1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS 5766-19:2000 ISO 6493:
2、2000 ICS 65.120 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Methods for analysis of animal feeding stuffs Part 19: Determination of starch content Polarimetric methodThis British Standard, having been prepared under the direction of the Consumer Products and Services Secto
3、r Committee, was published under the authority of the Standards Committee and comes into effect on 15 April 2000 BSI 04-2000 ISBN 0 580 34737 0 BS 5766-19:2000 Amendments issued since publication Amd. No. Date Comments National foreword This British Standard reproduces verbatim ISO 6493:2000 and imp
4、lements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee AW/10, Animal feeding stuffs, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the i
5、nterpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards
6、 which implement international publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purpo
7、rt to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front co
8、ver, the ISO title page, pages ii and iii, a blank page, pages 1 to 10, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued.Referencenumber ISO6493:2000(E) INTERNATIONAL STANDARD ISO 6493 Firstedition 2000-02-01 Anima
9、lfeedingstuffsDeterminationof starchcontentPolarimetricmethod Aliments des animaux Dtermination de la teneur en amidon Mthode polarimtriqueISO6493:2000(E) ii ISO6493:2000(E)iii Foreword ISO(theInternationalOrganizationforStandardization)isaworldwidefederationofnationalstandardsbodies(ISO memberbodie
10、s).TheworkofpreparingInternationalStandardsisnormallycarriedoutthroughISOtechnical committees.Eachmemberbodyinterestedinasubjectforwhichatechnicalcommitteehasbeenestablishedhas therighttoberepresentedonthatcommittee.Internationalorganizations,governmentalandnon-governmental,in liaisonwithISO,alsotak
11、epartinthework.ISOcollaboratescloselywiththeInternationalElectrotechnical Commission(IEC)onallmattersofelectrotechnicalstandardization. InternationalStandardsaredraftedinaccordancewiththerulesgivenintheISO/IECDirectives,Part3. DraftInternationalStandardsadoptedbythetechnicalcommitteesarecirculatedto
12、thememberbodiesforvoting. PublicationasanInternationalStandardrequiresapprovalbyatleast75%ofthememberbodiescastingavote. AttentionisdrawntothepossibilitythatsomeoftheelementsofthisInternationalStandardmaybethesubjectof patentrights.ISOshallnotbeheldresponsibleforidentifyinganyorallsuchpatentrights.
13、InternationalStandardISO6493waspreparedbyTechnicalCommitteeISO/TC34, Agricultural food products, SubcommitteeSC10, Animal feeding stuffs. AnnexesAandBofthisInternationalStandardareforinformationonly.INTERNATIONALSTANDARD ISO6493:2000(E)1 AnimalfeedingstuffsDeterminationofstarchcontent Polarimetricme
14、thod 1 Scope ThisInternationalStandardspecifiesamethodforthepolarimetricdeterminationofthestarchcontentofanimal feedingstuffsandrawmaterialsforanimalfeedingstuffs. Themethodisnotapplicabletoproductswhich,besidesstarch,containothersubstanceswhichareopticallyactive duringtheanalysisanddonotdissolvein4
15、0%ethanol.Examplesoftheseproductsarepotatopulp,beetchips, beetleaves,beettops,yeast,soyaproducts,lupineandproductsrichininulin(e.g.chicoryrootsandJerusalem artichokes).Inthesecasesanenzymaticdeterminationofthestarchcontentmaybeused. Thismethodisnotapplicableforthequantificationofstarchwithanamylosec
16、ontentexceeding40%(e.g.high amylosemaizestarchlikeHylonVII). CAUTIONDependingontheintensityoftheheat/moisturetreatmenttheproducthasbeensubjectedto, toolowastarchcontentmaybedetermined. 2 Normativereferences Thefollowingnormativedocumentscontainprovisionswhich,throughreferenceinthistext,constitutepro
