Grape Berry Flashcards
What are the four steps of ripening?
Herbaceous phase
Veraison
Maturation
Sur-maturation
At which point in ripening do many of the desirable flavour compounds accumulate in the grape?
Just after the increase in sugar formation slows down; max reached then decline during sur-maturation
What are the main constituents of grapevine berry juice?
Water (80%)
Sugars and other carbs (20%)
Acids (1%)
Phenolic compounds (0.1%)
What mineral salts are present in grapevine berry juice and what do they do?
Mainly potassium and calcium salt
Buffer (mask) effect of acids
What is the effect of pectins?
High concentrations make it difficult to extract and.or clarify grape juice; broken down by pectolytic enzymes during grape processing
Gemurztraminer and Viognier are high in pectins
What are the main acids in grapes?
Tartaric and malic
Can also contain low levels of citric, ascorbic and acetic acids
What types of grapes may have high malic acid?
Those picked early or ripened in very cool conditions
What are phenolic compounds?
Group of chemical compounds that affect a wine’s colour, texture, astringency and bitterness
What are anthocyanins?
Phenolic compounds the give red wine colour
Found in pulp directly underneath skins of black grapes
What are tannins?
Large phenolic compounds that determine body and astringency of wine
Antioxidant, preservative
Precursor to aromatic compounds when wines are aged
What affects the chemical composition of grapes?
Grape variety
Environment: climate, soil
Viticultural management
Seasonal variation
What is the herbaceous phase?
From formation of berry until veraison
What is veraison?
Marks beginning of berry ripening when grapes change color
Berry stops photosynthesizing (all sugars that accumulate after are photosynthesized by the leaves)
What is maturation?
Grapes swell, sugar concentration increases, acidity decreases
Lasts for 40-60 days
At physiological maturity berries attain max diameter and sugar
What is sur-maturation?
When berries are left on vine and become over-ripe
What are the main criteria when selecting vines?
Adaptation to climate
Resistance to disease
Adaptation to soil conditions
Economic characteristics
What are American hybrids bred with vitis vinifera?
Concord, Black Hamburg, Clinton
What is the group name “teinturier”?
Grape varieties that give deep red juice on pressing because they have anthocyanins in pulp as well as skin (e.g., Alicante Bouschet–cross between Petit Bouschet and Grenache)
What is Petit Bouschet?
Cross between Aramon and Teinturier
What is mass selection?
Traditional method of selecting vines
Passing through vineyard before harvest and marking out best plants from which to take cuttings during the winter
What is clonal selection?
Selecting plants originating from a single parent with desirable qualities
What is layering?
Vine canes are buried in the ground then separated from parent once they establish their own roots
Used in Argentina and in Champagne for Bollinger’s “Vieilles Vignes Francaises”
What is vitis vinifera sativa?
Vitis vinifera subdivision
Cultivate vine with 5-10,000 wine-producing varieties (including all classics)
Selected to be hermaphroditic for good fruit set and for relatively large fruit
What is vitis vinifera silvestris
Vitis vinifera subdivision
Wile European vines
Not usually hermaphrodite
Mostly eliminated by phylloxera
What is vitis labrusca?
Wild vine species found in north eastern US
Produces strongly flavoured, dark berries; described as “foxy”
Common parent in American hybrids (Conford)
Not often used as parent for rootstock production
What is vitis riparia?
Wild vine species on river banks and alluvial soil in central-eastern parts of North America
Used principally as a rootstock
Low vigour, surface rooting, encourages early ripening, good resistance to phylloxera, suffer from chlorosis in chalky soil
What is vitis rupestris?
Wild vine in light soils in southern center US
Used primarily as rootstock
Vigorous, deep rooting, good resistance to phylloxera, suffer from chlorosis
What is vitis berlandieri?
Wild vine on chalky slops in southern US and Mexico
Vigorous, deep rooting, high resistance to chlorosis, cuttings have poor ability to root
Often hybridized with riparia and rupestris to produce lime-resistant rootstocks that growth and root easily with different levels of vigour
Why is Chardonnay an ideal component in the blend for quality sparkling wine production?
Supplies acidity, elegant light body, citrus and green fruit
Why does the winemaker have to be extra vigilant with Syrah/Shiraz?
It is prone to develop reductive (mercaptan) flavours