Introduction

Milkfatmeasurementisacommontaskinthedairyindustry,becausemilkfatcontentisonefactorthatdeterminesmilkpriceandisnecessarytoknowforcasein/fatrationormalization.Itisalsoimportantforthedairymantoknowmilkfatcontentexactly:discrepanciesintheresultsofmilkfattests(usuallyperformedinthedairyindustrialplant)haveeconomicrelevance.Inaddition,alowmilkfatcontentcouldindicatetheexistenceofanimalhealthdeficiencies.

Principle

Thefatcanbeseparatedfromfat-containingmilk/milkpowderthroughtheadditionofsulphuricacid.Theseparationismadebyusingamylalcoholandcentrifugation.Thefatcontentisreaddirectlyonaspecialcalibratedbutyrometeraftercentrifugation.

Apparatus

1. Goodqualitybalance
2. Specialbutyrometer
3. Caoutchoucstoppers
4. Pipettes-1and10ml
5. Centrifuge,-1200rpm,equippedwithheatingelement

Reagents

1. 90%Sulphuricacid
2. 100%Amylalcohol

Procedure

1. Mixthemilksample(temperatureabout20°C)thoroughly,takingcaretominimizeincorporationofair.Allowthesampletostandforafewminutestodischargeanyairbubbles.Mixgentlyagainbeforepipetting.
2. Pipettesequentiallyintothebutyrometer:
   1. 10mlof90%sulphuricacid.
   2. 10.75mlmilk(mustnotbemixedwiththeacid).Note:Pipettetherequiredvolumeofmilkintothebutyrometer.Caremustbetakentoavoidcharringofthemilk,byensuringthatthemilkflowsgentlydowntheinsideofthebutyrometer.Itthenrestsontopoftheacid.
   3. 1mlamylalcohol
   4. somedropsofdistilledwater
3. Cleantheneckofthebutyrometerwithatissueordrycloth.
4. Closebutyrometerwithcaoutchoucstopperandshakuntilthemilkwasdissolved.Thebutyrometerwasturnedupside-down5ormoretimes.
5. SpinintheGerbercentrifugefor15minutes.
6. Thefatcolumnwasadjustedbyusingthestopper,sothatitwillbeinthegraduatedpartofthebutyrometer.Thefatpercentagewasreaddirectly.
7. Note:Measurementsshouldbecarriedoutinduplicate.

Hazards

Sulphuricacidistoxic,highlycorrosiveandwillcausesevereburningifitcomesincontactwiththeskinoreyes.Whenmixingthebutyrometercontents,considerableheatisgenerated.

Ifthestopperisslightlyloose,leakagemayoccurduringmixing,centrifugingorholdinginthewaterbath.

Precautions

WearprotectiveeyegogglesAvoidallspillageanddroppingofsulphuricacidfromaciddispensers.Whenmixing,holdthebutyrometerstopperfirmlytoensurethatitcannotslip.Useaclothorglovetoprotectthehandswhenmixing.Donotpointthebutyrometeratanyonewhenmixing.

Authors**SanjeevSharma1,BRYadav1,AartiBhardwaj2,ShaliniJain3andHariomYadav31LivestockGenomeAnalysisLab,3AnimalBiochemistryDivision,NationalDairyResearchInstitute,Karnal-132001,India2MeerutInstituteofEngeeneringandTechnology,Meerut,U.P.,India