Food tests Flashcards
What is the biological test for lipids?
Emulsion test
Sudan III
How do we carry out the emulsion test for lipids?
- Shake the sample with ethanol
- Add water and shake
- A cloudy white suspension/emulsion is formed if lipids are present
How does sudan III tell us if there are lipids present?
It stains lipids orange
What is the purpose of a control variable?
It allows for a comparison to show the independent variable is having an impact
For measuring impact of pH practicals, why do we need to use denatured enzymes as a control?
You need to use it as a control as perhaps it is the protein in the enzyme that causes the reactions to work and so you need an enzyme that doesn’t work
What could be happening when a reaction levels off on a graph?
- The reaction is finished
- The enzyme has been denatured
What is standard deviation?
The range of results
When is the difference between data not significant?
When there is an overlap in standard deviation
What is the test for proteins?
Biuret test - goes from pale blue to lilac/purple
What is the test for reducing sugars?
Benedict’s solution
How do we carry out the test for reducing sugars?
- Mix food sample with water
- Add a few drops of benedict’s solution
- Heat
- Turns green, yellow, brick-red
How do we carry out the test for non-reducing sugars?
- Set up a water bath
- Add sample into a test tube
- Add drops of dilute HCl
- Place in water bath until boiling point
- Then cool the test tube in cold water
- Add sodium hydrogen carbonate powder until in excess
- Add 10 drops of benedict’s reagent
- Heat to boiling point and continue heating for a few minutes
- Should turn same as positive benedict’s test
Why do we need to add excess sodium hydrogen carbonate powder in the test for non-reducing sugars?
It needs to be alkaline for the benedict’s reagent to work
What is the test for starch?
Iodine - turns from brown blue/black
