Food Tests !

• benedict’s test


  reducing sugars
• iodine test


  for starch
• ethanol emulsion test


  for fats
• biuret test


  for proteins
• sucrose is not a reducing sugar
• The alcohol emulsion test involves adding equal amounts of ethanol and then water to the sample being tested. If the substance is fat or oil, it will form a white emulsion - small droplets that are dispersed throughout the liquid. This indicates the presence of lipids. If mixture remains clear, fat is absent

  
• Benedict's Test is used to determine if a solution contains reducing sugars by turning from blue to green / yellow / orange / brick red
• Iodine Test is used to detect the presence of starch by forming a dark blue color when iodine reacts with starch molecules.
• Alcohol Emulsion Test is used to identify the presence of fats or oils by forming small droplets that disperse evenly in water when mixed with ethanol.
• The biuret test is based on the formation of a violet-colored complex when peptide bonds are present in a protein molecule.
• Biuret test- add equal amount of sodium hydroxide to food sample and shake throughly. Add 1% copper (II) sulfate solution, dropwise, shaking after every drop. If mixture remained blue, protein is absent. If mixture turned from blue to violet, protein is present
• Benedict’s test - equal amount of food sample and benedict’s solution and mix. heat in boiling water bath for 2-3 minutes. mixture remained blue means reducing sugar is absent. mixture turned from blue to brick-red with precipitate means reducing sugar is present
• If benedict’s test negative - boil food sample with hydrochloride acids (hydrolysis of glycosidic bonds in sucrose if present), carry out benedict’s test. mixture remained blue, non-reducing sugar is absent. mixture turned from blue to brick-red with precipitate, non-reducing sugar is present
• benedict’s test result - blue

  0 g%
• benedict’s test result - green


  0.5 - 1 g%
• benedict’s test result - yellow

  1 - 1.5 g%
• benedict’s test result - orange-red

  1.5 - 2 g%
• benedict’s test result - brick-red

  >2 g%