StudentLectureNotesLecture16-WineGrapeQuality–WhenisitTime
toPick?Slide1WineGrapeQuality:WhenisIttimetoPick?Wine
qualitydependentongrapequalityatharvestGrapesshouldbema
tureorripebutnotbeyondSlide2Measurements:Quantitative,Tabl
e16.1Solublesolids,titratableacidity,pH,anthocyanins,volat
ilesVisualColor,fruitintegrity,seedcoatcolor,peduncleligni
ficationSlide3Practical/economicLabortopick,impendingweathe
r,vineyardcondition,tankspace,latepesticideapplicationsSli
de4Phenology:Developmentalgrowthstages,Figure16.1Vegetative
cycletakesoneyearReproductivecycletakes14to16monthsSlide
5KeydevelopmentalgrowthstagesBudburst,bloom,bunchclosure,
veraison,harvest,leaffallFigures16.2and16.3Slide6Berrygr
owthanddevelopment:Threestagesrepresentedbyadouble-sigmoid
curve,Figure16.41st–berryformationthroughcelldivisionan
dtissuedifferentiationSlide72nd–lagphaseiswhereseedsmat
ure,endpointiswhereseedsharden,Figure16.53rd–berryripen
ingthroughcellenlargement,waterandsugaraccumulationSlide8
Seednumber(1-4)importanttoberrysizeCultivatedvarietiesvar
yinberrysizeatharvestSlide9Physiologicaleventsthatstart
atveraison,thebeginningofripeningColoring,softening,sugar
accumulation,berryenlargement,aciditydecrease,pHandaminoa
cidsincreaseSlide10Berriesareastrong‘sink’forcarbohydrate
sorsugarsSizeincreaseupto400%Flavordevelopment,calledeng
ustment,occurslateinberryripening,becomesthevarietalflav
orandaromaSlide11Berrycomposition:Water–70to80%Sugar–17
to26%,glucoseandfructose,convertedtoalcoholinfermentati
on,measuredassolublesolidsconcentration(%or°Brix)Acidity
–5to9g/L,tartaricandmalic,measuredbytitrationwithaba
seSlide12pH–2.8to3.7,measurewithpHmeterPhenolics–antho
cyanins,tannins,flavanolsFlavor(taste)andaroma(smell)compo
undsFermentationNitrogencompoundsVitaminsSlide13Mesoandmicro-
climateinfluenceonberryripeningAirtemperatureandsunlighte
xposureBothcauseberry‘heating’orwarmingCoolclimates–benef
icialWarmclimates–detrimentalSlide14Waterhasgoodandbadef
fectsNeededforvineandfruitgrowthExcessnearharvestdetrimen
talDilutessugar,flavor,andaromaSlide15Samplingforfruitmat
urityorripening7to10daysamplingover3-weekperiodleading-
uptoharvest200berrysampletakenfrom:Clustersthroughthecan
opyBerriesfromtop,middle,bottom,frontandbackofclustersSl
ide16CrushberriesthoroughlySettleanddecantjuiceMeasuresolu
blesolids,titratableacidity,pHTanninandvarietalflavorWorkcloselywithwinerypeopletotrackjuicevaluesanddecideonharvest1 |
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