15 Keys to Winemaking Success

As we look back at the many wines we made, we cherish the memories of those winners that amazed our friends and family. But there have been failures too and perhaps some disappointments when we expected that “great” wine to fetch gold at competitions but failed to earn any medals. Have we learned anything from those as well as from the winners? So it’s a wise time to reflect back on those wines and review — and perhaps update — 15 important steps, axioms, tips and recommendations to (consistent) winemaking success.

Plan Well Ahead

You can never plan too much when you are winemaking. The cycles, from vineyard to bottle to imbibing, are very long. Poor planning can often spell disaster. So plan, and plan early in the season.
First, figure out which varietals and what styles of wines you want to make. If you make wine from grapes, be prepared to process the grapes as soon as you get that (unexpectedly early) call that the fruit is in. Have a backup plan in case no grapes will be coming in after all or if you are getting less than what you originally ordered.

Be sure you have adequate carboys, tanks and barrels to handle your expected production. Remember that you will be using those at around 75% capacity to allow for foaming during fermentation. And have plenty of smaller glass jugs to handle surplus wine to minimize headspace in containers.

Take out your equipment well in advance of winemaking season and check that everything is in proper working order. You don’t want to be stuck having to order hard-to-get parts or tools at the last minute.

Also, stock up on additives and processing aids, including those that you don’t think you’ll ever need. That includes potassium metabisulfite, tartaric acid, yeast and nutrients, malolactic culture and nutrients, fining agents, cleaning and sanitizing agents, reagents and other chemicals for lab analysis.

Get Rid of Molds

Mold will negatively impact the quality of your wine, and can also possibly cause outright spoilage.
Botrytis cinerea is a common vineyard mold responsible for gray rot. Sure, it is also responsible for the great, golden-colored sweet wines of Sauternes and Tokaj where perfect climatic conditions in only such areas can produce noble rot worthy of making these nectars of the gods. But for us home winemakers the rot is not so noble. The slight trace of gray rot can prove difficult to eradicate.
The mold secretes laccase, an oxidative enzyme that causes browning in wine. Its oxidation power is much stronger than that of polyphenoloxidases (PPOs) responsible for browning in healthy grapes. Both types of enzymes accomplish this by oxidizing colorless polyphenols into brown-colored compounds called quinones. In the same oxidation reaction, they also cause red-colored anthocyanins to take on brownish hues. But whereas PPOs are easily managed with judicious use of sulfite, SO2 has little effect on laccases; these can only be inhibited by a thermal treatment at 113 °F (45 °C).

With fresh juice, it’s impossible to tell by visual inspection only if it is affected by gray rot. But you should not hesitate to refuse delivery of mold-laden grapes. Some small amount is okay if grape bunches look healthy in general and if you think you will be able to remove rotten berries. Thin-skinned, tightly bunched grape varieties are most prone to B. cinerea.

At the crusher or press, sort grapes and remove all rotten berries prior to processing. Remember, laccase can carry into the wine and survive well into the bottle to continue on its destructive path.

The Yeast Makes the Wine

Making great wine goes well beyond transforming sugars into ethanol using a workhorse S. cerevisiae yeast. Without taking anything away from viticulturists and winemakers, yeast plays a much bigger role in shaping the wine than we like to think — the yeast makes the wine.

Amongst other metabolites, S. cerevisiae yeast produces a little acetaldehyde that adds complexity, aromatic esters and terpenes, higher alcohols, and organic acids. But more important, yeast, and more specifically, yeast enzymes, also transforms what are called flavor precursors into varietal compounds and non-precursor flavor-active compounds into flavor-active compounds. (Here, we use “flavor” to mean “flavor and aroma.”)

Flavor precursors are grape compounds that are attached to, for example, sugar molecules, and that’s what makes those compounds non-volatile. Compare this to the very aromatic Muscat varietals where you can smell and taste the juice right at the crusher. Yeast enzymes then cleave that bond between those compounds from their binding sugar molecules to make the compounds volatile and so aromatic and tasty. This cleavage is what allows wine to express their varietal characteristics.

Non-precursor flavor-active compounds include acids and polyphenols that interact with various other wine constituents to form more complex compounds. These are particularly important in reds as they impact color, color stability, mouthfeel, and aging potential.

So spend time researching the hundreds of yeast strains and choose one that is specifically suited for your varietal and desired style of wine. And be sure to supplement the yeast with nutrients at inoculation and during fermentation.

Don’t Forget the Enzymes

Yeast is equipped with an assortment of enzymes to accomplish various “winemaking” tasks; however, S. cerevisiae yeast strains are not significant producers of all required enzymes, and therefore, they must be supplemented exogenously. There is a plethora of such commercial enzymes for improving processing efficiency and/or wine quality; they are easy to identify as their names invariably have the suffix “ase.”

