session 2-milk and milk product.ppt

8/11/2019 Session 2-Milk and Milk Product.ppt

1/39


2/39

dsw (c) 2013 dept. of chemistry

Introduction

Milk normal secretion of the mammarygland for the feeding of the young

mammals,c.q.lacteal secretion, practically free fromcolostrums, obtained by the completemilking with contain not less than 8.25%milk solid-not-fat and not less than 3.25%milk fat


3/39

Composition

Major component:Lactose (occur naturally in milk)Casein (occur naturally in milk)

Proteins (essential amino acids)Milk fat (palatable mix. of glycerides of fatty acids)

Lactose and mineral salt------ true solutionProtein and casein phosphate ------ colloidal solt.Fat ------ macroscopic dispersion of the milk plasmaOther constituents ----vitamin, enzyme, pigment, andlactic acid



4/39

Composition (cont.)Cows milk in average gross composition: water 87%, fat 3.7%,lactose 4.9 %, proteins 3.5%, ash 0.7 %

Water87%

Solid13%

27% Protein: casein

30% Fat: combinedwith water is calledcream

37% lactose: milk

sugar6% ash/minerals:vitamins andminerals includingcalcium andphosphorus

Protein27%

Fat30%

Lactose37%

Ash/mineral6%

Milk Solids

dsw (c) 2013 dept. of chemistry Back


5/39

Variation in composition is due to breed diff., time of year, time of day,individual diff., age of mammals, period of lactation, portion of any onemilking, feeding etc.

Breed difference: greatest magnitude effect

Time of year/day:Milk in fall and early winter is richer than spring and summerMorning milk is richer in fat than evening milk

After first few days after calving, it is known as colostrums anddiffer materially from normal milk

Lactation period:In the final lactation: there is some increase in fat and casein

Portion: first portion (fore milk) of milk drawn in milking process arelower in fat than the last portion

Composition (cont.)



6/39

Fat

Fat and associated lipids material as an emulsionof small individual globule in an aqueous phaseSurrounding each milk fat globule is a number ofmembrane composed of cholesterol, phospholipidsprotein, and other surface-active moleculesThe membrane prevent individual fat globules fromcombining with others to form a larger globule(emulsifying agent for the fat suspended in milk)Fat globule membrane:

Inner layer: phospholipids-protein complexOuter layer: enzymes originating in mammary gland

Membrane agitation 1. disruption of the membrane (rancid flavor)2. cause for globule to coalesce to form larger globuleand butter


7/39

Milk Fat: 12.5% glycerol, 85.5% fatty acid (by weight)Glyceride tri- (98-99%), di- (0.05%), mono- (0.04%)

contains more than 16 diff. fatty acids combined with in anumber of diff. ways.

Fatty Acids (even number of carbon atom)Milk Fat is the only natural food fat that contains butyric acid in its glyceridestructure

Butyric acid, C 6, C 8, C 10 saturated fatty acids give strongcharacteristic odour60-75% saturated fatty acids

25-35% unsaturated fatty acids4% polyunsaturated fatty acidsOleic acid and palmitic acid constitute 50% of the total fatty acid inmilk fat

Minor component: FFA, cholesterol, phospholipids, Fat-soluble vitamins(A,D,E,K)

Fat (cont.)


8/39

Princ ipal fat ty ac ids fo un d in m i lkt r ig lycer ides

Molecular formula Chain length Melting point

Butyric CH 3(CH 2)2COOH C4 8 C

Caproic CH 3(CH 2)4COOH C6 2 C

Caprylic CH 2(CH 2)6COOH C8 16 C

Capric CH 3(CH 2)8COOH C10 31.5 C

Lauric CH 3(CH 2)10COOH C12 44 C

Myristic CH 3(CH 2)12COOH C14 58 C

Palmitic CH 3(CH 2)14COOH C16 64 C

Stearic CH 3(CH 2)16COOH C18 70 C

Arichidonic CH 3(CH 2)18COOH C20

Oleic CH 3(CH 2)7CH =CH(CH 2)7COOH C18: 1 13 C

Linoleic CH 3(CH 2)4(CH=CH.CH 2)2(CH 2)6COOH C18: 2 5 C

Linolenic CH 3.CH 2(CH=CH.CH 2)3(CH 2)6COOH C18: 3


9/39

Proteins

Principles protein: casein, lactalbumin (0.1-0.4%), lactoglobulin (0.4%)

