Making Wine from Riesling Grapes

Introduction to Riesling

Riesling stands as one of the noble grape varieties of the world, revered by wine professionals and collectors for its extraordinary ability to express terroir, age gracefully, and produce wines across the entire sweetness spectrum -- from bone-dry to lusciously sweet. For the home winemaker, Riesling presents both a fascinating challenge and a deeply rewarding project.

Origins and Historical Significance

Riesling's documented history traces back to 1435 in the Rhine region of Germany, making it one of the oldest identified grape varieties still widely cultivated today. The grape found its spiritual home along the steep, slate-covered slopes of the Mosel, Rheingau, and Pfalz regions, where it produces some of the most sought-after white wines on earth.

German immigrants brought Riesling to the New World in the 19th century, establishing plantings in the Finger Lakes region of New York, parts of Washington State, and the Clare and Eden Valleys of Australia. Today, Germany remains the largest producer, followed by Australia, France (Alsace), and the United States.

Why Riesling Appeals to Home Winemakers

Riesling's appeal for home winemakers lies in its versatility. From the same batch of grapes, you can produce a dry, off-dry, or sweet wine simply by managing fermentation and residual sugar. The grape's naturally high acidity provides a built-in safety net, keeping wines fresh and balanced even with significant residual sugar. Riesling also ages beautifully -- well-made examples develop complex petrol, honey, and lanolin notes over years of cellar storage.

Growing Conditions and Grape Selection

Climate and Terroir

Riesling is a cool-climate grape that performs best where temperatures stay moderate during the growing season. The variety buds late, reducing frost risk, but also ripens late, requiring a long growing season to develop full flavor maturity. Ideal regions offer warm days and cool nights to build sugar while preserving acidity.

The grape has a particular affinity for slate and mineral-rich soils, which many believe contribute to Riesling's characteristic mineral and petrol notes. Steep, south-facing slopes maximize sun exposure in cooler regions, helping the late-ripening grape reach maturity.

In North America, top regions for Riesling include the Finger Lakes (New York), Columbia Valley (Washington), and parts of Michigan and Ontario. Home growers in USDA zones 5-7 can successfully cultivate Riesling with proper site selection.

Selecting and Sourcing Grapes

When purchasing Riesling grapes, the sugar level at harvest determines your wine style:

• Dry wine: Harvest at 18-21 Brix, targeting 10-12.5% alcohol
• Off-dry wine: Harvest at 21-24 Brix, fermenting partially
• Sweet/late harvest: Harvest at 24-30+ Brix for dessert-style wines

Look for grapes with titratable acidity (TA) between 8-12 grams per liter and a pH of 2.9-3.2. Riesling's naturally high acidity is one of its defining characteristics and should be preserved.

Understanding Botrytis in Riesling

Unlike most white grapes where botrytis is unwelcome, noble rot (Botrytis cinerea) is prized in certain Riesling styles. Noble rot concentrates sugars and adds complex honey, apricot, and ginger notes to the wine. German classification terms like Beerenauslese (BA) and Trockenbeerenauslese (TBA) describe wines made from botrytis-affected grapes at extreme sugar concentrations.

For home winemakers, achieving controlled botrytis is difficult. If you encounter grapes with clean, uniform golden-brown botrytis infection, consider making a small-batch dessert wine. Discard any grapes with gray, fuzzy mold -- this is undesirable gray rot rather than noble rot.

Winemaking Process

Crushing, Pressing, and Juice Handling

Handle Riesling grapes gently to avoid excessive phenolic extraction. Whole-cluster pressing is the preferred method, producing the cleanest, most delicate juice. If you must crush first, minimize skin contact time -- no more than 2-4 hours at cold temperatures.

Add 25-40 ppm sulfite to the juice immediately after pressing. Allow the juice to cold settle at 40-50 degrees Fahrenheit for 24-48 hours, then rack the clear juice off the heavy lees.

Riesling juice often starts with very high acidity. If the TA exceeds 10 grams per liter, consider a partial acid reduction using potassium bicarbonate or calcium carbonate before fermentation. However, be conservative -- Riesling needs its acidity for balance, especially if you plan to leave residual sugar.

