JB mw Flashcards
(26 cards)
Why do tartrate
crystals form?
Tartaric acid = naturally present in grapes. After AF some wines become supersaturated
(ie. there is more tartaric acid in solution than the wine can naturally sustain).
The excess tartaric acid will solidify and form crystals of: potassium bitartrate (&
calcium tartrate).
What is tartrate
stabilization?
A method used to keep tartaric acid crystals from forming after a wine as been
bottled.
Why is it risky
to leave tartrate
crystals in wine?
Not harmful to consumption, but consumers could confuse with glass shards (esp.
in white wine). Extremely important in sparkling wines as tartrate crystal act as
nucleation causing bubbles to be released excessively.
What are the
7 methods of
tartrate stabilization?
- Cold stabilization
- contact process
- ion exchange
- electrodialysis
- metatartaric acid
- cmc
- mannoproteins
Cold Stabilization:
explain process,
give pros & cons
and examples
PROCESS:
1) Chill wine to just above its freezing point (ie. -4°c for a 12% abv wine).
2) Store in insulated tanks for up to 8 days
3) Reduced solubility of substances at lower temperatures = rapid crystallization
CONS: Costly initial investment in refrigeration unit & insulated tanks, cooling
consumes high amounts of energy, removes concentration & body (+ colour in
reds), only works if thorough fining prior to minimize level of protective colloids
PROS: no tartrates
Example: Constellation Quebec
Contact Process:
explain process
PROCESS:
1) Chill wine to 0°c
2) “Seeding” - addition of finely ground potassium bitartrate crystals at 2g/L + vigorous stirring for 1-2hrs
3) added micro-crystals act as nuclei, enabling more rapid crystallization
4) Filtered while still cold, crystals ground down & added to next batch of wine
5) Continuous process today = Crystals packed into the conical base of a vertical tank, cooled wine is pumped upwards through the crystal bed, stabilized wine drawn off the top of the tank
PROS: Faster, cheaper & more effective than traditional cold stabilization.
CONS: Same as cold stabilization (though enery costs lower as half the time)
EXAMPLE: Valdivieso (Curicó Valley) uses continuous process on young, early
release wines as is fastest & most energy efficient way of stabilizing wines. Only
efficient for high volume blends
Ion Exchange:
process,
pros & cons
and examples
PROCESS:
1) Passing wine though a resin charged with either Na+ (Sodium ions) or H+
(hydrogen) = replacement of K+
2) Usually treating 2-10% of wine is enough for stability
PROS: Replacing with H+ lowers pH significantly = beneficial in warm regions with
high pH
CONS: Replacing with Na+ can lead to excess sodium = cardiovascular health risks
(EU legal limit of 200mg/L Na+ in wine)
EXAMPLE: Bodegas Monteabellon (Ribera del Duero) - for tartrate stable & to lower
pH for fresher wine
Electrodialysis:
process,
pros & cons
and examples
PROCESS:
1) Passage of potassium, calcium & tartrate ions through selective membranes
under influence of an electrical charge
PROS: Removal of K+ will also result in decrease pH (up to 0,2), small amounts
of VA removed (up to 0,15g/l), low energy consumption, wines don’t need to be
pre-treated (ie. fined), results are reliable
CONS: Very high capital cost + membranes very expensive. Ion exchange is often
preferred today.
EXAMPLE: Gallo Frei Ranch
Metatartaric Acid:
process,
pros & cons and
examples
PROCESS: crystallisation inhibitor
1) Produced by heating tartaric acid to high temp in a closed vessel. During
process, molecules partially polymerize.
2) When added to wine it coats any micro-crystals present in wine & prevents
development to a visible size
3) Added just before filling (bttling) - generally just reds, CMC better for white &
rosé
PROS: Cheap and effective for wines which are consumed young. Ideal for
bag-in-box (12mth shelf life)
CONS: Temporary fix. With time, metatartaric reverts to ordinary tartaric acid
(= possibility of even more tartrate crystals). Happens faster when wine stored
warmer: 25°C for 6 months/ 18°C for 12 months/ 10°C for 24 months.
LEGALS: EU limit is 100mg/L, illegal in Japan
EXAMPLE: Gabriel Meffre, high volume reds wines for early consumption
Carboxymethyl
Cellulose
PROCESS: crystallisation inhibitor
1) Extracted from wood. Like metatartaric acid - coats micro-crystals present &
prevents development to a visible size
2) Add just before bottling (48hrs prior to membrane filt)
PROS: In very stable wine, effects can last up to 4 years
CONS: In very unstable wine, recommended to first use cold, electrodialysis or ion
exchange for best results. Not suitable for reds and rose - reacts with tannins causing haze & becomes ineffective.
