Things to take note of for Food Test

Things to take note:

For Benedict's Test,

• It is a quantitative test
• All monosaccharides and disaccharides are reducing sugars, except sucrose. 
• To record results: must write precipitate.  e.g. A green/ red/ orange precipitate was obtained. 
• Must add equal amounts of Benedict's solution. 
• Must be placed in a water bath. Note: water bath must be boiling before the test tubes are placed in it. 

For Iodine Test, 

• Never say the iodine turns blue black --> mixture turns blue black
• starch present: blue black
• starch absent: brown

positive results for B, negative for A

Biuret Test, 

• Must add equal amount of sodium hydroxide
• protein present: turned from blue to purple/ violet
• protein absent: mixture remained blue

Ethanol Emulsion Test, 

• Test tubes must be dry
• 1. Add alcohol, if lipid is present, it will dissolve
• 2. Add water, white emulsion observed 
• --> exergonic reaction -- heat is given off

negative results for both A and B

Have to remember the procedures and the reactions.