Food test lab discussion PDF

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Discussion: We eat many complex foods which contain mixtures of carbohydrates, fats and proteins. Food tests enable you to find out what food types a food contains. There are different tests which can be used to detect carbohydrates, proteins and lipids. They involve adding a reagent to a food sample which changes colour depending on what biological molecules are present. Sometimes it may be necessary to crush the food or add water to the food, as done in this experiment, before adding the reagent. The first test done was for the presence of starch in Solution A. This test was a positive test since a blue-black solution was observed after the iodine was added. The test tube was shaken to ensure that as much interaction as possible took place between the iodine and starch molecules. This colour is obtained as a result of a characteristic chemical reaction between the iodine and starch molecules. If no blue-black colour was observed, then this would have been a negative test meaning no starch is present. The second test was done for reducing sugars. Benedict’s solution was added to Solution B. The test tube was placed in a boiling water bath in order to facilitate the reduction of Copper (ii) ions in the Benedict’s solution by carbohydrates (reducing sugar). This is the main principle of benedict’s test. This was a positive test for reducing sugars the solution since a brick red precipitate was observed. If a blue colour was obtained, then the test would have been a negative test. The next test was for fats and oils and was done using an ethanol test. This test is called an emulsion test because it causes test solutions to be suspended in the ethanol, allowing lipids present to dissolve since fats are soluble in alcohol. When water is added the fats “fallout” the solution since they are not soluble in water. This forms a cloudy emulsion. This was a positive test since a yellow creamy substance was observed. The final test was for proteins. This test was done using Biuret’s test. This test relies on the colour change of test samples after biuret’s solution is added. If the colour change results in a purple colour, then protein is present. This purple colour is derived from a chemical reaction between amino acids in protein and the copper ions in the biuret solution. This was a positive test since a purple colour was observed after adding the solution.

Conclusion: Food tests were done to test for the presence of starch, reducing sugars, lipids and protein. Positive tests were obtained for all nutrients....