lecture 3: the harvesting decision: viticulture from the winemaker’s perspective

Lecture 3:

The Harvesting Decision:

Viticulture from the Winemaker’s Perspective

Reading Assignment:

Text, Chapter 2, pages 52-64

The Winemaker’s Perspective

• Grapes must be harvested at the ideal time for the style of wine desired to be made

• Characters of the finished wine will be largely dictated by the composition of the fruit at harvest

• Goal: to have the ideal composition at time of harvest

Berry Ripening:Acids

Time

Con

cent

ratio

nMalate

Tartrate

Veraison

Berry Ripening:

Sugars

Time

Con

cent

ratio

n

Net synthesis

Dehydration

Synthesis stops

Berry Ripening:

Arginine

Time

Con

cent

ratio

nThought to signal deterioration of fruit

Berry Ripening:Evolution of berry flavors in red grapes

Vegetation Herbaceous Unripe Fruit

Red Fruit Black Fruit Jam

Vegetation: Plant matter

Herbaceous: Straw, Vegetable

Unripe Fruit: Green apple, Citrus rind

Red Fruit: Cherry, Strawberry, Raspberry

Black Fruit: Plum, Black Cherry, Blackberry

Jam: Prune, Date, Raisin

Stems:

Unripe: Green = vegetal, leafy

Ripe: Brown = resinous wood, spices: clove,

pepper, cinnamon

Over-ripe: Brittle Brown: Dried leaf, tea, herbal

Decision to Harvest

• Berry compositional factors

• Berry physical traits

• Non-berry factors

Berry Compositional Factors

• Sugar: ranges from 19-26 Brix– Depends upon style of wine– Maturity of flavors– 1.7% sugar 1% ethanol


• Sugar

• pH: 3.0-3.8– Affects solubility of tartrates and

proteins– Affects microbial populations


• Sugars

• pH

• Acids: – Contribute Sourness and Tartness– Titratable Acidity: Whites (0.7-0.9 g/L)

Reds (0.6-0.8 g/L)

Wine Acidity

Total Acidity: Sum of anionic species

Titratable Acidity: Amount of base needed to reach a specific end

point

Fixed Acidity: Not distillable

Volatile Acidity: Distillable (acetic acid)


• Sugar• pH• Acids• Balance of sugar and acidity

– Brix/TA = 30 or less, depending . . .• 22 Brix/ 0.8 TA= 27.5

– (Brix)(pH)2 = 220-260, depending . . .• (22 Brix)(3.2)2 = 225.3


• Sugar

• pH

• Acids

• Balance of sugar and acidity

• Ratio of malate to tartrate


• Sugar

• pH

• Acids



• Arginine levels


• Sugar

• pH

• Acids



• Arginine levels

• Taste


• Sugar• pH• Acids• Balance of sugar and acidity• Arginine• Ratio of malate to tartrate• Taste• Phenolics/Anthocyanin levels

Berry Compositional Factors• Sugar• pH• Acids• Balance of sugar and acidity• Arginine levels• Ratio of malate to tartrate• Taste• Phenolics/Anthocyanin levels• Terpene content

Terpene content

• Measure terpenes directly

• Measure free/bound terpenes

• Measure all bound aromatic precursors (GG) analysis

Berry/Cluster Physical Traits

• Berry firmness and deformability

• Seed characteristics– Color– Integrity

• Stem characteristics– Color– Integrity

Non-Berry Factors

• Environmental factors

Environmental Factors

• Rain

• Humidity

• Temperature

• Disease Pressure

Non-Berry Factors

• Environmental Factors

• Tank capacity/limitation

Non-Berry Factors



• Labor availability

Non-Berry Factors



• Labor availability

• Fruit availability

Which factors are most important in the decision to harvest will vary with the wine style, the winemaker, and the vintage

Sampling the Vineyard

• Need to obtain an unbiased representation of the entire crop– How uniform is the vineyard?

• Soil• Climate• Elevation

– How uniform are vineyard treatments?

• Sampling protocol should lead to a statistically significant evaluation

Types of Sampling

• Berry: 100-200 berries randomly picked

• Cluster: 20-50 clusters also randomly chosen

• Cluster/Berry: remove all berries from clusters; randomly select 200 berry lots

• Vine: select typical vine and sample all clusters

Berry sampling is most robust statistically but more susceptible to harvester bias than cluster or vine sampling

Harvesting Conditions

Once the decision has been made that it is time to harvest, the winemaker/vineyard manager must then decide how the fruit is to be harvested

Harvesting Options

• Temperature

• Machine

• Hand

Temperature of Harvest

• Lower temperature: – Less flavor loss– Less extraction from skins– Less microbial activity

• Elevated temperature:– More extraction– Initiate fermentation earlier

Machine Harvesting• Faster• Cheaper• Can be done day or night• Less gentle• Mixture of “good” and “bad” clusters• More “MOG” (material other than grapes)• Berries can be crushed

– Juice loss– Oxidation– Microbial Growth

Hand Harvesting

• Slower

• More labor intensive

• More expensive

• More selective of clusters

• Less MOG

• Lower yield

This concludes the first section on viticulture for winemakers. The next section will cover juice and must treatments and processing decisions.

lecture 3: the harvesting decision: viticulture from the winemaker’s perspective

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