This was planned by discussing the actual food products we commonly take in a day. There are few diary products that are commonly known to contain a lot of protein, necessary carbohydrates for each meal (bread, pasta and cereal) as well as the vegetables that contain many various healthy nutrients including glucose (simple sugar), vitamins, minerals etc. Also, there is meat that is supposed to contain some fatty substances and protein. The essential nutrients that we need daily for our body to function properly are mainly six.
They are water, carbohydrates (glucose, starch, sucrose etc. ), proteins, fats, vitamins and minerals.  In the lab, we are going to find out the presence of different nutrients and decide whether the planned list of daily diet food products is good enough to provide the necessary nutrients. The chemical tests that are used for the experiments are: Benedict test, Biuret test and Iodine test, which test for glucose, protein and starch. All the tests indicate if the product contains the certain type of nutrients by the change of colors.
One more testing would be HCl/Benedict test, and the purpose of this test will be explained further. Let me explain them, one by one, into details. 1. Benedict test Benedict test is used to determine the presence of reducing sugar which is monosaccharide and some disaccharides. However, non-reducing sugars such as sucrose won’t have Benedict reaction. In order to have the result with Benedict test, the non-reducing sugars first would have to be transformed into reducing sugars. This can be done by adding hydrochloric acid (HCl) and hydrolyzing them.
Here is the purpose of HCl/Benedict test.  So basically, Hcl/Benedict test is used for determination of sucrose. The Benedict reagent has to be added to the substance and has to be heated in order to make the reaction occur and observe the color. The color change depends on the amount of reducing sugar in the substance. It differs like this: Green Yellow Orange Red Brown More and more the sugar there is, it will be closer to red & brown. Commonly, though, it is known to show the orange color. 1. Biuret test
Biuret reagent detects the presence of peptide bonds, which hold the amino acid molecules together and build up proteins. This basically means that Biuret test is used to determine the presence of protein in the substance. The reagent has a color of light-blue, and it includes sodium hydroxide (10% NaOH) and copper (II) sulphate (1% solution of CuSO4). The indicator-color is purple. 1. Iodine test This test indicates the presence of starch in the substance. The starch is the stored form of glucose (monosaccharide’s that form carbohydrates) in plants.
We can easily find rich amount of starch in potatoes, rice, cereal etc).  Iodine, itself has a brownish yellow color but when it comes in contact with the substance that contains starch, it turns blue black. In order to make sure the test works for the food products, we pre-tested with pure protein, starch and glucose substances and collected data. Of course, we needed a control and therefore we tested distilled water as well. The data of this pre-test as well as the actually experiment data will be presented later in Data Collection and Data Process section.
It is a shame that the tests are only for determining the presence of protein, non-reducing & reducing sugars such as starch, sucrose, etc. It basically means that we can get a conclusion only for carbohydrates and proteins that are only two out of six of the essential nutrients. More detailed evaluation will be included in Evaluation part. Research Question Determine the presence of reducing sugar, protein and starch in the food products by using Benedict test, Biuret test and Iodine test, in order to decide whether the diet planning was successful enough to allow a person to take in the necessary nutrients (carbohydrates and proteins).
Hypothesis Using the common background knowledge I have read or seen in various diet-related TV programs as well as my biological knowledge, my hypothesis is following: The meal-plan for a day that we have made does contain all the nutrients that could have been tested for, therefore it is possible to say that the meal-plan was pretty successful; however due to the limitation of testing methods, some of the nutrients that are needed for proper body functioning such as vitamins, minerals, fatty acids could not be determined to be present.
The bold letters are the ones have significant color change for the Iodine test. The products are: cereal, bread and pasta. Three of the products are assumed to have starch as their components. The diet plan seems to have succeeded to have at least one of the essential nutrients. There are two products that have dark yellow color: yogurt and apple, which might cause confusion. However, based on what I know and I’ve learned, starch is energy stored in plants, therefore it will not make sense if there is starch present in yogurt which is a dairy product, produced by animals.
Also, since the part of an apple we tested was a body of it but not a seed, apple is not supposed to contain starch. The conclusion, therefore, is that the slight difference in colors can be ignored. The reason why they show a little darker yellow color than others might be because of the initial color of the food product or, in case of yogurt, the thickness of the solution (when the substance is thick, the color appears to be matte, darker. ). Another confusion that we had in this set of data is Red Wine; it shows purple color.
However, since wine is not made of grape seeds but the flesh of grape, it is assumed that there is no starch present. So the purple color is just from the initial color of the wine, dark red. 1. Biuret test Biuret test determines the presence of protein by showing the color purple. The results were following: The result was actually very surprising. We could not see any purple color in the test tube filled with milk! Though, other products that we assumed as protein-containing products had positive result. Dairy products are normally, commonly known to contain a lot of protein.
One of the big reasons why many people tend to drink it is, actually, protein! So it was very shocking that it did not show any positive reaction of presence of protein. This test could not be repeated due to the time limitation, therefore it is not possible to evaluate if it was a random error, but just depending on the data collected, it can be concluded that milk does not have enough protein (or not at all) to show the purple color by Biuret solution. The products that showed positive results are: yogurt, meat (chicken) and cheese.
The yogurt especially reacted very fast and very clearly. Since it had a white color initially, it was very easy to see the color. It is very hard (almost impossible) to determine the amount of protein with the simple test as Biuret test, however, I would still suppose yogurt has the most amount of protein than meat or cheese due to the fact that it had darker and clearer purple. In this test, again, Red Wine is causing the confusion with its initial color. Even though it is showing the dark blue-black color, it can be ignored.
All the other products did not seem to have any kind of color change, however, there were three products that contain protein, therefore it is concluded that the diet plan has achieved to have another essential nutrient. 1. Benedict test Benedict test generally shows orange color, indicating the presence of non-reducing sugar (monosaccharide, some disaccharides). Depending on the amount of non-reducing sugar, it can also show more yellow, green (smaller amount) or red and brown (bigger amount). This was proven in the pretest by adding the solution into glucose.