Food tests (required practical): Organisation: Biology: GCSE (9:1)

• Qualitative reagent


  A substance used in chemical analysis to test for the presence of specific molecules
• Qualitative


  Relates to measuring the quality of something rather than its quantity
• Benedict's reagent


  When heated will turn from blue to a brick-red precipitate in the presence of reducing sugars

  
• Results for Benedict's reagent


  The solution will change from blue to green to yellow to brick-red depending on the level of reducing sugars present

  
• Biuret reagent

  Turns from blue to purple in the presence of proteins

  
• Iodine test


  Turns from orange to blue-black in the presence of starch

  
• Ethanol and water


  When shaken will turn from colourless to a milky-white emulsion in the presence of lipids

  
• Sudan III

  When shaken will turn from brick-red to a red-stained oil layer in the presence of lipids

  
• Carbohydrates

  Provide energy for chemical reactions and can break down into sugars

  
• Reducing sugars

  A sugar such as glucose or fructose that can act as a reducing agent

  
• Lipids


  An energy store of fats and oils that can break down into glycerol and fatty acids

  
• Proteins

  The building blocks of cells and tissues that can break down into amino acids

  
• Precipitate


  Deposits of solid in a solution

  
• Mortar and pestle


  Devices used for crushing and grinding up food substances

  
• Water bath

  A container of water heated to a given temperature for control purposes

  
• Positive result


  A result that shows the presence of a specific substance
• Negative result

  A result that does not show the presence of a specific substance