Question

To determine amount of casein present in different samples of milk

Answer 1

AIM To study the quantity of Casein in different samples of milk. REQUIREMENTS    

Beakers (250 ml)    

Filter-paper                

Glass rod                  

Weight box        

         Filtration flask  

       Buchner funnel      

         Test tubes        

       Porcelain dish      

           Different samples of milk  

            1 % acetic acid solution

              Ammonium sulphate solution Theory Natural milk is an opaque white fluid Secreted by the mammary glands of Female mammal . The main constituents of natural milk are Protein, Carbohydrate, Mineral Vitamins,Fats and Water and is a complete balanced diet . Fresh milk is sweetish in taste. However , when it is kept for long time at a temperature of 5 degree it become sour because of bacteria present in air . These bacteria convert lactose of milk into lactic acid which is sour    in    taste.    In    acidic condition casein of milk starts separating out as a precipitate. When the acidity in milk is sufficient and temperature is around 36 degree, it forms semi-solid mass, called curd. PROCEDURE Urn- 1. A clean dry beaker has been taken, followed by putting 20 ml of cow’s milk into it and adding 20 ml of saturated ammonium sulphate solution slowly and with stirring. Fat along with Caesin was precipitate out. 2. The solution was filtered and transferred the precipitates in another beaker. Added about 30 ml of water to the precipitate. Only Caesin dissolves in water forming milky solution leaving fat undissolved. 3. The milky solution was heated to about 40oC and add 1% acetic acid solution drop-wise, when casein got precipitated. 4. Filtered the precipitate, washed with water and the precipitate was allowed to dry. 5. Weighed the dry solid mass in a previously weighed watch glass. 6. The experiment was repeated with other samples of milk. Visit www.icbse.com for more projects OBSERVATIONS CONCLUSION Different samples of milk contain different percentage of Caesin.

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