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Winemaking Questions & Answers

The Vancouver Amateur Winemakers Association receives many messages containing questions on home winemaking techniques, and those messages are passed to senior winemakers in the club for reply. This section is intended to contain some of the questions and answers thought to be of interest to VAWA members.

Please note that, for the sake of clarity, both questions and answers may be paraphrased.

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You have a link on your website to an article on Acid Reduction Techniques in Must and Wine. I have tried using potassium carbonate on overly acidic wine from several BC and Washington grapes, but the rate of acid reduction has been inconsistent and generally much lower than suggested in the article. Is there a reason for this?

Potassium carbonate works on tartaric acid; it does not work on malic acid. Depending upon the tartaric/malic acid ratios, the addition of potassium carbonate will slightly increase the pH and reduce the TA if the tartaric acid is reduced; however, if the significant acid is malic, the pH will increase with no discernable decrease in TA because the malic acid is dominant.

It is not unusual to notice different acid compositions in grapes grown on different sites or in different regions. It may be noticeable in grapes grown on the same site from one year to the next depending on factors such as temperature during the growing season, irrigation, time of harvest, etc. Two batches of wine made from the same grape, such as Riesling, from two different sites could quite conceivably have the same TA and pH but with different tartaric/malic acid ratios. If the tartaric acid is dominant, the addition of potassium carbonate will reduce the acid and increase the pH; conversely, if the malic acid is dominant, there may be no reduction in acid in spite of the increase in pH.

Malic acid does not precipitate as does tartaric acid either by cold stabilization or the addition of any carbonate. A few years ago, this same winery needed to reduce the acid a bit and added Acidex. The acidity was reduced but the dominant taste was malic. The acidex reduced the tartaric but not the malic acid. If malic acid needs to be reduced, it must be done with the juice, not with the finished wine.

This topic is dealt with more fully in my article on Acid / pH Adjustments(B. Collings)

I am currently maturing 2006 Pinot Noir from excellent fruit I purchased in the Yarra Valley, a cold climate near Melbourne, Australia. The yields were cut back to approximately one ton per acre, so the concentration and flavours are fantastic. The wine was fermented with wild yeast, and no enzymes were added. It has just finished MLF and is now resting on fine lees in two-year-old French oak. Can you tell me how long it should take to achieve the mouthfeel benefit from yeast autolysis?

Also, I am a little unsure of rigorous mixing with a cordless drill as suggested in some texts. Is that too much of a rough treatment for the wine?

I tasted a bottle sample with food and found it exceptionally fruity, with a highly jammy, sticky aroma. I am just not happy with the development of the body at this early stage. I am sure that more time with the lees will ensure the creamy texture I am trying to achieve. Just on that, do you know if the 'barnyard' aromas common to lovely burgundies are developed in the fermentation process or from the ageing process?

I was just in Melb'n and the Yarra Valley in March and enjoyed a wonderful Pinot at Yering Farm. With the low yield, one would hope for your description of fruit being fantastic, and having good acidity.

My preference is to stir the lees every time the barrel is topped, about every two or three weeks. The last thing I want are any off characters that might come from any sulfide problems that might start in the lees. I believe stirring will help avoid that problem and the stirring helps to better infuse the lees character into the wine.

One very important part of the topping stirring is to use your nose to detect any off character that might be creeping in, as well as tasting to monitor the effect of the lees. Some chardonnays are held sur lees for up to nine months, so it may take longer to achieve the complexity and mouth feel you want in your pinot.

The wild yeast may be the greatest unknown. You have no way of knowing what kind of character you may get from that yeast. It may not be what you want. I would tread very cautiously with the complexity aspect, and try to retain the wonderful fruit quality you seem to already have. The great thing about a good Pinot is that it will usually develop it's own wonderful complexity with a little time.

