1、A Referencenumbe r ISO751:1998 (E) INTERNATIONAL STANDARD ISO 751 Secondedition 19980801 Fruitandvegetableproducts Determinationofwaterinsolublesolids ProduitsdrivsdesfruitsetlgumesDterminationdursidusec insolubledansleauISO751:1998(E) ISO1998 Allrightsreserved.Unlessotherwisespecified,nopartofthisp
2、ublicationmaybereproducedorutilizedinanyformorbyan ymeans,electronic ormechanical,includingphotocopyingandmicrofilm,withoutpermissioninwritingfromthepublisher. InternationalOrganizationforStandardization Casepostale56 CH1211Genve20 Switzerland Internet isoiso.ch PrintedinSwitzerland ii Foreword ISO(
3、theInternationalOrganizationforStandardization)isaworldwidefederationofnationalstandardsbodies(ISO memberbodies).TheworkofpreparingInternationalStandardsisnormallycarriedoutthroughISOtechnical committees.Eachmemberbodyinterestedinasubjectforwhichatechnicalcommitteehasbeenestablishedhas therighttober
4、epresentedonthatcommittee.Internationalorganizations,governmentalandnongovernmental,in liaisonwithISO,alsotakepartinthework.ISOcollaboratescloselywiththeInternationalElectrotechnical Commission(IEC)onallmattersofelectrotechnicalstandardization. DraftInternationalStandardsadoptedbythetechnicalcommitt
5、eesarecirculatedtothememberbodiesforvoting. PublicationasanInternationalStandardrequiresapprovalbyatleast75%ofthememberbodiescastingavote. InternationalStandardISO 751waspreparedbyTechnicalCommitteeISO/TC34 ,Agriculturalfoodproducts, SubcommitteeSC3, Fruitandvegetableproducts . Thissecondeditioncanc
6、elsandreplacesthefirstedition(ISO751:1981),whichhasbeentechnicallyrevised.INTERNATIONALSTANDARD ISO ISO751:1998(E) 1 FruitandvegetableproductsDeterminationofwaterinsoluble solids 1Scope ThisInternationalStandardspecifiesamethodforthedeterminationofthecontentofwaterinsolublesolidsinthe ediblepartsoff
7、ruitandvegetableproducts. 2Principle Thewatersolublematterinatestportionisdissolvedinwater,followedbyfiltration,dryingoftheresidueand weighing. 3Apparatus Usuallaboratoryapparatusand,inparticular,thefollowing. 3.1 Beakers,ofcapacity250mlor400ml. 3.2 Buchnerfunnel . 3.3 Filterpaper ,mediumtexture. 3.
8、4 Indicatorpaper . 3.5 Weighingvessel . 3.6 Desiccator,containinganefficientdesiccant. 3.7 Oven,capableofbeingmaintainedat103 C 2 C. 3.8 Centrifuge. 3.9 Analyticalbalance, capableofweighingtothenearest0,001g. 4Sampling Itisimportantthelaboratoryreceiveasamplewhichistrulyrepresentativeandhasnotbeenda
9、magedorchanged duringtransportorstorage. SamplingisnotpartofthemethodspecifiedinthisInternationalStandard.AsthereisnospecificInternational Standarddealingwithfruitandvegetableproducts,itisrecommendedthatthepartiesconcernedcometoan agreementonthesubject.ISO751:1998(E) ISO 2 5 Preparationoftestsamplea
10、ndofapparatus 5.1 Preparationoftestsample Separateandremovefromthelaboratorysamplestalks,stones,hardseedcavitywallsand,wheneverpossible, pips(afterthawinginthecaseoffrozenordeepfrozenproducts).Mixthesamplethoroughly. Allowfrozenordeepfrozenproductstothawinaclosedvesselandaddtheliquidformedduringthis
11、processtothe productbeforemixing. Ifitisdesiredtoexpresstheresultintermsofthesampleasreceived,weighthelatterbeforeremovingstalks, stones,etc.Weightheseafterwashinganddryingandtakethemintoaccountintheexpressionofresults(see8.2). 5.2 Preparationofapparatus Placeafilterpaper(3.3)intheweighingvessel(3.5
12、)anddryintheoven(3.7)setat103 Cfor30min.Coolinthe desiccator(3.6)andweightothenearest0,001g. 6Procedure NOTEIfitisrequiredtocheckwhethertherepeatabilityrequirement(clause9)ismet,carryouttwosingledeterminations in accordancewith6.1to6.2. 6.1Test portion Weigh,tothenearest0,01g,intoa250mlbeaker(3.1)(4
