FoodChemistry124(2011)501–513 ContentslistsavailableatScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem q Volatile profiles of aromatic and non-aromatic rice cultivars using SPME/GC–MS R.J. Bryant*, A.M. McClung USDA-ARS,DaleBumpersNationalRiceResearchCenter,2890Hwy130E.,Stuttgart,AR72160,USA a r t i c l e i n f o a b s t r a c t Articlehistory: Rice(OryzasativaL.)isenjoyedbymanypeopleasastaplefoodbecauseofitsflavourandtexture.Some Received2September2009 cultivars,likescentedrice,arepreferredoverothersduetotheirdistinctivearomaandflavour.Thevol- Receivedinrevisedform30April2010 atileprofileofricehasbeenexploredbyotherinvestigators,someofwhomhavealsodeterminedacor- Accepted16June2010 responding aroma using GC/olfactometry. However, little research has been done to determine if differentaromaticricecultivarsproducedifferentflavourvolatilesthatwouldmakethemmoredesirable thanotherswhencooked.Inthisstudy,sevenaromaticandtwonon-aromaticcultivarswereexamined Keywords: fortheirvolatileprofilesbothbeforeandafterstorageusingsolidphasemicroextraction(SPME)fibresin Aroma conjunction with gas chromatography/mass spectrometer (GC–MS). Ninety-three volatile compounds Flavour were identified, 64 of which had not been previously reported in rice. Differences were found in the OryzasativaL. Rice volatilecompoundsofaromaticandnon-aromaticricebesides2-acetyl-1-pyrroline(2-AP).Mostofthe Scentedrice volatile compounds were present in freshly harvested rice and rice following storage, with very few SPME new compounds being identified only after storage. Dellrose, an aromatic cultivar, and Cocodrie, a GC/MS non-aromatic cultivar, had the most complex volatile profiles (over 64 volatiles). Sixteen compounds Volatiles werefoundonlyinthearomaticcultivars,andsomevolatileswerefoundtobeuniquetospecificaro- maticcultivars. However,no distinctive pattern was observed thatwould identifya cultivaras being derivedfromBasmati,KhaoDawkMali105(i.e.jasmine),orothersourcesofaroma.Thisstudyshowed that there is a great diversity of volatiles in both aromatic and non-aromatic rice cultivars and, with furtherresearch,thismayleadtoabetterunderstandingofthecombinationofcompoundsthatgives acultivarauniqueflavour. PublishedbyElsevierLtd. 1.Introduction sensory attributes that distinguish these types of aromatic rice cultivars in preference tests (Fitzgerald & Hall, 2008; Fitzgerald, Rice(OryzasativaL.)isastaplefoodformanycountries.Unlike McCouch, & Hall, 2009). Currently, 2-acetyl-1-pyrroline (2-AP), othergrains,e.g.wheat,corn,oroats,riceiscookedandconsumed which is a primary determinant of flavour in aromatic rice asawholegrain.Aromaticricehasanaturalnutty,popcornflavour (Buttery,Ling,&Juliano,1982),istheonlyflavourcomponentthat andaccountsfor86%ofimportsintotheUnitedStates(USDAEco- breedershavetheabilitytoselectfor. nomicResearchService,2010).JasminericefromThailandandbas- Genetics, growing conditions, and post-harvest handling are matiricefromPakistanandIndiaarethemainsourcesofaromatic factors which have been shown to affect the aroma and flavour imports. Because this is an expanding market and imported jas- of rice (Champagne, 2008). There are several studies that have mineandbasmatiricecultivarsarenotadaptedfordomesticpro- evaluated a number of rice cultivars from different genetic back- duction, breeders have endeavoured to develop aromatic rice grounds (Bergman et al., 2000; Laguerre, Mestres, Davrieux, cultivars that can be grown in the USA and favourably compete Ringuet, & Boulanger, 2007; Yang, Lee, Jeong, Kim, & Kays, withimports.Jasmine,Basmatiand‘‘Della’’typeofaromaticculti- 2008a; Zeng, Zhang, Chen, Zhang, & Matsunaga, 2008) and rice vars are distinguished by their grain shape, cooked rice texture, which has been stored under different conditions (Suzuki et al., andflavour(Bergman,Bhattacharya,&Ohtsubo,2004),andbreed- 1999;Tulyathan,Srisupattarawanich,&Suwanagul,2008;Widjaja, ersusethesetraitsintheselectionofcultivarsfordifferentmarket Craske, & Wootton, 1996a; Wongpornchai, Dumri, Jongkaewwat- segments.Studieshavedemonstratedthatconsumerscandiscern tana, & Siri, 2004; Zhou, Robards, Helliwell, & Blanchard, 2002). A major focus has been on 2-AP, the primary volatile compound inaromaticrice,however,lipidoxidationproductshavealsobeen q Mentionofatrademarkorproprietaryproductinthisarticleissolelyforthe identifiedwhichareknowntohaveanegativeimpactonaccept- purposeofprovidingspecificinformationanddoesnotimplyrecommendationor