You should get nice subtle oak without the danger of hard tannins with your barrel. You may wish to add a little oak in chips or cubes to enhance the vanilla character. I use a poly stir stick (not porous wood) that will reach the bottom and gently stir the lees. It doesn't take a lot to move it if it's done more often. You can also feel the bottom and determine how much tartrates you are picking up on the inside of the barrel. I only use a stir on a drill if I am adding a fining from the top and have a short time to integrate it into the wine. The smoothness will also come from the reduction of CO2 in the wine which will happen more quickly with stirring and using a solid silicone bung which will give you a good vacuum in your barrel. Body of the wine might also depend on your tannin levels and how this softens over time. Wines with too little tannin can seem thin in body.

Some of Scott Labs tannin additive products can do wonders with body and mouthfeel. Their “Tan'Cor Grand Cru” will amaze you, if you can get some for a bench trial. The “Tanin Plus” is also quite remarkable with much more vanilla character, as it is extracted from American oak, and may be more suited to reds other than pinot. I believe fruit comes from the grape, obviously, but the complexity will come from your choice of yeast, longer fermentation times, (extended skin contact is probably the greatest factor of complexity - greater tannin pick up and the break down of skins and seeds etc), barrel type and age, MLF, sur lees, and time. Don't be too concerned if your pinot takes on odd medicinal characters as it goes through a period around year three or four as the 'barn-yard' character develops - by year six, it should be wonderful. (C. Joyce)

I'm concerned with the smell of plastic fermentors leaching into the fresh grape juice as it ferments. Given the three different FDA approved choices below, which would be considered the best choice for use as a primary wine fermentor, about two weeks time around a temp of 80°F:

  • High Density Polyethylene Resin - maximum service operating temperature 110°F, or
  • Polypropylene Resin - maximum service operating temperature 220°F, or
  • Polyvinylidene Fluoride Resin - maximum service temperature 230°F.

Some of us order grapes from California and Washington which are crushed and destemmed at the vineyard, then packed in 220L (55 US gallon) blue drums for shipment up to Vancouver. I just looked at a few of the empty drums still hanging around my house and they are marked 1H2/Y150/S and 1H2/250/S. They are HDPE (High Density Polyethylene), the first one on your list. I have always done the primary fermentation right in these drums, as have many other winemakers. We have never detected any odors or other faults that could be traced back to these drums. (Note that I’m not saying our wines have no faults: just that we can’t blame the drums, however much we might want to!) (J. McMaster )

I have a batch of Cab Franc that I have been bulk aging in two 20 L carboys, with about ½ inch of air space below a solid bung. It had been developing nicely and I was very happy with it. Then one day I noticed that a thin, patchy, white-grey film floating on the surface of the wine in both carboys, and when I pulled the bungs the wonderful nose was gone. Is there anything I can do to restore this wine

The thin patchy film is mycoderma – a combination of aerobic bacteria, yeast and molds that will eventually spoil your wine if left untreated. The infection results from the wine having too much air contact, most often combined with high pH and low SO2 levels. Mycoderma is highly oxidative; it will oxidize ethanol into acetaldehyde, which contributes to an objectionable oxidized odor. It is inhibited by SO2, low pH and high levels of alcohol (above 12%–13%).

The existence of mycoderma is an excellent reason for frequently checking your wine. If caught early, this condition can be easily and effectively treated; if left too long, the wine may be fit only for the kitchen sink (or some unsuspecting relatives).

If your wine develops mycoderma, the first step is to carefully remove the film as quickly as possible. The film is fragile and will disintegrate easily, sinking into the wine. This is to be avoided at all costs. The removal method you choose will depend on the type of container. If the film is near the top of a carboy, I think the best method is to scoop it with a spoon and then wipe the edges with a clean cloth. Others have had success using a syringe to suck out the film. Still others will add liquid and float the film off (but this is often only partially successful because it tends to leave some film attached to the inside of the neck). If for some reason you are not successful in removing all (or almost all) of the film, you might want to consider filtering the wine through multiple layers of cheesecloth.