17、visionsof thisInternationalStandard.Fordatedreferences,subsequentamendmentsto,orrevisionsof,anyofthese publicationsdonotapply.However,partiestoagreementsbasedonthisInternationalStandardareencouragedto investigatethepossibilityofapplyingthemostrecenteditionsofthenormativedocumentsindicatedbelow.For u
18、ndatedreferences,thelatesteditionofthenormativedocumentreferredtoapplies.MembersofISOandIEC maintainregistersofcurrentlyvalidInternationalStandards. ISO3310-1, Test sieves Technical requirements and testing Part 1: Test sieves of metal wire cloth. ISO3696, Water for analytical laboratory use Specifi
19、cation and test methods. ISO6498, Animal feeding stuffs Preparation of test samples. 3 Termsanddefinitions ForthepurposesofthisInternationalStandard,thefollowingtermsanddefinitionsapply. 3.1 starch naturalvegetablepolymerconsistingoflongunbranchedchainsof -1,4-linkedglucose-units(amylose)and/or long
20、 -1,6-branchedchainsof -1,4-linkedglucose-units(amylopectine)ISO6493:2000(E) 2 3.2 starchcontent massfractionofstarchanditshighmolecularmassbreakdownproducts,insolublein40%ethanol,and determinedinaccordancewiththisInternationalStandard NOTE Thestarchcontentisexpressedingramsperkilogram. 4Principle A
21、testportionisdecomposedwithdilutehydrochloricacid,thenthesolubilizedstarchisgelatinizedandpartially hydrolysed. Thetotalopticalrotationoftheclarifiedsolutionisdetermined. Correctionismadefortheopticalrotationcausedbyothersubstanceswhicharesolublein40%ethanoland opticallyactiveaftertreatmentwithdilut
22、ehydrochloricacid. Thestarchcontentiscalculatedbymultiplyingthecorrectedopticalrotationbyaknownfactor. 5 Reagents Useonlyreagentsofrecognizedanalyticalgrade. 5.1Water,complyingwithatleastgrade3inaccordancewithISO3696. 5.2Ethanol(C 2 H 5 OH),40%volumefraction. 5.3Methylred,solutioninethanol(96%volume
23、fraction), (methylred)=1g/l. 5.4Hydrochloricacid,c(HCl)=0,31mol/l. Checktheconcentrationbytitrationwitha0,100mol/lsodiumhydroxidesolutionusingmethylredasindicator.An aliquotportionof10mlofhydrochloricacidshallneutralize(31,0 0,1)mlofthesodiumhydroxidesolution. CAUTIONToohighortoolowahydrochloricacid
24、concentrationwillleadtoincorrectvaluesofthe determinedstarchcontent. 5.5Hydrochloricacid,c(HCl)=7,73mol/l. 5.6Clarifyingsolutions,accordingtoCarrez,asfollows. 5.6.1Potassiumhexacyanoiron(II)solution,cK 4 Fe(CN) 6 =0,25mol/l. Ina1lvolumetricflask,dissolve106gofpotassiumhexacyanoiron(II)trihydrateK 4
25、Fe(CN) 6 3H 2 Oinwater.Dilute tothemarkwithwater. 5.6.2Zincacetate,solutionin0,5mol/laceticacid,cZn(CH 3 CO 2 ) 2 =1mol/l. Ina1lvolumetricflaskdissolve219,5gofzincacetatedihydrateZn(CH 3 CO 2 ) 2 2H 2 Oand30gofglacialacetic acidinwater.Dilutetothemarkwithwater. 5.7Saccharosesolution, (C 12 H 22 O 11
26、 )=100,0g/l.ISO6493:2000(E)3 6 Apparatus Usuallaboratoryapparatusand,inparticular,thefollowing. 6.1Analyticalbalance,capableofweighingtothenearest1mg. 6.2pH-meter,capableofmeasuringtothenearest0,1pHunit. 6.3Boilingwaterbath,withsufficientcapacitytomaintainthewateratboilingpointwhileimmersingtheconic
27、al flasks. CAUTIONIfthewaterbathisnotboilingconstantly,toohighastarchcontentwillbedetermined. 6.4Polarimeter,accuratetoatleast0,01andsuitablefor200mmlongtubes. Measuretheopticalrotationatawavelengthof589,3nm(sodiumDline).Whenusingpolarimetertubesof deviatinglengths,measurewithacorrespondingaccuracy.
28、 Asaccharimetermaybeusedifithasanaccuracyofmeasurementatleastequaltotheaccuracyofthe polarimeter.Inthiscase,convertthereadingstodegrees. Thepolarimetermaybecalibratedwiththesaccharosesolution(5.7).Thissaccharosesolutionyieldsanoptical rotationof13,30whenmeasuredat(20 1) Cusinga200mmpolarimetertube.
