Port vs Ice Wine vs Late Harvest: Making Sweet Wines at Home

Sweet wines represent winemaking at its most concentrated and indulgent. Port, ice wine, and late harvest styles each achieve sweetness differently. Here is how to make them at home.

Understanding Residual Sugar

Sweet wines retain unfermented sugar. This happens three ways:

• Fortification: Adding spirits kills yeast before fermentation completes
• High initial sugar: So much sugar that yeast die from alcohol before finishing
• Stopping fermentation: Chilling, sulfiting, or filtering to halt yeast activity

Port-Style Wine

Port is fortified during fermentation, trapping sweetness while boosting alcohol.

Process:

1. Start with high-Brix grapes (24-26 Brix minimum)
2. Ferment with frequent punch-downs for extraction
3. When specific gravity reaches 1.020-1.030 (still sweet), add grape brandy
4. Add enough brandy to reach 18-20% alcohol (kills yeast)
5. Press and age

Brandy calculation: Use the Pearson Square to determine how much spirit to add. Target final alcohol and current alcohol determine the ratio.

Aging: Ruby-style ages briefly; Tawny-style ages in barrel for years.

Late Harvest Wine

Grapes left on the vine past normal harvest dehydrate and concentrate sugars.

Process:

1. Leave grapes on vine until Brix reaches 30-35+
2. Harvest carefully (grapes are fragile)
3. Press gently to extract thick, syrupy juice
4. Ferment with yeast capable of high sugar environments (BA-11, S. bayanus)
5. Fermentation will likely stop naturally around 12-14% alcohol with residual sugar
6. Stabilize to prevent refermentation

Challenges: Bird and rot losses on the vine. Very slow fermentation. Potential stuck fermentation.

Ice Wine (Eiswein)

True ice wine freezes grapes on the vine, then presses while frozen to concentrate sugars.

Process:

1. Leave grapes until hard freeze (below 18°F)
2. Harvest while still frozen (usually before dawn)
3. Press immediately while frozen—water stays as ice, concentrated juice flows out
4. Ferment resulting high-Brix juice (35-42+ Brix)
5. Long, slow fermentation yields low alcohol and high residual sugar

Challenges: Requires sustained cold climate. Risk of losing entire crop to weather. Tiny yields.

Cheat method: Freeze-concentrate regular juice in your freezer. Not technically ice wine, but produces similar results.

Stabilization Is Critical

Sweet wines must be stabilized to prevent refermentation:

• Potassium sorbate prevents yeast reproduction
• Sulfite (K-meta) provides additional protection
• Sterile filtration removes remaining yeast
• High alcohol (fortified wines) naturally inhibits yeast

Unstabilized sweet wine in bottles eventually referments—potentially explosively.

Start Simple

Port-style is the most accessible sweet wine for beginners—the fortification process is forgiving. Late harvest requires excellent fruit and patience. Ice wine demands specific climate conditions most home winemakers cannot provide naturally.