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Old 01-26-2006, 02:18 PM
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Biuret solution...

Go to, type in biuret solution, and you have lots of information. But basically, when you put it in liquid, and it mixes with protein (or polypeptides), there will be a chemical reaction and a color change. It is orginally blue. In the presence of proteins, it will turn purple instantaneously with a little mixing. In the presence of polypeptides (smaller strands that make up protein), it will turn pink. If the solution becomes blue, there is no protein, because the blue would have come from the biuret solution.

Why you need to blend the food or buy baby food, because you can't put biuret solution on a solid banana. You have to mix biuret solution in a liquid. And not even on plain baby food. You'll have to dilute the baby food with water so 1) it is thin enough so you can see the color 2)More surface area for the biuret to react with.

Make sure you have access to biuret solution at your school.

It would be even better if you have access of Lugol's iodine solution as well. It tests for starch. If you're going to be testing for Biuret Solution anyways, might as well get some Lugol's iodine solution. It tests for starch. So add some into the food, and if it turns from tanish brown to dark purple/black, there is starch. So you can see which foods have starch, which have proteins, and if you want a sugar test, you'll need Benedict's solution. But it isn't instantaneous. You have to heat up the solution. If you're interested, ask me for more info, cause the Benedict's test is a little more complicated.

You might want to look online if you want to look at some other nutrient tests. I've gave you ideas for proteins, sugar, and starch. I know of a fat test, but I'm not sure how accurate it is. You basically put your food on a paper towel. After it dries, if there's an oil spot on it, there are fats.

good luck!
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