The process for making dry red wine from grapes substantially differs from that of other types of wines or ciders. Rather than pressing the grapes before fermentation, the grapes are crushed and left in contact with the juice during fermentation. Pressing does not occur until the very end of the fermentation process. The goals for red wines are often quite different from that of white and fruit wines, leading to an entirely different set of processes and parameters. Here, I will do my best to lay out in detail the steps used to make a high quality red wine from grapes and the reasons why each step is performed.
Before I get too deep in the winemaking side, I will note that many of the most important steps occur in the vineyard before you even get the grapes. It is important to get the best grapes you can afford and thoroughly inspect any crates before accepting an order. Things to look for in high quality red wine grapes are small, ripe berries with mature brown seeds. Make sure that the sugar and acid levels are appropriate for the variety that you are making. Sugars generally range from 23 to around 27 brix (percent sugar by weight). The finished wine pH for red varieties generally falls around 3.6 to 3.7. The grapes should come in slightly lower though (3.4-3.5), leaving some room for the pH to rise during alcoholic fermentation and malolactic fermentation. The skins should be dark purple. Lighter, reddish skins usually indicate under-ripe grapes. Watch out for excessive raisining. A few raisins are okay, but you don't want entire clusters of raisins. Taste the grapes. They should taste very sweet and flavorful and the seeds should crunch relatively easily in your teeth but will be bitter and tannic. Watch for obvious signs of late sulfur additions in the vineyard. Grapes with visible yellow sulfur dust will cause fermentation challenges like stinky hydrogen sulfide and should be avoided. If you get healthy grapes, you should not need to rinse them at all. Grapes readily absorb water and you don't want to accidentally water down your wine by liberal rinsing.
So, now that you have your grapes, let's get into the winemaking steps!
Crush and Destem
This is the the process of separating the berries from the stems and lightly popping them to release the rich and flavorful juice. You will normally add around 50ppm of sulfite (SO2) in the form of potassium metabisulfite at this time. This will curb any unwanted microbes and spoilage yeasts, but will not kill the more resilient wild strains of Saccharomyces cerevisiae (wine yeast). It is important to crush and destem as soon as possible to prevent any risk of oxidation. Crushing and destemming is usually performed by a mechanical crusher destemmer, but can be performed by your hands or feet if you are feeling energetic. A clean milk crate can also be used to crush and destem if you are doing small batches.
During the crush and destem phase, you should consider if you want to ferment a percentage of whole clusters or whole berries. Using whole clusters delays the release of juice from these berries and helps to drag out the fermentation and increase fruity aromas. 20-25% whole clusters is common in wines like Merlot, Pinot Noir, and other fruit forward wines. Whole berry fermentation is another similar technique and involves removing the berries from the stems without popping them. This is very difficult to achieve at home though since berries readily break when separating from the stems. Delicate, specialized destemmers are used to destem for whole berry fermentation.
Cold Soak
Extended maceration is common with red wines and is the process of extending the skin contact time with the juice either before or after fermentation. Extending the skin contact time can improve both color and flavor extraction. Soaking before fermentation helps to extract water soluble components like fruity esters while soaking after fermentation can extract more alcohol soluble components such as tannin.
Cold soaking is the more common form of extended maceration and involves chilling your freshly crushed and destemmed must to an ideal temperature around 35-45°F for several days before starting the fermentation. This is cold enough to suppress yeasts and spoilage organisms. Do not let the wine linger in the 50-55°F range because in this range the spoilage yeast kloeckera thrives over wine yeast strains.
During cold soak, consider adding fermentation enzymes like lallzyme ex to improve extraction. At this time you can also consider the addition of untoasted oak cubes or fermentation tannins to help retain anthocyanins which contribute to color and structure of the wine. The use of untoasted oak and fermentation tannin can also help to reduce vegetal (bell pepper) aromas in wines from colder growing regions.
