Sparkling Wine Production: From Grape to Glass
Protein Bankruptcy in Wine
Protein bankruptcy occurs when grape proteins and yeast in wine coagulate due to heat, cold, or the presence of tannins. This coagulation creates a haze in the bottle, affecting the wine’s clarity. Red wines are less susceptible to protein bankruptcy because tannins bind with proteins during barrel aging. White wines, however, retain proteins that need removal before bottling.
Treatment
Bentonite, a clay material with a negative charge, effectively removes positively charged wine proteins through electrostatic adsorption. Available in powder or granular form, bentonite swells tenfold in water, forming a large-surface-area colloid that enhances its adsorbent properties. To use bentonite:
- Hydrate it in cold or warm water for 24 hours, stirring to form a gel or paste.
- Gradually add the bentonite mixture to the wine while stirring continuously for 5-10 minutes.
Heat Test for Protein Stability
To assess protein stability, perform a heat test:
- Fill a test tube with wine and add a pinch of tannin.
- Stir the mixture and heat it in a water bath at 80°C for 30 minutes.
- Cool the test tube in a refrigerator for 4 hours.
If the wine remains clear, it indicates protein stability. However, a whitish deposit or haze suggests the presence of proteins prone to bankruptcy. Tannin is used in this test as it promotes protein precipitation and flocculation. A nephelometer can also detect protein presence.
Identifying Protein Bankruptcy
To differentiate protein bankruptcy from iron haze:
- Add a few drops of hydrochloric acid to the cloudy wine.
- Increased turbidity indicates protein bankruptcy.
- Heating the wine to 80°C will solubilize protein deposits, confirming protein bankruptcy.
Sparkling Wine Production
Sparkling wines, characterized by their effervescence, contain significant amounts of carbon dioxide (CO2) derived from natural or induced fermentation. This CO2 can originate from the initial alcoholic fermentation of grapes or a secondary fermentation in the bottle.
Types of Sparkling Wine
- Champagne: Produced exclusively in the Champagne region of France using the traditional method, involving secondary fermentation and aging in the bottle.
- Cava: Spanish sparkling wine with a Denominación de Origen (DO) status, made from specific grape varieties using the traditional method.
- Other Sparkling Wines: Produced using similar methods but without specific geographical indications.
Sparkling Wine Production Phases
1. Tirage and Secondary Fermentation
- Bottled wine is mixed with a”tirag” solution (sugar and yeast) to initiate secondary fermentation.
- Bottles are sealed with a temporary cap and stacked horizontally for 1-2 months at 10-15°C.
- Slow fermentation creates fine bubbles and enhances quality.
2. Aging on Lees
- Yeast cells settle to the bottom of the bottle after fermentation.
- Aging on lees (dead yeast cells) for 9 months to 5 years imparts complex flavors and aromas.
- Periodic riddling (rotating bottles) prevents yeast adherence to the bottle walls.
3. Disgorging and Dosage
- Bottles are gradually rotated neck-down (remuage) to collect lees in the neck.
- The bottle neck is frozen, trapping the lees.
- The bottle is opened, expelling the frozen lees (dégorgement).
- A”dosag” (sugar solution) is added to adjust sweetness levels, resulting in different styles (e.g., brut, extra dry, demi-sec).
4. Corking and Aging
- Bottles are sealed with a cork and wire cage.
- Further aging enhances complexity and integration of flavors.
Other Sparkling Wine Production Methods
- Transfer Method: Similar to the traditional method, but after secondary fermentation, the wine is transferred to a tank, filtered, and re-bottled.
- Tank Method (Charmat): Secondary fermentation occurs in large, pressurized tanks, followed by filtration and bottling. This method is faster and more cost-effective but may result in less complex flavors.