General Winemaking Flashcards
How can the effect of oxygen on must/wine be limited?
Avoid ullage in vessels
Use inert gases
Add SO2
Cool, constant temps
How can you increase oxygen exposure in wine/must
Cap mgmt - spray or splash must/wine
Use small wooden barrels - oxygen enters through bung hole and staves
Increase number of rackings
Increase amount of lees stirring during aging
Allow ullage in wine containers
Hyperoxidation, micro-oxygenation
Describe the protective properties of SO2
Anti-oxidant - reduces effects of oxidation - inhibits oxidative enzymes
Anti-microbial - inhibits development of microbes (yeast & bacteria)
What is the most effective timing to add SO2 throughout the winemaking process
Add larger amounts:
When grapes are crushed
At end of MLC
At bottling
More effective than adding smaller amounts throughout winemaking process
In General Winemaking, what is the order of high level categories for winemaking processes
Oxygen and SO2
Transportation to Winery
Grape Reception
Pressing
Must Adjustments
Alcoholic Fermentation
MLC
Post-Fermentation Adjustments
While grapes are being transported to the winery, how can you minimize the threat of oxidation and microbial infection
Harvest at night when temps are lower
Adding SO2 at time of harvesting
Reduce grapes’ temps - put in cold storage
Sanitize harvesting equipment/bins
Collect grapes in small crates to minimize crushing
During the Grape Reception stage, what processes can the winemaker use
Chilling - lower temp before crush/pressing begins
Sorting - (french word triage)
Destemming
Crushing
List the sorting options for winemakers
Remove unwanted grapes/bunches before picking or during hand harvesting
Sort by hand on a table
Sort on a moving or vibrating belt - before or after destemming
Optical sorting - 100-grape sample - costly
Describe how destemmers work
Destemmers work by a series of blades within a rotating drum that remove grapes from stems
Give examples when grapes are not destemmed
Red wine fermentations use some whole bunches - Pinot Noir, Burgundy
Carbonic maceration - Gamay, Beaujolais
Whole bunch pressing for white wines - high-quality sparkling wine
List the types of presses
Pneumatic Press - most popular
Basket Press
Horizontal screw press
Continuous press
How does a pneumatic press work?
Press is made of a cylindrical cage with a bladder that runs down the side or middle
Grapes loaded into tank
Other side filled with air. As bladder inflates, grapes are pushed against grates on the side of the cage, separating juice of wine from skins
What are the advantages of using pneumatic presses
Can be programmed to exert different amounts of pressure
Can be flushed with inert gas to protect must/wine from oxidation
How does a basket press work?
Basket filled with grapes and pressure applied from above
Must/wine runs through gapes/holes in the side of basket and collected at bottom of the press
Pipe transfers must/wine to another vessel
What is the advantage of using basket presses
Gentler than pneumatic presses
What are the disadvantages of using basket presses
Hold smaller press load
More labour intensive
Suited to small wineries making premium wine
Not sealed vessels - cannot be flushed with inert gas to avoid oxygen exposure
List the types of must adjustments that can be made before alcoholic fermentation
Enrichment
Reducing Alcohol
Acidification
Deacidification
Adding Tannins
What is the aim of enrichment
Common practice for winemakers in cooler climates to enrich the must before or during fermentation to increase the alcoholic content of final wine
What can be added to must to enrich it
Dry sugar (beet or cane sugar)
Grape must
Grape concentrate
Rectified Concentrated Grape Must (RCGM) - manufactured flavourless syrup from grapes
What processes of concentration can be used to enrich must
Reverse osmosis
Vacuum extraction
Chilling
How is potential alcohol reduced in wine
Adding water - dilutes grapes
What types of acid can be added in the acidification process
Tartaric acid - most commonly used
Citric acid (not permitted in EU)
Malic acid - less used
Lactic acid - may be used if needed after MLC
When is the best time for winemakers to acidify
Can be done before, during or after fermentation
Preferred to do before fermentation - benefit from lower pH; integrates better within profile of wine
How is deacidification carried out? How does it lower acidity?
Adding calcium carbonate (chalk)
Or adding potassium carbonate
Lowers acidity by formation and precipitation of tartrates
What is a high tech option for deacidifcation?
