Ch. 13 General Winemaking Options Flashcards
Why is oxygen generally threatening for the production of fresh, fruity wines?
- loss of fruitiness - aroma compounds that give wines fruity style (thiols in SB for ex) break down w oxygen
- oxidation reactions can contribute unwanted aromas to wine - ex acetaldehyde and its nutty, apple aromas
- color becomes darker - gold then brown
- threat of bacterial spoilage is greater
** phenolics in red wine protect more against oxidation
What does reductive or protective winemaking refer to? What techniques are involved?
The practice of minimizing oxygen exposure during winemaking process.
- avoiding ullage
- ullage is headspace of air between wine and top of container –> fill to top, or “top up” w more wine, especially in wooden vessels where evaporation happens - use of inert gases - nitrogen, carbon dioxide, argon flush out O2 –> add to presses, pipes, vessels or to fill ullage
- addition of sulfur dioxide
- use of impermeable containers - stainless steel, concrete vs wood
- cool, constant temperatures - slow rate of oxidation - so storage in fridges after picking, picking at morning, maturing wine in cool cellars
What are benefits of controlled oxidation?
- Oxygen is required at the start of fermentation of all wines to promote healthy yeast population
- lack of enough O2 in winemaking or storage can lead to reductive off flavors
- white wine - exposing must to oxygen before fermentation helps w oxidation stability and aging potential
- red wine - O2 essential for color stability (bc of reaction between anthocyanins and tannins)
- lack of complexity - some wines need exposure to oxygen to develop a range/diversity of flavors from oxidation, essential to wines like Oloroso Sherry, Madeira, Tawny Port (dried fruits, honey, caramel, coffee, leather, mushroom
What are some techniques to increase oxygen exposure? Considerations?
- cap management techniques - spray/splash must
- small wooden barrels - O2 permeates, small volume of wine so effect is greater
- increasing interventions - rackings, lees stirring
- allowing ullage
- techniques that pump oxygen through must or wine
- Wines exposed to oxygen must be carefully monitored for spoilage organisms encouraged by oxygen, like Brettanomyces and acetic acid bacteria
What are the effects of sulfur dioxide in winemaking?
- anti-oxidant - reduces the effects of oxidation by reacting with the product of oxidation reactions
- anti-microbial - reduces risk of bacterial spoilage by inhibits development of microbes such as yeast and bacteria
What determines how much SO2 is found/needed in a wine?
- Naturally ocurring during fermentation (10 mg/L or less)
- Local laws (diff areas regulate depending on style of wine eg 150 mg/L max for red in EU)
- Winemaking practices - organic, natural
- winemaker preferences - high levels of SO2 can dull wine aromas/flavors and can sometimes cause wine to taste harsh
- good practice - hygiene and keeping grapes/must/wine at cool temps reduce amount of SO2 needed
What is the difference between bound SO2 and free SO2?
Bound So2 –> dissolved, reacts with compounds in must or wine, ineffective against oxidation and microbes
Free SO2 –> not bound, relatively inactive, small proportion exists as molecular SO2 which is effective against oxidation and microbes
What influences the efficacy of SO2?
- pH level of must or wine –> more SO2 needed at higher pH levels (lower acidity) to protect against oxidation, spoilage
- timing and size of SO2 additions - more effective to add larger amounts fewer times (at crushing, end of malo and bottling)
What are the threats posed to grapes during transportation to the winery?
- oxidation- loss of fruitiness, unwanted aromas, spoilage risk
- ambient yeasts- start fermentation early if grapes have split
- acetic acid bacteria (turn alcohol to acetic acid, vinegar-y smell)
- high temps during harvest increase risks
- black grapes less vulnerable to oxidation bc phenolics have anti-oxidative properties
What measures can be taken to minimize threats of oxidation and microbial infection?
- harvesting, transporting grapes at night when temps are cooler; harvesting at sunrise if by hand
- addition of SO2 at time of harvesting
- cold storage once received at winery (Albariño, Lagar da Condesa, fridges)
- Sanitizing harvesting equipment/bins
- Collecting/transporting grapes in small crates to minimize crushing
What are the options for physical transport to the winery?
Hand harvesting:
- grapes put in small crates, transported to winery like this –> minimize crushing, prevent oxidation and spoilage
EX - Champagne - where PN or PM are destined for white wine - need to prevent extraction of phenolics or colors; small-scale one hectare harvest and can use own tractor
- small crates tipped into large bins - involves some crushing, threat from spoilage, some growers add SO2
Machine harvesting
- fruit already de-stemmed, transported in large containers, some release of juice, add SO2
What processes take place at grape reception?