Casein: as a colloidal calcium caseinate calcium phosphate complex and forms about3% of the whole milkOther component: small amount (2%) of

heat-stable milk serum protein



10/39

Milk p rotein f rac t ion s



11/39

Casein

Casein is defined as the fraction of skim milkthat is precipitated by acidifying to pH 4.6-4.7,leaving the milk serum protein in solutionThree electrophoretic components designatedas , , and -casein in order of decreasingmobilitycomplex of -casein -casein which ishydrolyzed from casein via the action of rennin to give para- -casein

para- -casein is insoluble in the presence ofcalcium ion, but precipitate, instead, as a clot orcurd

Basis of cheese manufacture Milk of ruminant (buffalo, cow, ewe, goat, etc.)contain at least 2.5% casein give cheese-type-curd with rennet (milk of others, not)

Rennin : enzymeproduced bycellsencapsulatingdigestion trackto coalescemilk. Thisenzyme effectssoluble-milkprotein whichconvert to

insolubleensuring milk totake more timebeforehydrolysis byprotein-digesting

enzyme


12/39

Whey proteins

After the casein proteins have been precipitated, the wheyproteins remain in solution.Whey soluble protein retained in the supernatant

include lactalbumin and lactoglobulin unaffected by diluted acid and rennin (caseinaffected) both are coagulated by heat (depend on pH,T , t , and salt concentration)

Component: -lactalbumin , lactoglobulin , protease- peptone, blood serum, (serum albumin,immunoglobulin)


13/39

Other proteins

After removal of casein, albumin, globulin from skim milk filtrate contains a fraction that may be precipitated bysaturation with ammonium sulfateFraction protease-peptone fraction that consist of smallermolecules size than true protein

Nonprotein Nitrogen

Includes: Amino acid, vitamin, uric acid, ammonia, creatin, creatininEnd product of nitrogen metabolism and in synthesis of milk inthe udder


14/39

Lactose (milk sugar)

Composed of D-glucose and D-galactoseContent: 4-5% (the more lactose contains, the sweeter itstaste), 1/3 as sweet as sucrose)

Reducing Fehlings solution Soluble in hot acetic acid, insoluble in alcohol and etherFermented by bacteria lactic acid (souring of milk), butodor is due to other volatile product (during fermentation)Hydrolyzed by lactase (in digestive track) intomonosaccharide as well as -galactosidase (from bacteria)Over lactose intake (exceeds the amount that it canhydrolyse) symptoms of lactose intolerance (flatulence,cramps, diarrhea)


15/39


16/39


Vitamins

Fat-soluble vitamins: A, D, E, K Ascorbic acidThiamin, riboflavin, niacin, pantotenic acid, pyridoxine, folicacid, and cyanocobalamin

Water-soluble vitamins

(CH=CH-CH=CH) 2CH2OH

CH 3 CH 3 H3CVitamin A:Uses Maintains skin and mucous membrane oforal cavity, and digestive, respiratory, reproductive,and urinary track. Critical for vision


17/39

Vitamins (cont..)


18/39

Vitamins (cont..)


19/39

Vitamins (cont..)


20/39


21/39


22/39

Enzyme

Lypase catalyze the hydrolysis of lipidsPhosphatase hydrolyze ester ofphosphoric acidLactoperoxidase, catalase, amilase,protease, xanthine oxidase



23/39

Grade of milk

GradeGrade A raw milk

Grade A pasteurized milkCertified milk

Classes

Class 1: fluid purpose (highest price milk)Class 2:any other purpose


24/39

Analysis of Fluid Milk Product

Sampling:Collecting milk in one container from one or more containerMixing (with no shaking) just stirStorage in a nonadsorbing, airtight container; cold (but notfreezing)

Addition a suitable preservative may allowedTablet of HgCl 2-K2Cr 2O7 not exceeding 1 g;formal dehyde 36% (0.1 % per 30 mL milk);if phosphatase test is to be made, chloroform is the onlypermisible preservative)

Bring sample to about 20 0C, mix by pouring sample into areceptacle and back again several timesWeigh or measure the test portion



25/39

Weighing MethodPrinciples:

Transferring a weighed quantity of milk into a flatdish (porcelain, aluminum) containing a layer ofsand (to increase the drying surface)Drying the dish and content to a constant weightCooling it in desiccatorThe increasing in weight correspond to the totalsolid in the sample

Analysis of (cont.): Total Solids

Dried solidshould be

practicallywhite . Anyappreciablebrowning indicates thatsome of lactosehas beencaramelized(error in result)



26/39

Procedure:Add 10-15 g of white sand to flat dishHeat the dish at 100 0C in drying oven until a

constant weighWeigh 5 g of prepared milk into the dishDry on a steam bath for 15 minutes, then in airoven at 98 0-100 0C for 3 hr.