29、6.5Burette. 6.6Refluxcondensers. 6.7Volumetricflasks,ofcapacity100ml. Ifthevolumetricflasksneedtobefittedtoarefluxcondenser(see9.3.3),theuseofwide-neckedKohlrausch conicalflasksisrecommended. NOTE Kohlrauschconicalflasksarecommerciallyavailablevolumetricflasksusedforsugardeterminations. 7 Sampling S
30、amplingisnotpartofthemethodspecifiedinthisInternationalStandard.Arecommendedsamplingmethodis giveninISO64971. Itisimportantthatthelaboratoryreceiveasamplewhichistrulyrepresentativeandhasnotbeendamagedor changedduringtransportorstorage. 8 Preparationoftestsample PreparethetestsampleinaccordancewithIS
31、O6498. Ifsolid,grindthelaboratorysample(usually500g)sothatitpassescompletelythroughasievewith0,5mm aperturescomplyingwithISO3310-1.Mixthoroughly.ISO6493:2000(E) 4 9 Procedure 9.1Determinationofacidconsumption 9.1.1Weighapproximately2,5gofthepreparedtestsampletothenearest1mgandtransferitquantitativel
32、ytoa 50mlconicalflask.Add25mlofwaterandshakeuntilahomogeneoussuspensionisobtained. 9.1.2PlacetheelectrodesofthepH-meter(6.2)inthesuspensionand,usingaburette,addhydrochloricacid (5.4)untilthepHofthesuspensionis3,0 0,1.Checkwhetherthecompleteacidconsumptionofthetestportion hasbeencompensatedfor,byshak
33、ingthesuspensionvigorouslyandallowingittostandfor2min.Ifduringthis periodthepHhasincreaseduptoavalueexceeding3,1,addmorehydrochloricacid(5.4),usingtheburette,as manytimesasnecessaryuntilnomoreacidisconsumed. 9.1.3Calculatetheacidconsumptionofthetestportionfromthevolumeofhydrochloricacid(5.4)added. 9
34、.2Determinationoftotalopticalrotation 9.2.1Weighapproximately2,5gofthepreparedtestsample(m 1 )tothenearest1mgandtransferitquantitatively toadry100mlvolumetricflask(6.7).Add25mlofhydrochloricacid(5.4).Shakeuntilahomogeneoussuspension isobtained,thenaddafurther25mlofhydrochloricacid(5.4). 9.2.2Compens
35、atefortheacidconsumptionofthetestportion(see9.1)byaddinghydrochloricacidofasuitable concentrationsothatthevolumeofthecontentsoftheflaskischangedbynotmorethan1ml. EXAMPLESupposethat5,0mlof0,1mol/lhydrochloricacidisusedin9.1.2forcompensationofasamplerichinchalk,then theacidconsumptionofthetestportioni
36、s0,5mmol(9.1.3).Inthatcase,add0,5mlof1,0mol/lhydrochloricacidin9.2.2. CAUTIONIfthehydrochloricacidconcentrationinthesuspensiondeviatesfrom0,31mol/l,awrong starchcontentwillbedetermined.Toohighortoolowahydrochloricacidconcentrationwillresultintoo lowortoohighvalues,respectively,ofthedeterminedstarchc
37、ontent. 9.2.3Immersetheflaskintheboilingwaterbath(6.3).Duringthefirst3min,regularlyshaketheflaskvigorously topreventclottingandtoobtainequalheatdistributioninthesuspension.Whenshaking,keeptheflaskimmersed. Inthecaseofmultipleanalyses,immersetheflasksoversuitabletimeintervalssoastokeepthewaterbathat
38、boilingpoint. After15min 5s,removetheconicalflaskfromthebath.Immediatelyadd30mlofwater(5.1)atatemperature notexceeding10 Candswirl.Cooltoatemperatureofabout20Cinawaterbathwithrunningcoldwater. CAUTIONIftheflaskstaysintheboilingwaterbathtoolongorifthetemperaturedecreaseistooslow, toolowastarchcontent
39、willbedetermined. Add5mlofpotassiumhexacyanoiron(II)solution(5.6.1)andshakefor1min.Add5mlofzincacetatesolution (5.6.2)andshakeagainfor1min.Dilutetothemarkwithwater,mixandfilter.Discardthefirstfewmillilitresofthe filtrate. Determinetheopticalrotationofthefiltrate( 1 )withthepolarimeterorsaccharimeter
