D13: General Winemaking Options Flashcards
1
Q
Describe oxygen’s impact in winemaking
A
1) responsible for reactions that occur between compounds in grape must or wine
2) significantly impacts style and quality
3) reactions create products which then react with must and wine compounds (oxidative reactions)
4) timing and amount of oxygen exposure has impact on whether it is positive or negative
5) can favour growth of SPOILAGE MICROBES (e.g. ACETIC ACID BACTERIA or BRETTANOMYCES) so need to ensure that wines are monitored for microbes and faults
2
Q
What is an oxidative reaction?
A
reactions create products which then react with many must and wine compounds
3
Q
What are the negative impacts of oxygen exposure
A
1) threatens production of fresh fruity wines
2) give unwanted aromas
3) cause discolouration
4
Q
Negatives of Oxygen Exposure:
1) threatens production of fresh fruity wines
A
Aroma compounds which give fruitiness break down in presence of oxygen and leads to loss of fruitiness
EXAMPLE: THIOLS (Sauv B)
5
Q
Negatives of Oxygen Exposure:
2) give unwanted aromas
A
Products of oxidation contribute to unwanted aromas
EXAMPLE: ACETALDEHYDE (from oxidation of ethanol)
gives nutty, apple aroma
6
Q
Negatives of Oxygen Exposure:
3) cause discolouration
A
Oxidation causes white wines to turn darker, becoming gold, then brown with increased oxidation
7
Q
What compounds have an anti-oxidative effect?
A
PHENOLIC
Phenolic compounds in red wine have anti-oxidative effect so can absorb more oxygen before such effects are perceptible
8
Q
What five things can you do to limit oxygen’s effect on the must or wine?
A
- avoid ullage
- use inert gases
- add SO2
- use impermeable containers
- cool constant temps
9
Q
Limiting Oxygen’s Effect: avoid ullage
A
- headspace of air between wine and top of container
- avoided by ensuring vessels are filled to top (especially those containers at risk of higher levels of evap)
- need to top up vessels regularly
10
Q
Limiting Oxygen’s Effect: using inert gases
A
- Nitrogen, CO2 and Argon can be used to flush out oxygen from vessels, pipes and machinery
- these gases don’t react with compounds in wine
- can fill empty headspace in containers
11
Q
Limiting Oxygen’s Effect: using impermeable containers
A
- stainless steel
- concrete
- impermeable to oxygen
- screwcap glass bottles minimise exposure during bottle storage
12
Q
Limiting Oxygen’s Effect: cool constant temps
A
- slow rate of oxidation reactions
13
Q
What are the positive impacts of oxygen exposure?
A
- required to start fermentation of ALL wines so as to promote growth of healthy yeast population
- lack of enough oxygen in winemaking or storage can lead to reductive off-flavours
- in some whites, exposure to oxygen pre-ferm can lead to greater oxidation stability in wine, increasing age potential
- in reds, essential in reaction between ANTHOCYANINS and TANNINS for colour stability
- good for changes in aromas/flavours in wine over time (more dried, nutty, honeyed characters)
- vital in some styles e.g. sherry, madeira, tawny port
14
Q
What five techniques can you use to increase oxygen exposure?
A
- cap management techniques
- using small wooden barrels
- small volume of wine relative to intake of oxygen through bung hole and staves
- Increased racking/lees stirring
- increased oxygen exposure every time bung of barrel or lid is removed
- allowing ullage
- techniques involving pumping oxygen through must or wine
- HYPEROXIDATION (pumping o2 through must)
- MICRO-OXYGENATION (pumping o2 through wine)
15
Q
What is the role of sulfur dioxide in winemaking?
A
- Preservative universally used in winemaking
Anti-oxidant
- SO2 only reacts with oxygen very slowly
- reduces effects of oxidation by reacting with products of oxidation reactions so they cannot oxidise further compounds in the wine
- inhibits oxidative enzymes
Anti-microbial
- inhibits development of microbes (e.g. yeast and bacteria)
- vary in tolerance levels to SO2
16
Q
In what form is SO2 used in winemaking?
