Food Tests Flashcards
How to prepare a food sample
1.Break piece of food up using a pestle and mortar
2.transfer to beaker and add distilled water
3. Give mixture stir with glass rod to dissolve some of the food
4. Filter solution using funnel and filter paper to get rid of solid food
What does the Benedict’s test test for
Reducing sugars
How to do Benedict’s test
- Prepare food sample and transfer 5cm^3 to test tube
- Prepare water bath at 75 degrees
- Add Benedict’s solution using pipette
- Place test tube in water bath using test tube holder and leave for 5 mins
- If reducing sugar is present the solution will turn from blue to green, yellow or brick-red
What colour will Benedict’s solution change if sugar is present
From blue to either green,yellow or brick-red depending on strength
What does iodine test for
Starch
What colour will iodine solution change if starch is present
Browny-orange to blue-black
How to do iodine test
- Make food sample and transfer 5cm^3 to test tube and add iodine solution
- Gently shake to mix contents
- If starch present solution will change colour
What does biuret test for
Protein
How to do biuret test
1.Prepare food sample and transfer 2^3 to test tube
2. Add 2cm^3 of biuret solution and gently shake to mix
3. Solution will change from blue to pink or purple if present
What colour does biuret solution change if protein is present
Blue to pink/purple
What does Sudan III solution test for
Lipids
How to do Sudan III test
- Prepare sample of food and transfer 5cm^3 to test tube
- Use pipette and add 3 drops of solution and gently shake tube
- If lipids are present mixture will separate into two layers and top one will be bright red
What will happen if lipids are present in Sudan III solution
Split into 2 layers and top layer will be bright red