Cool in a desiccator and weigh rapidlyReport the percentage of residue as total solid



composition
http://localhost/var/www/apps/conversion/tmp/scratch_3/Session%202-Milk%20and%20Milk%20Product.ppthttp://localhost/var/www/apps/conversion/tmp/scratch_3/Session%202-Milk%20and%20Milk%20Product.ppt


27/39

Lactometer MethodConstituents of normal milk are present in a fairly constantratio total solid can be calculated with a fair degree ofaccuracy if sp .gr . and fat percentage are knownProcedure:

Bring sample to 16 0 , determine the sp gr of the milk with aQuevenne lactometerTotal Solid (TS) = L + 1.2f + 0.14

with L = Lactometer readingf = percentage of fat in the milk (by the method later in

det. of crude fat bellow)




28/39

Determination of Crude Fat

Volumetrically:Babcockmethod as arapid method forgeneral dairy

testing

Gravimetrically:Mojonniermethod

BABCOCK Method

Principle:

Milk H2SO 4 (concentrated)

Protein denaturated hydrolyzed

Fat to coalesce processes follows(centrifuging, water adding)



29/39


Babcock MethodSample of well-mixed milk in a standard test milk bottleHold the bottle at an angle then pour H 2SO 4 slowly, in small portion,while rotating the bottleMix the acid and milk until all traces of curd have disappeared. The

mixture become hot and turns uniformly dark coloredTransfer the bottle to a centrifuge, counter balance with bottlecontaining water then centrifuge for 5 min.Remove the bottle, add hot distilled water until the bulb of the bottle isfilledCentrifuge for 2 min., again. add hot water until the fat column isforced up to the neck, centrifuge 1 min., at 55-60 0CPlace the bottle into the water bath (immerse to the top of the fatcolumn)

After equilibrium, remove bottle from the bath, dry and measure theheight of the column (read directly by weight of the fat in the milk)



30/39

Babcock Method:

Well-mix milk- ----------- Mixing -----------centrifuging

----hot water adding ------------- centrifuging ---hot water

again -----------centrifuging -----------------measurement


Test milk bottle

H2SO 4

Dark colored

Until bulb filled

Fat forced up Cooling in bath


31/39

Mojonnier Method

Fat is released from other milk constituent by treatment withammonium hydroxide and ethanol then dissolved in a mixtureof ether and PEEther layer (containing fat) is decanted into a weighed dish,the ether is evaporated then the dish again weighedDifferent in weight is the amount of the fat extracted

Procedure:

Weighing approx. 10 g of well-mixed milk into a Mojonnierextraction flask and adding 1.25 mL of concentratedammonium hydroxide . Add 10 mL of 95% ethanol , stopperthe flask and holding it in horizontally with a finger on thestopper, shake thoroughly. Add 25 mL of ether and shake for1 min., add 25 mL PE and again shake for 1 min., centrifuge the flask or let stand until upper layer is clear. Remove thestopper then decant off as much as possible of the ether layerinto an aluminum dish.Repeat the extraction of the liquid remaining by addingsuccessively 5 mL ethanol, 15 mL ethyl ether and 15 mL ofPE, shaking after each addition as before. Let stand, thendecant the layer. Evaporate the ether layer and dry in an ovenat 135 )C for 5 min., Cool in desiccator then weigh.Calculate the percentage of the fat obtained



32/39

Determination of AshOrganic matter is oxidized by combustionin a muffle furnaceRemaining residue ash is weighed andpercentage of ash calculated

Ashing should be done at temperature of 500 0C in order to preventvolatilization of the chloride (sodium and potassium)Procedure:

Heat a crucible at 500 0C for 1 hr, cool and weighPipette 10 mL of well-mixed milk into crucible and weigh.

