food tests

Question 1

how to test for starch

Answer 1

• iodine solution
• iodine solution is orange
• if starch is present the colour turns to blue black

Question 2

how to test for proteins

Answer 2

• biuret test
• add potassium hydroxide to make the solution alkaline
• then add copper sulphate
• if protein is present, the colour changes from blue to lilac

Question 3

how to test for sugars

Answer 3

• benedict’s reagent
• place in water bath at 75 degrees
• will turn either blue, green, yellow, orange, brick red
• brick red = most sugars
• blue = least sugars

Question 4

how to test for lipids

Answer 4

• emulsion test
• add ethanol and shake
• then add water and shake
• will turn milky colour if lipids are present