Describe and explain the difference in the procedure for biuret test when carried out on an unknown solid food sample compared to a liquid food sample
Answers
Answer:
Explanation:
Three procedures are outlined below using different reagents.
For each of the procedures, a liquid sample must be prepared from solid foods as follows.
PREPARATION OF LIQUID SAMPLE
Crush the solid food, add a little de-ionized water and decant the liquid. This liquid should be used for the food test. The quantity of food crushed and water used depends on the number of tests to be conducted.
What is the procedure for the Biuret Test for proteins using Biuret Reagent?
Add 2 cm3 of the liquid food sample* to a clean, dry test tube
Add 2 cm3 of Biuret Reagent.
Repeat steps the steps above with de-ionized water to prepare a negative control and with albumin (egg white) to prepare a positive control.
Shake well and allow the mixture to stand for 5 minutes
Observe any color change.
What is the procedure for the Biuret Test for protein using sodium hydroxide and copper sulphate solutions?
Add 1 cm3 of sodium hydroxide solution (40% or bench solution) and 1% copper (II) sulphate solution dropwise (one drop at a time) to the food sample
Repeat the steps above with de-ionized water to prepare a negative control and with albumin (egg white) to prepare a positive control.
Shake well and allow the mixture to stand for 5 minutes
Observe any color change.