13、00mlinthecaseofsweetenedproducts)10gto100gof thetestsample(5.1),accordingtotheconsistencyoftheproductandtheexpectedcontentofwaterinsoluble solids;forexample: tomatoconcentrates 10g jam,fruitpreserves 25g pulpyproducts 50g fruitandvegetablejuices 100g NOTEForliquidproducts,itisalsopossibletotakethete
14、stportionbyvolume. 6.2Determination Add100mlto150mlofdistilledwaterorwaterofequivalentpuritytothebeakercontainingthetestportion(6.1). Stirwithaglassroduntilahomogeneousmixtureisobtained.Heattoboiling(inthecaseofsweetenedproducts, see7.3). Pourthecontentsofthebeakerquantitativelyontothedriedfilterpap
15、er(see5.2)placedintheBuchnerfunnel(3.2) andfilter(see7.4).Washthefilterpaperwithalittlehotwater. Transferthefilterpaperanditscontentsquantitativelytotheweighingvessel(see5.2)anddryintheoven(3.7),set at103 C,toconstantmass;i.e.untilthedifferencebetweentwoconsecutiveweighings,after30minintheoven follo
16、wedbycoolinginthedesiccatorforabout20min,doesnotexceed0,001g.Carryouttheweighingstothe nearest0,001g.ISO ISO751:1998(E) 3 7Special cases 7.1Grape juice Ifcrystalsofpotassiumhydrogentartratearefoundtobepresentingrapejuice,thequantityshouldbedetermined. Forthispurpose,usinganothertestportion,collectth
17、ecrystalsonafilter,washthemwiththesamejuiceandthen with50%( V/V)ethanolsolutionsaturatedwithpotassiumhydrogentartrate. Dryandweighthecrystals.Themassofthecrystalsofpotassiumhydrogentartrateshallberecordedinthetest report. 7.2Citrus products Asimilarprocedureshouldbefollowedwhencrystalsofhesperidenor
18、naringinarepresentincitrusproducts. 7.3Sweetened products Fortheanalysisofsweetenedproducts,addabout250mlofwater.Bringtotheboilandboilgentlyfor5minto 10min. 7.4 Productsdifficulttofilter Ifitprovesdifficulttofiltertheproduct(productswithhighcontentsofpectinorprotein),orinthecaseofproducts havinghigh
19、sugarcontents(fruitpreserves,jam,etc.),separatethesolidmatterbymeansofacentrifuge(3.8). Decanttheclearliquid,recovertheresidue(deposit)withhotwaterandagaincentrifuge.Repeattheseoperations severaltimes,untilthewashingsarefreefromsugars,salts,acids,etc.,thencollecttheresidueobtainedby centrifugingonth
20、efilter,asdescribedin6.2. 8 Expressionofresults 8.1 Thecontentofwaterinsolublesolidsintheediblepartsoffruitandvegetableproducts,expressedasa percentagebymass,isequalto (m 2 - m 1 ) 3 100 0 m where m 0 isthemass,ingrams,ofthetestportion(6.1); m 1 isthemass,ingrams,oftheweighingvesselanddriedfilterpap
21、er(5.2); m 2 isthemass,ingrams,oftheweighingvessel,filterpaperandresidueafterdrying(6.2). 8.2 Itisalsopossibletoexpresstheresultinrelationtothesampleasreceived(see5.1)or,forliquidproducts,in gramsper100mlforatestportiontakenbyvolume. 9Repeatability Theabsolutedifferencebetweentwoindependentsingletes
22、tresults,obtainedusingthesamemethodonidentical testmaterialinthesamelaboratorybythesameoperatorusingthesameequipmentwithinashortintervaloftime, willinnotmorethan5%ofcasesbegreaterthan0,1gofwaterinsolublesolidsper100gofsample.ISO751:1998(E) ISO 4 10Test report Thetestreportshallspecify: allinformatio
23、nnecessaryforthecompleteidentificationofthesample; thesamplingmethodused,ifknown; thetestmethodused,togetherwithreferencetothisInternationalStandard; alloperatingdetailsnotspecifiedinthisInternationalStandard,orregardedasoptional,togetherwithdetailsof anyincidentswhichmayhaveinfluencedthetestresult(s); thetestresult(s)obtained; iftherepeatabilityhasbeenchecked,thefinalquotedresultobtained.ISO751:1998(E) ISO ICS67.080.01 Descriptors: agriculturalproducts,foodproducts,plantproducts,fruitandvegetableproducts,tests,determinationofcontent,inso luble matter,solids. Pricebasedon4pages
