4.2.2.1
Food tests
Foods can contain carbohydrates (starch and sugars), protein, lipids (fats) and small amounts of minerals and vitamins. Qualitative tests can be used to test for the presence of different food groups. You are going to test some different foods for glucose (a simple sugar), protein, starch and lipid. This practical may take more than one lesson. Learning outcomes
Maths skills required
Use apparatus methodically when completing food tests.
Measure small volumes.
Understand how to test for carbohydrates, lipids and proteins. Interpret results to identify the types of substances present in food. Apparatus list
food: potato, carrot, crisps, biscuits, cheese
kettle or water bath
pipette
Benedict’s reagent
spotting tile
iodine solution
10 cm measuring cylinder or plastic syringe
biuret reagent
3
beaker
ethanol
boiling tubes
eye protection
test tubes
Safety notes Make sure you wear eye protection. Wash off spills on skin immediately. Do not eat or drink in the lab!
Inform your teacher if you have any food allergies. Do not use ethanol around naked flames. Common mistakes For the glucose test, make sure you heat the reagents for long enough.
You only need a small amount of the reagents – do not use more than the volumes stated in the method. The colour change for the protein test is hard to determine – you are looking for blue changing to purple.
Method Read these instructions carefully before you start work. 1.
Choose a sample of food to test.
2.
Carry out the four tests as described in Table 1.
AQA GCSE (9–1) Combined Science: Trilogy Required Practicals Lab Book
9
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