Once the film has been removed, you need to determine if the wine is worth saving. If you have caught it early enough and the wine has merely lost its good nose (ie, it has no nose), removing the film and preventing its recurrence should fully restore the wine (although it may take some time for the nose to redevelop). You can prevent it from recurring using one or more of the following techniques:

  • Gently add a small amount of pure alcohol to the top of the carboy. The lower specific gravity of the alcohol should keep it at the top.
  • Spray the surface of the wine liberally with a 10% sulfite solution.
  • Add 25 to 50 ppm SO2 to the body of the wine.
  • Keep the head space to an absolute minimum. One method is to use a fermentation lock with the wine visible part way up the centre tube, effectively reducing the surface area of the wine to a diameter of about 5 mm. However, even moderate changes in cellar temperature may cause the level of the wine in the tube to rise and fall dramatically.

If, after removing the surface film, the oxidation remains noticeable, you may wish to try treating with potassium caseinate. If the wine has developed a strong acetic acid smell, its time to put it out of its misery. (D. Vick)

I am a new wine maker in New Jersey. I made my first batch this year with my father and have a question about a phenomenon I've experienced with my wine. After crushing and fermenting for about a week, we placed our wine in 5 gal glass jugs for continued fermentation (last September). In late December after the fermentation stopped, we decanted the wine into other 5 gal jugs. As we did that, I took a taste and noticed that it was bubbly, not visibly, but when you drank it you could feel it on your tongue. Otherwise it tastes great. Do you have any idea why this has occurred?

Residual CO2 is the bubbly/spritzy sensation that you are noticing and there are at least a couple of possible reasons for this phenomenon.

The most likely reason is that there is residual CO2 left in the wine - a natural by-product of the fermentation process. There are several ways to get rid of this CO2. My preferred method is barrel storage for a few months - the barrel's natural wood surface breathes and literlly sucks out all the CO2. However, if you are making wine in 5 gallon carboys this is not likely practical for you. The next option is to vigorously stir the wine several times/day over a period of a few days. You can do this with a long stir-stick or with a mechanical aid attached to a drill (Fizz-X is available at most wine making supply stores).

The other possible reason for residual CO2 is the from a malolactic fermentation (MLF). It may be a wild fermentation or you may have innoculated for MLF. If your sulphite levels are above 25 ppm you are not likely to have a wild MLF. The treatment is the same as above. (J. George)

I am barrel fermenting some Chardonnay and am thinking about leaving the wine “sur lees” for a couple of months following fermentation, which I understand is a fairly common practice at many wineries. However, other sources seem to insist that failure to first rack off the gross lees will likely result in off aromas and flavors. How do you reconcile these views?

I think these views can be easily reconciled by examining the process and goals of “sur lees” in a commercial environment. So lets first look at why commercial wineries submit wines to the process, what the process is and then reconcile the two views. If you just want the answer skip to the last paragraph.

Two of the common reasons for “sur lees” aging are: to impart specific flavours and aromas to the wine, or to put a marketing spin on the label and increase the selling price of the wine. We will deal with the first reason.

“Sur lees” is the practice of letting the wine rest for a period on some or all portions of the yeasts and solids that have precipitated out during fermentation. This generally occurs in a 225 litre oak barrel. There are no rules about the wine having to be fermented in the barrel or for that matter where the lees came from or what constitutes them.

Principles and Practices of Winemaking by Boulton, Singleton, Bison and Kunkee points out that timeframe for autolysis of yeast is generally considered close to a year rather than the three to six months that seems to be the timeframe for most “sur lees” contact. I think this emphasises that the commercial winemakers are seeking a complex combination of aromas and flavours rather than just the autolysis of yeast.

