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The demonstration of starch and glucose in different articles of food.

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Introduction

Tobias Nederkoorn 3VM Mr. Van Dijk Biology June 2003 Introduction. In the experiment we tried to find out which particles contained starch and / or glucose. We tried to find that out by using iodine to find the starch and by using a test strip to find the glucose. When the substance in the test tube turned blue/purple, it meant that the substance contained starch. When the test strip changed colour, it meant that the substance in the test tube contained glucose. How are different particles of food composed? In the experiment with starch and iodine we tried to discover what article of food reacts with starch and/or with glucose. We discovered that iodine is an indicative agent for starch. We also discovered that it is a cross reaction. That means that iodine only reacts with starch, and starch only with iodine. We also discovered that glucose is in some particles of food. Hypothesis. I expect starch in bread because it is made of flower. I expect starch in potato because you there is so called 'aardappel zetmeel'. I expect starch in liver sausage because it is heavily bounded. ...read more.

Middle

We than added two drops of iodine solution to the test tube. We wrote the name of the article in our notebook and we also wrote down the final colour of the solution in the test tube. When the water turned dark blue/purple we knew there was starch in it. We did the same for the other articles of food. The second glucose experiment, Glucose in articles of food. We took an article of food and, if necessary, we minced the article. We put an article of food into a test tube and 3/4 of the length of the test tube was filled with water. The right end of the test strip was plunged in the liquid. We wrote down the name of the article that was in the test tube and we wrote down the results and the colour of the right end of the test strip. We did the same for the other particles of food. We did all the other articles the same way. Observations. First starch experiment: We saw that the test tube that contained water and iodine turned yellow, transparent yellow. ...read more.

Conclusion

We know that iodine is an indicative agent for starch. The colours of the materials in the test tube changed because bread is made of wheat, and liver sausage is heavily bounded. So that is why the colour changed. The test strip which measured the glucose in water turned green. So when there is glucose in a liquid, the test strip turns green, when there is much glucose; the strip turns dark green. A test strip in normal water does not change. It only changes when there is glucose in a substance. So the test strip is an indicative agent for glucose. Now we know that a test strip is an indicative agent for glucose. The test strip changed when it was put in a substance with water and milk, because sugar is added to the milk. The colour also changed when the strip was put in a substance with tomato or apple, because those are both fruits. Discussion/Reasoning The hypothesis was correct. There was some starch in bread, potato and liver sausage. They are all made of wheat except the liver sausage, which is bounded with starch. There was some glucose in ketchup, apple, tomato and milk. They all taste sweet and sugar is added to the milk and ketchup. And because the apple and tomato are fruits. 1 ...read more.

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