EXAMPLE: Product name = celstab
Mannoproteins:
PROCESS: crystallisation inhibitor
1) Purified mannoprotein (in white powder form) added day before bttlng at 200
- 250mg/L
2) Act as protective colloid covering surface of crystal nucleus, inhibiting crystallization process
Technique discovered due to observations that wines aged long time on lees =
greater tartrate stability due to mannoproteins released during yeast autolysis.
PROS: long-lasting effect as protein molecules are relatively stable, can add body
to wine
CONS: much more expensive than CMC and metatartaric acid
EXAMPLE: Product name = Claristar
Gum Arabic
Polysaccharide; added to young wine (meant for early consumption) to slow the
precipitation of colouring matter. Add after cold stabilization.
STATIC STORAGE
Post blending, analysis, stabilization, etc. ’ ensure neutral storage until bottling.
4 key factors:
1) Inert storage vessel (ie. no oxygen ingress possible)
2) Neutral vessel walls; no flavour exchange between wine & vessel walls
3) Vessel must be as large as possible to void “surface effect” (chemical changes occur at interface between liquid & surface. Smaller container = greater ratio of
surface to vol. = greater change in contents over given period)
4) Vessel must be full to top or blanketed by inert gas
- Nitrogen good as does not dissolve in wine, but if wine left too long under pure
N, residual CO2 is lost ’ wine becomes flat (residual CO2 gives wine “lively” taste)
- CO2 = heavier than air. Good for sweeping air out of empty vats but dissolves in
wine, eventually creating room for air to enter headspace
- Best = mixture of N & CO2 (proportions depend on desired CO2 content in wine) or argon
Final Sweetening
Commercial blends often contain added sugars to soften mouthfeel.
Sweetening must occur at last possible moment just before bottlng to decrease risk of microbial attack (esp. yeasts; risk of re-fermentation)
Added sugar:
1) RCGM (rectified concentrated grape must)
2) Süssreserve (unfermented grape juice) for QbA level German wine (Blue Nun,
Black Tower, etc.)
*European regulations forbid adding sucrose (only Champagne liqueur d’expedition is exempt)
Why assess microbial stability
before bottling
(and 4 criteria to use)
Assess to determine if sterile filtration necessary.
1) Does wine have residual fermentable sugar (over 0.5 g/L glucose + fructose)?
2) Does wine have residual malic acid if in pH range for MLF (this pH will vary)?
3) Does wine have Pediococcus?
4) Does wine have Brettanomyces?
If answer to all questions no, sterile filtration not necessary. If yes, determine
population density of microorganisms & critical levels.
Surface film yeasts can only grow in bottle for few days, until dissolved oxygen
depleted. Acetobacter cannot grow unless closure compromised
Sterile filtration
Filtration (~0.45 microns) just prior to bottling to achieve microbiological stability.
Inital coarse filtration necessary to ensure cartridges not clogged overly quickly.
MEMBRANE FILTRATION
Filter very clean wine through cartridge filter:
- Positives: Sterile. Re-usable cartridges. Suitable for all size operations.
- Negatives: Filters = very expensive (300$+/ cartridge). High risk of clogging if
care not taken (wine must be pre-filtered).
- Examples: Globus Wine (Denmark) filter all white & rosé with 0,45μm to avoid risk
of bacteria & MLF after filling. Filter reds with 0,65μm to avoid yeast. 0,65μm are
1/3 price of 0,45μm filters.
Martini & Rossi on all sparkling wines
Cross flow filtration
TANGENTIAL FILTRATION (cross-flow):
- Uses a selective porous membrane whereby circulation of liquid is parallel to
membrane. Technique consists in creating turbulent stream on surface of membrane
= prevents filtered particles to settle on membrane.
- 2 types of membranes: organic (polymers) & inorganic (ceramics)
- Positives: High capacity. Can be automated & run at night. Eco-friendly: no waste.
No need for initial, coarse filtration (1 single filt.). Gentle process; less aroma/
flavour stripping than other methods.
- Negatives: extremely expensive capital investment; only feasible for medium and
large wineries
- Examples: Agricola Sanz (Rueda), Gabriel Meffre. Both companies still do membrane before bttling for max. security.
Alternatives to
sterile filtration - DMDC
Dimethyl dicarbonate
Organic compound in form of colourless liquid added to wine just before bttlng.
Acts as sterilant by inactivating the enzymes in microorganisms (killing them)
Alternative to sterile filtration, pasteurization, & sulphur. Often used in Germany (recently deemed legal throughout EU).
- Similar action to Sorbic Acid (used more widely in USA) aid to bttlng wines with
RS
- Useful as is hydrolyzed by water ’ methanol + C02 after 4hrs. at 20°c so does not
have to be listed as ingredient
- Trade name = VELCORIN
- Example: Serial Wines (Paso Robles ) uses 200ppm just before bttlng to ensure
microbiological stability . Paso = high pH = plus RS makes filtration hard, high chance refermentation in bttle.