Depending on hand or machine harvested, health and quality of grapes:
- Chilling
- Sorting phase
- Destemmer/crusher
What are the advantages and disadvantages of chilling grapes at winery?
- chill to lower temps before crushing and pressing begins
ADV
- help preserve fruity aromas
- help reduce spoilage threat
- fridges can serve as storage if other equipment in use
DIS
- chilling takes time from processing of grapes (heat exchangers work more quickly than fridges)
- cost of equipment and energy
What determines the level of sorting required?
- ripeness and health of fruit arriving at the winery - poor years/cool climates may require sorting to remove mouldy/under ripe grapes
- intended final wine quality and price –> more sorting=more cost (labor, time, lower yields/less wine) ** key to determine quality of wine made in relation to price gained for wine
- whether sorting has been carried out in vineyard
- physical state of grapes (bottom grapes in large containers already crushed partially)
What are the sorting options for quality wines?
- remove unwanted grapes/bunches before picking/hand harvesting
- sorting by hand on table or moving belt (which removes MOG, can be done before or after destemming or both)
- Optical sorting - using digital imaging and software to scan - costly, usually for premium or super premium wines
What considerations need to be made in relation to de-stemming?
In which situations are stems not removed?
- Stems might add unwanted greenness to tannins
- Fermentation with stems absorbs some alcohol
- Red wine fermentation that use some whole bunches (PN in Burgundy)
- carbonic maceration (Gamay in Beaujo)
- whole bunch pressing for some white wines (high quality sparkling wine)
What happens during crushing?
At beginning of winemaking process, application of enough pressure to grapes to break skin and release juice, making it available for fermentation
Needs to be gentle enough to not crush seeds, which add phenolic bitterness
Can be combined w destemmer-crusher machine - so sorting can be done at level of whole bunches
Define must
Mix of grape juice, pulp, skins and seeds that comes from crusher
For white wines, must may also refer to grape juice that is fermented
Typically refers to substance that is being fermented
What are differences and similarities in pressing for white vs red wines
WHITE: grapes pressed to extract juice, separate skins before fermentation
RED: grapes crushed before ferment, pressed after desired number of days (when ferment starts w/skins and continues off, some lighter reds) on skins or after fermentation
SIMILAR: soft pressing is important, don’t want to extract any (in white) or excessive tannin and bitterness from skins and seeds
Describe mechanism of pneumatic press. What are advantages and disadvantages of a pneumatic press?
- Bladder inflates with gas inside a cylindrical cage, grapes pushed against grates separating juice or wine from skins
Also called air bag presses
ADV
- can be programmed to exert diff amounts of pressure - can create diff blending components for added complexity
- can be flushed w inert gas to protect from oxidation
DIS
- need to afford initial investment
better suited to medium to large scale wineries
Describe mechanism of basket press. What are advantages and disadvantages of a pneumatic press?
Also called vertical press, champagne press
Basket is filled with grapes and pressure is applied from above. Juice runs though holes on the side, collects in a tray at bottom, pipe transfers juice to another vessel
ADV:
- gentler than pneumatic
DIS
- aren’t sealed, can’t be flushed with inert gases
- hold smaller press load
- more labor intensive
- better suited to small wineries making premium wines
What are other types of presses?
- Horizontal screw press - similar to basket press, mounted horizontally above draining tray - less gentle, less popular
- continuous press - only one of discussed presses that doesn’t require batch processing - grapes can be loaded onto press continually - allows for quicker pressing of large volumes, less gentle–> better for inexpensive, high-volume wines - cheap, bulk wine
What is the compromise between quality and volume of wine?
Press cycle can be mechanised. A winemaker must decide length and pressure of press.
Softer, shorter pressing will extract fewer tannins, color but result in less volume of juice.
Longer press cycle extracts more aroma/flavor and tannin extending the contact between skins and juice (in case of red wine)
What is pomace?
Solid remains of grapes left after pressing
Why would a winemaker make must adjustments? When are adjustments made and which are available?
AIM: to create a more balanced wine, especially if there has been a compromise in achieving optimum ripeness of sugars, acids, tannins and flavors
Adjustments usually made after must clarification for wine wines. lso after fermentation.
