CCEA GCSE Double Award Science Biology Factfile - Unit 1.3 Food tests

Sep 5, 2026

CCEA GCSE Biology Unit 1.3 Food tests covers learning outcomes for identifying positive results from key biochemical reagents used on food samples. It explains colour changes and observable outcomes for Benedict’s solution, iodine solution, Biuret and ethanol, and links each test to reducing sugars, starch, protein/amino acids and lipids (fats). The unit also outlines the importance of carbohydrates, fats/lipids and proteins, and includes a practical on determining energy content by burning food samples.

LanguageEnglish

CategoryExam

FormatPDF

Pages6

Reading Time15 min

AccessFree to download

Learning Outcomes

1.3.1 Reagent colour changes

1.3.2 Food tests for key nutrients

1.3.3 Importance of biological molecules

Practical 1.3 Energy content of food

Food tests procedures

Testing for reducing sugars (Benedict’s)

Testing for starch (iodine solution)

Testing for protein/amino acids (Biuret)

Testing for lipids (ethanol)

FACTFILE: GCSE DAS BIOLOGY UNIT 1.3 Food Tests Learning Outcomes 1.3.1 recall the colour changes for the following reagents, Benedicts, iodine solution, Biuret and ethanol. | Reagent | Initial Colour | End colour for
positive test | | --- | --- | --- | | Benedicts | Blue | Brick red
precipitate | | Iodine solution | Yellow-brown | Blue-black | | Biuret | Blue | Lilac-purple | | Ethanol | Colourless | White emulsion | 1.3.2 investigate food samples using food tests, including: • reducing sugar (Benedict’s); • starch (iodine solution); • amino acid or protein (Biuret); and • fats (ethanol) . 1.3.3 explain the importance of the following biological molecules: • carbohydrates, made up of simple carbohydrates (sugars, glucose and lactose) as sources of energy and storage, complex carbohydrates (cellulose, starch and glycogen); • fats/lipids, including oils, made up of fatty acids and glycerol, as sources of energy and storage; • proteins, made up of amino acids, as structural and functional molecules in cells; Practical 1.3 investigate the energy content of food by burning food samples. Food tests When testing samples of food for the food groups they contain, scientists use a range of biochemical tests. The solutions added to the samples are called reagents. Reagents are substances that cause a chemical reaction when they are added to the sample. The chemical reaction usually causes a visible colour change or the formation of a precipitate or emulsion. In this unit you need to be able to identify the positive result seen when food is tested for reducing sugars, starch, protein/amino acids and lipids (fats) . Testing for reducing sugars using Benedict’s solution. Step one: Place a sample of the food into a boiling tube with some water and add a few drops of Benedict’s solution. Benedict’s solution Water Food sample Figure 1 FACTFILE: GCSE BIOLOGY : CELLS, LIVING PROCESSES AND BIODIVERSITY Step two: Place the boiling tube into a water bathand heat. Food sample and Benedict’s solution Food sample and Benedict’s solution Figure 3 Result: A colour change from blue to green toorange to brick red will occur depending on the amount of sugar present. Reducing sugars include glucose and lactose. Testing for starch using iodine solution Step One: Add a few drops of iodine solution to the food sample. Water Food sample ~~ ~~ Iodine solution Figure 4 Food sample ~~ ~~ Figure 5 Result: the iodine turns from yellow/brown to blue/ black if starch is present. Testing for protein/amino acids using Biuret *Note: Biuret is a solution of sodium hydroxide and copper sulphate Step one: Add a few drops of Biuret to the food sample and shake. Water Food sample Biuret solution Figure 6 Water Food sample Figure 7 Result: The biuret turns from blue to purple Testing for lipids using ethanol Step one: Add the ethanol to the food sample and mix Food sample Ethanol Figure 8 Food sample ~~ ~~ Figure 9 | | | --- | | | 2 FACTFILE: GCSE BIOLOGY : CELLS, LIVING PROCESSES AND BIODIVERSITY Result: the ethanol turns from clear to form a white emulsion. Find the nutrition and food words in the word search Source: generated using [http://www.word-search](http://www.word-search)[world.griddler.co.uk/Word-Search-Generator.aspx](world.griddler.co.uk/Word-Search-Generator.aspx) amino acid benedictsbiuret carbohydrates cellulose energy ethanol fat glucose glycogen iodine lactose lipids nutrition protein starch 1. The table shows the results of food tests carried out on a biscuit. | Test reagent | Reagent
colour at
start | Result of food
test | | --- | --- | --- | | Benedict’s | Blue | Positive | | Ethanol | Clear | Positive | | Biuret | Blue | Negative | | Iodine | Yellow-brown | Positive | Look at the table Use the information in the table to draw conclusions about the types of food in the biscuit. Describe the colo

FAQs

What colour changes indicate a positive test for reducing sugars using Benedict’s solution?

A blue to green to orange to brick red colour change occurs depending on the amount of sugar present. Reducing sugars include glucose and lactose.

How does iodine solution show a positive test for starch?

Iodine turns from yellow/brown to blue/black if starch is present.

What is the positive result when Biuret is used to test for protein or amino acids?

Biuret turns from blue to purple when protein/amino acids are present.

Sep 5, 2026

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