Hydrolases and lyases can enhance phenolic and color extraction during maceration in red winemaking, increase press yield, clarify juice or wine, hasten flocculation and sedimentation of colloidal matter, improve filterability, enhance the release of aroma compounds from their non-volatile precursors, and protect against microbial spoilage.

Pectinases are particularly important in red winemaking to break down pectin in grape skins that could otherwise cause wine to go cloudy and to improve polyphenolic aromatic and color compound extraction during maceration. This has the added benefit of improving free-run yields. Wines treated with pectinases will also reduce filter medium clogging thus improving filterability. Pectinase formulations typically include hemicellulases and cellulases that break down other large haze-causing polysaccharide chains that are extracted from grape skins.

And an extra dose of exogenous glycosidases towards or at the end of fermentation can further break down those bonds in flavor precursors and release volatile flavors to give wine more character and complexity.

Give That Red Some Extra Oomph

Making well-balanced, full-bodied wines that rival some of your favorite commercial wines can be a challenge. It makes one wonder how the pros do it. In red winemaking, patience is a virtue, and knowing the tricks of the trade can help you turn a so-so wine into a winner.

Full-bodied reds from grapes generally need a minimum of 18–24 months to “come around” and show their full potential. Don’t rush to bottle. Use the time to let the polyphenols and wine chemistry do their magic, and regularly taste the wine to assess development and make adjustments.

Reds generally benefit from barrel aging — the combination of oak and toasted wood and barrel micro-oxygenation can do amazing things to flavors, color, mouthfeel and overall wine structure. If you don’t have barrels or if your barrels have become neutral, toss in some oak chips being careful not to overdo it. Taste the wine every couple of days and rack when you have achieved the desired level of “oakiness.”

Once you feel the wine is ready to be bottled and you have done extensive taste tests, you may need to hone those sharp tannins with egg whites or perhaps with some polyvinylpolypyrrolidone (PVPP) if you are not fining. Try adding gum arabic for added mouthfeel or perhaps a little sugar to balance that extra natural acidity.

The Magic of Mannoproteins

Mannoproteins are very large molecules consisting primarily of mannose (a sugar) units and proteins, and are found in yeast cell walls. Mannoproteins are partially released during alcoholic fermentation (AF) but vast amounts more are released from yeast autolysis during sur lie (on the lees) aging in conjunction with stirring.

Though they have high protein content, mannoproteins do not cause protein instabilities or haze; in fact, they act as protective colloids against haze formation. Mannoproteins from sur lie aging have greater capacity to reduce turbidity than a bentonite treatment does, and as a bonus, the practice requires less bentonite for fining, which means less lees, less aroma stripping, and reduced stability-impacting mineral and metal content from bentonite clay.

But the story doesn’t end there. Mannoproteins can also prevent or remove foul-smelling thiols (e.g. hydrogen sulfide), reduce tannin astringency, enhance malolactic bacteria growth, inhibit tartaric salts crystallization, enhance wine aromas, and if you make sparkling wine, they promote much-desired flocculation and yeast autolysis. And when they are used in barrels, the benefits multiply.

Pretty impressive! So why not consider making sur lie aging part of your winemaking?

Following fermentation, stir the lees 2–3 times per week to get them into suspension without introducing excessive oxygen to avoid forming thiols or other volatile sulfur compounds (VSCs). And if you do run into VSCs because of, for example, a sluggish fermentation, poor yeast nutrient supply, or simply having left the wine on the lees for too long without stirring, French researchers Valérie Lavigne-Cruège and Denis Dubourdieu have proposed a procedure involving a racking with aeration and temporary removal of the lees.

Rack the wine with aeration, stir the lees in the barrel frequently over a 48-hour period, and then re-introduce the lees into the wine. The researchers demonstrated a decrease in hydrogen sulfide (H2S) but a complete elimination of methanethiol and ethanethiol. What was also interesting is that the lees stopped producing VSCs once re-introduced into the wine.

Stay on Top of FSO2

Monitoring and controlling free (and total) SO2 is crucial to sound winemaking, and yet, amateurs still pass up on investing in an SO2 analyzer. It’s a crapshoot after all trying to get SO2 to work effectively in preventing oxidative and microbial spoilage, especially if you are in the camp that believes that less sulfite is better.

To put this into perspective, a wine bottled at 35 mg/L (ppm) free SO2 (FSO2) can age more than 5 times longer than the same wine bottled with 25 mg/L. That extra bottle aging will reward you with greater aroma and flavor complexity, softer tannins, more wine-loving friends, and medals.