40、(6.4). 9.3Determinationofopticalrotationofethanol-solublesubstances 9.3.1Weighapproximately5gofthepreparedtestsample(m 2 )tothenearest1mgandtransferitquantitatively toadry100mlvolumetricflask(6.7).Add40mlofethanol(5.2).Shakeuntilahomogeneoussuspensionis obtainedthenaddafurther40mlofethanol(5.2).ISO6
41、493:2000(E)5 9.3.2Compensatefortheacidconsumptionofthetestportion(see9.1)byaddinghydrochloricacidofasuitable concentrationsothatthevolumeofthecontentsoftheflaskischangedbynotmorethan1ml.Inprinciple,the amountofhydrochloricacidtobeaddedistwiceasmuchasthataddedin9.2.2. 9.3.3Shakevigorouslyandleavetost
42、andfor1hatroomtemperature.Duringthistime,shakevigorouslyatleast every10min. Ifthelactosecontentofthesampleexceeds50g/kg(asforwheypowderandseparatedmilkpowder),dissolvethe samplebyheatingtheflask,fittedwitharefluxcondenser,inawaterbathat(50 2)Cfor30min. Dilutetothemarkwithethanol(5.2),mixandfilter.Di
43、scardthefirstfewmillilitresofthefiltrate. Pipette50mlofthefiltrateintoa100mlvolumetricflask(6.7).Add2,0mlofhydrochloricacid(5.5)andswirl vigorously.Fitarefluxcondensertotheflaskandimmersetheflaskintheboilingwaterbath(6.3). After15min 5s,removetheconicalflaskfromthebath.Immediatelyadd30mlofwater(5.1)
44、atatemperature notexceeding10 Candswirl.Cooltoatemperatureofabout20Cinawaterbathwithrunningcoldwater. Add5mlofpotassiumhexacyanoiron(II)solution(5.6.1)andshakefor1min.Add5mlofzincacetatesolution (5.6.2)andshakeagainfor1min.Dilutetothemarkwithwater,homogenizeandfilter.Discardthefirstfew millilitresof
45、thefiltrate. Determinetheopticalrotationoftheclearfiltrate( 2 )withthepolarimeterorsaccharimeter(6.4). 10Calculationandexpressionofresults Calculatethestarchcontentofthetestsamplebytheequation: w mm L N M O Q P 20000 25 5 20 1 1 2 2 D , where w isthenumericalvalueofthestarchcontentofthetestsample,in
46、gramsperkilogram; 1 isthenumericalvalueofthetotalopticalrotation,indegrees,measuredin9.2; 2 isthenumericalvalueoftheopticalrotation,indegrees,oftheethanol-solublesubstancesmeasuredin 9.3; m 1 isthenumericalvalueofthemass,ingrams,ofthetestportionforthedeterminationofthetotaloptical rotation(9.2); m 2
47、 isthenumericalvalueofthemass,ingrams,ofthetestportionforthedeterminationoftheopticalrotation oftheethanol-solublesubstances(9.3); D 20 isthenumericalvalueofthespecificopticalrotation,indegrees,ofpurestarchmeasuredatawavelength of589,3nm(NaDline): D 20 =185,9 forricestarch; D 20 =185,7 forpotatostar
48、ch(seeannexA); D 20 =184,6 formaizestarch;ISO6493:2000(E) 6 D 20 =184,0 forryestarch; D 20 =183,6 fortapiocastarch(seeannexA); D 20 =182,7 forwheatstarch; D 20 =181,5 forbarleystarch; D 20 =181,3 foroatstarch; D 20 =184,0 forothertypesofstarchandstarchmixturesinanimalfeedingstuffs. Roundtheresulttot
49、henearest1g/kg. 11Precision 11.1Interlaboratorytest DetailsofaninterlaboratorytestontheprecisionofthemethodaregiveninannexB.Thevaluesderivedfromthis testmaynotbeapplicabletoconcentrationrangesandmatricesotherthanthosegiven. 11.2Repeatability Theabsolutedifferencebetweentwoindependentsingletestresults,obtainedusingthesamemethodonidentical testmaterialinthesamelaboratorybythesameoperatorusingthesameequipmentwithinashortintervaloftime, willinnotmorethan5%ofcasesexceedtherepeatabilitylimitrgiven
