Pre-Bottling Stabilization Checklist
Comprehensive technical checklist for wine stabilization before bottling; analytical targets, treatment protocols, and quality verification procedures.
Pre-Bottling Stabilization Checklist
Problem Definition
Bottling unstable wine leads to post-bottling defects including protein haze, tartrate crystals, microbial spoilage, oxidation, and refermentation. A systematic pre-bottling stabilization protocol ensures all potential instabilities are addressed before the irreversible bottling step. This checklist approach covers microbiological, chemical, and physical stability with analytical targets and treatment options.
Technical Context
Stability Categories
Microbiological Stability:
Chemical Stability:
- Oxidation potential
- Sulfur dioxide levels
- Color stability (red wines)
Physical Stability:
- Protein stability (white wines)
- Tartrate stability
- Particulate matter (clarity)
Checklist Protocol
Phase 1: Microbiological Assessment
1.1 Yeast Activity
| Test | Target | Risk if Failed |
|---|---|---|
| Residual sugar | <2 g/L (dry wines) | Refermentation |
| Yeast count (plating) | <10 CFU/mL | Refermentation |
| Microscopy | No budding cells | Active fermentation |
Action if Failed:
- Complete fermentation if RS present
- Sterile filtration (0.45 μm)
- SO₂ adjustment
1.2 Bacterial Activity
| Test | Target | Risk if Failed |
|---|---|---|
| Malic acid (if MLF unwanted) | <0.3 g/L or >2.5 g/L | Unwanted MLF in bottle |
| Lactic acid bacteria (plating) | <10 CFU/mL | MLF, spoilage |
| 4-EP/4-EG (optional) | <400 µg/L (4-EP) | Brettanomyces |
Action if Failed:
- Complete or prevent MLF
- Sterile filtration
- SO₂ adjustment
- DMDC treatment (where legal)
Phase 2: Chemical Assessment
2.1 Sulfur Dioxide
| Parameter | White Wine Target | Red Wine Target |
|---|---|---|
| Free SO₂ | 25-40 mg/L | 20-30 mg/L |
| Molecular SO₂ | 0.5-0.8 mg/L | 0.5-0.6 mg/L |
| Total SO₂ | <150-200 mg/L | <150 mg/L |
Calculate Molecular SO₂:
Molecular SO₂ = Free SO₂ × (% molecular at wine pH)Action if Low:
- SO₂ addition (potassium metabisulfite)
- Retest after 24 hours equilibration
2.2 pH and Titratable Acidity
| Parameter | Typical Range | Concern |
|---|---|---|
| pH | 3.0-3.8 | High pH = instability risk |
| TA | 5.0-8.0 g/L | Balance verification |
Action if pH High:
- Acid adjustment (tartaric acid)
- Increase SO₂ to maintain molecular levels
2.3 Volatile Acidity
| Parameter | Target | Action Threshold |
|---|---|---|
| VA | <0.6 g/L (preferred) | >0.8 g/L concerning |
| Legal limit | <1.2 g/L (varies) | Regulatory compliance |
Action if High:
- Blending with low-VA wine
- No correction treatment available
- Prevent further increase (temperature, SO₂)
Phase 3: Physical Stability
3.1 Protein Stability (White Wines)
Heat Test Protocol:
- Heat wine sample to 80°C for 6 hours
- Cool to 4°C for 24 hours
- Compare to unheated control
- Visual assessment: Haze or precipitate = UNSTABLE
Action if Unstable:
- Bentonite fining (0.25-1.0 g/L)
- Retest after settling
- Iterate until stable
Cold Stability Test:
- Cool wine to -4°C for 72 hours
- Check for crystal formation
- Alternatively: Conductivity-based testing (DIT)
Action if Unstable:
- Cold stabilization (traditional)
- CMC addition (where legal)
- Metatartaric acid (temporary)
- Electrodialysis or ion exchange
3.3 Clarity
| Test | Target |
|---|---|
| NTU (turbidity) | <1.0 (white); <2.0 (red) |
| Visual | Bright, no haze |
Action if Unclear:
- Extended settling
- Fining (isinglass, gelatin)
- Filtration (pad or membrane)
Phase 4: Final Verification
4.1 Sensory Evaluation
- No off-aromas (reduction, VA, Brett)
- Style confirmation
- Closure decision (cork, screwcap)
- Blend approval
4.2 Analytical Panel
| Parameter | Test |
|---|---|
| Alcohol | Ebulliometry or NIR |
| Residual sugar | Enzymatic or reducing sugar |
| Free/Total SO₂ | Ripper or A/O |
| pH | Meter |
| TA | Titration |
| VA | Cash still or enzymatic |
| Color (red) | Spectrophotometric |
4.3 Label Compliance
- Alcohol declaration (tolerance: ±0.5%)
- Allergen labeling (sulfites, fining agents)
- Origin claims verified
- Varietal claims verified
Phase 5: Bottling Preparation
5.1 Equipment Verification
- Filter integrity (bubble point test)
- Bottle inspection (clean, no damage)
- Closure quality check
- Fill head calibration
- Labeler alignment
5.2 Environment
- Bottling line sanitation
- Ambient temperature (avoid thermal shock)
- Inert gas supply verified
- Dissolved oxygen monitoring
5.3 Documentation
- Lot traceability
- Batch records
- Retention samples
- QC sign-off
Treatment Timing
Recommended Sequence:
| Treatment | Timing Before Bottling |
|---|---|
| Fining (protein) | 2-4 weeks |
| Cold stabilization | 1-3 weeks |
| Tartrate treatment (CMC) | 1-2 weeks |
| SO₂ adjustment | 3-7 days |
| Final filtration | 24-48 hours |
| Bottling | Day 0 |
Rest Period:
- Minimum 24-48 hours post-treatment before bottling
- Allows equilibration and settling
Practical Implications
Style-Specific Considerations
- Base wine fully stable before tirage
- Secondary fermentation follows
- Final stabilization at disgorgement
- Sterile filtration mandatory
- Enhanced microbial testing
- Aseptic bottling environment
Unfiltered Wines:
- Higher settling time
- Accept sediment formation
- Consumer communication important
Red Wines:
- Color stability assessment
- Protein stability usually not required
- Tartrate assessment still needed
References
-
Zoecklein, B.W., Fugelsang, K.C., Gump, B.H., & Nury, F.S. (1999). “Wine Analysis and Production.” Springer. Publisher Link
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Ribéreau-Gayon, P., Glories, Y., Maujean, A., & Dubourdieu, D. (2006). “Handbook of Enology, Volume 2.” Wiley. Publisher Link
-
OIV (2023). “International Code of Oenological Practices.” https://www.oiv.int
-
Boulton, R.B., et al. (1999). “Principles and Practices of Winemaking.” Springer. Publisher Link
Last Updated: January 6, 2026