A
- can be gas, liquid or solid
- sulfur dioxide, potassium metabisulfite or potassium bisulfite
- small amount of SO2 produced naturally during fermentation
17
Q
What are the concentration levels for SO2 in winemaking?
A
- max concentration levels defined by local laws as it is a toxic substance
- max permitted levels lower for organic wines
- natural wine producers may choose to not add any additional SO2
- even small amounts of SO2 can cause allergic reactions
- if over 10 mg/L, the label MUST state that wine contains sulfites
For the EU the levels are:
- 160 mg/L (red)
- 210 mg/L (white)
- sweet wines can be higher
18
Q
When is SO2 added to wine?
A
- usually added once grapes are picked, or have reached winery
- can be added during winemaking and usually at bottling
- when added, it dissolves
- can react with compounds in liquid
19
Q
What is ‘bound SO2’?
A
- reacts with compounds in liquid
- ineffective against oxidation and microbes
20
Q
What is ‘free SO2’?
A
- relatively inactive
- small proportion exists as molecular SO2 and most effective against oxidation and microbes
21
Q
What impact does pH have on SO2?
A
- key effect on efficacy of SO2
- greater proportion of free SO2 is in molecular form at lower pH levels
- therefore greater amount of SO2 needs to be added to musts and wines with higher pH to protect them from oxidation and microbes
22
Q
What impact does the timing and size of SO2 dose have?
A
- Adding larger amount when grapes are crushed, at end of MLC and at bottling seen as more effective than smaller doses throughout winemaking process
23
Q
What are the negative impacts of SO2?
A
- can dull wine aromas/flavours and can cause wines to taste harsh
24
Q
What role does management have on SO2 used in winemaking?
A
- Good winery hygiene and effective grape sorting can limit harmful microbes
- limiting oxygen exposure and keeping cool temps can reduce amount of SO2 needed to protect from oxidation and microbial spoilage
25
What are the three transportation options to the winery and what are the pros and cons of each?
"Small crates
- could be done for quality purposes or due to size of operation "
"- minimal crushing of grapes
- therefore limited oxidation and microbial spillage "
"Large Hoppers
- small crates tipped into larger hoppers for transport to winery "
"- would involve some crushing of grapes and oxidation and potential microbial spoilage
- some growers will add SO2/Potassium Metabisulfite to minimise this "
```
"Machine Harvested
- already destemmed
- transported in large containers "
"- some release of juice, oxidation etc
- some growers may had SO2
- mainly seen in much larger estates "
```
26
What are the risks once the grapes are picked, and how can you minimise it?
"- Once picked, grapes at risk of oxidation, to ambient yeast and acetic acid bacteria
- threat increases at higher temps
- black grapes less at risk "
"Minimise threat by:
- harvest at night or at sunrise so temps are lower
- add SO2 at time of harvest
- put grapes in cold storage when arrive at winery
- sanitise harvest equipment and bins
"
27
Grape reception for large volume
- conveyor belt (gentler and higher quality)
- screw conveyor
- then moved to sorting phase or destemmer/crusher
28
Grape reception for small volume
- moved manually with pallet truck/forklift
29
Why might you chill grapes following grape reception and what would be the positives and negatives (8)
- may want to chill grapes before crushing and pressing if too warm
- warm temps increase rate of oxidation
- chilling preserves fruity aromas
- reduces risk of microbial spoilage
- takes place in refrigeration unit
- can take time which slows whole process of grape processing
- can use HEAT EXCHANGER if grapes are already in more fluid format and work very quickly
- incur costs in terms of equipment and energy
30
Describe 'sorting' and the options behind it
- AKA in french as TRIAGE
- level of sorting and how it takes places depends on several factors
- more sorting = higher cost, so therefore is it worth it in terms of style of wine being made
- poor years or cool climates made need additional sorting to remove mouldy, unripe grapes
- MOG: material other than grapes - still need removing
- inexpensive wines probably wouldn't be sorted (due to costs)
Factors:
- ripeness and health of fruit
- quality of final wine
- any vineyard sorting
- physical state of grapes
31
What sorting options do you have for quality wines?