I recommend keeping a busy eye on free and total SO2 (TSO2). I strive to make FSO2 work effectively while keeping TSO2 down as much as possible, and so, I shoot for a high FSO2:TSO2 ratio. Some winemakers recommend a ratio of 0.35–0.40 but I prefer to state the numbers explicitly as they provide a better picture of SO2 management. For example, a ratio of 35:125 shows better use of sulfite than 55:200 although the two ratios are equal. Never let FSO2 drop below the critical threshold of 10 mg/L.

And the first post-fermentation sulfite addition should be done only 10 days after the completion of the alcoholic fermentation (AF) or malolactic fermentation (MLF) to avoid those stinky VSCs from forming.

Feed Reds, Starve Whites

If kept unchecked, oxygen can spoil wine outright. Whites are most susceptible to oxidation and should be completely protected throughout winemaking, except for such varietals as Chardonnay when crafted into a full-bodied wine.

Reds vastly improve with controlled doses of oxygen. Polyphenols act as natural antioxidants and also help shape the wine as they react with other wine compounds under oxidative conditions. It is not simply a matter of giving wine a single shot of oxygen, but rather, giving it plenty of oxygen in slow, progressive fashion. To put things into perspective, whereas whites rapidly decline in quality at very low total oxygen consumed (e.g. 10–15 mg/L) over the lifetime of the wines, reds improve with increasing oxygen consumption and are at their best when total consumption is in the range of 130–160 mg/L.

And so, aerate reds at each racking, including during an active alcoholic fermentation (AF) (not MLF though) if you wish to extract more polyphenols for a fuller bodied wine. You may also wish
to explore micro-oxygenation techniques to emulate barrel aging without the
barrels and the long wait to achieve similar results.

Stabilize Your Wines

Tiny crystals on the cork or at the bottom of the bottle, a perfectly clear wine that has gone cloudy, a wine that won’t clear, or a wine that starts refermenting are all symptoms of wines that were inadequately stabilized.

Let’s review some fundamentals in wine stabilization.

Whites have high protein content that can cause perfectly clear wine to go cloudy if subjected to rising temperatures. A bentonite treatment stabilizes wine against the phenomenon of protein denaturation. Reds have all those tannins to bind and precipitate proteins and are therefore typically not affected.

But reds have high haze-producing pectin content resulting from grape skins macerating in fermenting wine. Musts from high-pectin, thick skinned varietals as well as press-run wines are particularly prone to pectin haze. A pectinase treatment at the crusher to break down the pectin is always recommended.

All wines contain potassium ions that, along with tartaric acid, can bind to form insoluble potassium bitartrate, which crystallizes and precipitates with dropping temperatures. Reds are better protected due to high polyphenol content, but whites should always be cold stabilized or treated with metatartaric acid, carboxymethyl cellulose (CMC), or exogenous mannoproteins.

If you will be bottling wine with 5 g/L (0.5%) residual sugar or more and you can’t “sterile” filter (as most of us can’t), be sure to add potassium sorbate (except for MLF’d wine) at bottling to prevent a renewed fermentation in the bottle.

And remember to keep a nominal level of free SO2 throughout your winemaking and at bottling based on wine pH. Use WineMaker’s online sulfite calculator at http://winemakermag.com/
guide/sulfite.

To Filter or Not to Filter?

Wine filtration is one of the most controversial winemaking techniques. Many claim that filtration strips wine of color, aromas, and flavors — claims that the science does not support. Consider the fact that almost all commercial wines are filtered, except possibly for premium or super premium wines where sediments are perfectly acceptable. Commercial wines need to be protected against possible microbial spoilage, and that requires filtration through a “sterile” membrane down to at least 0.6 micron, which first requires that the wine be progressively filtered through finer grades of pads.

Aroma and flavor molecules are much, much smaller than 0.6 micron and are therefore not stripped. As for color, what is removed is colloidal matter or polymerized pigments that would eventually either settle or stain bottle glass.

Unfiltered wine can be easily dismissed at competitions, and dinner guests may well wonder why your bottle of red is stained to the point where you can’t see its content.

You can bottle unfiltered wine if you have bulk aged it for 24 months or more and racked it periodically and possibly fined; otherwise, and particularly if you bottle within 18 months or so, filter your wine.

Taste, Taste, and Taste Again

Much too often wine is bottled “as is” without much time spent on assessing quality or identifying improvement opportunities. Remember — this is your last chance to make adjustments before bottling. So, taste, taste, and taste again. Set up a tasting session and invite friends and family to get their opinions. You want as much feedback as possible.

