Q.Zhangetal./FoodChemistry179(2015)15–2523Fig.3(continued)Hence,extractiontimeof50minwasselectedasthecenterpointforfurtherexperiment.3.5.Model?ttingandoptimizationforextractionofresveratrol3.5.1.Model?ttingTheexperimentaldatawasanalyzedaccordingtopreviousreportedmethods(Guo,Zou,&Sun,2010;Jiangetal.,2011).Thecorrelationbetweenresponsevariablesandtestvariables(theextractionratioofresveratrol)associatedwiththefollowingsec-ond-orderpolynomialequation:Y?à17:43308t0:48687X1t111:69417X2t0:29284X3t0:091158X4à0:12X1X2t0:00055X1X3à0:00011X1X4à0:96250X2X3à0:0325X2X42t0:0000725X3X4à0:0051346X21à801:16667X22à0:016998X23à0:000874917X4thatthemodelwashighlysigni?cant.Therewasonlya0.01%chancethatamodelF-valuecouldoccurduetonoise.Thedetermi-nationcoef?cientR2ofthemodelwas0.9854,indicatingthat98.54%ofthevariabilityintheresponsecouldbeexplainedbythemodel.Inaddition,theP-valueofP=0.1259forlack-of-?timpliedthelack-of-?twasnotsigni?cantrelativetothepureerror,indicatingthemodelequationwasadequatetopredicttheextrac-tionratioofresveratrolwithintherangeofexperimentalvariables.Thesigni?canceoftheregressioncoef?cientswastestedbyF-test,andthecorrespondingP-valuesforthemodeltermsarealsolistedinTable2.TheP-valueisusedasatooltocheckthesigni?canceofeachcoef?cient,whichinturnmayindicatethepatternoftheinteractionbetweenthevariables.ThesmallertheP-valueis,themoresigni?cantthecorrespondingcoef?cientis.Accordingly,X1,222X3,X4,X2X3,X21,X2,X3andX4weresigni?cant(P<0.05),whileX2,X1X2,X1X3,X1X4,X2X4,X3X4werenotsigni?cant(P>0.05).e5TwhereYrepresentstheextractionratioofresveratrol,andX1,X2,X3andX4representextractiontemperature,CaOtorawmaterialratio,watertorawmaterialratioandextractiontime,respectively.TheresultsofANOVA,lack-of-?tandtheadequacyofthemodelaresummarizedinTable2.ThemodelF-valueof65.7847implied3.5.2.OptimizationforextractionofresveratrolProcessvariablesandexperimentaldataareshowninTable1.Inordertobetterunderstandtheinteractionsofthevariables,theresponsesurfaceplotsandcontourplotsforthemodelwereproducedbytheStat-EaseDesign-Expertsoftware.Theshapesofthecontourplots,circularorelliptical,indicatewhetherthe24Q.Zhangetal./FoodChemistry179(2015)15–25Table3

ThecomparisonofMSCEandSPEundertheoptimalconditions.MethodEvaluationindexesAmountofpotAmountofsamples(kg)Extractiontemperature(°C)Timeconsumption(min/kg)Solventconsumption(L/kg)CaOconsumption(kg/kg)Extractionratio(%)MSCE42047b41.6aSPE4206051.5a,bDesignateasigni?cantdifferences.aP<0.05comparedwithSPE.bP<0.01comparedwiththeSPE.mutualinteractionsbetweenvariablesaresigni?cantornot(Xiong,Li,etal.,2014;Xiong,Zhang,etal.,2014).Acircularcon-tourplotindicatesthattheinteractionbetweenrelatedvariablesisnegligible,whileanellipticalcontourplotindicatesthattheinteractionbetweenrelatedvariablesissigni?cant(Muralidhar,Chirumamila,Marchant,&Nigam,2001;Zhang,Li,Xiong,Jiang,&Lai,2013).TheresponsesurfaceplotsandcontourplotsasshowninFig.3weregeneratedusingDesign-Expert,whichdepictedtheinteractionsbetweentwovariablesbykeepingtheothervariablesattheirzerolevelsforextractionratioofresveratrol.Itwasevidentthatthesethree-dimensionalplotsandtheircorrespondingcon-tourplotsprovidedavisualinterpretationoftheinteractionfortwovariablesandfacilitatedthelocationofoptimumexperimentalconditions.ByusingthesoftwareDesign-Expert,thesolvedopti-mumvaluesofthetestedvariablesfortheextractionofresveratrolwereextractiontemperatureof46.6°C,CaOtorawmaterialratioof6:100,watertorawmaterialratioof8.8:1andextractiontimeof51.7min.Undertheoptimalconditions,themaximumpredictedextractionratioofresveratrolwas0.903%,whichcorrespondedfairlywelltothatofrealextraction(0.897±0.035%,n=3).Theresultsuggestedthattheregressionmodelwasaccurateandade-quateforthepredictionofresveratrolextraction.3.6.ComparisonofMSCEandSPEAsdescribedabove,MSCEwascarriedoutbycreatingaconcen-trationdifferencebetweenthesolventandsolidsamples.IntheMSCEprocess,theconcentrationofresveratrolwasdynamicgradi-entcourseandenhancedcontinuouslyinfourextractionunitsbystages.Ithasbeenreportedthatmasstransferfromthesamplesurfacetotheliquidphaseisresultedmainlyfromthediffusionfromoneregiontoanotherregionofdifferentconcentrations(Geller&Hunt,1993;J?nsson,L?vkvist,Audunsson,&Nilvé,1993).OnthebasisofFick’s?rstlawforsteady-stateconditionstates,themasstransfer?uxbyordinarymoleculardiffusionisequaltotheproductofthediffusioncoef?cient(diffusivity)andthenegativediffusionwiththeconcentrationgradientincreased(Docˇekalová&Divi?,2005;Straub,Graue,Heitmeir,Nebendahl,&Wurst,1987;Ujihara,Fujiwara,Sazaki,Usami,&Nakajima,2002).Therefore,MSCEcouldgreatlyfacilitatemasstransferbetweenimmisciblephasesthroughtheincreaseofthedrivingforce,resultinhigherextractionef?ciency.InordertoevaluatetheadvantagesanddisadvantagesofMSCE,acomparisonofMSCEandSPEwasperformedbasedonthedifferenceofextractiontem-perature,extractionratio,consumptionoftime,andconsumptionofsolventandCaO,withsamesamples,solventandCaO.TheexperimentalresultwasshowninTable3.AlthoughtheextractionratioofresveratrolfromMSCEwasslightlylowerthanthatofSPEoperationwithinsigni?cantdifference(P>0.05),MSCEofferedoverwhelmingadvantageswithrespecttoextractiontemperature,extractiontime,andconsumptionofsolventandCaO.Forthesameweightofsamples,MSCEwascompleteinaboutfour-?fthofextractiontime,usinghalftheamountofCaOandonethirdof8.8b0.06b0.897±0.03524.00.150.908±0.041theamountofsolventrelativetoSPE.Moreover,theSPEtechniquehadtheextractiontemperatureof60°ChigherthanMSCEprocess.ThismayduetoafterheatandredundantCaOofpreviousunitswerereusedalongwithcountercurrentoperationofthesolventintheMSCEprocess.ThesefactsindicatedthatSPEneedslongerextractiontime,higherextractiontemperature,andmoreextractionsolventsandCaOtoobtaintheequivalentamountofresveratrolrelativetoMSCE.HigherconsumptionofsolventandCaO,meaninglowerres-veratrolconcentrationandmoreCaOresiduesinextractionsolu-tion,wouldinevitablyresultinmoreenergyandacidcostforthesubsequentconcentrationandacidicprecipitationprocess.There-fore,MSCEisatime-saving,energy-saving,andcost-savingextrac-tiontechnologyformanufacturingextractionofresveratrolfrompeanutsprouts.4.ConclusionsBasedonsingle-factorexperiments,BBDwasemployedtodeterminetheoptimalparametersforextractionofresveratrolinthispaper.Throughoptimization,theoptimizedconditionsweregainedasfollows:extractiontemperatureof46.6°C,CaOtorawmaterialratioof6:100,watertorawmaterialratioof8.8:1andextractiontimeof51.7min.Undertheseconditions,theextractionratioofresveratrolwas0.897±0.035%,whichwasclosetothepre-dictedvalue(0.903%).ComparedwithSPE,MSCEwasfaster,workedatlowertemperatures,andconsumedlesssolventandCaO,whichgivesMSCEanoverwhelmingadvantagefortheextrac-tionofresveratrolfrompeanutsprouts.AcknowledgementsThisworkwaspartlysupportedbytheNationalNaturalScienceFoundationofChina(No.81460435),KeyProjectsofAppliedbasicResearchofYunnanProvince(No.2014FA022),ProjectsofApplica-tionandTechnologyResearch(Agriculture)ofHuaian(No.HAN2014026)andOpenFundProjectofJiangsuProvincialEngi-neeringLaboratoryforBiomassConversionandProcessIntegration(No.JPELBCPL2013008).ReferencesAlexandre,M.,&Dubois,P.(2000).Polymer-layeredsilicatenanocomposites:Preparation,propertiesandusesofanewclassofmaterials.MaterialsScienceandEngineering:R:Rep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