ability (Champagne, 2008). The latter are compounds that may endorsementbytheUnitedStatesDepartmentofAgriculture. become more prevalent with the length of storage time or due * Correspondingauthor.Tel.:+18706729300x227;fax:+18706737581. E-mailaddress:[email protected](R.J.Bryant). to poor post-harvest handling. The rice that is imported to the 0308-8146/$-seefrontmatterPublishedbyElsevierLtd. doi:10.1016/j.foodchem.2010.06.061 502 R.J.Bryant,A.M.McClung/FoodChemistry124(2011)501–513 UnitedStatesissubjectedtomonthsofstorageandvariabletrans- including2-aminoacetophenoneandbis-(2-methyl-3-furyl)disul- portconditions.Moreover,thebasmatiriceisfrequentlyagedfor phide,whichhadnotbeenpreviouslyreported.Zengetal.(2008) atleastayearbeforeitismarketed(Fitzgeraldetal.,2009).Thus, foundthatthevolatileprofilechangedduringcooking. the imported aromatic rice that is in the USA marketplace, may This study was conducted using SPME-GC/MS to evaluate the have much different flavour profiles as compared to freshly har- volatile profiles of the rice cultivars that were produced in the vested rice. Champagne (2008) noted that studies were needed same environment and were then subjected to different storage usinglargersetsofricecultivarsthatwerehandledunderidentical timesandtemperatures.Thespecificobjectivesweretodetermine pre-andpost-harvestconditionstoaddressflavourattributes. (1)ifvolatileprofilepatternsorcompoundsareuniquetojasmine, Thevolatileprofileofricehasbeenexploredbyseveralinvesti- basmati,orDelladerivedcultivarsand(2)ifvolatileprofilesofcul- gators,someofwhomhavealsodeterminedacorrespondingaro- tivarsdifferinresponsetostoragetimeandtemperature. ma using gas chromatography (GC)/mass spectroscopy (MS) olfactometry for most of the compounds detected (Jezussek, Juli- 2.Materialsandmethods ano,&Schieberle,2002;Widjaja,Craske,&Wootton,1996b;Yang, Shewfelt,Lee,&Keys,2008b;Zengetal.,2008).Asaresult,more 2.1.Samplepreparation than200volatilecompoundshavebeenidentifiedinrice(Bergman etal.,2000;Champagne,2008;Widjajaetal.,1996a,1996b;Yaj- Sevenaromatic(Table1)andtwonon-aromatic(Cocodrieand ima, Yani, Nakamura, Sakakibara, & Hayashi, 1979; Zeng et al., Wells)ricecultivarsweregrowninafieldexperimentattheDale 2008), some of which, e.g. 2-AP, 2-acetyl-pyrrole, a-pyrrolidone, Bumpers National Rice Research Center/University of Arkansas and pyridine, have been identified as enhancing the consumer RiceResearchandExtensionCenternearStuttgart,ARin 2008.A acceptability of rice, while other compounds, e.g. lipid oxidation randomised complete block design with three replications was products,suchashexanal,aceticacid,andpentanoicacid,canhave used.Plotswereharvestedastheyapproached18–22%grainmois- anegativeaffectonacceptability. ture.Theroughricewasdriedto12%moistureusingaforcedair The analysis of volatiles using solid phase microextraction drier(29.4(cid:2)C),and25gofeachsamplewasdoublebaggedinZi- (SPME)fibresinconjunctionwithGC/MShasproventobeaneffec- ploc(cid:3)freezerbagsandstoredatthreedifferenttemperatures,30, tive method since its development in the 1990s (Arthur & Paw- 4, and (cid:2)10(cid:2)C. Each sample was analysed for its volatile profile liszyn,1990). Severaldifferentcombinationsofstationaryphases priortostorageandevery30daysthereafterfor3months.Before andfilmthicknessonfibresareavailabletochoosefrom(Supelco, removing the samples from the freezer bags they were allowed Bellefonte, PA), depending on the molecular weight of the com- to equilibrate to room temperature (21–23(cid:2)C) overnight after poundsofinterest.Smallermoleculesarebetterretainedusingfi- whichtheyweredehulledandmilledto10–12%weightlossusing bres containing Carboxen (CAR) or divinylbenzene (DVB) as a aKettmill(KettElectricLaboratory,Ofa-Ku,Tokyo). stationary phase, whereas, higher molecular weight compounds desorb better from fibres which contain polydimethylsiloxane 2.2.GC–MSanalysis (PDMS)asastationaryphase.Fibrescontainingacombinationof stationaryphaseshavebeentestedandusedbyseveralinvestiga- Asampleofwholemilledricekernels(20mg)wasplacedina tors.Marsili(1999,2000)testedvariousfibresbutfoundthatthe 10ml vial; 20ll of ultra-pure (18.2MX) water containing 1ng CAR/PDMScombinationextractedmoredifferenttypesofvolatiles of 2,4,6-trimethylpyridine (TMP) (Sigma-Aldrich, St. Louis, MO) when evaluating off-flavours in milk than other fibres. The DVB/ astheinternalstandardwasadded,andthevialwassealedwith CAR/PCMS combination fibre has been used to analyse volatiles aTeflonlinedmagneticcap.Thesampleswereplacedinanauto- in rice (Grimm, Bergman, Delgado, & Bryant, 2001; Laguerre samplertray,andweremaintainedatroomtemperatureuntilana- et al., 2007; Zeng et al., 2008). This combination has been found totrapagreaterrangeofvolatilecompoundswithdifferentpolar- lysed. The samples were preheated for 5min at 80(cid:2)C prior to evaluation. A CTC Combipal SPME autosampler equipped with a ities, e.g.ketones,alcohols,aldehydes,estersand terpenichydro- heatedsampleshakerandaneedleheaterforthermalcleaningof carbons, than other fibres, which is important when analysing the SPME fibre was employed (Leap Technologies, Carrboro, NC). complexcomponents,suchasricevolatiles(Ceva-Antunes,Bizzo, Volatilecompoundswereadsorbedontoa1cm50/30divinylben- Silva,Carvalho,&Antunes,2006;Mondelloetal.,2005). zene/carboxen/polydimethylsiloxane stableflex fibre (carboxen/ DuetothesensitivityofSPME,contaminantsaregenerallyob- DVB/PDMS) (Supelco, Bellefonte, PA) using an 18min adsorption served.Themostpredominantpeaksdetectedwhenfibrescontain- periodat80(cid:2)Cwhileshakingthesample.Blankswererunfollow- ingPDMSareusedcontainingmassm/z73andm/z147,andhave ingevery5thsampleasacontrol. beenidentifiedassilylderivatives(Grimm,Champagne,&Oktsuba, Samples were desorbed for 25s on a Varian Chrompack CP- 2002;Laguerreetal.,2007;Marsili,1999).Laguerreetal.(2007)la- 3800 gas chromatograph with a Saturn 2000 mass spectrometer belledsixofthem(Si-1throughSi-6),identifyingthefirstthreeas attached (GC–MS) (Varian Analytical Instruments, Walnut Creek, hexamethyl-cyclotrisiloxane, octamethylcyclotetrasiloxane, and CA). The injector temperature was held constant at 260(cid:2)C. The decamethylcyclo-pentasiloxane,respectively.Grimmetal.(2002) GCoventemperaturewasheldfor1minat50(cid:2)C,thenincreased listedothercontaminantsidentifiedintheanalysisofricevolatiles andtheirpossiblesources. SPMEhas been reportedas a successful tool for screeningbut not for the quantification of 2-AP in fragrant rice (Grimm et al., Table1 2001).IntheGrimmetal.(2001)study,SPMEgave<0.3%recovery, Sevenaromaticcultivars,theirparentalsource,andcountryoforigin. withalargeerrorassociatedwiththeabsoluteconcentrationsof2- Aromaticcultivars Parentalcultivar(country) APinrice.Theaveragestandarddeviationwas11%withwhiterice, Aromaticse2 Basmati370(India) and20%errorwithbrownrice.Thestaticheadspacegaschroma- Dellmati Domsiah(Iran)orDella(USA) tography method developed by Sriseadka, Wongpornchai, and Dellrose Della(USA) Kitsawatpaiboon(2006)wasvalidatedforthequantitativeanalysis IAC600 Unknown(Japan) of2-AP.Widjajaetal.(1996a)foundcamphor,2-methylbenzalde- Jasmine85 KhaoDawkMali105(Thailand) hyde and butyl benzoate in Australian rice, which had not been JES KhaoDawkMali105(Thailand) Sierra Della(USA)orBasmati370(India) previously reported. Jezussek et al. (2002) found 11 compounds R.J.Bryant,A.M.McClung/FoodChemistry124(2011)501–513 503 Fig.1. Typicalchromatogramof(A)aromaticriceand(B)non-aromaticricewithoverlayofselectedions(m/z83,100%;m/z82,45%;m/z111,28%)usedforidentificationof 2-AP. to 260(cid:2)C at 5(cid:2)C/min, and then held at 260(cid:2)C for 4min. A carrier gas under a constant flow of 28.6cm/s (1ml/min), in the 30m(cid:3)0.25mm ID with a 0.25lm thickness of 5% diphenyl – splitless mode. The total GC cycle time consisted of a 47.0min 95%dimethylpolysilosanecrossbondedliquidphase(DB-5)capil- run and a 5min re-stabilisation time. The MS was operated in larycolumnwasused,withresearchgradehelium(99.999%)asthe thescanmodefromm/z40to650.Eachcompoundwasidentified 504 R.J.Bryant,A.M.McClung/FoodChemistry124(2011)501–513 bythepresenceofselectedionsandtheirratio(Fig.1),andbycom- Table2 paringtheMSspectratothereferencespectraintheNationalInsti- SiloxanederivativesdetectedusingSPMEGC/MS. tute of Standards and Technology (NIST, ver. 2.0f, 2008) mass Majorsilosane Chemicalname Retention spectral database. A typical chromatogram showing the location derivatives time of2-APandTMPisshowninFig.2a. S1 Dimethylsilanediol 3.531 Trans-2(clorovinyl)dimethylylethoxysilane 3.765 S2 Octamethylcyclotetrasiloxane 8.159 3.Resultsanddiscussion 2,5-Bis(trimethylsily)oxybenzaldehyde 11.5 S3 [[4-[1,2-bis(trimethylsilyl)oxy]ethyl]-1,2- 12.592 Althoughquantitativedatawerenotdeterminedinthisstudy, phenylene)bis(oxy)bis(trimethyl)]silane 