Food Tests
This practical lesson covers:
- How to use qualitative reagents to test for starch, sugars, lipids and proteins.
Investigating the presence of sugars, starch, protein, and lipids in food samples.
Aim:
- To use qualitative reagents to test for a range of nutrients, including; sugars, starch, protein, and lipids.
Background information:
This practical lesson focuses on qualitative tests used to identify different nutrients in food samples. Each test is specific to a particular type of nutrient:
- Benedict's Test for Reducing Sugars - Benedict's solution changes colour from blue to green, yellow, or brick-red, depending on the concentration of reducing sugars present.
- Iodine Test for Starch - Iodine solution turns from yellow-orange to blue-black when it reacts with starch.
- Biuret Test for Protein - This test causes a colour change from blue to purple if proteins are present in the food sample.
- Sudan III and Emulsion Tests for Lipids - The Sudan III test results in a distinct red upper layer if lipids are present, whereas the emulsion test forms a white emulsion.
Which reagent is used in the carbohydrate test?
benedict's solution
iodine solution
biuret solution
ethanol
|
What is the purpose of preheating the water bath in the carbohydrate test?
to cool down the water bath
to sterilise the water bath
to accelerate the reaction between the food sample and Benedict's solution
to prevent the water bath from boiling
|
What is the purpose of adding iodine solution in the starch test?
to cool down the test tube
to accelerate the reaction between the food sample and iodine solution
to observe any changes in colour
to prevent the test tube from breaking
|
What is the purpose of shaking the test tube in the lipid test?
to accelerate the reaction between the food sample and ethanol
to mix the food sample with distilled water
to prevent the test tube from breaking
to observe any changes in colour
|
Which protein test reagent is added in addition to the food sample in the protein test?
ethanol
biuret solution
test tube
measuring cylinder
|
What is the purpose of adding Biuret solution A and Biuret solution B in the protein test?
to prevent the test tube from breaking
to accelerate the reaction between the food sample and the Biuret solution
to cool down the test tube
to observe any changes in colour
|