My experience touring commercial wineries and talking to people on the production side indicates that grapes destined for a “sur lees” experience undergo a more labour intensive treatment than their regular production. We will assume a barrel fermentation to match your situation. The grapes destined for “sur lees” are chosen for their intense fruit characteristics and healthy state. The juice will be clarified to minimize solids at the start of fermentation. Yeast inoculation generally occurs in large bulk tanks and fermentation with the correct yeast strain validated prior to the wine moving to barrel. Yeast that is not prone to the generation of H2S or other undesirable properties is used. Throughout the fermentation, a laboratory monitors the wine for yeast strains and bacterial activity. Racking may occur. At the end of fermentation, a decision is made as to the percentage of wine that will be exposed to lees and for how long and to how much. Throughout the “sur lees” period they monitor the wine for the achievement of the desired aromas and flavours and for bacterial activity. Once the goals have been achieved or there is any indication of problems the wine is racked off the lees and enters the next phase of their plan. The final product is generally a blend of different barrel and lees treatments. In summary very little is left to chance and they are trying to achieve a specific result in a controlled environment.

Your approach: There are several options. One is to have a plan for the fermentation and be after specific flavours and aromas, and another is just let things happen and see what comes out. I will deal with the first option, as the second requires no decisions or expertise and is very risky.

Your approach: Emulate the commercial process. Taste commercial examples and find the aromas and flavours that you would like to emulate. Ensure you are dealing with clear juice that is well balanced and has intense varietal characteristics that will be enhanced by the complexities of the “sur lees” process. Should your fermentation be troublesome or exhibit off smells rethink your plan. Hold some wine back for blending should you achieve more “character” than desired. Have a serious look, smell, and taste of the lees. Are they exhibiting characteristics that indicated decay or spoilage? Do you have a very thick layer of lees in a very small barrel? Smell and taste your wine frequently to ensure only the desired characteristics are developing. Remember you are trying to enhance your wine by layering on complexities not by encouraging bacterial spoilage.

Summary: The two views are reconciled by understanding that we are talking about two different approaches. In one approach, the winemakers plan is a final racking at the end of fermentation to “clean up” the wine and contribute to its stable and protected state. Ignoring this final racking and letting the wine sit is a recipe for off flavours and aromas. In the “sur lees” approach a number of decisions in preparing and fermenting the must has the winemaker convinced that the postponing of the final racking will enhance the wine and not expose it to the risk of spoilage. The potential gain justifies the risk. The “sur lees” winemaker now enters a period of constant tasting and analysis to ensure a premium wine. (T. Shillemore)

I allowed the headspace in my barrel to get to big and had a lactobacillis contamination. I treated it with lysozyme, but ended up with noticeable VA and ethyl acetate odors. Is there any way to reduce the odors, or treat?

The only viable methods are industrial solutions requiring reverse osmosis and specific exchange columns which strip only the volatile acidity and ethyl acetate. Unfortunately, simple solutions are not available. (E. Urquhart)

True or false: Exposing the primary fermenting skins/juice to oxygen is good. Exposing fermenting juice in carboys to oxygen is bad. If both are true, then where does the oxygen/no oxygen point occur?

The question does not lend itself to a true or false answer. Oxygen is a very important component of yeast growth and sustainability for a healthy fermentation in the initial stages of the fermentation process. Lack of oxygen when yeast is building causes it to move into the anaerobic process of just converting sugar to alcohol and if the yeast population is not built up sufficiently, it may not have enough population to complete the ferment as the yeast gradually dies off. How much oxygen exposure may depend on the grape, yeast nutrients present, style desired, and cap management. Some micro-oxygenation programs have shown to be very beneficial to not only completing the fermentation but also improving general wine mouth feel.

Excessive exposure to oxygen will leave wine lacking in aroma and flavour, even during fermentation.

What's the fine balance? Commercial wineries use the pump over process that aerates must much more so than simply pushing the cap down with a plunger. The CO2 caps in fermenters blanket the must making it difficult to get air into it. So we home winemakers are probably not overexposing our musts to excessive oxygen during fermentation, and in some cases where we have high sugar musts, which make for long and stressful ferments for the yeast, we have insufficient oxygen available in the early ferment for the process to complete.

Fermenting juices are probably not much different in that they will also require sufficient oxygen for the yeast to grow enough to complete.