12.651 the absence of a compound indicates that it is absent or present decamethylcyclopentasiloxane 15.399 dimethyl(dimethyl(dimethyl(2- 16 in concentrations below the detection limits. The combination of isopropylphenoxy)siolyloxy)(2- 16.439 volatilecompoundsdetectedinricepriortostoragegivesanindi- isopropylphenoxy)silane3,5-dibutoxy- 17.295 cationofthedifferencesthatmayexistintheflavourandaromaof 1,1,1,7,7,7-hexamethyl-3,5 freshly harvested rice. After storage, the presence or absence of bis(trimethylsiloxy)tetrasiloxane7-chloro-1,3- dihydro-5-phenyl-1-(trimethylsilyl)-2H,-1,4 volatilecompoundsmayreflectachangeintheflavourandaroma benzodiazepin-2-one2-[trimethylsily)amino]- duetoaging.Elevenaldehydes,15alkanes,10alkenes,10ketones, 3-[trimethysilyl)oxy]estra-1,3,5(10)-trien-17- 19 alcohols, 4 amines, 5 acids, and 19 miscellaneous compounds one wereidentified.Table3liststhecompoundsthathavebeenprevi- S4 Dodecamethylcyclohexasiloxane 17.476 ously identified and/or aromas that have been detected using a S5 Tetradecamethylcycloheptasiloxane 21.603 S6 Hexadecamethylcyclooctacilosane 25.452 sniffing port (Widjaja et al., 1996a, 1996b; Jezussek et al., 2002; S7 2,3-Bis(trimethylsilyl)oxy-estra-1,3,5(10)- 28.975 Yang et al., 2008a, 2008b). The internal standard TMP was found trien-17-one ineachsample, and2-APwas foundin allaromaticsamples,but S8 Eicosamethylcyclodecasiloxane 31.8 not in the non-aromatic cultivars (Wells and Cocodrie), as ex- pected. 2-AP gives rice a pleasant sweet popcorn flavour, which is characteristic of all aromatic rices, but is missing in non-aro- maticrice(Butteryetal.,1982). Sevenscentedcultivarswereevaluated,andnoclearpatternof AsreportedbyotherinvestigatorswhousedSPMEfibrescon- volatileprofilesemergedfortheBasmati,Della,orKhaoDawkMali taining PDMS (Grimm et al., 2002; Laguerre et al., 2007; Marsili, 105 derived cultivars(Table 4a–g). Other investigators have con- 1999),siloxanederivativescausedbythefibrewerethemostpre- ducted comparative research on both scented and non-aromatic dominantpeaks seenin thechromatogram(Fig. 2b).A list ofthe rice cultivars with similar results. Widjaja et al. (1996a, 1996b) major and minor siloxane derivatives detected in this study are comparedthevolatilecomponentsofcookedmilledricecultivars, shown in Table 2. Other contaminants were also detected in this andfoundnodifferencesinthevolatilecompoundspresent,only study, some of which have been reported by other investigators, inthequantity.Jezusseketal.(2002)comparedthevolatilecom- suchas butylatedhydroxytoluene(BHT),methoxy-phenyl-oxime, ponents of cooked brown (one non-aromatic and three scented) anddiethylphthalate(Grimmetal.,2002).Somecontaminantsab- rices,andalsofoundthatnoonecompoundorsetofcompounds sorbedfromthecontainer(e.g.plasticorclothbags)duringstorage definedacultivar,onlytheconcentration.Zengetal.(2008)com- maygivethericeanoff-flavouriftheconcentrationishighenough. paredthevolatilecompoundsofthreenon-aromaticricesatfour All93volatilecompoundswereidentifiedinthesamples;theyare differenttimesduringcooking.Theyfoundthatalthoughtheculti- showninTable3,alongwiththeirretentiontimes. varsdifferedinthepresenceoffattyacidesters,themajordiffer- Fig.2. Typicalchromatogram:(A)riceextractusingSPME/GC–MSshowingthelocationof2-APandtheinternalstandardTMP;(B)blankshowingmajorsiloxane(seeTable 2). R.J.Bryant,A.M.McClung/FoodChemistry124(2011)501–513 505 Table3 Volatilecompoundsdetectedinricecultivars.a,b Refs.c Chemicalname Aroma Retentiontime(min) Propiolonitrile 2.31 3-Dimethyl-2-(4-chlorphenyl)-thioacrylamide 2.35 X 2,5 Pentanal Woodyandfruity 2.80 1-Chloro-3-methylbutane 3.59 X 1–5 Hexanal Greentomato,green,grass-like 4.17 1-Chloro-3,5-bis(1,1-dimethylethyl)2-(2-propenyloxy)benzene 4.29 X 2,4,5 Hexanol Herbaceous 5.50 5-Methyl-2-hexanone 6.00 X+ 3 Methoxy-phenyl-oxime 6.25 X 1,2,4,5 Heptanal Fatty,rancid,fruity 6.26 Pyrolo[3,2-d]pyrimidin-2,4(1H,3H)-dione 6.42 5-Amino-3,6-dihydro-3-imino-1(2H)pyrazineacetonitrile 6.78 2-Butyl-1,2-azaborolidine 6.80 X 1,2,4,5 2-AP Popcorn,sweet,andpleasant 6.96 + 2-Chloroethylhexylesterisophthalic 7.28 2-Chloro-3-methyl-1-phenyl-1-butanone 7.90 Tetrahydro-2,2,4,4-tetramethylfuran 8.10 N,N-dinonyl-2-phenylthioethylamine 8.20 X 1,4,5 1-Octen-3-ol Mushroom 8.35 6-Methyl-5-hepten-2-one Banana-like 8.46 X 1–5 2-Pentylfuran Floral,fruit,nutty,andbean 8.61 X 1–5 Octanal Citrus,fruity,floral,andfatty 9.03 + 