Evaporate to dryness on a steam bath.Transfer the crucible and dried sample to a muffle furnace untilthe ash is carbon free (white ash)Cool in desiccator, weigh and calculate the percentage of ash


33/39

Determination of Total Acidity

The acidity of fresh milk ( apparent acidity )is due to the presence of casein, phosphates, albumin, CO 2, andcitrates

Any increase in acidity is due to the fermentation of lactose to lacticacid by bacteria present ( real acidity ).When lactic acid is sufficient produced, proteins coagulate (milk istermed sour )Procedure:

Weigh 20 g (about 20 mL) of well-mixed milk into beaker placed on awhite background), dilute with an equal volume of CO 2-free water

(recently boiled and cooled), add pp indicator, titrate the milk solt. with .0.1 N NaOHReport the acidity as percentage of lactic acid by weigh (1 mL NaOH isequivalent to 0.090 (cek! Benar apa salah) g lactic acid

OH

O

OH



34/39


Determination of Total Protein

Kjeldahl methodCasein and lactalbumin the major proteinconstituent in milk, are contained approx. 15.7% nitrogenconverting factor to protein = 6.38 (=100/15.7)

Procedur:Transfer accurately a weighed sample of appox. 5 g of well-mixedmilk into an 800-mL Kjeldahl flask. Add the various kjeldahlreagent, digest, distill and titrate the distillate (as previousdiscussion)

Conduct a back determinationCalculate the percentage of protein present in the milk:

% protein = sample titration (mL) - blank titration (mL) xNsolution x 0.14 (meq of N) x 6.38


35/39

KMnO 4

Determination of Lactose (milk sugar)Polarimetric determination: based on optic activity character of thelactose

Munson- Walker method: based on reducing properties (Fehlings A andB to produce Cu 2O)Iodine-Thiosulfate method: based on oxidation of Cu 2O with nitric acidto give soluble cupric saltPermanganometric: also based on oxidation of Cu 2O with ferric sulfateand H 2SO 4, titration of the ferrous with standard potassium

permanganateCu + + Fe 3+ Cu 2+ + Fe 2+

Folin-Wu Colorimetric method:

Milk sample is freed from suspended component, then heated with analkaline copper solt. In a Folin-Wu sugar tube to prevent reoxidation.Cu 2O is oxidized by phosphomolybdic acid and bleu color is measuredin a colorimeter. Concentration of lactose is det. by comparison with asugar solution of known concentration treated in the same manner


36/39

Residual Phosphatase Test

The test is commonly used for detection ofimproperly pasteurized milkFact: alkaline phosphatase, an enzyme present

naturally in raw milk, is progressively inactivated atthe temperature employed in pasteurizationBasis:

hydrolysis of disodium phenyl phosphate by the enzyme

Phenolate then is quanititated by any colorimetric reaction Any addition of unpasteurized milk to pasteurized milk canbe detected


37/39

Determination of MineralsGreatest interest: Calcium, ironOther cations: sodium, potassium

AAS as an also sensitive method in detecting small amount ofcontaminant (Pb Hg, etc.)Method

Preliminary:Removing organic matter (dry ashing or wet digestion for non-Hg analysis)Dissolving the residue in dilute acid

Measurement: Aspiration to the flame

Determining absorption at spesific (a resonance line)

Preparation:Stock solution of a salt of the metal to be determined in acid

Preparation a series of standard solutiondsw (c) 2013 dept. of chemistry


38/39

Chemical Analysis of Calcium(Volumetrically)

Calcium is precipitated at pH 4 as the oxalateThe oxalate dissolve in acid liberating oxalic acidOxalic acid then is titrated with potassium permananganatewith bromocresol green as an indicator (until pink colour )

Equation :2 KMnO 4 + 5 CaC 2O 4 + 8 H 2SO 4 2 MnSO 4 + K 2SO 4

+ 5 CaSO 4 + 10 CO 2 + 8 H 2OCalculation:Jumlah calcium (mg) = Vol. KMnO 4 (mL) x N KMnO4 x meq Ca

Follow the procedure!


39/39

Basis: formation of coloured complex of ferrous ion and2,2-dipyridyl

Chemical Analysis of Iron(UV-Vis Spectrometrically)

sample

protein solution

acid

heating

pH adjustment

2,2-dipyridyl

Colouredsolt. Measuring A at 522 nm

Comparing with standard

data

session 2-milk and milk product.ppt

Documents