- remove unwanted grapes/bunches before picking or during hand-harvesting
Sorting by hand on table or moving/vibrating belt which can take place before or after detemming
"Optical sorting - uses digital imaging and software tech to scan individual grapes
- scans 100-grape sample chosen by grower as reference
- full-load of grapes then put through sorter and it rejects ones which aren't up to scratch
- typical option for very high quality grapes (e.g. Bordeaux Grand Cru Classe) "
32
What is 'optical sorting'?
- uses digital imaging and software tech to scan individual grapes
- scans 100-grape sample chosen by grower as reference
- full-load of grapes then put through sorter and it rejects ones which aren't up to scratch
- typical option for very high quality grapes (e.g. Bordeaux Grand Cru Classe)
33
Destemming
"- hand-harvested grapes for red and white are destemmed on arrival
- series of blades within a rotating drum that removes grapes from stems
- very common in wineries around the world
- stems contain tannins which can be extracted if left in contact with wine and are not wanted in white wines.
- can convey unwanted green flavours and bitter tannins to wine "
34
What three reasons would grapes NOT be destemmed?
- RW fermentations which use whole bunches (e.g. Burgundy PN or Sonoma)
- carbonic maceration
- whole bunch pressing for some white wines (e.g. high quality white wine)
35
Describe 'crushing'
"- beginning of winemaking process
- application of sufficient pressure of grapes to break skins and release juice
- do NOT confuse it with pressing
- important that pressure applied is gentle enough not to crush seeds which would be better
- many wineries use a combined destemmer-crusher machine. Can only be done for whole bunches
- mixture of grape juice, pulp, skins, seeds - MUST
36
White wine pressing
WHITE WINE: grapes pressed to extract juice from grapes and to separate skins from juice before fermentation
37
Red wine pressing
RED WINE: grapes crushed before fermentation and pressed after some days on skin, or at end of fermentation
38
Batch processing
grapes loaded into press, pressed, skins removed, press is cleaned, next batch loaded, can take a lot of time
39
What are the benefits of computer-controlled presses?
Most presses now computerised
- can programme pressure and length of press cycle to get desired results
- less pressure: extract less tannin and colour from skins BUT get smaller vol of juice/wine
- longer press cycle: extends contact between skins and juice/wine so extract MORE aroma/flavour/tannins
40
What is pommace?
solid remains of grapes left after pressing
41
What is a pneumatic press and what are the THREE advantages of it?
"- most popular type of press used in wineries
- AKA 'air bag presses'
- cyclindrical cage with a bladder that runs down side or middle of it
- grapes loaded into tank (on one side of bladder)
- other side of cage is filled with air and, as bladder inflates, grapes are gradually pushed against grates on side of cage, separating juice or wine from skins
ADVANTAGES:
- can be programmed to exert different amounts of pressure (light pressure: less extraction; harder pressure: greater extraction and can provide different blending components if needed)
- can be flushed with inert gas before use to protect juice or wine from oxidation
BATCH PROCESSING
42
What is a 'basket press' and describe the advantages and disadvantages of it?
- more traditional
- AKA 'vertical presses' or 'champagne presses'
- basket is filled with grapes and pressure is applied from above
- juice or wine runs through gaps or holes in side of basket and is collected by tray at bottom of press
- then piped into another vessel
- NOT sealed and therefore risk oxygen exposure
ADVANTAGES:
- believed to be gentler than pneumatic
DISADVANTAGES:
- hold small press load
- more labour intensive
- suited to smaller wineries making premium wines
BATCH PROCESSING
43
What is a horizontal screw press?