2-Methyl-1,3-pentanediol 9.15 2,2-Dihydroxy-1-phenyl-ethanone 9.47 X 2 2-Ethyl-1-hexanol 9.75 5-Methy-3-Hepten-2-one 10.05 X 1–5 2-Ocetenal(E) Nutty,green,andfatty 10.65 1-(1H-pyrrol-2-yl)-ethanone 10.79 3,5-Dimethyl-1-hexene 10.99 X+ 3 2-Methoxyphenol Smoky 11.45 (E)-2-Nonen-1-ol 11.93 X 1–5 (E)-2-Nonenal Beany,cucumber,fatty,woody,andtallowy 13.60 Nonene 13.90 X+ 1,2,4 Naphthalene Naphthalene 14.43 7-Chloro-4-hydroxyquinoline 14.49 O-decylhydroxamine 14.67 2-Methyldecane 14.70 2-Decen-1-ol Citrusandrose 14.90 Cyclodecanol 14.91 [(1-Methylethyl)thio]cyclohexane 14.97 4Methyl-2-pentyne 15.02 N,N-dimethylchloestan-7-amine 16.04 X 2 Benzothiazole Slightlysweet 16.53 1-Tetradecyne 16.90 X 1–5 Indole Mothball,floral,sweet,andburnt 17.42 Pentadecanal 17.70 Isobutylnonylesteroxalicacid 17.86 4-Cyclohexyl-dodecane 18.66 2-Hexyl-1-decanol 18.70 2-Butyl-1-octenal 19.30 X 2 2-Butyl-2-octenal 19.42 7-Tetradecene 19.91 Dotriacontane 20.14 + 2,4,7,9-Tetramethyl-5-decyn-4,7-diol 20.36 Z-10-pentadecen-1-ol 20.40 3-Tridecene 20.42 Octadecyne 20.50 5-Ethyl-4-methyl-2-phenyl-1,3-dioxane 21.19 6-Methyl-octadecane 21.28 6,10-Dimethyl-5,9undecadien-2-one 21.40 2,6-Bis(1,1-dimethylethyl)-2,5-cyclohexadiene-1,4-dione 21.70 2-Methyl-hexadecanal 21.90 X 5 1-Hexadecanol 22.08 17-Pentatricontene 22.42 1-Docosene 22.46 X+ 2 Butylatedhydroxytoulene 22.75 + 2,4-Bis(1,1-dimethylethyl)-phenol 22.87 n-Nonadecanol 23.02 Pentacontonal 23.03 X 2 Nonadecane 23.80 3,5-Di-tert-butyl-4-hydroxybenzaldehyde 23.99 X 2 2-Hexyl-1-octanol 24.17 2,2,4-Trimethyl-3-carboxyisopropyl,isobutylesterpentanoicacid 24.78 X+ 1,2 Diethylphthalate 24.88 (continuedonnextpage) 506 R.J.Bryant,A.M.McClung/FoodChemistry124(2011)501–513 Table3(continued) Refs.c Chemicalname Aroma Retentiontime(min) X 2 Heptadecane 25.57 1-Chloro-nonadecane 25.81 Hexadecylester,2,6-difluro-3-methylbenzoicacid 26.06 2-Butyl-1-octanol 26.10 Tritetracontane 26.20 3,5,24-Trimethyltetracontane 26.22 + Eicosanol 26.36 Decylbenzene 26.84 2-Hexadecanol 27.00 4-Acetoxypentadecane 27.04 2-Methyl-1-hexadecanol 27.09 Isobutylhexadecylesteroxalicacid 27.65 Hexylpentadecylester-sulphurousacid 28.40 Heptylcyclohexane 28.65 n-Heptadecylcyclohexane 28.72 2-Hexyl-decanol 29.46 1-Hexacosene 30.80 7,9-Di-tert-butyl-1-oxaspiro-(4,5)deca-6,9-diene-2,8-dione 31.67 a X=previouslyidentifiedcompoundsinrice. b +=Putativecontaminants. c Refs.=(1)Widjajaetal.(1996a,1996b),(2)Grimmetal.(2002),(3)Jezusseketal.(2002),(4)Yangetal.(2008a,2008b),and(5)Zengetal.(2008). Table4a Ketonesdetectedinfreshlyharvestedriceandfollowingstorage.a Ketones 5- Pyrolo[3,2- 2-Chloro-3- 6- 2,2- 5- 1-(1H- 6,10- 2,6-Bis(1,1- 7,9-Di-tert-butyl-1- Methyl- d]pyrimidin- methyl-1- Methyl- Dihydroxy- Methy- pyrrol-2- Dimethyl- dimethylethyl)- oxaspiro-(4,5)deca- 2- 2,4(1H,3H)- phenyl-1- 5- 1-phenyl- 3- yl)- 5,9 2,5- 6,9-diene,2,8-dione hexanone dione butanone hepten- ethanone hepten- ethanone undecadien- cyclohexadiene- 2-one 2-one 2-one 1,4-dione 4a-1 4a-2 4a-3 4a-4 4a-5 4a-6 4a-7 4a-8 4a-9 4a-10 Aromatic X X X X X X se2 30(cid:2)C F/S/T F S F/S/T F/S/T 4(cid:2)C F/S/T F/S/T F/S F/S/T F/S/T (cid:2)10(cid:2)C F/S/T F/S/T F/S/T F/S/T Dellmati X X X X X 30(cid:2)C F/S/T S/T S/T F/S/T S/T S/T 4(cid:2)C F/S/T F S F/S/T T F/S/T (cid:2)10(cid:2)C F/S/T F/S/T F/S/T Dellrose X X X X 30(cid:2)C F/S/T F/S/T F/S/T F/S/T F/S/T 4(cid:2)C F/S/T S/T F S/T (cid:2)10(cid:2)C F/S/T F/S/T IAC600 X X X X 30(cid:2)C F/S/T F/S S/T F/S/T 4(cid:2)C F/S/T F S/T F/S/T (cid:2)10(cid:2)C F/S/T F F/S/T F/S Jasmine X X X X X X X 85 30(cid:2)C F/S/T F/S/T F/S/T F F/S/T F/S/T F/S/T 4(cid:2)C F/S/T F F/S/T F/S/T (cid:2)10(cid:2)C F/S/T F/S/T JES X X X X X X 30(cid:2)C F/S/T T F S F/S/T S/T S/T 4(cid:2)C F/S/T F/S/T S/T (cid:2)10(cid:2)C F/S/T T F/S/T F/S/T F/S/T Sierra X X X X 30(cid:2)C F/S/T F/S/T S F/S/T S/T 4(cid:2)C F/S/T F F/S/T F/S/T (cid:2)10(cid:2)C F/S/T F/S/T F/S/T Cocodrie X X X X X X 30(cid:2)C F/S/T F/S/T F/S/T F/S/T F/S F/S/T S/T S/T 4(cid:2)C F/S/T F/S/T F/S/T F/S/T (cid:2)10(cid:2)C T F/S/T F T F/S/T S/T Wells X X X X X X 30(cid:2)C F/S/T F/S/T F F/S/T F/S/T 4(cid:2)C F/S/T F/S/T F F/S/T F/S/T (cid:2)10(cid:2)C F/S/T T F/S/T F/S/T F/T a X=priortostorage,F=firstmonth,S=secondmonth,andT=thirdmonth. R.J.Bryant,A.M.McClung/FoodChemistry124(2011)501–513 507 2-Hexyl-decanol 4b-19 X F/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TX F/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TX F/S/TF/S/T 