analysis of milk

1. Presented by Y .Narayudu Analysis of milk

2. What is milk ? Normal mammary gland secretion of female mammals It is the first food for the baby mammaline Freezing point – 0 C(water) / -0.55 C(solids) RIBOFLAVIN Ca.caseinate Carotene&xanthophyl

3. Composition of milk Buffalo milk : high fat content (7.44%) Cow milk : low fat content ( 3.66%)

4. TYPES OF MILK Standardized milk: buffalo milk & skimmed milk ( fat -4.5% & SNF is 8.5%) Whole milk : 3.25% milk fat & 8.25% milk solids (50% of its calories 4m fat) Reduced-fat milk (2%) : This milk contains 2% milk fat (35% of its calories) Low-fat milk (1%):   23% of its calories from fat

5. Skimmed milk/non-fat milk: NMT 0.5% milk fat 5% of its calories from fat. Skimmed milk has about half the calories of whole milk. Pasteurized : milk kill bacteria(not spores) Pasteurized milk will keep fresh for 2-3 days in a fridge Unpasteurized  - raw or untreated milk It is recommended that babies, young children, the elderly, pregnant women and anyone with an impaired immune system should avoid drinking unpasteurized milk. 63 C for 30min 72 C For 15sec

6. Long - life -  milk pasteurized & homogenized and then kept at a high temp for destroy bacteria. odd burnt caramel flavour stored for 1 week UHT( ultra-heat treatment ) milk heated at high temp (132 C / 270 F) Stored for upto 3 months

7. Dried Milk: in powdered form. Evaporated :  homogenized milk with considerably reduced water content Condensed milk  :simply evaporated milk to which sugar has been added to thicken and sweeten it. It is mainly used for making desserts and sweets.

8.   146 calories     49% Fat 30% carbhydrates 21% protein Cup of milk

9. IS IT MILK IS CONTAMINATED….?

10. Contamination of milk THE NATIONAL NEWS(11-1-2012)& BBC: “68% of Indian milk contaminated’’ diluted with water sweeteners Fat se volume non-edible solids glucose and skimmed milk powder

11. Addition of water not only reduces the nutritional value of milk but contaminated water may also pose health risks The presence of detergent "indicates lack of hygiene and sanitation in the milk handling”

12. Method of analysis of milk

13. Preparation of sample Warm the sample to 37 – 40 C by transferring it to the beaker & keep it in a water bath maintained at 40 - 45 C Stir slowly for proper homogenisation . Mix sample thoroughly by pouring back into the bottle, mixing to dislodge any residual fat sticking to the sides and pour it back in the beaker. Allow the sample to come to room temperature (26 - 28 C) and withdraw immediately for analysis.

14. SPECIFICGRAVITY LACTOMETER 1.025-1.035 (25 C-35 C) After 12hr of milking rise 0.0013

15. DETERMINATION OF P H P H Meter Calibrate the P H Meter Avg . P H 6.6 Due to lactic acid

16. Determination of total solid: take a weight of crucible. weigh 5 g of milk in a crucible put a crucible in a water bath until dryness. after complete dryness put the crucible in an oven, and weigh after cooling. determination the percent of total solid. %Of total solid = (wt of crucible +sample) after drying – wt of crucible/ wt of sample * 100

17. RICHMOND’S Formula For Total Solids : For cow milk 0.66 W here, D = Density F = % Fat T=0.25D+1.22F+0.72

18. DETERMINATION OF CHLORIDE CONTENT 10 ml milk + 40 ml water add 10 drops of pot.chromate Titrate with 0.1 N AgN0 3 1 ml of o.1 N AgN0 3 equivalent to 3.55mg of Cl - Brick red ppt INDICATIVE OF DISEASED STATE OF ANIMAL

19. TITRABLE ACIDITY 10 ml milk + 1 ml phnolpthalein indicator Titrate with 0.1N NaOH 1 ml 0.1 N NaOH ≈ 0.009 g of lactic acid

20. Determination of Fat in Milk Gerber Method : Principle: milk +H 2 S0 4 + iso -amyl alcohol permitting dissol n of the protein and release of fat. The tubes are centrifuged and the fat rising into the calibrated part of the tube is measured as percentage of the fat content of the milk sample

21. Procedure: 10 ml of H 2 S0 4 into a butyrometer tube & Mix the milk sample Add 1 ml of Amyl alcohol,close with a lock stopper shake until homogeneous sol n .Keep in a water bath for 5 min at 65 o C centrifuge for 4 min. at 1100 rpm. Remove the butyrometer tubes and place in water bath for 5 min.at 65 C . Read the percentage of fat

22. Werner Schmidt Method(by Acid Digestion Method): PRINCIPLE: Milk proteins are digested with conc. HCl Liberated fat is extracted with alcohol, ethyl ether & petroleum ether Ethers are evaporated Residue left behind is weighed to calculate the fat content.