- less widely used
- similar to basket press
- mounted horizontally above draining tray
- less gentle than other types
- less popular
- requires batch processing (like other two)
44
What is a continuous press?
- grapes can be continually loaded into press
- uses a screw mechanism
- quicker pressing of large volume of grapes
- less gentle than basket or pneumatic
- suited to high volume, inexpensive wine
45
What are the four types of presses used in pressing?
PNEUMATIC PRESSES
BASKET PRESSES
HORIZONTAL SCREW PRESS
CONTINUOUS PRESS
46
What are the four must adjustments which can be made and why would you adjust the must?
- can adjust must to create more balanced wine
- generally made after must clarifications (white wines)
ENRICHMENT
REDUCING ALCOHOL
ACIDIFICATION
DEACIDIFICATION
47
What is 'enrichment', why would you do it?
EU definition:
- covers range of practices
* adding dry sugar
* grape must
* grape concentrate
* rectified concentrated grape must (RCGM)
* concentration (reverse osmosis, vacuum extraction, chilling)
- common in cooler climate
- before or during fermentation
- increases alcohol content of final wine
48
Why is the EU different when it comes to enrichment?
- wine regions in EU split into different zones to determine levels of enrichment (inc acidification and deacidification)
e. g. ZONE A (Germany, excluding Baden and UK)
- min natural alc: 8%
- max enrichment: +3%
- Max alc post-enrichment: 11.5%/12.5% (white/red)
49
What is chaptalisation?
- adding dry sugar
- can be beet or cane sugar
- allowed in cooler parts of Europe
- not allowed in warmer areas (but can add RCGM within limits)
- rising temps in Europe means there is less need for this
- adding sugar is done when ferm is underway because yeasts are already active and cope with additional sugar in must
50
What is concentrating grape sugars (as part of enrichment)?
Concentrating sugars:
- done by removing water (using technology)
- REVERSE OSMOSIS
- VACUUM EVAPORATION
- CRYOEXTRACTION (freezing must or final wine and removing ice from it)
- all expensive options (first two most expensive) so only really seen in high volume wineries
51
Describe the process of 'reducing alcohol'
- done in hot countries where sugars accumulate in grapes quickly.
- add water to grape must
- only legal in some countries (e.g. in Cali)
- adding water dilutes grapes' aromas/flavours and acids
52
Why might you acidify wine?
- warm climates without cooling influences may see MALIC ACID levels drop dramatically during ripening
- if don't acidify it can lack freshness
- acidification lowers pH
- acidification routine in warmer parts of world for inexpensive, mid-priced and premium wines
- typically add TARTARIC ACID but other options available
53
What are your three acidification options?
- CITRIC (not allowed in EU)
- MALIC (need to make sure that not turned to lactic acid by MLC)
- LACTIC (used post-MLC and tastes less harsh than other acids)
54
When can you acidify and why might a winemaker choose to do this before fermentation?
- before, during or after ferm
- winemakers tend to do before ferm because:
* benefit from effects of lower pH
* believe that acidity added to this stage integrates better in wine as whole
- need to be aware that total acidity and pH affected during winemaking processes (including MLC and tartrate stabilisation) so need to consider this when adding acid in
55
What are the EU rules on acidification?
strictly controlled by EU and done in bands (like enrichment)
- cool climates: deacidifcation only allowed
- warm climates: acidification only allowed
*** winemakers CANNOT both chaptalise and acidify musts so as to not stretch the wine by the two additions
Zone A: -1 to 0 g/L (expressed as tartaric acid)
Zone CI (inc Bordeaux, Trentino-Alto-Adige), winemakers can deacidify or acidify according to seasons
56
Why might a winemaker choose to deacidify?
- in cool climates
- where grapes may have to be picked before fully ripe
- need to consider lowering of acidity caused by MLC
- add CALCIUM CARBONATE or POTASSIUM CARBONATE
- lowers acidity by formation and precipitation of tartrates
- can do high-tech option using ION EXCHANGE but needs considerable investment
- EU limits on deacidification
- not legal in some countries so need to check if it is so in intend country of sale
57
What is yeast?
