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CollegeofEnology,NWSUAF2葡萄的成熟与采收《葡萄酒工艺学》教学大纲规定：本章主要讲述葡萄浆果的各种成分及其在成熟过程中的变化以及与酒质的关系。要求学生建立“潜在质量”、“优良品种”以及“品种结构”、“品种适应性、特异性”、和“成熟系数”的概念，深刻理解葡萄是葡萄酒的物质基础，掌握确定最佳采收期的原则和方法。教学重点和难点：葡萄浆果与酒质的关系，最佳采收期的确定。CollegeofEnology,NWSUAF2.1葡萄浆果的成熟(p20)•葡萄酒只能是新鲜葡萄果实或葡萄汁经完全或部分酒精发酵后获得的饮料（P15）。葡萄浆果的质量（成熟度）决定着葡萄酒的质量和种类，是影响葡萄酒生产的主要因素之一。•好的产区是指能生产成熟度良好的葡萄，从而才能生产品质优良的葡萄酒的产区；好的年份也是指夏天的气候条件有利于葡萄果实充分成熟的年份。•可通过控制葡萄的成熟度控制葡萄酒的质量和种类。如在气候较为炎热的地区，由于葡萄果实成熟很快，为了获得平衡、清爽的葡萄酒，应尽量避免葡萄过熟；在有的产区，根据采收时期的早迟，既可生产具有一定酸度、果香味浓的干白葡萄酒，也可生产酸度较低、醇厚饱满的红葡萄酒或具有一定残糖的葡萄酒。CollegeofEnology,NWSUAF2.1葡萄浆果的成熟(p41)因此，了解葡萄果实的成熟和果实中的成分及其在成熟过程中的变化，即葡萄浆果的生物化学，并根据需要进行控制，是保证葡萄酒质量的第一步。•2.1.1葡萄浆果成熟的不同阶段•2.1.2葡萄浆果中的主要成分•2.1.3葡萄浆果主要成分的变化CollegeofEnology,NWSUAF2.1.1葡萄浆果成熟的不同阶段(p41)葡萄浆果从座果开始至完全成熟，需要经历幼果期、转色期、成熟期、过熟期等不同的阶段(图2-12)。CollegeofEnology,NWSUAF葡萄酒工艺学主讲王华幼果期幼果期的持续时间从座果开始，到转色期结束。在这一时期，幼果迅速膨大，并保持绿色，质地坚硬。糖开始在幼果中出现，但其含量不超过10～20g/L。酸的含量迅速增加，并在接近转色期时达到最大值，约24g(酒石酸)/L。见图2－13（P43）CollegeofEnology,NWSUAF葡萄酒工艺学主讲王华转色期转色期就是葡萄浆果着色的时期。在这一时期，浆果不再膨大。颜色：果皮叶绿素大量分解，白品种果色变浅，丧失绿色，呈微透明状；有色品种果皮开始积累色素，由绿色逐渐转为红色、深蓝色等。糖：浆果含糖量直线上升，由20g/L上升到100g/L。酸：含酸量开始下降。CollegeofEnology,NWSUAF葡萄酒工艺学主讲王华成熟期从转色期结束到浆果成熟，大约需35～50天。在此期间，浆果再次膨大，逐渐达到品种固有大小和色泽，果汁含酸量迅速降低，含糖量增高，其增加速度可达每天4～5g/L。浆果达到生理成熟。所谓生理成熟（P42）,即浆果含糖量达到最大值，果粒也达到最大直径时的成熟度。CollegeofEnology,NWSUAF过熟期在浆果成熟以后，果实与植株其它部分的物质交换基本停止。果实的相对含糖量可以由于水分的蒸发而提高(果汁浓度增大)，浆果进入过熟期。过熟作用可以提高果汁中糖的浓度，这对于酿造高酒度、高糖度的葡萄酒是必须的。CollegeofEnology,NWSUAF2.1.1葡萄浆果成熟的不同阶段BerryDevelopmentandRipeningThewinemakerisdirectlyconcernedwiththeripeningoftheberries,particularlyinthelatestages.Theperiodfromberrysettoveraison(onsetofripening)islesssubjecttoproblemssuchasovercropping,becausethetinyberries,althoughnumerous,arelesstotalconsumersofphotosynthatethantheybecomeasripeningandrapidsugaraccumulationbegins.CollegeofEnology,NWSUAF2.1.1葡萄浆果成熟的不同阶段BerryDevelopmentandRipeningNevertheless,considerablegrowthtakesplaceduringthisearlyperiod.Berrysizeincreasesbutpulpcompositionremainsrelativelyconstantespeciallyintermsofhighacidandlowsugarconcentration.Initialberrysizeincreaseismostlyfromcellmultiplicationfollowedsoonbybothcellenlargementandcellmultiplication.Inthefinalstagesberryenlargementisexclusivelyfromcellenlargement(Staudtetal.1986).CollegeofEnology,NWSUAF葡萄酒工艺学主讲王华BerryDevelopmentandRipeningFigure2-2p36Figure2-2showsatypicalexampleofthiscurve.ThesedataarefromTokay,alarger-berry,lower-sugar,tablegrape,butaretypical.CollegeofEnology,NWSUAF葡萄酒工艺学主讲王华2.1.1葡萄浆果成熟的不同阶段BerryDevelopmentandRipeningTwoperiodsofrapidvolumeincreaseareseparatedbyashortslowerlagperiod.Thefirstrapidenlargementpriortoveraisoninvolvesgrowthfromperhaps50mgtoabout1gforatypicalwinegrapegivinga20-foldincrease.Thesecondrapidgrowthperiodproducedonlyanotherdoublingorso,buttheamountofincreasedfreshweightisequivalenttoorgreaterthanthewholepreviousperiod.Furthermorethemoisturecontentishigherinthefirststagewithnearlyallthesugaraccumulationinthelaterone.Thereforedryweightincreaseismuchgreaterlate.Moisturestresscanaffectthefirstenlargementstageespeciallystrongly.CollegeofEnology,NWSUAFTheintermediatelagperiod_VeraisonTheintermediatelagperiodmarksthetransitionfromgrowingtoripening(Figure2-2).Veraison,theonsetofripening,markstheresumptionofrapidenlargementandcoincideswiththebeginningofcolorchanges(lossofchlorophyllandproductionofanthocyaninsinredvarieties)andsugaraccumulation.Veraisonisanabruptchangeinaberry,butvariesalittlewithinaclusterandincreasinglyoverthevine,thevineyard,andthearea.CollegeofEnology,NWSUAFTheintermediatelagperiod_VeraisonVeraisonisconsideredtofollowthecompletionofdevelopmentofviableseeds.Withseedmaturitypresumablyassured(butatasimilarstageforseedlessvarieties),thevineisfreetomaketheberryasattractiveaspossibleforbirdsandotherpotentialseeddispersers.Desirableripenessistheculminationoftheproductionofmoreattractiveodorsandflavorsbegunatveraison.Highsugar,loweracid,richcolor,andfullvarietalfruitinessarecriteriaforharvestingtheripefruit.CollegeofEnology,NWSUAFFruitmaturityAtnormalfruitmaturity,enlargementceasesandphysiologicalaccumulationofsugarceasesatabout25Brix(Singletonetal.1966a)inwinegrapes.FurtherincreaseintheBrixofthejuiceistheresultofwaterlosswhichdecreasesberryvolumeandturgor,eventuallyleadingtoraisining.Shrivelingoftheberriesisordinarilyundesirableespeciallyfortablewines,sincelossormodificationofflavorandcolorarelikely.Inovercroppedberrieswithinadequatesugar,concentrationwilloccur,butthisisapoorwaytocompensateforovercropping.CollegeofEnology,NWSUAFLate-harvestedtablewinesAfewspecialtylate-harvestedtablewinesmakeuseofshrivelingtogetmustsugarcontentsohighthatthewinesremainsweetafterfermentation.Inthesecases,infectionbythesocallednoblemold,Botrytiscinerea,isarequired,desirablefactor.Anappropriateweathercycleofsufficienthumidityforinfectionfollowedbydryingconditionsisneeded.TheBotrytisinfectionmakestheberryskinpermeabletorapidwaterlossanddehydrationconcentratesthesugarto30%ormore.Owingtoredcolorlossviaoxidationbythemold'senzymelaccase,theprocessisnotsuitableforredwines.CollegeofEnology,NWSUAF2.1.2葡萄浆果中的主要成分及其变化一穗葡萄浆果包括果梗和果粒两个部分(图