Protein testing

Question 1

Testing for proteins

Answer 1

• Biuret
• React with peptide bonds
• Add NaOH to food solution making it alkaline
• Add Copper (II) Sulfate

Blue -> Lilac means positive test

Limitations :
- Qualitative
- Amino acids or dipeptides, result is negative because of lack of peptide bonds

Question 2

Lipids testing

Answer 2

• Emulsion test
• Add ethanol, shake, test tube
• Milky white cloud of emulsion forms

Limitations
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Question 3

Reducing sugars

Answer 3

• Benedicts
• Add excess benedicts reagent (blue)
• Heat in water bath
• If reducing sugar present, goes brick red

Positive : blue -> brick red

Semiquantiotive

Question 4

Non-reducing sugarts

Answer 4

• benedicts
• Dilute HCL
• HCL breaks any glycosidic bonds
• SO monosaccharides left are reducing sugars
• Use benedicts as normal
• Add, heat, blue to brick red is positive

Question 5

Starch testing

Answer 5

Iodine
Orange brown to blue black