SB1f Testing Foods

Question 1

Why do bananas taste sweeter as they ripen

Answer 1

As enzymes develop they are mainly made up of a carbohydrate called starch . As they ripen enzymes break down these carbohydrates into smaller carbs including sugars such as sucrose and glucose . Making the banana sweeter

Question 2

How to test for starch

Answer 2

Take a small piece of the food you want to test .
Drop iodine on top of the sample .
The iodine will go from a yellow/orange color to blue/black if iodine is present

Question 3

How to test for reducing sugars

Answer 3

Benedict’s test :
Mix a food solution with an equal amount of Benedict’s solution and place in a hot water bath for a few minutes .
Reducing sugars in the food cause a reduction reaction which changes the color of the solution.
It will turn from light blue to dark red and any color in between depending on how much sugar is present .

Question 4

How to test for protein

Answer 4

Biuret test :
Potassium hydroxide mixed with a solution of the food . Two drops of copper sulfate solution are the added . If the pale blue solution turns purple this indicates protein is present.

Question 5

How to test for lipids

Answer 5

Ethanol emulation test :
The food is mixed with ethanol and shaken then water is added
If the solution turns cloudy then lipids are present

Question 6

How to measure the amount of energy in a food .

Answer 6

Calorimeter :
Take a piece of food and hold it under the calorimeter .
A calorimeter is almost like a cup filled with water with a hole for a stirrer and thermometer on top.
The food is burnt under the calorimeter and you measure how much energy it has by seeing the temp change of water .