Yeast Selection for Riesling

Choosing the right yeast profoundly impacts Riesling character. Recommended strains include:

• Lalvin QA23: Excellent for aromatic white wines, enhances citrus and floral notes, ferments well at cool temperatures.
• Lalvin W15: Promotes tropical fruit character with good acid preservation.
• Steinberger (available from some specialty suppliers): Traditionally used for German Riesling, produces classic petrol precursors.
• Uvaferm SVG: Low nutrient requirement, good for delicate styles.

For sweet wines where you want fermentation to stop naturally, select a yeast with lower alcohol tolerance (12-13%) so it dies off before consuming all available sugar.

Fermentation Temperature and Protocol

Riesling demands cool fermentation at 48-58 degrees Fahrenheit (9-14 degrees Celsius). This slow, extended fermentation preserves Riesling's delicate floral and fruit aromatics -- particularly the monoterpene compounds (linalool, geraniol, nerol) responsible for its characteristic floral bouquet.

Follow a staggered nutrient addition protocol to support healthy yeast through the long, cool fermentation:

1. Add one-third of total nutrients at yeast pitching
2. Add one-third when fermentation is visibly active (around 2-3 Brix drop)
3. Add the final third at approximately one-third sugar depletion

Total nutrient addition should be about 25-30 grams of Fermaid-O per hectoliter or equivalent. Monitor fermentation daily with a hydrometer and be prepared for a slow process -- cool Riesling fermentations often take 4-6 weeks.

Managing Sweetness Levels

The most distinctive aspect of Riesling winemaking is the ability to produce wines at various sweetness levels:

• Dry (Trocken): Ferment to complete dryness (less than 4 g/L residual sugar)
• Off-dry (Halbtrocken/Feinherb): 10-20 g/L residual sugar
• Medium-sweet (Spatlese): 20-50 g/L residual sugar
• Sweet (Auslese and above): 50+ g/L residual sugar

To produce an off-dry or sweet Riesling, you must stop fermentation before all sugar is consumed. Methods include:

1. Chilling: Drop temperature to 28-32 degrees Fahrenheit to halt yeast activity
2. Sulfite addition: Add 100+ ppm SO2 along with chilling
3. Sterile filtration: Filter to 0.45 microns to remove yeast cells
4. Fortification: Add grape spirits to raise alcohol above yeast tolerance (for dessert styles)

After stopping fermentation, add potassium sorbate (1/2 teaspoon per gallon) to prevent refermentation in the bottle.

Flavor Profile and Characteristics

Aromatic Complexity

Riesling is among the most aromatically complex white grapes. Young wines typically display:

• Floral notes: Orange blossom, jasmine, honeysuckle, lime blossom
• Fruit notes: Green apple, white peach, apricot, lime, mandarin
• Mineral notes: Wet slate, crushed rock, saline, chalk

As Riesling ages, it develops distinctive secondary and tertiary aromas including petrol (from TDN, or trimethyldihydronaphthalene), honey, beeswax, lanolin, toast, and dried fruit.

Acid Structure

The hallmark of great Riesling is the interplay between sweetness and acidity. Even sweet Riesling wines taste balanced and refreshing because their high acid (often 7-10 g/L TA) counteracts the sugar. This balance is what makes Riesling one of the longest-lived white wines in the world.

Dry vs. Sweet Riesling

The debate over dry versus sweet Riesling is ongoing in the wine world. Dry Riesling showcases pure mineral and citrus character with a steely backbone. Off-dry and sweet Riesling offers a more generous, fruit-forward experience that many consumers find immediately appealing. As a home winemaker, experiment with both styles to discover your preference.

Post-Fermentation Care

Malolactic Fermentation Considerations

Most Riesling producers avoid malolactic fermentation entirely, as it softens the crisp acidity that defines the variety. Add sulfite after primary fermentation to inhibit MLF. In rare cases where acidity is excessively high (TA above 12 g/L), a partial MLF can be beneficial, but this requires careful monitoring and the ability to halt the process once sufficient acid reduction has occurred.

Aging and Stabilization

Riesling benefits from extended lees contact (sur lie aging) for 2-4 months after fermentation. Stir the lees gently every 1-2 weeks (batonnage) to enhance mouthfeel and complexity. Rack off lees when you are satisfied with the texture.