- yeast is collective term for group of MICROSCOPIC FUNGI which convert sugar into alcohol and affect aroma/flavour characteristics of wines
- yeast need oxygen to multiply quickly but switch to fermentation once oxygen is used up
- perfect conditions:
* temperature
* access to yeast nutrients (esp nitrogen)
* absence of oxygen
58
Yeast and Aromatics
- from aroma precursors
* released by action of yeast and create aromas in wine
* e.g. THIOLS and TERPENES
- created by yeast
* e.g. ESTERS (in carbonic maceration)
* can get some undesirable reductive sulfur compounds (rotten eggs) and acetaldehyde (bruised apple, paint thinner)
59
What does glycerol increase the perception of?
Body
60
What does fermentation produce?
- Alcohol
- CO2
- Yeast
61
What are the four possible types of yeast?
SACCHAROMYCES CEREVISIAE
SACCHAROMYCES BAYANUS
AMBIENT YEAST
CULTURED YEAST
62
SACCHAROMYCES CEREVISIAE
"- most common used species of yeast in winemaking
- can withstand high acidity and high alc in must during ferm
- resistant to SO2
- reliably ferments to dryness
- few different strains within species which give winemakers option to choose strain (AKA SELECTION) for particular outcomes
* e.g. boost aromatic character of Sauv B
63
SACCHAROMYCES BAYANUS
- good for must with high potential alcohol or for re-fermenting sparkling wine
64
AMBIENT YEAST (inc advantages and disadvantages)
- AKA 'WILD YEAST'
- present in vineyard and winery
- range of yeast species
- most die as alc rises above 5%
- Saccharomyces Cerevisiae typically becomes dominant yeast even in wild ferms
Advantage:
- add complexity due to number of yeast species producing different compounds
- no cost
- dominant yeast population in must is unique to place or regoin so gives additional individuality
- can be used as part of marketing strategy
Disadvantage:
- Fermentation starts slowly so can get build up of unwanted characteristics (VA) and growth of spoilage yeasts (Brett) and bacteria - can lead to off-flavours
- Ferm to dryness can take longer which doesn't suit high volume production
- can get stuck in fermentation which risks spoilage
- can't guarantee consistency
65
CULTURED YEAST (inc advantages and disadvantages)
- selected or commercial yeast
- selected in laboratory and grown in volumes for sale
- tend to be single strains of SC
- to use: it is added to cooled must (so that no ambient yeast can work) and it overwhelms natural yeast population (can also add SO2 to must in order to suppress ambient yeast). A starter batch, made up of fermenting grape must is activated with cultured yeast and is then added to tank of must to be fermented.
Advantage:
- reliable, fast fermentation to dryness
- produces low levels of VA and, because of speed, less danger of spoilage yeasts and bacteria
- produces consistent product for each vintage
- large selection of cultured yeast available so can help determine style of final wine
Disadvantages:
- can lead to similarity of fruit expression (industrial wine)
- cost
66
What does yeast need to begin with to help the fermentation start?
- needs some exposure to oxygen to begin with to enable yeast to multiply at beginning of fermentation
- can add yeast nutrients, esp if nitrogen levels are low (can lead to stuck ferment and smells of rotten eggs)
- DIAMMONIUM PHOSPHATE (DAP) or THIAMINE (vit B1) can be added as yeast nutrients
67
Temperature: cool temp fermentation
- 12 - 16 degrees
- fresh, fruitier white wines and rose
- promote production and retention of fruity aromas and flavours
68
Temperature: mid temp fermentation
17 - 25 degrees
- easy-drinking fruity red wines
- retain fruit aromas
- low tannin extraction
- mid-range for less-fruity whites
- top-range for barrel-ferm whites
69
Temperature: warm temp fermentation
26 - 32 degrees
- powerful red wines
- max extraction of colour and tannins
- can loose some fruity flavours
70
Temperature: above 35 degrees
- ferm may slow and stop
| - need to control temp to stop this from happening
71
What are your options for temperature control?