So, oxygen in the initial yeast growth phase is extremely important. Oxygen after fermentation is an enemy to wine, producing aldehydes that give wine a dullness to sherry character. Minimum exposure to oxygen after ferment is advisable. (C. Joyce)

Last Fall I purchased some Yakama Merlot on which I did a MLF. In late April I filtered and bottled a 5 gallon carboy of the Merlot because I needed the carboy for some different wine. On Memorial Day weekend I had company over and opened a bottle - although young it had a great nose and was very smooth. One month later I opened another bottle and to my surprise the wine was fizzy. It did not pop when I opened it but when poured it had a hazy cloud of bubbles in the middle of the glass and I could feel it in my mouth. I tested the sugar which was bone dry and did a MLF test which came out with just a slight trace of MLF (99% was complete). I measured the S02 and I had 50 ppm. Later I went to try the bulk of the Merlot which I had in a stainless steel tank and it also was slightly fizzy. What’s going on?

It is likely that the sugar fermentation never completed as thought, and started up again when it was exposed to air during filtering and bottling. The yeast used may have been a weak finishing yeast or short on nutrient and just trickled along slowly with the carbon dioxide gradually building up. Although we all use a hydrometer for testing specific gravity, it's nearly impossible to tell if a wine has any residual sugar. Few wines finish with absolute zero sugar. (Use Dextrocheck or newer more accurate diabetic testers for greater certainty.) Most have some residual sugar, which can make a young wine appear soft and smooth. With the push to get commercial wines on the market a soon as possible, many reds today will have residual sugar to make them smoother, rounder and more consumer friendly while still presenting fresh fruity appeal. A yeast ferment in the bottle will usually also have a dusty sediment on the lower side of the bottle if laying down.

It's also very common for wines to undergo a release of carbon dioxide in the spring when temperatures warm a little, especially if stored and fermented coolish as a lot of white wines are. It is sometimes mistaken for a renewed ferment. Wines that are not racked routinely can retain CO2.

Although less likely, your problem may have been MLF completing. As MLF is anaerobic bacteria, it doesn't require any exposure to air for it to start up or just continue. I've had red wines where it seemed that MLF was not going to start and I couldn't wait any longer. I sulphited 50 ppm only to find that ML slowly fermented all winter and early spring, that the wine was full of CO2 and that the pH had gone up and required acid addition to balance. MLF responds to temperature and will slow down dramatically if allowed to cool too much so is somewhat unpredictable. A good ambient temperature for MLF is about 20° – 25°C. Even 50 ppm free sulphite will not necessarily stop a sugar or ML fermentation. Very few winemakers will give a guaranteed ppm level that will stop a ML fermentation. Several factors that include sugar, alcohol, pH, temperature, nutrient, ML strain and sulphite levels can affect the start, rate or completion of the MLF. A thorough winemaker will on completion of fermentation test for residual sugar (Dextrocheck or better), total titratable acidity, pH, alcohol, free and total SO2 (even if none has been added) andMLF completion (paper chromatography), and subject the wine to critical tasting. Your wines should be checked by taste every month or two, and your palette should tell you if your wine is going down the road you want. (C. Joyce)

Last fall I had problems with off aromas being produced by my fermenting wine. Not the sometimes rotten egg smell I get which can be corrected by adding DAP or a complete nutrient. This smell was more metallic or sewage-like. Is there any way of preventing this problem?

The problem you are likely having is due to limited amounts of B vitamins present in the fermenting wine. Often this problem doesn't occur immediately but after active fermentation has started (day 2 or later).  The use of complete yeast nutrient mixes such as Fermaid-K or Superfood containing B-vitamin mixes, DAP and mineral nutrients can help provide a cleaner smelling and tastier wine.

