Riesling is revered the world over for its versatility. The aromatic white wine grape can be made in various styles – often with a focus on sweetness levels. The possible pairings with food are wide-ranging, thus so are the ways Riesling can be made. It is because of these possibilities that I love making Riesling.
If you aren’t familiar with Riesling, set up a tasting with friends. Find the myriad styles available. Supermarkets will have a few inexpensive, low alcohol, off-dry Rieslings. A wine shop is a better place to look, the proprietor is likely dedicated to finding more unique versions of Riesling than the larger chain markets. If possible, focus on having one of each style represented: dry, off-dry, medium sweet, sweet and luscious.
Now, let’s find some grapes. Establish contact with your local grape growers association and get in touch with any growers who have Riesling. Arrange to harvest your grapes. It is best to establish this relationship early in the year, shortly after fruit set (June).
Visit the vineyard regularly to monitor the vintage. Everyone’s preferred ripeness level varies. Essentially, what you are looking for is a subtle shift in the acidity (@ about 3.00 pH) and a development of aromas (oil, mineral, white peach) at about 22 Brix.
At the Winery
When the grapes arrive at the winery, they should be gently pressed to about 150 Gal/Ton. Adding sulfur at 40 ppm. helps to retain Riesling’s aromatics. Adding pectolytic enzymes at 25 mL/Ton aids the settling of the vineyard lees. The must (juice) should be cold settled at about 45ºF for a minimum of one day.
While the must settles, a comprehensive analysis, including Brix, pH, and TA (Titratable Acidity) should be done. Barring anything unexpected, lets suppose we have a must that is 3.1 pH and 22 Brix with a TA of about 8. These are generally “good” numbers for a light, aromatic white wine.
Let’s backtrack to the tasting. There were several styles of Riesling, including dry, slightly sweet, and sweeter. How can we make our own version of each wine from one grape juice?
Save The Juice
A small portion of the juice should be reserved (~10%), sulfured with another 50 ppm, and kept cold (<40ºF). This will and/or can be added back to any of the wines at a future time. If you choose to, the juice can be filtered to reduce the potential for rogue yeasts to initiate fermentation. A simple in-line (10”/10 micron) filter can clean up small amounts of unfermented juice inexpensively. The more juice there is to filter, the bigger the filter should be. Filtering is not necessary if the temperature of the must is kept below 40ºF with a relatively high level of sulfur.
Making Dry Riesling
Draw off one third of your total must volume into a fermentation container. There is no need to adjust the must. For our purposes, we will use a cultivated yeast that has a high tolerance to alcohol and does not produce sulfides. The appropriate amount of yeast (2#/kgal) should be hydrated and acclimated slowly (1 hour) to the temperature of the juice (>50ºF).
A healthy dose of fermentation-friendly yeast nutrients can help things get started. Another dose of the nutrients should be made at about 12 Brix to help the fermentation finish cleanly. A cool fermentation (~55+ºF) is best.
When the must reaches a density of about –1 Brix, your Riesling is “dry.” It should be sulfured at about 50 ppm to kill off any remaining yeasts and allowed to settle out. Once sulfur is added, the wine should be left without headspace and topped up regularly.
Making Off-Dry Riesling
The same steps that are required to make dry Riesling can be applied to making an off-dry style. The juice should be drawn off from the settlings and inoculated with a cultivated yeast. Yeast nutrients can help get the ferment started and keep it going. A cool fermentation (~55+ºF) is best.
Somewhere between +1 Brix, you should begin considering adding sulfur to arrest the fermentation before the wine goes completely dry. The wine can also be chilled (<30ºF) to kill the remaining yeast. The still wine should be topped up regularly. The resulting wine will retain some of the natural sweetness from the unfermented sugars.
Another way to make an off-dry Riesling is to ferment to dryness, add sulfur, and re-introduce some of the unfermented juice. Bench trials (tasting) are the best way to determine how much of the reserve juice to add to the dry wine. Rieslings that are slightly sweet and/or very sweet require more attention than their dry counterparts, especially prior to bottling. They can, however, exemplify the very best of the Riesling grape.
Making Sweet Riesling
Truthfully, the best way to make an incredible sweet Riesling is to let the grapes become infected by botrytis, a water depleting mold, while still on the vine. Barring your access to Riesling blessed with this “noble rot,” the grapes can be allowed to hang on the vine until they reach very high sugar levels (~40+ Brix). These grapes are typically much more expensive to purchase.
At the winery, an extended pressing of the grapes with pectolytic enzymes can yield some incredible aromas and flavors. There will be significantly less juice than a less ripe yield would produce (~80 Gal/Ton). This loss of juice directly proportional to the amount of water that is lost as the grapes mature and dehydrate/raisin. The must should be chilled and racked clean from the settlings. Fermentation should be initiated following the dry Riesling model.
Ultimately, the yeast will have trouble fermenting all of the sugar and will likely die out before the wine goes dry. The still wine should then be sulfured and topped up regularly. Usually, the alcohol will be a little high (~15% abv) and there will be a significant amount of residual sugar Another way to make a sweet Riesling is by first making an off-dry or semi-sweet wine and adding back some of the reserve juice to sweeten the sweet wine even more. Ultimately, it depends on your preference.
For each style of Riesling, there are important procedures to follow. Depending on your preferences and your wine program, each wine could be fined. Small amounts of Bentonite (1-2#/kGal) and/or Isinglass (1-2.5 oz/kGal) can clean the wine up and polish any rough edges on the palate.
The dry wine will need to be racked off any lees and bottled with a free sulfur of about 50 ppm. The off-dry and all versions of sweet wine will have to be racked off any lees, and filtered. A sterile filtration is best because it removes the potential for the residual sugar to spontaneously re-ferment in the bottle. This is not something you want.
After filtration, the wine should be bottled with a free sulfur of about 50 ppm – although 75 ppm would be “better.” The higher the residual sugar level (and the higher the pH), the easier the wine metabolizes and absorbs the sulfites. Ascorbic Acid can be used to inhibit the potential of bottle fermentation in wines that are not sterile filtered. There are trade-offs, however. Too much ascorbic acid can deliver vegetal aromas and advanced browning in the wine as the amount of sulfur decreases over time.
Ultimately, experimenting with Riesling should serve two purposes. First, it will produce three (or more) distinctly different wines from one or two batches of grapes. Second, it will give you another set of tools with which to make more wine in the future.
* For articles about acidification, sulfuring, and grape processing, read the other articles about winemaking in this series.