- ferm temp can be affected by temp of cellar
- sluggish ferments can be moved to warmer room and vice versa (if vessels are small enough to move)
- most modern wineries have temp controlled vats (either jackets around vessels or inserts in tanks)
- controlled by computers
- can bring down temps during pump overs
72
What are the four options for fermentation vessels?
Stainless Steel
Concrete
Wood
Others
73
Fermentation Vessel: Stainless Steel
"- modern
- easy to clean
- range of sizes
- neutral
- prevent contact with oxygen
- don't add any flavours
- commonly used in high-vol wineries due to price, hygiene, high level of mechanisation
- initial pricey upfront investment "
74
Fermentation Vessel: concrete
"- coming back in fashion
- high thermal inertia
- maintain even temp (more efficient than stainless steel)
- set up convection currents that mix fermenting must and mix lees during maturation "
75
Fermentation Vessel: Wood
"- popular in some areas of Europe
- retains heat well
- care needed with hygiene as can harbour bacteria and spoilage organisms
- can get a small amount of oxygen coming into the wine during ferm which can be good
- can be reused many times so inexpensive in long term
- require large capital investment when first purchased
- white wine can be fermented in small wooden barrels but not possible for red due to cap management "
76
Fermentation Vessel: Others
"Plastic: light, versatile, good for small batch fermentation but permeable so oxygen risk, and difficult to control temps
Terracotta: historical uses and only used in small scale productions today "
77
Describe malolactic conversion
- result of LACTIC ACID bacteria converting MALIC ACID into LACTIC ACID and CO2. Also produces heat
- happens after alc ferm (and occasionally during it which can increase fruity characteristics and reduce production times)
- need right conditions:
* 18-22 degrees
* moderate pH (3.3-3.5)
* low total SO2
- used to happen spontaneously in spring following harvest as temps rose in cellar
- now, add cultured lactic acid bacteria and making sure conditions are available
78
When will MLC NOT happen?
* temps below 15 degrees
* low pH
* moderate levels of SO2
79
What can winemakers add to prevent MLC taking place?
LYSOZYME (enzyme) - kills LA bacteria
Can also filter our LA bacteria
80
Where can MLC take place?
Can do it in barrels rather than in tanks which allows for lees stirring and better integration of flavours
* more work as barrels will do this at individual temperatures so need careful monitoring
81
What are the four outcomes of MLC?
- reduction in acidity and rise in pH
* LA is weaker than Malic Acid
* good for overly acidic wines
* not good for low acidity wines
* gives softer, smoother style of wine
- some colour loss in red wines
- greater microbial stability
* prevents MLC happening spontaneously later (when in bottle)
* raising pH can make wine more vulnerable to spoilage organisms and may result in wine not being refreshing as acidity has decreased
- modification of flavour
* loss of fruit character
* added buttery notes
* increased risk of volatile acidity
82
What two post-fermentation adjustments might a winemaker choose to make?
- removal of alcohol
- colour
* should only aim to make small adjustments so as to not upset balance of final wine
83
Post-fermentation adjustment: removal of alcohol
- what two techniques might be used for this process?
REVERSE OSMOSIS
- cross-flow filtration
- removes a flavourless permeate of alcohol and water
- this can be distilled to remove alcohol
- permeate is then blended back to recreate the wine
- most common high-tech option
- very costly
SPINNING CONE
- extracts volatile aroma compounds from wine
- then removes alcohol
- flavour components are blended back into wine of desired alcohol level
- only financially possible for large volumes of wine
84
Post-fermentation adjustment: Colour
- may want to reduce unwanted colour tints
- can do this by fining the wine
- in volume red wines, can add small amount of MEGAPURPLE (MegaPurple) - grape derived colouring agent
- not permitted in some regions (e.g. Ribera del Duero)
