required practical - food tests

Question 1

how do you turn food sample into a food solution

Answer 1

1. take food sample and grind with distilled water using mortar and pestle
2. transfer the paste into a beaker and add more distilled water and stir the samples so chemicals in the food dissolve in the water
3. filter the solution to remove any food particles

Question 2

how two things do you test for when testing for carbohydrates

Answer 2

starch and sugar

Question 3

how do you test for starch

Answer 3

add a small amount of food solution to test tube. add iodine solution
if starch is present solution will turn blue/black

Question 4

how do you test for sugar (glucose)

Answer 4

add a small amount of food solution, add ten drops of Benedict solution (blue). place test tube into a beaker and half fill with hot water. leave for five minutes.
if sugar is present solution will change colour. the colour can tell us roughly how much sugar is present
green - small, yellow - more, red - a lot

Question 5

how do you test for protiens

Answer 5

add small amount of food solution to test tube and add Biuret solution (blue)
id protein is present solution will turn purple

Question 6

how do you test for lipids/ fats

Answer 6

add small amount of food solution (unfiltered) to a test tube and add few drops of distilled water and few drops of ethanol. gently swirl solution
if lipids are present: white, cloudy emulsion is formed