23. 10 g milk+10 ml conc.HCl stir with a glass rod until the contents turn dark brown Mojonnier fat extraction flask 10 ml of C 2 H 5 0H+ 25 ml of ethyl ether 25 ml of petroleum ether Shake vigorously for 1 min Centrifuge Mojonnier flask at about 600 rpm heat on a Bunsen burner cool to room temp Shake vigorously for 1 min

24. Decant the ether sol n Repeat extraction Evaporate the solvent Dry the fat in oven Weigh

25. Calculation: 100 (W1 - W2) Fat, percent w/w ---------------------- W3 Where W1 = Wt in g of contents in the flask before removal of fat . W2 = Wt in g of contents in the flask after removal of fat W3 = Wt in g of material taken for the test.

26. Detection of Adulterants in Milk

27. Detection of Cane Sugar in Milk Modified Seliwanoff Method: PRINCIPLE: Fructose + resorcinol in HCl red colour procedure Procedure: milk + conc. HCl filter 1 ml filtered milk serum & 5 ml modified resorcinol - HCl reagent Withdraw the tube &observe the colour red colour std for 10 min water bath for exactly 1 min

28. Test for QAC (Detergents) To a centrifuge tube add 1 ml milk, 5 ml water, 1 ml EOSIN sol n & 0.2 ml buffer and shake hard for 10 sec. Centrifuge for 5 min at 3200 rpm. If QAC is present the bottom layer assumes a red or pink colour . Samples containing 1 mg / kg of QAC show a faint pink If the colour is deep pink or red , the amt of QAC can be approx. determined by titration with a std anionic detergent sol n

29. Detection of added Urea in Milk 5 ml of milk is mixed with 5 ml of 1.6 % of p – Dimethyl amino benzaldehyde (DMAB) is added observed in milk containing added urea. The control (normal milk) shows a slight yellow colour due to presence of natural urea. : Distinct yellow colour

30. Estimation of Urea in Milk Prep n of standard Curve: Pipette 5 ml std sol n s into 25 ml T.T Add 5 ml DMAB sol n to each. Prepare reagent blank of 5 ml buffer and 5 ml DMAB sol n . Shake tubes thoroughly and let stand for 10min. Read a@ 420 nm

31. Preparation of sample: 10 ml of milk sample add 10 ml of Trichloro acetic acid (TCA) to ppt the proteins and filtered. 5 ml of filtrate + 5 ml of DMAB The optical density of the yellow colour is measured @ 420 nm . From standard curve the amount of urea in milk is calculated. 70 mg per 100 ml (700 ppm )

32. Detection of preservatives

33. Hehner’s Test (HCHO): 2 ml milk in T.T 2 ml of 90 % H 2 SO 4 traces of FeCl 3 Formaldehyde purple color ring at the junction

34. Test for presence of Salicylic acid: 50ml milk + 5 ml of dil.HCl + 50 ml ether Wash ether layer with water evaporate ether 1 drop of 0.5 % (v/v) FeCl 3 Violet colour

35. Test for presence of H 2 O 2 Milk + conc.HCl Mix well drop of HCHO sol n 60 C place starch-Iodine paper into sol n oxidesation of iodine BLUE COLOR

36. Bacteriological Examination of milk

37. Normal flora of milk: Bacteriological Examination of Milk Enterococcus faecalis Streptoccus lactus Lactobacillus sp. Candida albicans (yogurt)

38. Determination of viable bacterial count : The pour plate method: After preparation of 10 fold serial dilution from the milk sample with ringer solution

39. Using 10 fold serial dilution method Viable Bacterial Count 9 ml Saline 1 2 3 Milk sample 1 ml milk 1 ml 1 ml 1/10 1/10 x 1/10 1/100 1/100 x 1/10 1/1000 1 ml 1 ml 1 ml Melted NA 1 2 3

40. Results: Dilution factor 1 2 3 X X . y 10 x 1 X 1 .y 1 10 2 x 2 X 2 .y 2 10 3 x 3 X 3 .y 3 Viable Bacterial Count No. of colonies per plate Y No. of cells per 1 ml = X 1 .y 1 + X 2 .y 2 + X 3 .y 3 3

41. Results: Permissible number of bacterial flora in pasteurized milk is 5 x 10 4 cfu /ml Permissible number of bacterial flora in long life milk is 10 cfu /ml

42. Methylene Blue Reduction Test: Increasing the number of bacterial flora will reduce the colour of methylene blue more rapidly due to increasing consumption of oxygen. i.e : The speed of reduction of methylene blue colour is directly proportional to the number of bacteria present in milk sample. determine quality of the milk

43. Results: The shorter the decolorization time, the higher the number of bacterial flora present in milk, and the poor quality of milk Decolorization time Result 30 min – 2 hrs Poor quality 2 – 6 hrs fair quality 6 – 8 hrs good quality Over 8 hrs excellent quality

44. Test for coliforms : Done by inoculation of MacConkey’s broth with 0.1 ml of milk sample. Examine for the production of acid detected by changing the color of the medium from purple to yellow.