2-Methyl-1-hexadecanol 4b-18 X F/S/T XF/S/T S/T XF/S/TF/S/T X S/T X F/S/T ol n 2-Hexadeca 4b-17 XF/S/T X F/S/T X F/S/TF/S/TX S/TF/S/T ol n #Eicosa 4b-16 X F/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TX F/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TX F/S/TF/S/T 2-Hexyl-1-octanol 4b-15 X F/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/T F/S/TS/TF/TX F/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TS/TF/S/TXF/S/TF/S/TF/S/TX F/S/T ol n n-Nonadeca 4b-14 S/T XF/S/TF/S/TF X F/S/TF/S/TXF/S/T 1-hyl)- #2,4-Bis(1,dimethyletphenol 4b-13 X F/S/TFF/S/TXF F/S/TXF/S/TF/S/TF/S/TX F/S/TF/S/TX F/S/TSF/S/TX F/S/TF/S/TXF/S/T XF/S/TF/S/TFX F/S 2-Butyloctanol 4b-12 XF/S/T X F/S/T XF/S/TS/T X F/S/TF/S/T ol n 1-Hexadeca 4b-11 X S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXSF/TF/S/TX F/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/SF/S/TXF/S/TF/S/TF/S/T n- Z-10-pentadece1-ol 4b-10 F/S/T X F/S/T XF/S/T F/S/TX F/S/T XF/S/TF/S/TF/S/TXF/S/TF/S/T S/T #2,4,7,9-Tetramethyl-5-decyn-4,7-diol 4b-9 X F/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXS/TF/S/TF/S/TX F/S/TF/S/TF/S/TXF/S/TS/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TS/TXF/S/TF/S/TF/S/T nts. nol mina Cyclodeca2-Decen-1-ol 4b-74b-8 X F/S/TF/S/T XXF/S/TF/S/TF/S/TXXF/S/TF/S/TF/S/TXF/S F/S/TX F/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/T #=putativeconta d astorage. (E)-2-Nonen-1-ol 4b-6 X F/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TX F/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TX F/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/T month;an following #2-Methoxyphenol 4b-5 F/S/T T=third freshlyharvestedriceand 2-Ethyl-#2-Methyl-1-1,3-hexanolpentanediol 4b-34b-4 XX TF/S/TF/S/TF/S/TS/TF/S/TXTF/S/TS/TTSF/S/TXS/TF/S/TS/TSTF/S/TXXS/TF/S/TF/S/TF/S/TF/S/TF/S/TX F/S/TS/TS/TS/TF/S/TXTF/S/TS/TF/S/TS/TF/S/TXTF/S/TS/TS/TF/S/TXXS/TS/TF/S/TTF/S/TXS/TF/S/T S/TF/S/T month,S=secondmonth, phenolsdetectedin Alcohols Hexanol1-Octen-3-ol 4b-14b-2 X F/S/TF/S/TSF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TFF/S/TX F/S/TF/S/TF/S/TXF/S/TTF/S/TF/S/TXF/S/TF/S/TF/S/TXXF/S/TF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/T tostorage,F=first Table4bAlcoholsand Aromaticse230C(cid:2)4C(cid:2)10C(cid:2)(cid:2)Dellmati30C(cid:2)4C(cid:2)10C(cid:2)(cid:2)Dellrose30C(cid:2)4C(cid:2)10C(cid:2)(cid:2)IAC60030C(cid:2)4C(cid:2)10C(cid:2)(cid:2)Jasmine85C30(cid:2)4C(cid:2)10C(cid:2)(cid:2)JES30C(cid:2)4C(cid:2)10C(cid:2)(cid:2)Sierra30C(cid:2)4C(cid:2)10C(cid:2)(cid:2)Cocodrie30C(cid:2)4C(cid:2)10C(cid:2)(cid:2)Wells30C(cid:2)4C(cid:2)10C(cid:2)(cid:2) aX=prior 508 R.J.Bryant,A.M.McClung/FoodChemistry124(2011)501–513 Table4c Acidsandaminesdetectedinfreshlyharvestedriceandfollowingstorage.a Acids Amines Isobutyl 2,2,4-Trimethyl-3- Hexadecylester, Isobutyl Hexylpentadecyl N,N-dinonyl- N-methoxy O-decyl N,N- nonyl carboxyisopropyl, 2,6-difluro-3- hexadecyl ester- 2-phenylthio methanamine hydroxamine dimethyl ester isobutylester methylbenzoic esteroxalic sulphurousacid ethylamine chloestan- oxalicacid pentanoicacid acid acid 7-amine 4c-1 4c-2 4c-3 4c-4 4c-5 4c-6 4c-7 4c-8 4c-9 Aromatic X X X X X se2 30(cid:2)C F/S/T F/S/T F/S/T S/T F/S/T 4(cid:2)C F/S/T F/S/T F/S/T F/S/T F/S/T S/T (cid:2)10(cid:2)C F F/S/T F/S/T F/S/T Dellmati X X X X X 30(cid:2)C F/S/T F/S/T S/T S/T 4(cid:2)C S/T F/S/T F/S/T F/S/T (cid:2)10(cid:2)C F/S/T F/S/T F/S/T F/S/T Dellrose X X X X X X 30(cid:2)C F/S/T F/S/T S/T F/S/T 4(cid:2)C F/S/T S/T F/S/T (cid:2)10(cid:2)C F/S/T F/S/T F/S/T F/S/T IAC600 X X X 30(cid:2)C S F/S/T F/S/T F/S/T 4(cid:2)C F/S/T F/S/T S/T F/S/T (cid:2)10(cid:2)C F T/S F/S/T Jasmine X X X X X X 85 30(cid:2)C F/S/T F/S/T F/S/T 4(cid:2)C F/S/T F/S/T F/S/T F/S/T (cid:2)10(cid:2)C F/S/T F/S/T F/S/T F/S/T JES X X X X X X X 30(cid:2)C F/S/T F/S/T F/S/T S/T F F/S/T 4(cid:2)C F/S/T F/S/T F/S/T F/S/T F/S/T F/S/T (cid:2)10(cid:2)C F/S/T F/S/T F/S/T F/S/T F/S/T F/S/T Sierra X X X X X 30(cid:2)C F/S/T F/S/T F/S/T F/S/T 4(cid:2)C F/S/T F/S/T S/T F/S/T (cid:2)10(cid:2)C F/S/T F/S/T F/S/T Cocodrie X X X X X X X 30(cid:2)C F/S/T F/S/T F/S/T 4(cid:2)C F/S/T F/S/T F/S/T F/S/T S/T F/S/T (cid:2)10(cid:2)C F/S/T F/S/T S/T F/S/T F/S/T F/S/T Wells X X X X X 30(cid:2)C F/S/T F/S/T F/S/T 4(cid:2)C F/S/T F/S/T F/S/T (cid:2)10(cid:2)C F/S/T F/S/T F/S/T F/S/T a X=priortostorage,F=firstmonth,S=secondmonth,T=thirdmonth;and#=putativecontaminants. encewasthetimewhichthecompoundappearedduringcooking, ketone