Agric.Biol.Chem.,49(2),311~317,1985311ComparisonofCompositionsofOdorComponentsofNattoandCookedSoybeansEtsukoSugawara,TetsuoIto,*SatoshiOdagiri,*KikueKubota**andAkioKobayashi**IwatePrefecturalMoriokaJuniorCollege,Sumiyoshi,Morioka020,Japan*DepartmentofAgriculturalChemistry,IwateUniversity,Veda,Morioka020,Japan**LaboratoryojFoodChemistry,OchanomizuUniversity,Bunkyo-ku,Tokyo112,JapanReceivedMay1,1984Natto,atraditionalJapanesefoodproduct,waspreparedfromcookedsoybeansbyfermentationanditsodorconcentratewasobtainedwithasimultaneousdistillationandextractionsystem.Itwascomparedtothoseobtainedfromsoybeanscookedfor0~3,3~5.5and5.5~8hr,respectively,bygaschromatographyandgaschromatography-massspectrometry.Intheodorconcentratesofthecookedsoybeans,hexanal,(£>2-hexenalandhexanolcontributingtothegreenandgrassyodorofsoybeansdisappearedordecreasedwhilethecookingwasinprogress.2-Pentylfuranandl-octen-3-olcontributingtothebeanyodorremainedevenifthesoybeanswerecookedfor8hrandwerefermentedintoNatto.IntheodorconcentrateofNatto,pyrazinesandsulfurcontainingcompoundswereimportantcontributorstothecharacteristicodorofNatto.AsthebeanyodorwasnotdetectedforNatto,itwasconcludedthatthepyrazinesandsulfurcontainingcompoundscausethecharacteristicodorofNattoandmaskthebeanyodor.Recentlysoybeanshavebeenwidelyutilizedasafoodmaterial.However,thegreengrassyandbeanyodorofsoybeanslimitthedevelop-mentofnewfooditems.Anumberofin-vestigatorshavereportedonthevolatileflavorcompoundsidentifiedfromsoybeans,andkeycompoundsofthecharacteristicsoybeanfla-vorhavebeenconfirmed.1~6)Butaneffectiveproceduretoeliminatetheobjectionableflavorofsoybeanshasnotbeenestablished.Inourcountry,therearevariouskindsoftraditionalfoodsmadefromwholesoybeansandsoybeanprotein,amongwhichNattoisoneofthemostinterestingproductsbecauseitismadefromcookedwholesoybeans,anditdoesnothavethecharacteristicsoybeanodor.ItisexpectedthatinvestigationoftheodorcomponentsofNattowillresultinnotonlytheidentificationofthecharacteristicodorcom-poundsbutalsosuggestsomeusefulmethodtoeliminateormasktheunfavorableodorofsoybeans.ToprepareNatto,soybeansweresoakedovernightandcookedforabout8hr,andthenfermentedwithBacillusnatto.ThereforewefirstinvestigatedtheeffectsofcookingtimeonthesoybeanodorandthencomparedtheodorofcookedsoybeanstothatofNattotoclarifytheeffectofthefermentationontheodor.InspiteofthefactthatNattoretainstheorig-inalbeanshape,theodoriscompletelydifferentfromthatofraworcookedsoybeans.Kosugeetal.7)reportedthattetramethylpyrazinewasacomponentoftheNattoflavor,butthecharacteristicflavorofNattohasnotbeenexplainedindetail.8~10)Inthisstudy,wetriedtoidentifyasmanyNattoodorcom-poundsaspossibleanddeterminethechangesintheirconcentrationsduringthecookingandfermentationofsoybeans.*ApartofthisworkwaspresentedattheAnnualMeetingoftheAgriculturalChemicalSocietyofJapan,Sendai,March30,1983.312E.Sugawaraetal.MATERIALSANDMETHODSMaterials.SoybeansimportedfromChinain1980wereused.Nattowasprocessedaccordingtothetraditionalmethodfromthesoybeans.Soybeans(300g)weresoakedin1.2litersofwateratroomtemperaturefor15hr,andthencookedfor8hrwithasufficientamountofwater.ThecookedsoybeanswereinoculatedwithB.natto(0.06g,NaruseFermentationChemicalLaboratory)andthenincubatedat37°Cfor15hr.ThisNattowasdesignatedasthehome-madeone.CommercialNattowasalsoanalyzedforcomparisonwiththeformer.Preparationofodorconcentr...
