Required Practical activity - Food Test

• The major nutrients required for a healthy diet are carbohydrates, proteins and lipids.
• The digestive system breaks down large molecules of food, which are then absorbed into the bloodstream.
• Part of Biology (Single Science)
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• In this guide
• Audio Test Pages
• Molecules of life
• Structures of carbohydrates, proteins and lipids
• Required practical activity - food tests
• The human digestive system
• Digestive enzymes
• Required practical activity
• The liver and digestion
• Use qualitative reagents to test for a range of carbohydrates, lipids and proteins
• Qualitative tests for foods
• These can be used to detect the presence of food chemicals, but not how much is present
• Test for sugars
• A simple carbohydrate that is sweet to the taste
• Heat in a water bath
• After heating, it may go through stages - green, yellow, orange, red or brown - depending on how much glucose is present
• Sugars classed as reducing sugars
• Sugars that act as reducing agents
• Glucose, fructose, lactose and maltose are reducing sugars
• Sucrose is a non-reducing sugar
• Glucose is an example of a reducing sugar
• Biuret solution B is an irritant
• The biuret test is used to detect proteins
• Iodine solution is an irritant
• Biuret reagent is sometimes available as a single solution
• A mixture formed by a solute and a solvent
• The Sudan III test is one test used to test for lipids
• Hazards Wear safety goggles
• Mix the liquids
• The emulsion test is an alternative test for lipids
• Benedict's solution is an irritant
• If there's not much glucose present, the final colour may be green or yellow, or orange if there's a little more
• Avoid contact with skin and eyes
• The iodine test can also be used with a microscope to stain starch grains in plant cells
• Reducing sugars give a red-brown precipitate close precipitate A suspension of particles in a liquid formed when a dissolved substance reacts to form an insoluble substance, eg in a precipitation reaction