Food Tests

Question 1

Benedictus test for reducing sugars

Answer 1

Add excess Benedictus solution to food sample
Same volumes each time
Remove precipitate
Calibrate colorimeter if necessary
If sugar is present brick red precipitate is formed
Make a graph

Question 2

Food test for starch

Answer 2

Food sample in test tube / on white dish
And few drops of iodine solution
If starch present the solution turns blue-black

Question 3

Test for lipids

Answer 3

M1- add a few cm3 of ethanol to food sample
Pour mixture into test tube of equal volumes of distilled water
Which emulsion is formed on the surface

M2-
Rub or place drop of the food sample into sugar paper and allow it to try
View paper against a light source. If a translucent spot remains lipid is present

Question 4

Test for protein

Answer 4

Add a few drops of biurets reagent to food sample
Add slowly few drops at a time
Shake solution and wait for a few mins
Solution will turn blue/purple if protein is present

Question 5

test strips for reducing sugars

Answer 5

Benedict test strips
The strips are Dipped in a Test Solution and Change Colour if Glucose is Present. The test strip can be Compared to a Chart to Estimate the Concentration of Glucose present

Question 6

How to distinguish between a non reducing and a reducing sugar

Answer 6

Molecules that contain keytone or aldehyde groups are reducing sugars