SB1f Testing Foods

Question 1

Why do bananas taste sweeter as they ripen .

Answer 1

When bananas develop they mainly contain a complex carbohydrate calles starch . As they ripen enzymes break down starch into smaller carbohydrates including sugars such as sucrose and glucose . These sugars make the bananas sweeter

Question 2

For starch

Answer 2

Iodine solutions changes from a yellow - orange to a blue-black colour when in contact with starch

Question 3

Testing for sugars

Answer 3

When a food solution is mixed with an equal volume of Benedict’s solution and placed in a hot water bath for a few minutes reducing sugars in the food may cause a reduction reaction which changes the color from light blue to a dark red and may form a precipitate

Question 4

Test for protein

Answer 4

In the biuret test , potassium hydroxide is mixed with a solution of the food . Two. Drops of copper sulfate solution are then added . If the pale blue solution turns purple this indicates protein in the food.

Question 5

Test for lipids

Answer 5

Ethanol emulsion test , the food is mixed with ethanol and shaken .some of that mixture is then poured into water and shaken again. Gays and oils dissolved in the the ethanol float towards the surface forming a cloudy emulsion .

Question 6

How to measure the amount of energy in food

Answer 6

By burning it in a calorimeter . It works by setting the food on fire and holding under a sealed glass of water . Their is two holes at the top of the seal for a thermometer and stirrer . To work out the calories you see how much the water has been heated by .

Question 7

How to measure the amount of energy in food

Answer 7

By burning it in a calorimeter . It works by setting the food on fire and holding under a sealed glass of water . Their is two holes at the top of the seal for a thermometer and stirrer . To work out the calories you see how much the water has been heated by .