1. OMEIAT SCENCE FAIR- 2012 by I MAX NURSERY & PRIMARY SCHOOL Royapettah Branch Chennai

2. Principle: The methylene blue reduction test is based on the fact that the color imparted to milk by the addition of a dye such as methylene blue will disappear more or less quickly. The removal of the oxygen from milk & the formation of reducing substances during bacterial metabolism causes the color to disappear. Oxygen is consumed by the bacteria The greater the number of bacteria in milk, the quicker will the oxygen be consumed, & in turn the sooner will the color disappear. Thus the time of reduction is taken as a measure of the number of organism in milk

3. Formulation of Hypothesis: MBR test shall be used to detect the quality of the milk.

4. Materials and Method: Samples: a) Sample 1-Aawin Milk b) Sample 2-Ealumalai Milk c) Sample 3-Tirumala Milk d) Sample 4-Appu Milk

5. Procedure: 1.0 g of methylene blue dye was dissolved in 250ml of distilled water. Four different types of milk packets were selected for the experiment. 10ml from each type was taken in the test tube. 1.0 ml of methylene blue dye was added to all the samples. The color change was noted. Test tubes were closed with cork. Samples were kept on a water bath at 37 degree Celsius. Temperature was maintained using low flame candle. The color change from pale blue to milky white was noted down. Experiment was repeated to get concordant values

6. Apparatus The necessary equipment consists of test tubes with rubber stoppers, a pipette or dipper graduated to deliver 10 ml of milk and a water bath for maintaining the samples at 35o to 37oC. The bath is protected from light during the incubation period. PREPARATION OF METHYLENE BLUE SOLUTION : The solution is prepared by boiling 200 ml of distilled water in a brown stoppered flask and then adding one methylene blue tablet to the flask of hot water and stirring to dissolve completely under hot condition. The solution may be stored in the stoppered brown flask to protect from light

7. Factors Affecting the Test.– Many factors affect the methylene blue reduction test Cold milk holds more oxygen than warm milk; Pouring milk back and forth from one container to another increases the amount, At milking time much oxygen may be absorbed The kind of organisms affect the rate of reduction. Light hastens reduction and therefore the tests should be kept covered. The concentration of the dye should be uniform as an increased concentration lengthens the time of reduction. Increasing the incubation temperature augments the activity of the bacteria and therefore shortens the reduction time.

8. Advantages of the Methylene Blue Test:- All apparatus are simple. Anybody can do the test Large samples are taken, thus eliminating many sources of error. In expensive equipments Applied for grading the quality of milk More accurate method

9. SAMPLES: Sample 1. Aawin Milk – green color Sample 2. Aawin Milk – orange color Sample 3. Aawin Milk – blue color Sample 4. Ealumalai Milk Sample 5. Thirumala Milk Sample 6. Appu Milk Sample 7. Jersy Milk Sample 8. Raw Milk Sample 9. Arokya Milk Sample 10. Heritage Milk Sample 11. Dodla diary Milk – blue color Sample 12. Dodla diary Milk – black color Sample 13. Fresh Milk

10. Table 1. Sl. Types of milk Quantity Ml Initial time Time of color change Duration Quality grade. 1. Aavin milk green color 103:307:003hr:30minJ 2. Aavin milk orange color 1011:4512:451hr:00minN 3. Aavin milk blue color 1011:455:255hr:40minD 4.Ealumalai milk103:308:204hr:50minF 5.Thirumala milk103:309:155hr:45minC 6.Appu milk103:3010:056hr:35minA 7.Jersy milk1011:454:434hr:58minE 8.Raw milk1010:041:453hr:41minI 9.Arokya milk1010:542:494hr:45minG 10.Heritage milk1010:042:074hr:3minH 11. Dodla diary milk blue color 1010:043:505hr:46minB 12. Dodla diary milk black color 1010:071:012hr:54minM 13.Fresh milk1010:071:353hr:28minK 14.Mother diary milk1010:071:253hr:18minL

11. Table 2. Sl. Types of milk Quantity Ml Initial time Time of color change Duration Quality grade. 1. Aavin milk green color 103:307:053hr:35minJ 2. Aavin milk orange color 1011:4512:541hr:09minN 3. Aavin milk blue color 1011:455:375hr:52minD 4.Ealumalai milk103:308:254hr:55minF 5.Thirumala milk103:309:155hr:55minC 6.Appu milk103:3010:106hr:40minA 7.Jersy milk1011:454:525hr:07minE 8.Raw milk1010:041:483hr:44minI 9.Arokya milk1010:042:564hr:52minG 10.Heritage milk1010:042:104hr:6minH 11. Dodla diary milk blue color 1010:044:003hr:56minB 12. Dodla diary milk black color 1010:071:073hrs:00minM 13.Fresh milk1010:071:403hr:33minK 14.Mother diary milk1010:071:293hr:22minL

12. Conclusion: According to the experiment made with 14 samples we find that most of the milks are comparatively worse in quality. And the quality of APPU brand milk will be the best in nature.

13. Pictorial representation of experiment: Test tube with milk sample

14. Water bath to keep the milk samples warm

15. Milk samples: Thirumala Milk