analysis of milk
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analysis of milk analysis of milk Presentation Transcript

  • Analysis of milk Presented by Y.Narayudu
  • What is milk ? • Normal mammary gland secretion of female mammals • It is the first food for the baby mammaline Ca.caseinate RIBOFLAVIN Carotene&xanthophyl • Freezing point – 00 C(water) / -0.550C(solids)
  • Composition of milk Buffalo milk : high fat content (7.44%) Cow milk : low fat content ( 3.66%)
  • TYPES OF MILK o Standardized milk: buffalo milk & skimmed milk ( fat -4.5% & SNF is 8.5%) o Whole milk: 3.25% milk fat & 8.25% milk solids (50% of its calories 4m fat) o Reduced-fat milk (2%): This milk contains 2% milk fat (35% of its calories) o Low-fat milk (1%): 23% of its calories from fat
  • o 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. 630C for 30min milk 0 72 C For 15sec o Pasteurized : kill bacteria(not spores) o Pasteurized milk will keep fresh for 2-3 days in a fridge o Unpasteurized - raw or untreated milk o It is recommended that babies, young children, the elderly, pregnant women and anyone with an impaired immune system should avoid drinking unpasteurized milk.
  • o Long - life - milk pasteurized & homogenized and then kept at a high temp for destroy bacteria. odd burnt caramel flavour stored for 1 week o UHT( ultra-heat treatment) milk heated at high temp (1320C / 2700F) Stored for upto 3 months
  • o Dried Milk: in powdered form. o Evaporated : homogenized milk with considerably reduced water content o 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.
  • Cup of milk 146 calories 49% Fat 30% carbhydrates 21% protein
  • 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
  • o Addition of water not only reduces the nutritional value of milk but contaminated water may also pose health risks o The presence of detergent "indicates lack of hygiene and sanitation in the milk handling”
  • Method of analysis of milk
  • Preparation of sample o Warm the sample to 37 0 – 40 0 C by transferring it to the beaker & keep it in a water bath maintained at 400 - 450C o 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. o Allow the sample to come to room temperature (26 0 - 28 0 C) and withdraw immediately for analysis.
  • SPECIFICGRAVITY o LACTOMETER o 1.025-1.035 (250C-350C) o After 12hr of milking rise 0.0013
  • DETERMINATION OF PH o PH Meter o Calibrate the PH Meter o Avg . PH 6.6 o Due to lactic acid
  • Determination of total solid: o take a weight of crucible. o weigh 5 g of milk in a crucible o put a crucible in a water bath until dryness. o after complete dryness put the crucible in an oven, and weigh after cooling. o determination the percent of total solid. %Of total solid = (wt of crucible +sample) after drying – wt of crucible/ wt of sample * 100
  • RICHMOND’S Formula For Total Solids : T=0.25D+1.22F+0.72 For cow milk 0.66 Where, D = Density F = % Fat
  • DETERMINATION OF CHLORIDE CONTENT 10 ml milk + 40 ml water add 10 drops of pot.chromate Titrate with 0.1 N AgN03 Brick red ppt 1 ml of o.1 N AgN03 equivalent to 3.55mg of Cl- INDICATIVE OF DISEASED STATE OF ANIMAL
  • 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
  • Determination of Fat in Milk Gerber Method: Principle: o milk +H2S04 + iso-amyl alcohol o permitting dissoln of the protein and release of fat. o 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
  • Procedure: o 10 ml of H2S04 into a butyrometer tube & Mix the milk sample o Add 1 ml of Amyl alcohol,close with a lock stopper o shake until homogeneous soln.Keep in a water bath for 5 min at 65o C o centrifuge for 4 min. at 1100 rpm. o Remove the butyrometer tubes and place in water bath for 5 650C. o Read the percentage of fat
  • Werner Schmidt Method(by Acid Digestion Method): PRINCIPLE: o Milk proteins are digested with conc. HCl o Liberated fat is extracted with alcohol, ethyl ether & petroleum ether o Ethers are evaporated o Residue left behind is weighed to calculate the fat content.