- Example: High volume Accolade wine brands (ie. Banrock Station)
Alternatives to
sterile filtration - Heat
Process kills micro-organisms.
Must be carefully managed (can damage wine) & requires energy (added
expense). Heating affects wine maturation (chemical reactions proceed more
quickly at elevated temps).
3 methods: Flash pasteurization, tunnel pasteurization or thermotic bottling
1) FLASH PASTEURIZATION:
- Heat exchanger raises temp rapidly to very high level (~75°C for up to 30 seconds)
then brings back down again to original temp just as quickly (process used for
pasteurized milk)
- Simple equipment = metal plate heat exchanger placed between wine vat & bttlng
machine. Wine is heated & cooled before reaching filler (knocks out all bacteria &
yeasts). Potentially problematic as wine could be re-infected by bttlng machinery
& materials. All must therefore be sterilized
- Example: Louis Latour does this on all red wines, considers it preferable/ less
harmful to aromas & flavour vs. filtration
2) TUNNEL PASTEURIZATION:
- Heating wine in bttle after bttlng & capping.
- Wine bttled cold then passed slowly through large tunnel spraying hot water ’
wine temp raised to 82°C for ~15 mins. ’ followed by sprays of cold water to bring
wine back to room temp.
- Equipment expensive to install (large heat tunnel fitted with conveyors, water
sprayers, pumps & heaters). Also expensive energy use; though modern wineries
make use of heat exchangers
- Pros: no need for sterile bottling
- Cons: expensive equipment, heat damage
- Example: low end sparklings
3) THERMOTIC BOTTLING:
- Wine passed through heat exchanger until reaches 54°C (much lower than
standard sterilizing temp of 82°C). Wine is bttled at 54°C, packed in cases & stored
in warehouse to cool slowly to ambient temp. Yeast & bacteria killed by exposure
to elevated temp for extended period.
- Previously considered controversial (wine damage), now, thanks to precise temp
control proven untrue.
- Pros: no need for sterile bottling; advance maturity of young reds (softer, rounder
mouthfeel)
- Cons: Allowance must be made for contraction of wine. When filled to standard
level hot, will be under filled when descends to room temp.
- Examples: bulk, low end wines (Castel, JeanJean)
Standard bottling
With time & quality oriented wmkg practices, wine will naturally self clarify ’ can be
bttled without fining / filtration (provided has fermented dry & cork is sound).
Minimalist tech approach
-fining only if necessary
- racking to ‘cellar bright ’
- bttlng with no further treatment (save readjusted SO2 levels if necessary)
Likely some harmless deposit will develop after few weeks/ months.
Principles of sterile
(aseptic) bottling
Removal of yeasts & bacteria which cause re-fermentation, VA, taint, etc.
Principles:
- Critical factor = microbiological “loading” (population density of microorganisms).
Above certain level = organisms will multiply & wine will spoil
- Only truly “aseptic” wine packaging = cardboard brick ’ packaging sterilized by UV
radiation + filling takes place in sterile enclosure
- Ordinary bttle filling machinery = no sterilization of enclosure or air entering filler
bowl, just strict hygiene
- Interior of filler, tanks holding filtered wine, pipework & filters all sterilized before
each operation. Purpose = eliminate any breeding colonies & keep n° of viable
microorganisms low
- Sterilization = flushing with high volume of hot water (90°C) for at least 20
mins. Dual effect of cleaning out any residues & killing microorganisms. Steam less
effective as can bake on residues if system not thoroughly flushed with water prior
to steaming. - Alternative = chemical sterilization ’ peracetic acid (breakdown products = non-toxic hydrogen peroxide + acetic acid). Can also be left inside equipment to act as
residual sterilant. - N.B. Chlorine-based sterilants (like hypochlorite) no longer advised. Could lead
to formation of TCA.
Examples: Gabriel Meffre
Avoiding contamination
risks: bottles
Bottles should be freshly purchased, packed on good pallets, tightly shrink
wrapped & not stored longer than 1 month to avoid possible contamination
Bottle rinsing = required by major retailers
- Bttle rinse machines ’ rinse water = filtered through a 0.2μ membrane and/ or
treated with SO2 or ozone
- After rinsing bttles held at angle to facilitate thorough drainage or rinsed with
filtered water
- Gallo uses nitrogen purge, validates bottle shape (mould #) can be rinsed
Avoiding contamination
risks: corks
Corks must be purchased in sealed plastic bags, sterilized either by SO2 or gamma
radiation
Bottling options:
small wineries
Most small wineries (~5000 - 20 000 cases/ year) start with limited bttling equipment:
- “bench top” manual filler & (possibly) a semi-automatic labeler
