P3

Question 1

Methods for Tartrate Stabilization

Answer 1

Cold Stabilization
Contact Process
Ion Exchange
Electrodialysis
Metatartaric acid
Carboxymethylcellulose (CMC)
Mannoproteins

Question 2

Electrodialysis - what? Advantages? Disadvantages?

Answer 2

Allows passage of potassium and calcium ions through a special membrane under the influence of an electric charge.
Adv: lower energy cost (wine treated at normal temp); treatment tailored to each wine; both K and Ca tartrates removed; filtration only required prior; results RELIABLE; very little wine loss; pH lowered ~ 0.15 units
Dis: high capital cost - mostly suitable only for large wineries (unless portable custom electrodialysis services in region).

Question 3

Mannoproteins

Answer 3

Released from yeast cell walls during yeast autolysis; act as protective colloid that covers surface of nucleus used for crystallization; works only for Potassium bitartrate, no effect on Sodium tartrate; long-lasting effect because the protein molecules are stable.

Question 4

Cold Stabilization - What? Advantages? Disadvantages?

Answer 4

Wine is chilled to ~-4C (just above freezing point, -8C for fortified), stored in insulated tanks for up to 8 days - this precipitates the tartaric acid into crystals which can be removed by racking and filtering.
Adv: can do large volumes, is a passive process, little impact on flavors and aromas
Dis: expensive (very energy intensive); inefficient (seed crystals lie on bottom of tank, not much convection to get more wine in contact with them); can be inhibited by colloidal protection (coating “seeds”) - later, colloids denature, protection gone, tartrates precipitate - ie, may not be adequately stabilized; can work for K bitartrate, but Ca tartrate’s solubility changes little by lowering the temperature.

Question 5

Contact Process - What? Advantages? Disadvantages?

Answer 5

Similar to cold stabilization in that the wine is chilled (less, 0C is adequate), then seeded with finely ground Potassium bitartrate (act as nuclei, enabling easier crystallization) - 4g/L is the common dose - vigorous stirring for 1-2 hours (keep seeds in suspension to have greater contact). Filtration removes crystals (can be used for next batch!) - new development is the continuous contact process (crystals packed into conical base of vertical tank, wine pumped upwards through crystal bed - need to regularly open and remove enlarged crystal bed).

Adv: relatively inexpensive, effective, quick
Dis: specialized equipment, trained operators