Can be: enrichment - adding "sugar" reducing alcohol acidification deacidification adding tannins
What does enrichment refer to? What practices does it include?
Enrichment refers to increasing the alcoholic fermentation in a final wine by enriching the must either before or during fermentation - most common in cooler climates
** In practice adding sugar is done when fermentation is in progress bc yeasts are active and can handle additional sugar in must
How?
- Adding dry sugar
- grape must
- grape concentrate
- RCGM (rectified concentrated grape must, manufactured flavourless syrup from grapes)
- concentration - reverse osmosis, vacuum extraction, chilling
What does chapitalisation refer to? What are the limitations to this practice?
This means adding dry sugar - can be beet or cane sugar
Only allowed within cooler parts of Europe
EX:
Zone A:Germany (excplusing Baden) and UK - minimim natural potential alcohol is 8%, max enrichment is +3%, max alc level if wine is enriched is 11.5% for white, 12 % for red
What are the methods and considerations for other methods of enrichment (concentration methods)
Sugar levels can be concentrated by removing water
BY:
- reverse osmosis - expensive
- vacuum evaporation - expensive
- cryoextraction (freezing must, removing ice)- cheaper
** less wine to sell in all 3 methods
What are considerations when removing alcohol?
- where sugars accumulate quickly (hot/warm regions), it may be desirable to lower potential alcohol by adding water to grape must
- legal? - not in Europe, yes in Cali
- style/quality - dilution of aromas/flavors and acids
- humidity - if high, you can lose alcohol in barrel, if low alcohol becomes more concentrated
How is acidification carried out? At what point in winemaking process?
Adding:
- tartaric acid (most common)
- citric acid (not permitted in EU)
- malic acid (less common bc can turn into lactic acid)
- lactic acid (common if adjustments need to happen after malo, tastes less harsh)
When:
usually before fermentation bc
- take advantage of benefits of lower pH (microbiological stability, effectiveness of SO2)
- acidity integrates better
What is acidification? Limitations?
Adding acid to wine (esp in warm climates w/o cooling influences) to increase freshness and structure.
Also used to lower pH
Routine in warmer parts of world for inexpensive and mid-priced wines, many premium wines
Legislation - EU creates “bands” to determine how much you can acidify. Some bands depend on season. Not allowed to chapitalise and acidify at same time
What are the aims and methods of deacidification?
AIM: lower acidity if grapes had to be picked before fully ripe (bc of threat of bad weather)
- add calcium carbonate
- add potassium carbonate
(these methods form tartates)
OR - ion exchange
(this method requires investment/$$ for machinery
What are the aims and methods of adding tannins?
- clarify musts
- help stabilise color of musts
- improve mouthfeel
- may be added as powder before fermentation or before maturation
Define process of fermentation.
The conversion of sugar into ethanol (ethyl alcohol) and carbon dioxide by yeast in the absence of oxygen, producing heat.
What conditions do yeast need for fermentation?
- viable temp range
- access to yeast nutrients (nitrogen)
- absence of O2 (though needs some at beginning to multiply, once consumed they start fermentation)
What are the byproducts of fermentation?
- heat
- alcohol
- CO2
- volatile acidity (vinegar, nail polish remover smell) - small amounts not perceptible
- small amount of SO2
- aromatics
- from aroma precursors –> no flavor in must, instead released when yeast ferment
- created by yeast –> esters, reductive sulfur compounds, acetaldehyde
- glycerol - increases body
Give examples of aroma precursors
- thiols –> 4MMP which gives gooseberry aromas in SM
- terpenes –> linalool and geraniol which give Muscat grapey aroma
Give examples of aromas created by yeast
- Esters - give fruity flavors like banana in wines made with carbonic maceration (Beaujo Nouveau)
- acetaldehyde – bruised apple, paint thinner
What is the most common species of yeast used in winemaking? Important features?
Saccharomyces cerevisiae - can withstand high acidity, increasing alcohol level, reliable fermenting musts to dryness, fairly resistant to SO2
What are the advantages and disadvantages of using ambient/native yeast?
ADV
- add complexity - many yeast species producing diff aroma compounds
- costs nothing
- can be unique to place or region - adding complexity
- markeitng of wine/trends
DIS
- slow start to fermentation - can give opportunity for build up of VA, spoilage organisms
- fermentation to dryness takes longer, taking up valuable time in high-volume production
- increased risk of stuck fermentation - risk of spoilage
- lack of consistency
What are the advantages and disadvantages of using cultured/commercial/selected yeast?
