SB1f Core Practical: Testing Foods

Question 1

What test do you use to test for starch (carbohydrates)?

Answer 1

iodine test.

Question 2

Explain what occurs during the iodine test.

Answer 2

.iodine goes blue/black when starch is present
.when starch is broken down into sugars, the iodine will remain brown

Question 3

What can iodine test be used for?

Answer 3

to test rate of digestion by amylase.

Question 4

What test do you use to test for proteins?

Answer 4

biuret test.

Question 5

Explains what occurs during the biuret test.

Answer 5

.potassium hydroxide is mixed with food, and two drops of copper sulfate are added
.if the pale blue solution turns purple, protein is present

Question 6

What test do you use to test for glucose?

Answer 6

Benedict’s test.

Question 7

What are small, simple sugars called?

Answer 7

reducing sugars.

Question 8

Explain what occurs during the Benedict’s test.

Answer 8

.food is mixed with an equal volume of Benedict’s and placed in a hot water bath for a few minutes
.reducing sugars cause a brick-red precipitate to form (origionally was blue)

Question 9

What test do you use to test for fats (lipids)?

Answer 9

emulsion test.

Question 10

Explain what occurs during the emulsion test.

Answer 10

.food is mixed with ethanol and shaken
.mixture is poured into water and shaken again
.dissolved fats float to the surface forming a cloudy emulsion

Question 11

How can we meausre the amount of energy in food?

Answer 11

by burning it in a calorimeter.