Required Practical: Food Tests Flashcards

All 5 cards in this deck

What are the steps in Benedict's test for sugars?
e.g. testing a sample of apple juice

1. Add Benedict's solution to the food sample.
2. Heat in a water bath at about 75 °C for 5 minutes.
3. Blue = no sugar; green/yellow/orange/brick-red = sugar present (apple juice turns brick-red).

What are the steps in the iodine test for starch?
e.g. testing a potato sample

1. Add a few drops of iodine solution to the food sample.
2. Orange-brown = no starch; blue-black = starch present (potato turns blue-black).

What are the steps in the Biuret test for protein?
e.g. testing egg white

1. Add Biuret reagent to the food sample.
2. Blue = no protein; purple/lilac = protein present (egg white turns purple).

True or false? A blue colour after Benedict's test shows that sugar is present.

False. Blue is a negative result; green, yellow, orange or brick-red shows sugar is present.

How should a solid food sample be prepared before carrying out food tests?

Grind or mash it with distilled water to make a solution, then filter it.