Take Another Measurement
Towards the end of cold soak, take sugar and acid measurements. This is a great time to get a more accurate reading. You can add tartaric acid or table sugar if measurements are low, or add water (cringe!) if acids or sugars are too high. Large wineries can adjust the must up front with vacuum distillation or later with reverse osmosis, though it is rarely talked about publicly.
Initiate Fermentation
If you performed a cold soak, warm the wine up as quickly as possible until you reach about 70 or 75°F. In this range, saccharomyces cerevisiae (the good guys) thrive and will generally overpower most other yeasts and microbes that may want to feast on your sugars. You have the option to add a cultured yeast or perform a wild fermentation here. The choice is really yours, but adding a cultured strain is WAY less risky. One trick if you do want to live on the edge and perform a wild fermentation is to pull aside a gallon of must before cold soak and allow a natural fermentation to start on the sample. If things look and smell healthy, add that batch to the larger batch after cold soak and you should be okay. If things are not looking or smelling good on the sample, then you know that you should inoculate with a cultured yeast.
If inoculating with a cultured yeast, choose a strain that is recommended for your variety and fermentation temperatures. Some strains are very aggressive (Lalvin EC-1118), which ensures a clean fermentation but can also reduce extraction since the skin contact time is often greatly reduced with fast fermenters. I like Lalvin RC212 which was isolated from the Burgundy, France wine region and is reliable but relatively slow which is good for red wine. This yeast likes to be fed, so be sure to have some Fermaid K or fermax on hand.
Punch Down and Monitor the Wine
Once fermentation has started, the grapes will fill with CO2 and float above the surface of the liquid. It is important to submerge these to prevent drying out and oxidation and also allow the active fermentation below to breathe and circulate. Yeast will consume a little air during active fermentation, so this churning/submerging doubles to help keep the yeast healthy and happy. Use a homemade or store bought punch down tool to push down the cap two or three times a day. Push the skins all the way to the bottom of the tank but don't smash the seeds. Make sure to churn up any gross lees that may have settled to the bottom. If you are dealing with very large volumes, you can do a pump over instead of a punch down. This is the practice of pumping the wine from the bottom of the tank onto the top of the must.
Monitor your temperature very closely during the active fermentation. I like to allow it to warm up a bit (80-85°F) during the first few days to extract any fruitier, water soluble flavors but cool it down (70-75°F) later on to drag out the skin contact time. To cool it down, you can use frozen water jugs on smaller batches, or dry ice on larger batches. Change out the water jugs as needed and be sure to sanitize them by spraying with Starsan or a homemade sanitizer before submerging.
If you smell any hint of rotten egg smell, feed your yeast and make sure your temperature is within a range that your yeast is compatible with. Do not feed your yeast all at once and don't feed it after the sugars have reached about 10° brix. Any yeast nutrient that is not consumed by the yeast can be consumed by unwanted microbes after fermentation has completed.
Press the Wine!
By now, your wine is starting to taste like wine... a hot, strong, overpowering version of a great wine. I generally like to press when the wine has fermented completely dry to avoid any risk of stalling the fermentation. It usually takes from seven days to three weeks to complete fermentation. You can press with a few percent sugar still left if you want to be hyper-oxygen-conscious. A little oxygen now though isn't a bad thing. It will act as a catalyst to convert short chain tannins (harsh) to long chain tannins (smooth), and help bind your colorful anthocyanins so they stick around for the long run.
When pressing, you may want to keep any free run wine separate from hard press wine. Free run is the wine that runs out of the press before pressing and is often considered more premium. You can decide how much hard press that you want to blend back in after aging has completed and the wine is expressing itself however it wants to.
Press into a temporary vessel like a stainless variable volume fermenter, a carboy, or a food grade barrel blanketed with argon gas. Within about 24 hours, the gross lees will settle to the bottom of the vessel. The gross lees will start to stink if they are allowed to compact on the bottom of the wine, so go ahead and rack your wine off of these once they settle. Some small amount of lees (fine lees) are okay and can help to feed malolactic bacteria which is usually a good thing. When racking off the gross lees, you can put the wine straight into a clean oak barrel, or into carboys or air tight stainless tanks. As long as you plan to perform malolactic fermentation, you do not need to add sulfites at this time.