Cold stabilize at 28-32 degrees Fahrenheit for 2-3 weeks to remove tartrate crystals. Fine with bentonite (1-2 grams per gallon) for protein stability. If making a sweet style, ensure the wine is perfectly stable before bottling -- any residual yeast activity in bottle can cause dangerous pressure buildup.

Bottling

Bottle Riesling 4-8 months after harvest for fresh styles, or after 12+ months for more complex, aged expressions. Use screw caps or technical corks to maintain freshness. Target 30-45 ppm free SO2 at bottling, adjusting upward for sweet wines that need additional microbial protection.

Food Pairing Suggestions

Riesling's high acidity and range of sweetness levels make it one of the most versatile food wines ever produced:

• Dry Riesling: Pairs beautifully with sushi, raw oysters, light fish dishes, and fresh salads
• Off-dry Riesling: Ideal with spicy Asian cuisine, Thai curries, Indian dishes, and Szechuan food -- the sweetness tames the heat
• Sweet Riesling: Classic with foie gras, blue cheese, fruit desserts, and apple-based dishes
• All styles: Excellent with pork, especially smoked pork chops, roast pork loin, and charcuterie

The wine's lower alcohol also makes it ideal for afternoon sipping and warm-weather entertaining.

Frequently Asked Questions

What makes Riesling different from other white wines?

Riesling stands apart due to its extraordinary aromatic complexity, naturally high acidity, low to moderate alcohol, and ability to produce wines across the entire sweetness spectrum. The grape also ages far better than most white varieties, developing complex petrol and honey notes over decades. Its high acidity provides a natural preservative that supports long-term cellaring.

How do I make a dry Riesling at home?

To make dry Riesling, harvest grapes at 18-21 Brix, ferment to complete dryness (specific gravity below 0.996), and add sulfite promptly after fermentation to prevent malolactic fermentation. Use a yeast with high alcohol tolerance like QA23 to ensure complete sugar consumption. The resulting wine should have less than 4 grams per liter of residual sugar.

Why does my Riesling smell like petrol?

The petrol or kerosene aroma in Riesling comes from a compound called TDN (1,1,6-trimethyl-1,2-dihydronaphthalene). TDN develops during aging from carotenoid precursors in the grape. Warm-climate Rieslings and wines exposed to heat or light develop more TDN. In moderate amounts, petrol is considered a positive characteristic of aged Riesling. Storing wine in cool, dark conditions slows TDN development.

Can I make sweet Riesling without it referementing in the bottle?

Yes, but it requires careful stabilization. After stopping fermentation at your desired sweetness level, add potassium sorbate (1/2 teaspoon per gallon) and potassium metabisulfite (1/4 teaspoon per 6 gallons). Ideally, also sterile filter to 0.45 microns. Store the bottled wine in a cool location and check a few bottles periodically for signs of renewed fermentation such as spritziness or pressure buildup.

What is the best yeast for Riesling?

Lalvin QA23 is widely regarded as the top choice for Riesling, offering excellent aromatic enhancement, reliable cool-temperature fermentation, and good acid preservation. W15 is another strong option for a more tropical profile. For traditional German-style Riesling, specialty strains like Steinberger can produce authentic character.

How long can homemade Riesling be aged?

Well-made dry Riesling can age 5-10 years or more with proper storage. Sweet Rieslings, with their higher sugar and acid levels, can age even longer -- sometimes 15-20 years or beyond. Key factors for aging potential include sufficient acidity (TA above 7 g/L), proper sulfite levels, quality closures, and storage at a consistent 50-55 degrees Fahrenheit.

Is Riesling a good grape for beginner winemakers?

Riesling is a moderately challenging grape for beginners because it demands cool fermentation temperatures and careful acid management. However, its natural acidity provides a buffer against many common winemaking faults, and the option to leave residual sugar can mask minor imperfections. If you can maintain cool fermentation temperatures, Riesling is an excellent choice.

How do I reduce excessive acidity in Riesling?

If your Riesling juice has TA above 10-11 g/L, you have several options. Potassium bicarbonate (3.4 grams per gallon reduces TA by about 1 g/L) is the most common chemical approach. Cold stabilization also removes some acidity as potassium bitartrate crystals precipitate. Blending with a lower-acid wine is another effective strategy. Always make acid adjustments before fermentation and confirm results with a test kit.