Ion exchange - expensive
When are tannins added to musts
Tannins added to must before fermentation or to wine before maturation
Why are tannins added to musts
Helps clarify musts
Red wines - helps stabilize colour of musts and improve mouthfeel
Describe alcoholic fermentation
Alcoholic fermentation is the conversion of sugar into ethanol and carbon dioxide carried out by yeast in the absence of oxygen (anaerobically) Conversion also produces heat, which has to be managed
What does the process of fermentation produce
Alcohol
CO2
Heat
Volatile acidity (vinegar, nail polish remover smell)
Very small amounts of naturally produced SO2
Aroma precursors and compounds
Aromas created by yeasts
Glycerol
Give examples of aroma precursors and compounds that are produced during alcoholic fermentation
Thiols - MMP - boxwood/gooseberry in Sauvignon Blanc
Terpenes - linalool and geranoil - gives Muscat its floral, grapey aroma
Give examples of aromas created by yeast during alcoholic fermentation
Esters - fruity flavours - banana from carbonic maceration - Beaujolais Nouveau
Undesirable reductive sulfur compounds - rotten eggs, rotten cabbage
Acetaldehyde - bruised apple, paint thinner
What effect does Glycerol have on wine
Increases the body of wine
Name some ambient yeast strains
Kloeckera
Candida
Saccharomyces cerevisiae - quickly becomes dominant yeast
Advantages of using ambient yeast
Adds complexity
Costs nothing to use
Yeast population unique to place/region
Can be used as part of marketing of wine
Disadvantages of using ambient yeast
Fermentation starts slowly - can build up unwanted volatile acidity and growth of spoilage organisms (Brett) - lead to off-flavours
Fermentation to dryness takes longer
Risk of stuck fermentation
Consistent product cannot be guaranteed
What is the main yeast strain used in commercially cultured yeasts
Saccharomyces cerevisiae
Advantages of using cultured yeast
Reliable, fast fermentation to dryness
Produces low levels of volatile acidity
Less danger of spoilage organisms and bacteria
Produces consistent product from one vintage to another
Large selection of yeast strains
Disadvantages of using cultured yeast
Leads to certain similarity of fruit expression - industrial wine
Adds cost of using a commercial product
What are the cool fermentation temps used for fresher, fruitier white wines and rose?
12-16C
Mid-range fermentation temps used for easy-drinking fruity red wines to retain fruit aromas and for low tannin extraction
17-25C
Warm fermentation temps used for red wines with pronounced flavour concentration and high tannins
26-32C
Above what temperature does fermentation slow down and yeast struggles to survive
35C
What are options for temperature control during fermentation
Sluggish ferments can be moved to warmer room
Overheating ferments can be moved to cooler room
Water or glycol jackets that surround vessels (typically SS)
Inserts that can be put into vessels
Monitor/control systems by computer
List fermentation vessel options
Stainless Steel
Concrete
Large wooden fermentation casks
Small wooden barrels
Plastic vessels - small-batch fermentations
Terracotta
Advantages of using stainless steel as a fermentation vessel
Easy to clean
Large range of sizes
High degree of control over temp of must/wine
Neutral vessels - protect wine from oxygen
Do not add flavours
List various names for terracotta fermentation vessels
Amphora
Qvevri (Georgia)
Tinaja (Spain)
Describe malolactic fermentation
Lactic acid bacteria converts malic acid into lactic acid and carbon dioxide, and it produces heat.
What conditions encourage MLC
Temperature 18-22C
Moderate pH (3.3-3.5)
Low total SO2
What conditions inhibit MLC
Temperature below 15C
Low pH
Moderate SO2 levels
Add enzyme lysozyme - kills lactic acid bacteria
Move batch of wine going through MLC to another part of winery to avoid spread of lactic acid bacteria
Filter out lactic acid bacteria
What are the outcomes/effects of MLC
Reduction in acidity and rise in pH
Some colour loss for red wines
Greater microbial stability
Modification of flavour - buttery notes, slight loss of fruit character
List the general winemaking post-fermentation adjustments
Removal of Alcohol
Colour
How is alcohol removed after fermentation
Marginal adjustment - add water to must - reduces intensity of flavour
How do winemakers reduce unwanted colour tints
Fine wines
How do winemakers enhance the colour of red wine
Adding small amounts of grape-derived colouring agent, MegaPurple