derivatives (7) of the aromatic rices, and all of them and its concentration. In our study, the non-aromatic cultivar remained present at 30(cid:2)C, while at 4(cid:2)C only four (#4a-2, 4a-5, Cocodriewasobservedtohavethehighestnumber(69)ofvolatile 4a-7, and 4a-8) were detected, and at (cid:2)10(cid:2)C only 2 (#4a-2 and compounds, and that all but seven of these were present in the 4a-8)weredetected.However,asimilarresponsetostoragecondi- freshly harvested samples. Twelve of the 14 volatiles that have tionswasnotobservedforthesesamecompoundsinotherculti- beenassociatedwithflavours,butarenotcontaminants,werede- vars. Jasmine 85 and Cocodrie were the only two cultivars that tectedinCocodrie.Incontrast,Wellshadthefewest(51)volatile contained 5-methy-3-hepten-2-one, which was found only in compoundsofallthecultivarstested,andthefewestnumber(5) freshlyharvestedriceandafterstorageat30(cid:2)C.Allcultivarsthat ofvolatilesassociatedwithflavour.Ofthearomaticcultivars,Dell- contained6-methyl-5-hepten-2-one,alsocontained6,10-demeth- rose had the most complex volatile profile (65 compounds), and yl-5,9 undecadien-2-one, except for Dellrose. Though previously likeAromaticse2andJES,italsohadalargenumberofthevolatiles reported in rice, no aroma has been associated with 6,10- associatedwithflavour(10–11compounds). dimethyl-5,9 undecadien-2-one (Grimmet al.,2002). In the non- Similarto2-AP,ketonescangiveapleasantaroma(e.g.banana- aromatic cultivars, Wells and Cocodrie contained six and eight like,fruity,caramel-like,nutty)torice.Ofthe10ketonesdetected ketone derivatives, respectively, all of which were also found in (Table4a),#4a-2,4a-8,and4a-10werefoundinmostcultivarsand the aromatic group. 7,9-Di-tert-butyl-1-oxaspiro-(4,5)deca-6, storageconditions.Ketone#4a-4,whichisassociatedwithabana- 9-diene,2,8-dione was detected at all storage temperatures in all na-like flavour (Zeng et al., 2008), was observed in Cocodrie and cultivarsexcept Jasmine 85. 2-Chloro-3-methyl-1-phenyl-1-buta- Wells across all storage treatments, but was found only sporadi- nonewasonlydetectedinJasmine85priortostorage,andinthe cally in the aromatic cultivars. Four of the ketones (#4a-1, 4a-3, 30(cid:2)C treatment, while 5-methy-2-hexanone was unique to Dell- 4a-6, and 4a-9) were rarely detected among any of the cultivar- rose at 30(cid:2)C. These two ketones help define a distinctive profile storage combinations, suggesting that they would have little for these cultivars, but neither of these compounds have been importance in flavour. Prior to storage, Jasmine 85 had the most linkedwithflavour. R.J.Bryant,A.M.McClung/FoodChemistry124(2011)501–513 509 Table4d Aldehydesdetectedinfreshlyharvestedriceandfollowingstorage.a Aldehydes Pentanal Hexanal Heptanal Octanal 2- (E)-2- Pentadecanal 2-Butyl-1- 2-Butyl-2- 2-Methyl- Pentacontonal Ocetenal nonenal octenal octenal hexadecanal (E) 4d-1 4d-2 4d-3 4d-4 4d-5 4d-6 4d-7 4d-8 4d-9 4d-10 4d-11 Aromatic X X X X X X se2 30(cid:2)C F/S/T F/S S/T F/S/T F/S/T S/T 4(cid:2)C S F/S F/S/T F S/T (cid:2)10(cid:2)C S/T F/S/T T F/S/T F/S/T F/S/T F/S/T Dellmati X X X X X X X X 30(cid:2)C F/S/T F/S/T F/S/T F/S/T F/S/T F/S/T S/T 4(cid:2)C F/S/T S/T F/S/T S/T (cid:2)10(cid:2)C F/S/T F/S/T F/S/T F/S/T F/S/T F/S/T F/S/T Dellrose X X X X X X X X 30(cid:2)C S/T F/S/T F/S/T S/T F/S/T F/S/T F/S/T 4(cid:2)C F/S/T F/S/T F/S/T F/S/T F/S/T S/T S/T (cid:2)10(cid:2)C F/S/T F/S/T F/S/T F/S/T F/S/T F/S IAC600 X X X X 30(cid:2)C S/T F/S/T F/S/T 4(cid:2)C T F/S/T F/S/T (cid:2)10(cid:2)C T Jasmine X X X 85 30(cid:2)C F/S/T F/S/T 4(cid:2)C F/S/T F/S/T (cid:2)10(cid:2)C F F/S/T F/S/T JES X X X X X X X 30(cid:2)C F/S/T F/T S/T F/S/T F/S/T 4(cid:2)C F/S/T F/S/T F/S/T F/S/T S/T F/S/T (cid:2)10(cid:2)C F/S/T S F/S/T F/S/T F/S/T F/S/T Sierra X X 30(cid:2)C S/T S S/T F/S/T S/T 4(cid:2)C T S/T F/S/T (cid:2)10(cid:2)C F/T F/S/T F/S/T F Cocodrie X X X X X X X X X 30(cid:2)C F/S/T F/S/T F/S/T F/S/T F/S/T F/S/T F/S/T F/S/T F/S/T 4(cid:2)C F/S/T F/S/T F/S/T F/S/T F/S/T F/S/T (cid:2)10(cid:2)C F/S/T F/S F/S/T S F/S/T F/S/T F/S/T Wells X X X X X 30(cid:2)C F/S/T F/S/T S/T 4(cid:2)C F/S/T F/S/T F/S/T (cid:2)10(cid:2)C F/S/T F/S/T F/S/T F/S/T F/S/T F/S/T a X=priortostorage,F=firstmonth,S=secondmonth,andT=thirdmonth. Alcohols, phenols, and amines can give a pleasant aroma like tions were observed to possess acids #4c-2, 4c-3, and 4c-4 and sweet, floral, or fruity to rice. Of the 19 alcohol derivatives de- theamine#4c-8(Table4c).Acid#4c-1wasfoundinallcultivars tected, five are believed to be contaminants (#4b-3, 4b-5, 4b-9, except Sierra, whereas acid #4c-5 was unique to Aromatic se2. 