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    1. 04-24-2008 02:39 AM #1
      skuruza
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      tell me about Benedict's test

      hello everyone!
      i am in the Science Olympiad (i do not know if anybody has heard of it) and one of my events is the food science event. i was researching a lot and i still could not find anything about the Benedict's test for sugars and was wondering if anybody could help me out about the procedure and getting results. thanks!

      also, please tell about the Biruet's test for protein, because i could not find anything on that, and in the regionals competition i ended up making something that reminded me a lot of poisonous jello... maybe it was a different chemical, but nonetheless i need help with the above mentioned solutions.

      thanks!!

      ps. GO MEAD!!


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    2. 04-24-2008 04:29 AM #2
      Spartiate
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      Huh, I did a lab with those things, documents are at school, I could get them Friday. What does Wiki say meanwhile?
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    3. 04-24-2008 09:40 PM #3
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      heh if you can get them Friday, i do not know if i would be able to see because i am leaving for Champlain on Friday, but thanks anyways

      oh yeah, and wiki says nothing helpful...


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    4. 04-25-2008 11:06 PM #4
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      Uhm, had to translate this, so bear with me ...

      When heated and in the presence of basic sugars, like maltose and glucose, Benedict's reagent changes colour and a precipitate will form. Since starch can't reduce the copper in Benedict's reagent, it will not produce any colour changes.

      Starch ---> No change in colour at boiling point.
      Maltose ---> Change of colour from blue to green at boiling point.
      Glucose ---> Change in colour from blue to orange. An orange precipitate will form after a while.

      Always perform Benedict's test in a boiling bain-marie. The results are interpreted in function of the precipitate's colour and not the solution's.



      Biuret's reagent (blue) contains a sodium or potassium hydroxide solution (NaOH or KOH) and a very small quantity of diluted copper sulfate (Cu++SO4-). The reagent changes colour in the presence of proteins or peptides because the amino groupings (- NH2) form complexes with the copper ions.

      Biuret's reagent ---> Blue

      Colour in presence of proteins ---> Violet

      Colour in presence of peptides ---> Pinkish
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