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Testing foods for proteins, lipids, sugars and starch. Aim: To test a variety of foods for various substances

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Introduction

Testing foods for proteins, lipids, sugars and starch. Aim: To test a variety of foods for various substances. Introduction: Proteins are large molecules which are made from a chain of amino acids. There are 22 different amino acids which can be found in proteins. Nine of these are classified as essential because they cannot be manufactured in the body and need to be acquired through the food we eat. The remaining 13 are classified as nonessential and can be manufactured by the body from other substances. Carbohydrates need to be broken down into sugars for them to be used as energy. Sugars are in carbohydrates: this means that they contain the elements Carbon, Hydrogen and Oxygen, and that there is twice as much Hydrogen as there is Oxygen. Hydrogen and Oxygen atoms are in the ratio of two to one as in water molecules. The simplest sugars are called monosugars or monosaccharides. Starch is made by plants as a way of storing chemical energy; starch comes in two common forms. Amylase is believed to be a long, unbranched chain of alpha-glucose molecules, in which the fourth carbon atom of one sugar is joined to the first carbon atom of the next sugar. The second form is Amylopectin a branched series of glucose chains. ...read more.

Middle

2. Then I added a couple of drops of iodine to the test tube using a pipette. 3. I observed the changes in the test tube and analysed my results to see whether there was a lot of starch present in the solution. (If starch is present should turn solution Blue/Black). Test for Protein: 1. Thirdly I completed an experiment to see how much protein was present in Albumin. I poured a small amount of Albumin into a test tube. 2. Then I added Potassium Hydroxide and Copper Sulphate solution to the test tube. 3. I observed the changes in the solution and analysed my results. (Protein was present in the solution if it turned purple). Test for Lipid: 1. For the last experiment I poured a small amount of cooking oil into a test tube. Cooking oil was used as it is high in fatty acids which are in lipids. 2. I then added ethanol to the cooking oil and shook the test tube. 3. Then I poured the cooking oil and ethanol solution into a beaker of distilled water. 4. I then observed and analysed my results. (A white emulsion should form if lipids are present in the cooking oil). ...read more.

Conclusion

Test for lipid: Colourless Test for starch: Blue Black Test for protein: Blue Black Test for sugar: Purple Test for lipid: Colourless Test for starch: Blue Black Test for protein: Blue Black Test for sugar: Orange Test for lipid: Colourless Test for starch: Orange Test for protein: Purple Test for sugar: Orange Test for lipid: Colourless Test for starch: Blue Black Test for protein: Purple Test for sugar: Blue Black Test for lipid: Colourless Positive Positive Positive Positive Negative Positive Positive Negative Negative Positive Negative Positive Negative Negative Positive Negative Positive Negative Negative Negative Positive Negative Positive Negative Negative Positive Positive Negative Positive Positive Negative Negative Conclusion: I conclude from this experiment that various solutions contain certain substances and that when testing for a particular substance such as protein; if protein is present the solution should turn purple. Or for Starch the solution would turn Blue Black. For Sugar the solution should turn Orange and for Lipids a white emulsion should form. Overall, I feel the experiment was successful. There where no major anomalies and precise results were given. If I where to do this experiment again I would have more test tubes to use during the experiment to prevent time wasting by thoroughly rinsing them to use again. ?? ?? ?? ?? 1 ...read more.

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