Food tests

Question 1

All monosaccharides and some disaccharides are

Answer 1

reducing sugars

Question 2

The two disaccharides that are reducing sugars

Answer 2

Maltose and lactose

Question 3

An OH group on carbon 1 of the monosaccharide / disaccharide means

Answer 3

It’s a reducing sugar

Question 4

Test for reducing sugar

Answer 4

Add benedict’s solution and see if it changes colour
Heat to 80 degrees

Question 5

Results for reducing sugar

Answer 5

Blue - No sugar
Green - Trace
Yellow - Low
Orange - Moderate
Brick red - High

Question 6

Reducing sugar test results are ….

Answer 6

Semi-quantitative (Results vary on how much sugar there is)

Question 7

Test for Non-reducing sugars

Answer 7

Add dilute hydrochloric acid
Heat in water bath
Neutralise using an alkali
Add excess beneficts raegant and heat to 80

Question 8

Two methods of finding the quantitative results of the amount of reducing sugar

Answer 8

1. Filter solution and weigh precipitate
2. Remove precipitate and use colorimeter to measure absorbency of remaining benedict’s solution

Question 9

3. Test for starch

Answer 9

Add iondine (brown)
If starch is present it will turn (Blue/black)

Question 10

Test for protein

Answer 10

Add biurets raegant (pale blue)
If protein is present it will turn purple
Results are semi-quantitative so the darker the purple the more protein

Question 11

How can you identify amino acids in a mixture

Answer 11

Use chromatography to separate them by the amino acids polarity

Question 12

Test for lipids

Answer 12

Add ethanol and water and shake
Cloudy emulsion means lipid is present