Nutriton lab

1a) In a positive test for sugar, one would see the colour of the substance change from blue to light green to greenish yellow to orange and lastly reddish brown.
b) In a positive test for starch the colour of the substance would change to black
c) In a positive test for protein the colour of the substance would be pink or purple/violet
d) In a positive test for lipids the substance would leave a translucent stain on the brown paper bag
2. The purpose of testing the four test tubes was to ensure that the colour change that occurred in the substance was due to a chemical change and not the substance being added to it.
3. The student saw a colour change happen because the heat causes the biuret to chemically react with the protein. The reaction should change the colour of the mixture from blue to purple in appositive test for protein.
4. Potatoes’ chips are predicted to have starch, lipid, sugar and protein in it. Potato chips main ingredients are potatoes and potatoes have starch in them. Potato chips are also fried in oil so it must contain lipid and sugar. Lastly potato chips may contain a little bit of protein.
5. Two percent milk tested negative for starch because the colour turned yellow which indicates that there is no starch present. It tested positive and that there is approximately 1.5 percent – 2.0 percent in sugar concentration because the colour changes from the chemical reaction was orange. It tested positive for protein because the reaction gave off a violet colour. Lastly two percent milk tested positive for lipids because it left a translucent stain on the paper bag.
Hard candy tested negative for starch as it turned brown and not black. It tested positive for sugar and approximately has over two percent in sugar concentration because it turned reddish brown. It tested negative for protein because it turned light blue, not pink or purple. Lastly hard candy tested negative for lipid because it did not leave a translucent stain it remained