  • 10 g milk+10 ml conc.HCl heat on a Bunsen burner stir with a glass rod until the contents turn dark brown cool to room temp Mojonnier fat extraction flask 10 ml of C2H50H+ 25 ml of ethyl ether Shake vigorously for 1 min 25 ml of petroleum ether Shake vigorously for 1 min Centrifuge Mojonnier flask at about 600 rpm
  • Decant the ether soln Repeat extraction Evaporate the solvent Dry the fat in oven Weigh
  • 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.
  • Detection of Adulterants in Milk
  • Detection of Cane Sugar in Milk Modified Seliwanoff Method: PRINCIPLE: Fructose + resorcinol in HCl procedure Procedure: std for 10 min milk + conc. HCl water bath for exactly 1 min red colour filter 1 ml filtered milk serum & 5 ml modified resorcinol - HCl reagent Withdraw the tube &observe the colour red colour
  • Test for QAC (Detergents) o To a centrifuge tube add 1 ml milk, 5 ml water, 1 ml EOSIN soln & 0.2 ml buffer and shake hard for 10 sec. o Centrifuge for 5 min at 3200 rpm. o If QAC is present the bottom layer assumes a red or pink colour. o Samples containing 1 mg / kg of QAC show a faint pink o If the colour is deep pink or red, the amt of QAC can be approx. determined by titration with a std anionic detergent soln
  • Detection of added Urea in Milk o 5 ml of milk is mixed with 5 ml of 1.6 % of p –Dimethyl amino benzaldehyde (DMAB) is added Distinct yellow colour observed in milk containing added urea. o The control (normal milk) shows a slight yellow colour due to presence of natural urea. o:
  • Estimation of Urea in Milk Prepn of standard Curve: o Pipette 5 ml std solns into 25 ml T.T Add 5 ml DMAB soln to each. o Prepare reagent blank of 5 ml buffer and 5 ml DMAB soln. Shake tubes thoroughly and let stand for 10min. o Read a@420 nm
  • Preparation of sample: o 10 ml of milk sample add 10 ml of Trichloro acetic acid (TCA) to ppt the proteins and filtered. o 5 ml of filtrate + 5 ml of DMAB o The optical density of the yellow colour is measured @ 420 nm. o From standard curve the amount of urea in milk is calculated. 70 mg per 100 ml (700 ppm)
  • Detection of preservatives
  • Hehner’s Test (HCHO): 2 ml milk in T.T 2 ml of 90 % H2SO4 traces of FeCl3 purple color ring at the junction Formaldehyde
  • 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) FeCl3 Violet colour
  • Test for presence of H2O2 Milk + conc.HCl Mix well drop of HCHO soln 600C place starch-Iodine paper into soln oxidesation of iodine BLUE COLOR
  • Bacteriological Examination of Milk Normal flora of milk: oEnterococcus faecalis oStreptoccus lactus oLactobacillus sp. o Candida albicans (yogurt)
  • Determination of viable bacterial count : The pour plate method: After preparation of 10 fold serial dilution from the milk sample with ringer solution
  • Viable Bacterial Count Using 10 fold serial dilution method 1 ml milk Milk sample 1 ml 1 1 ml 2 3 9 ml Saline 1/10 x 1/10 1/10 Melted NA 1 ml 1 1/100 x 1/10 1/100 1/1000 1 ml 2 1 ml 3
  • Viable Bacterial Count Results: Y Dilution factor No. of colonies per plate 1 2 3 X X.y 10 x1 X1.y1 102 x2 X2.y2 x3 X3.y3 103 No. of cells per 1 ml = X1.y1 + X2.y2 + X3.y3 3
  • Results: o Permissible number of bacterial flora in pasteurized milk is 5 x 104 cfu/ml o Permissible number of bacterial flora in long life milk is 10 cfu/ml
  • Methylene Blue Reduction Test: determine quality of the milk o o 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.
  • Results: The shorter the decolorization time, the higher the number of bacterial flora present in milk, and the poor quality of milk Decolorization time 30 min – 2 hrs 2 – 6 hrs 6 – 8 hrs Over 8 hrs Result Poor quality fair quality good quality excellent quality
  • Test for coliforms: o Done by inoculation of MacConkey’s broth with 0.1 ml of milk sample. o Examine for the production of acid detected by changing the color of the medium from purple to yellow.