food tests

Question 1

What nutrients do we test

Answer 1

1- Carbohydrates : Reducing sugar , starch

2- Protien

3- fats/lipids

Question 2

Define reagent

Answer 2

A reagent - a chemical that is used to detect the presence of another chemical or substance.

Question 3

define qualitative

Answer 3

produces a change that is judged by the experimenter, rather than an exact number/measurement.

Question 4

what is used to test for starch and describe the colour change

Answer 4

Iodine and it turns from orange/brown to blue/black

Question 5

what is used to test for reducing sugars and describe the colour change

Answer 5

Benedict solution and it turns from blue to brick red

Question 6

what is used to test for protien and describe the colour change

Answer 6

Biuret and it turns from blue to purple/violet

Question 7

what is used to test for fats/lipids and describe the colour change

Answer 7

ethanol and it goes from clear to emulsion : cloudy white, milky

Question 8

Explain how we can test for each of the following substance: Protein

Answer 8

We test for protein using a biuret solution..First you’re going to mash the food sample using a pestle and a mortar. Next you are going to put that into a filter paper and rinse it with water.Then you are going to collect the filtrate and you are going to put a few drops of biuret solution onto it and shake well. If protein is present in that food sample then the colour will turn to purple/violet. If protein is not present in that food sample then it will remain blue.

Question 9

Explain how we can test for each of the following substance: Reducing sugar

Answer 9

We test for reducing sugars using benedict’s solution.First you’re going to mash the food sample using a pestle and a mortar. Next you are going to put that into a filter paper and rinse it with water.Then you are going to collect the filtrate and you are going to put a few drops of benedict’s solution onto it and shake well. Then you are going to place it into a bath of water for 5 mins and heat. The colour will remain blue if reducing sugar is present and will turn brick red if it is not present.

Question 10

Explain how we can test for each of the following substance: starch

Answer 10

We test for starch using iodine solution. You place a few drops of iodine solution on the food sample directly,shake well and observe the colour change. If the colour is orange/brown, then starch is not present in that food sample. And if the colour changes to blue/black, then starch is present in that food sample.

Question 11

Explain how we can test for each of the following substance: fats/lipids

Answer 11

We test for fats/lipids using ethanol..First you’re going to mash the food sample using a pestle and a mortar. Next you are going to put that into a filter paper and rinse it with water.Then you are going to collect the filtrate and you are going to put a few drops of ethanol onto it. Then you’ll shake it and add water. If fats is not present it will be clear ( no emulsion formed), if fats are present then emulsion will form and it will turn cloudy,milky and bubbles will be formed.