ADV
- reliable, fast fermentation to dryness
- low levels of VA, less risk of spoilage –> clean complete ferment
- consistency from one vintage to next
- winemaker has more control in terms of profile/style of wine created, yeasts can contribute to aromas in specific ways
DIS
- perception of using an industrial product, leads to uniform fruit expression
- cost of using commercial product
What are requirements/considerations for using cultured yeast?
- Must may be cooled to prevent ambient yeast from starting fermentation
0R - ADD SO2 to must to suppress ambient yeast, then add a starter batch to kick off fermentation (fermenting grape must which has been activated w cultured yeast)
- cultured yeasts typically single strains of saccharomyces cerivisiae
What’s required at the early stages of fermentation?
- exposure to O2 - enables yeast to multiply at beginning of fermentation
- nitrogen - low levels can cause yeast to stress and produce undesirable sulfur compound (rotten egg smell) or stop fermenting
- DAP or thiamine - other yeast nutrients
- winemakers usually prefer warm temps at start - eg 25C/77F
Specify cool temperature range for fermentation and style of wine produced and why
12-16C
54-61F
Fresher, fruitier white wines and rose
cool temps promoted retention of esters, give fruity aromas
Specify mid-range temperature range for fermentation and style of wine produced and why
17-25C
63-77F
Easy drinking fruity red wines - retain fruit aromas and low tannin extraction
Mid of this mid range for less fruity whites
Top of this range for barrel-fermented white wines
Specify warm temperature range for fermentation and style of wine produced and why
26-32C
79-90 F
Red wines with pronounced flavors and tannins - max extraciton of color and tannins, but some loss of fruity flavors
Above what temps can fermentation stop?
Above 35C / 95F risk of stuck fermentation as yeasts die
What are methods for temperature control?
- adjusting temperature of cellar, moving vessels to cooler areas
- Fermentation control within vessels (computerized)
- Pumping over/delestage releases heat
What are advantages and disadvantages of fermenting wine in stainless steel?
ADV
- easy to clean
- comes in range of sizes
- high degree of control over temp of must or wine
- neutral, anaerobic, do not add flavors
- easy to clean and disinfect
- high level of mechanization possible
DIS
- can require substantial financial investment both for tanks and temp control systems
** typically found in modern, high volume wineries
What are advantages and disadvantages of fermenting wine in concrete?
ADV
- maintain even temp more efficiently than stainless steel
- set up convection currents that mix fermenting must and mix lees during maturation
DIS
- smaller egg shaped ones are very expensive
What are advantages and disadvantages of fermenting wine in wood?
ADV
- retains heat well
- small amount of O2 oak provides for fermenting red wine
- can be reused many times to inexpensive over long term
DIS
- more care taken with hygiene, risk of spoilage and bacteria from pores in wood
- large oak casks require initial capital investment
- small wooden barrels - harder for cap management (so rare for red wines)
What are alternative options for fermentation vessels?
- plastic - light + versatile; hard for temp control and permeable to O2
- Terracotta - historical, small-scale production today; known as amphora, qveri, tinaja
What is malolactic conversion?
Malic acid is converted into lactic acid, CO2 and heat by lactic acid bacteria
What conditions produce malolactic fermentation?
- 18-22C (64-72F)
- moderate pH (3.3-3.5)
- low total SO2
- can be kicked off by inoculating with cultured lactic acid bacteria in optimum conditions
What conditions inhibit MLF? How can a winemaker ensure MLF is blocked?
- temps below 59F (chilling wine)
- low pH
- moderate levels of SO2
winemakers can
- chill
- add enzyme lysozyme
- lactic acid bacteria can be filtered out
What are outcomes of MLF?
- reduced acidity, rise in pH - softer, smoother style of wine, may be desirable in overly acidic wines
- Some color loss in red wines - only problem in v pale read wines
- Greater microbial stability - once it happens during or after fermentation, it won’t happen spontaneously later like in bottle
- flavor changes -loss of fruit character, addition of buttery notes in white wine; increases VA
Where does MLF take place?
- can happen in large batches in tanks - easier if same time as alcoholic fermentation, shortening production time, saving money, increasing fruity characteristics
OR - in barrels - can stir lees at same time, better integration of flavors; more labor bc needs individual monitoring
