food tests Flashcards
what do you do first to the food sample?
take the food sample and grind this with distilled water using a mortar and pestle.- make a paste
what do you do once you make a paste?
transfer the paste into a beaker and add more distilled water. stir so the chemicals in the food dissolved in water
once the chemicals dissolve in water what do you do?
filter solution to remove suspended food particles
what is the Benedict test for?
sugars (reducing sugars)
what are sugars?
small units that all carbohydrates are made od
what is the first step for the benedicts test?
.Set up your traditional water bath set up using a Bunsen burner.
what is the second step for the benedicts test?
put 5cm^3 of food sample into test tube
once you put food sample in test tube for benedicts test what do you do?
Add a few drops of Benedict’s solution to the sample in the test tube.
what is the final step?
Put the test tube in the water bath at a minimum of 80 °C/65 degrees for about 5 minutes.
what do you use to put test tube in water bath?
place test tube holder in the water bath
what colour does solution change to if sugar present?
changes to green, yellow or brick red depending on how much sugar present.
If no sugar present , solution remains blue
what does iodine test for?
starch
first step for the iodine test for starch
put 5cm ^3 of food sample into a test tube
second step for the iodine test for starch
Add a few drops of Iodine solution. shake slightly
what is the colour change of the solution if starch is present?
solution goes from brown colour to blue-black colour
what does biuret test for?
proteins
what is the first step for test for protein
add 2cm^3 of food sample into test tube. Then add 2cm^3 biuret soltuion
what colour does biuret solution turn sample and if protein is present whats the colour change?
goes from blue to pink/ turns purple / lilac
what does test for lipids use?
ethanol
what are the steps for test for lipids?
- Put some of the food sample into a test tube.
- Add a few drops of distilled water.(2cm^3)
- Add a few drops of ethanol. (2cm^3)
Shake the solution gently.
why can ethanol be dangerous and what should you do?
Ethanol is highly flammable. Keep the solution away from any flames
how do you know if lipids is present?
solution turns cloudy
