AIM: To test for glucose, sucrose, proteins, fats & shows their presence in suitable plant & animal materials (e.g. – wheat, potato, groundnut, milk or other materials)
REQUIREMENTS: Wheat grain, potato, groundnut, milk, egg, grapes/apple/banana, filter paper, test tubes, funnel, beaker, burner, Benedict’s solution, Fehling’s solutions, Biuret reagent, Million’s, Sudan III, NaOH, HCl, HNO3 etc.
PROCEDURE: Soak the suitable material (wheat, groundnut or rice). Grind them separately & make their paste. Similarly make a paste of potato, fruits & egg album in separately. Filter the content of all these in separate test tubes & label them. Use these filtrates for testing.
|1.TEST FOR GLUCOSE
(i) BENEDICT’S TEST
Take 2ml of fruit juice in a test tube. Add 2ml of Benedict’s solution to it. Boil test tube for 2 minutes & cool.
(ii) FEHLING’S TEST
Take 2ml of fruit juice in a test tube & add 2ml of each of Fehling’s solution A & Fehling’s solution B in it & boil.
|A green ppt appears in the solution, which may later turn orange or brick red in colour
Orange or brick red ppt. appears in the test tube.
|Shows the presence of glucose. Green ppt shows presence of glucose in lesser concentration, orange or red ppt indicate the presence in higher concentration.
Shows presence of glucose (Monosaccharide)
|2. TEST FOR SUCROSE
Take 2ml of sugar cane juice. Add a few drops of HCl & boil the test tube gently for one or two minutes. This hydrolyses sucrose into glucose & fructose. Make the solution alkaline with NaOH. Now perform Benedict’s or Felling’s test with this solution for presence of glucose
|Orange or brick red ppt is observed in the test tube.||Positive test with Benedict’s/ Ferling’s solution shows the presence of sucrose in juice tested.|
|3. TEST FOR STARCH
(i) IODINE TEST
Take 2ml extract (potato/gram/rice) in a test tube & add a few drops of iodine solution to it.
Test after hydrolysis. Take 2ml of starchy solution. Hydrolyse it by boiling with a few drops of HCl. Make the solution alkaline by adding NaOH & perform Benedict’s/Fehling’s test.
|Blue-black colour is observed.
Brick red or orange ppt is observed.
|Shows the presence of starch.
Positive test with Benedict’s solution shows the presence of starch.
|4. TEST FOR PROTEINS
(i) BIURET TEST
Take 3ml of 5% NaOH in a test add 2 drops of 1% CuSO4. Shake it thoroughly now in a 2nd test tube take 2ml of the extract (grapeseed)
(ii) XANTHOPROTEIC TEST
|Pink, red or violet colour is observed.
Yellow ppt observed.
Yellow ppt changes to orange.
Rink or red colour is seen.
|Show presence of proteins.
Indicates the presence of protein
|5. TEST FOR FATS
(i) Take a 1 ml of extract (peanuts/castor seeds) in a test tube & shake the solution vigorously. Dip a glass red in the solution & put its spot on the white paper.
(ii) Crush peanut/ castor seed & rub it on a piece of white paper.
(iii) Take 2ml of the extract in a test tube & add 1ml of Sudan III to it.
|Paper becomes translucent at the spot.
A translucent spot appears the paper.
Pink droplets appear in the solution.
|Indicates presence of fat
Indicate presence of fat.
Shows presence of fat.