Prior to the taste test, be sure that the wine has had a chance to settle down since it was last processed. Have plenty of glasses and several bottles of the wine plus spittoons. Prepare a 10% (table) sugar solution for adjusting acidity-sweetness balance, and have on hand some gum arabic solution for adjusting mouthfeel, a graduated cylinder, and a 1 mL pipette.

Prepare several samples with varying levels of sugar with and without varying gum arabic additions, making sure to stir the samples thoroughly, and then let the panel taste the wines blindly side by side. Collect feedback and repeat the process until you zero in on a style that most prefer. You may need another round to fine-tune the wine until you get general consensus on a favorite style.
If you get more “serious” feedback, e.g., the wine is way too astringent or it needs more character or there is some flaw, you will need to redo the tasting after you have had a chance to address the comments. Treating the wine with some polyvinylpolypyrolidone (PVPP) to round out those sharp edges on tannins or adding some oak chips for more character will take a little time in the cellar.

Blend Artfully

Blending is truly an art; it can only be mastered with experience. Mono-varietal wines can be great on their own, but blending two or more varietals can make the difference between silver and gold, and perhaps Best of Show. There’s a reason why the French appellation of Châteauneuf-du-Pape allows up to 13 varietals to be blended and why vintage Ports are blends.

If you have never blended, first experiment with known blends such as Cabernet Sauvignon with Cabernet Franc and Merlot or Chardonnay with Pinot Blanc. Once you become comfortable with the process, you can blend different varietals and/or styles to suit your palate. The objective is to create a wine where, as the saying goes, the whole is greater than the sum of its parts.

The trick is not to blend wines too early in the process. This can be a personal preference, but I like to give my reds 18–24 months to evolve and then blend when I feel they are ready. Again, this is an art, not an exact science.

Once the wines are ready, try various combinations and permutations of varietals and percentages. Have lots of glasses on hand with a graduated cylinder as you’ll be doing a lot of trials. It will take time until you get to a blend that you like. And remember to taste, taste, and taste again.

Once you’ve created that perfect blend, don’t rush to bottle. If you can patiently wait another few weeks to 6 months, you can again assess the wine once the blend has had a chance to harmonize itself. Only when you are fully satisfied should you blend. And a little bottle aging won’t hurt either.

Choose the Right Closure

How many wines “die” so young! A common culprit? Closures. Why invest so much time, energy and money in making the best wine only to bottle with unsuitable or cheap closures? We are talking second-hand aluminum screw caps, recycled screw caps from other food and beverage containers, T-tops, and cork stoppers that simply perform poorly.

The material and its oxygen transfer rate (OTR), i.e. the amount of oxygen that a closure allows through and around the material, directly affect how well and how long wine can age.

Screw caps have proven to have extremely low OTRs, but home winemakers are not yet equipped to properly apply this type of closure. That leaves us with natural cork, agglomerates and synthetic stoppers.

The best natural corks have relatively low OTR and are best for aging wine. They come at a premium price, but, again, isn’t your wine worth it? Good-quality agglomerates manufactured from high-grade cork particles work well too. Colmated agglomerates — those patched on the surface with cork dust and glue to fill imperfections — with tapered tops and bottoms are only recommended for wines not meant for aging. Technical corks — those with an agglomerate body and a natural disc at the top and bottom — perform better than simple agglomerates, in general.

Synthetic corks manufactured from co-extruded polymers — those with a foam-looking body encased in an elastomer sleeve — have improved significantly and work well for short-term aging. So called injection-molded synthetic corks — those made of a single, dense piece of polymer in a variety of colors — still have high OTRs making them unsuitable for wines to be aged longer than one to two years. A wine under a good (lowest OTR) injection-molded synthetic cork can still only age half as long as under a co-extruded synthetic cork; and a natural cork will outlast the latter by a factor of 3–60 depending on cork quality.

Diagnose Before Solving the Problem

Have you ever tried fixing a problem in your homemade wine only to find nothing has changed or, worse yet, the wine seems to have suffered?

Don’t be tempted to jump in and try to fix a problem without doing a proper root cause analysis and having assessed potential solutions. There is no point in aerating an overly stinky wine affected by H2S; it will only make it worse.

Take a step back and identify the symptoms using color, smell and taste to guide your analysis. Use your experience, consult literature or the internet, or ask a winemaking friend to investigate and zero in on possible root causes and to identify solutions. Perform bench tests to assess the effectiveness of the solution before treating the entire batch.

Keep Good Records

The best winemakers are those who maintain accurate records of their activities. That includes dates, volumes treated, type of processing, type of equipment used (e.g. medium vs. fine filter pads), additives and dosages, blending wines and percentages, and any observations you make. If you run into a problem and need to investigate, or if you want to replicate that “recipe” from years ago, you will have the complete history.