution and stained the filter paper for one minute. I then used the forceps to remove the filter paper to the rinsing dish. Then, I rinsed the filter paper with water and collect the runoff in the dish. The last step, I placed the filter paper on the table and allowed it to air-dry.
For the second experiment for simple sugar detection, I added 20 drops of Benedict’s solution to the unknown milk samples (A, B, C) in test tubes. In order to mix the solution, I placed a cork in each of the tubes and then gently swirled these solutions. After the solutions were mixed, I carefully placed the tubes in a 90 degrees Celcius water bath and waited for 5 minutes for the samples to heat. The test tubes were too hot, therefore I used a test tube clamp to remove the tubes from the boiling water to the test tube crack.
The third experiment for starch detection, I added 5 drops of Lugol’s solution to the unknown milk samples in test tubes. Then, I placed a cork in each of the tubes in order to mix the solutions.
Sudan IV Test
Throughout this lab, I observed that sample A is whole milk, sample B is soy milk, and sample C is skim milk. The reason is when sample A reacted with Lugol’s solution, it proves that this sample is whole milk because whole milk does not contain starch. Skim milk does not contain fat; therefore when sample C reacted to Sudan IV solution, lipid was not present. Sample B reacted with Sudan IV solution showing the presence of lipid.