White Winemaking

Question 1

Steps to making white wine

Answer 1

1) hand or machine harvested
2) berries/ whole clusters transported to winery
3) sorting
4) de-stem or not
5) press or crush
- crushing for skin contact
6) press fractions
7) hyperoxidation/ clarification/must adjustments (can skip all)
8) alcoholic fermentation
9)post-fermentation adjustments / malo (can skip all)
10) newly made wine

Question 2

Skin contact

Answer 2

• the process of leaving the juice in contact with the skins (1-24hrs around 15C/59F) to extract compounds from the skins
• carried out on crushed white grapes
• done to enhance the texture of a wine by extracting a small amount of tannin
• not generally done on delicate, fruity grapes
• most often done on aromatic varieties: Riesling, Viognier, Gewurztraminer, Muscat, and Sauvignon Blanc / seldom see oak
• not meant to drink young as tannins don’t have time to soften
• underripe fruit with skin contact would be bitter with astringent tannins
• adds cost/ time
• can lead to homogenization

Question 3

Orange wine

Answer 3

White grapes fermented on their skins

Question 4

Pressing white grapes

Answer 4

• gentle press to avoid unwanted extraction
• usually grapes are de-stemmed and crushed before being loaded into the press (free run juice created) but whole clusters pressing does happen (gentlest form of pressing, also less risk of oxidation especially with inert gas)
• stems can help break up the mass of skins by providing channels for the juice to drain
• whole bunch pressing only done in small batches, adding to time and cost
• free run juice is the lowest in solids, tannin, color, and pH / highest in acid and sugar
• once pressing, the first press fraction is the most similar to free-run juice

Question 5

Hyperoxidation

Answer 5

• the technique of deliberately exposing the must to large quantities of oxygen before fermentation with the aim of a wine more stable against oxidation
• can also remove bitter compounds that come from unripe stems, seeds, and skins
• can destroy volatile aroma compounds so generally used on neutral grapes
• is targets the compounds that oxidize most readily, turning must completely brown (during fermentation they precipitate and the wine goes back to normal color)
• not particularly expensive but does add time

Question 6

Clarification of the must

Answer 6

• occurs between pressing and fermentation
• aims to reduce suspended solids in the must to 0.5-2% (levels below 1% can only be achieved through pectolytic enzymes or centrifugation)
• higher solids levels add texture to the wine via giving subtle astringency and gives a greater range of aromas from fermentatation
• lower solids levels are better for maintaining fruitiness
• fermentations with higher %’s of solids can lead to off-flavors (ex: sulfur) so careful management is needed, thus better suited to small production
• a small amount of solids are needed as it provides nutrients for yeast

Options:
1) sedimentation
2) floatation
3) centrifugation
4) clarifying agents

Question 7

Sedimentation

Answer 7

• the simplest form of clarification where the solids are left to fall over time with gravity
• must is commonly chilled to 4C/39F to reduce oxidation and threat of spoilage organisms and to avoid spontaneous fermentation
• sedimentation at low temps take longer
• rate depends on the size and shape of the vessel (depth solids need to fall)
• the clear juice is transferred to a fermentation vessel and the solids are often put through cross-flow filtration to extract more juice
• can be done on must or wine
• no xtra equipment or additives needed must it does take the most time and chilling adds cost
• small production of premium wines

Question 8

Flotation

Answer 8

• bubbling gas up through the must, bringing up solid particles with them which are skimmed off the top
• speeds up rate of clarification
• generally inert gas like nitrogen but oxygen/hyperoxidation can be done simultaneously
• can only be used on must
• equipment, gases, and fining agents needed but it is fast and doesn’t need chilling

Question 9

Centrifugation

Answer 9

• a machine that comprises a rapidly rotating container which uses centrifugal force to separate solids and liquids
• very fast, very expensive
• can be flushed with inert gas, adding more cost
• can be used on wine or must
• high volume production

Question 10

Clarifying agents

Answer 10

• compounds added to the must to speed up the rate of sedimentation
• aka pectolytics enzymes
• they break down pectins (naturally found in plant wall cells) in the must allowing for rapid separation between the juice liquid and solids
• can only be used in must (others exist for post-fermentation)
• must purchase but saves on energy and time

Question 11

Fermentation temperatures

Answer 11

• generally cooler for whites than red because the volatile aroma and flavor compounds desired in white wines (like esters) are better retained at cool temperatures (around 15C/59F)
• slightly warmer temperatures (17-25C / 63-77F) may be used for non-fruity wines that see oak to promote yeast health and avoid production of certain esters (like isoamyl acetate or banana smell)
• stainless steel easiest to control temp

Question 12

Fermentation vessels

Answer 12

• stainless steel best for fruity, floral whites due to the ability to control temperature
• concrete or old oak may be used for slightly warmer fermentations
• small oak fermentation have deeper color and fuller body due to oxidation, contact with lees, and oak-derived aromas (often seen on premium Chardonnay)