Unbalanced nutrients in the grape must can occur in several ways:

  • Grapes produced under stressful growing conditions (low nutrients, disease problems, high temperature, drought, etc.) or over-ripe grapes are often deficient in balanced nitrogen and other essential nutrients (vitamins and other yeast growth factors).
  • Vitamins – especially thiamine – can be destroyed by high levels of sulfite use.
  • Some yeasts require more vitamins to ferment cleanly, especially many of the newer strains. In contrast, EC-1118 is well known for having low nutrient and vitamin requirements.
  • Wild yeast fermentations are more prone to produce off aromas, but these tendencies can be reduced by using vitamin supplements.

In some years, the suggested additions of complete yeast nutrients will not be sufficient to control your problems. The addition of a vitamin supplement such as Vitamix from Winelab or Cerevit (Scott labs) will greatly reduce your problem. Suggested rates are 2 to 5 mg per litre or 46 to 115 mg (0.046 to 0.115 g) per 23 litre carboy. A solution of vitamins made in water at 50 mg/ml is an accurate way to add the vitamins. This amount in pure powder is a small amount on the end of a paring knife added directly to the wine a day after sulfiting or anytime during the fermentation. Fortunately, you don't have to be too accurate as even 5 times the suggested amounts will cause no off flavours. The best practise is too add only enough to remove the off aromas from the fermenting wine. You may have to do this more than once during the fermentation. Unlike DAP, you can add vitamin mix at any time during the fermentation. For a more complete information on sulfur problems see Bill Collings' article(E. Urquhart)

I have a zinfandel from 2003 and it is weak in colour and body, but has a spicy, fruit forward nose. Are there techniques I might have employed to obtain more colour and body? What grapes are best for blending with zinfandels and what are the usual proportions for blending?

There are several possible reasons for colour to be lacking in a red such as a Zinfandel. Steps that can be taken to maximize the colour that is retained in a red include:

  • frequent cap pushing, particularly at the early stages of active ferment results in increased colour extraction: 4–5 times a day is good.
  • note that colour does not increase with extended skin contact time. In an experiment with Cab. Sauvignon, 90% of the available colour was extracted in the first 4 days of fermentation. Colour begins to decrease after 8 days of fermentation; after 18 days the colour dropped to about 3/4 of maximum. Tannins will however continue to accumulate over the entire time of skin contact.
  • additives can be used to enhance the colour retained in some red grapes. Tannin and pectinase products aid in the maximization of colour extraction and colour retention.
  • fining with gelatine will remove some colour but fining early will remove less than if it is delayed for 1–2 years.

As for blending, 10–20% petit syrah will certainly add colour intensity to a zin. For complexity, syrah is a good grape to consider blending with zin. Trials with varying amounts prior to blending is the best approach, but if a decision needs to be made at the time of grape purchase (perhaps because the combination is intended to fill a barrel of a certain size), then any amount of syrah in the 10–35% range is likely to produce interesting results. (D. Ainslie)

I’ve purchased good quality Cab grapes and I want to end up with a big red wine that’s drinkable after 2 or 3 years of aging. How much skin contact should I be giving it, and how exactly do I know when to press?

Soak the crushed grapes for a few days before fermenting if temperature allows - this should be cool enough so that a wild yeast doesn't take over. I add an enzyme (Color-Pro) to help extract as much colour as possible - people associate big reds with big colour. Choose a yeast that is going to give you the characteristics you want in a big-red (fresh fruit, not jammy over-ripe fruit, spice, big mouth feel, etc.). I have used ICV-254 and ICV-D21 yeasts to achieve this. Ferment two batches, one for each yeast, then blend after fermentation. If you want soft tannins (skin tannins vs seed tannins) then it is a good idea to remove the seeds at some point during the fermentation (usually around 1.030 SG or when the skins and seeds have separated and the seeds have sunk to the bottom). This involves racking the must into clean fermenters and leaving the seeds behind; an extra benefit of this treatment is that you get some oxygen into the must at a point when it really needs it. At this point it doesn't really matter how long you leave the wine on the skins because you have removed the source of harsh tannins; however, I usually press within 24 hours of the cap falling. (J. George)