4b-13,and4b-16)(Table4b).Elevenwerecommonlyfoundinboth JES was the only cultivar to possess all four amines, and it was scentedandnon-aromaticcultivars,suggestingthattheymaynot the only one where N-methoxy methanamine was detected. Of be useful in distinguishing among cultivars. The most alcohols thefouraminesmeasured,IAC600andWellscontainedonlyO-de- (17) were observed in samples of JES, whereas, the fewest (11) cylhydroxamine. were detected in Wells. Hexanols (#4b-1) which are associated Aldehydes,alkanes,andalkenes,whichareassociatedwithlipid withagreenorgrass-likeflavourwerefoundinallbuttwosam- breakdownproductscanbelinkedwithflavourslikegrassy,fatty, ples,and#4b-3,whichisnotassociatedwithaflavourandisre- andsoapy(Table4d–f).However,dependingontheconcentrations ported as a contaminant, was detected in all cultivars generally ofthesecompounds,theymayhaveapleasantorobjectionablear- after two or more months of storage. Of the seven alcohols that oma.Generally,themorelipidbreakdownproducts,themorelikely wereuncommon,#4b-5,4b-7,4b-14,and4b-17wereonlyfound thericeistohavearancidodourandoff-flavour.Thepresenceof inaromatics.IAC600wastheonlycultivartopossess#4b-5,which hexanal has been used to determine off-flavour in rice (Bergman isassociatedwithasmokyflavour,butthiswasobservedonlyun- etal., 2000; Wongpornchai etal., 2004). Of the11 aldehydesde- der(cid:2)10(cid:2)Cstorageconditions.TheDellmatiandDellrosesamples tected,#4d-2,4d-4,4d-6,4d-7,and4d-10werecommonlyfound, that were freshly harvested and then stored under low tempera- andsix(#4d-1,4d-2,4d-3,4d-4,4d-5,and4d-6,)wereassociated tures, contained 2-decen-1-ol, which has a citrus or rose aroma. withflavours(Table4d).Infreshlyharvestedrice,octanalwasde- 1-Octen-3-ol (#4b-2), which is linked with a raw mushroom fla- tectedinallcultivarsandhexanalwasdetectedinallexceptSierra vour, was found in two scented cultivars, the Aromatic se2 and indicating that lipid breakdown products are produced quickly JES, but only when stored for 2months at 4(cid:2)C and 3months at after harvest. 2-Ocetenal (E), associated with a nutty, fatty, or 30(cid:2)C, respectively, and also in Cocodrie, prior to, and following grassyflavour,andpentacontonalweredetectedonlyinCocodrie, storage for 3months at 30(cid:2)C. Most cultivars and storage condi- Dellrose, and Wells. Cocodrie contained the highest number (10) 510 R.J.Bryant,A.M.McClung/FoodChemistry124(2011)501–513 y- n-Heptadecylcclohexane 4e-15 X F/S/TF/S/TXF/S/T XS/TF/S/T ne xa he o ycl Heptylc 4e-14 XF/S/T XF/S/T XF/S/T X F/S/T ne deca nta pe y 4-Acetox 4e-13 X F/S/T XF/S/TF/S/T S ne 3,5,24-Trimethyltetraconta 4e-12 X F/S/TF/S/TXF/S/TF/S/T XF/S/TF/S/T XF/S/TF/S/TF/S/TX F/S/TXF/S/T FXF/S/T X F/S/T ne nta o Tritetrac 4e-11 X F/S/T XF/S/TF/S/TF/S/TXF/S/T X F/S/T XF/S/T F/S/T XF/S/TF/S/T ne 1-Chloro-nonadeca 4e-10 XF/S/T X F/S/T ne deca Hepta 4e-9 X F/S/TF/S/T S/T X F/S/TF/S/T S/TF/S/T F/S/T X F/S/TF/S/TXF/S XF/S/TF/S/T XF/S/TF/S/TF/S/T ne deca Nona 4e-8 X F/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TX F/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TXF/S/TF/S/TF/S/TX F/S/TF/S/TX F/S/T 6-Methyl-octadecane 4e-7 F/T XF/S/TF/S/TF/S/T S/T X F/S/T 5-Ethyl-4-methyl-2-phenyl-1,3-dioxane 4e-6 X F/S/TS/TF/S/T S/TT XF/S/TT TTS/T TT XTF/S/T TTF/TXTF/S/T TF/T ne nta Dotriaco 4e-5 X F/S/T XF/S/T F/S/T XF/TF/S/T X F/S/T F/S/TX F/S/T XF/S/T XF/S/T XF/S/TF/S/T dmonth. Table4eaAlkanesdetectedinfreshlyharvestedriceandfollowingstorage. Alkanes 1-4-[(1-2-Chloro-Cyclohexyl-Methylethyl)thio]Methyl3-dodecanecyclohexanedecanemethylbutane 4e-14e-24e-34e-4 AromaticXXse230CSF/S/TF/S/T(cid:2)4CF/SF/S/TS/T(cid:2)10CF/S/TF/S/TF/S/T(cid:2)(cid:2)DellmatiXX30CF/S/T(cid:2)4CF/S/TF/S/T(cid:2)10CFF/S/T(cid:2)(cid:2)DellroseXX30CF/S/TS(cid:2)4CS/T(cid:2)10CF/S/TF/S/T(cid:2)(cid:2)IAC60030CS/T(cid:2)4C(cid:2)10CF/S/TF(cid:2)(cid:2)Jasmine8530CF/T(cid:2)4C(cid:2)10C(cid:2)(cid:2)JES30CS/T(cid:2)4C(cid:2)10C(cid:2)(cid:2)SierraX30CSF/S/TS/T(cid:2)4CTS/T(cid:2)10CF/T(cid:2)(cid:2)CocodrieXX30CF/S/TF/S/T(cid:2)4C(cid:2)10CF/S/T(cid:2)(cid:2)WellsXX30CF/TF/S/T(cid:2)4CF/S/T(cid:2)10CF/S/T(cid:2)(cid:2) aX=priortostorage,F=firstmonth,S=secondmonth,andT=thir
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