Perform MLF (malolactic fermentation)
This is the process that smooths out the sour apple like malic acid and converts it to the smooth, buttery lactic acid. Often times a wine will naturally go through MLF without much encouragement from you, but adding a freeze dried malolactic culture really seals the deal. Add the culture straight to the barrel, or aging vessel. A wine undergoing MLF will produce small CO2 bubbles. MLF will complete over a span of one to several months depending on the culture used, pH of the wine, and temperature. A slow MLF will yield more buttery flavors, where a fast, expedient MLF will minimize the buttery aspects. It is up to you to decide your strategy here. Your main tools to speed it up would be increasing the temperature a bit, feeding the bacteria, or using a more agressive bacteria culture. Do just the opposite if you want to encourage a slow MLF. If you want to discourage MLF all together (maybe your pH is already too high), then add a heavy dose of SO2 (100ppm), keep the wine stored under 60°F and consider adding lysozyme. Filtering the wine would be encouraged if you are not going to allow a complete malolactic fermentation.
Age the Wine
When you are confident that MLF has completed, rack the wine off the fine lees and add sulfites to protect the wine for the long haul. You can use a chart to find the correct addition for your pH level, but it is not a bad idea to over shoot it a bit now and add less later (still maintaining a low total SO2 addition number). If you are just guessing and cannot measure your SO2, go for about 60-75ppm now and you shouldn't need to add much, if any more later on. Tannin also helps to protect the wine against oxidation so if you like to err on the low side with SO2, then consider adding some aging tannins (especially if you are not oaking the wine).
If you are aging in an oak barrel, you will need to top up with more wine about once a month. A 59 gallon barrel will need topped up with between one and four bottles of wine each month depending on your humidity level. Dry air will really speed the evaporation, so try to store your barrel somewhere with sufficient humidity like a basement. Barrels also help to smooth out the tannin in the wine by a process called micro-oxidation. Micro Oxidation is very hard to replicate in stainless or glass containers. Be careful not to over-oak the wine by leaving it in a new oak barrel for too long of period of time.
If you are aging in glass or stainless, consider oak alternatives like chips, cubes, spirals, or staves. These are available in different toast levels and different types like French, Hungarian, or American. I personally love American, Medium +, but this all comes down to personal preference.
Make sure that at some point the aging wine is able to cool down below 50°F for a couple weeks. This will encourage any unstable tartrates to fall out of suspension in the storage vessel and not in the bottle. Crystals in the bottle won't negatively effect the wine, but they can be unsightly to the consumer.
Blend and Bottle
After many months of aging, your wine will be ready to bottle. Before committing to bottling, consider blending to get the wine just right. Almost any commercial wine has had some small amount of blending performed, even if it is listed as a single varietal. In the United States, you can blend up to 25% of other wines into a wine and still call it a single varietal like "Cabernet Sauvignon". If you have a few other wines around and have found a blend that is just right, then it is time to apply the blend to the entire batch and bottle. One note, is to be sure to do any blending and tasting at the proper serving temperature. Temperature can have a HUGE impact on the perception of balance and intensity of aroma and mouthfeel in a wine.
To bottle the wine, simply check your sulfite levels and add if necessary, then proceed to bottling and corking the wine. Make sure that all your bottles and bottling equipment are clean and sanitized and go for it! Once bottled, let the wine sit for a minimum of four weeks before serving. The oxygen introduced during bottling can cause a temporary bottle shock that should go away after several weeks.
Enjoy!
Drink your wine and give it away to your friends. Try to evaluate it each time you open a new bottle. It is important to compare your wine against similar commercial wines to keep your taste buds calibrated and know your competition. For more tips and tricks, check out the home page. Post your comments below and keep making that wine!
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