Chardonnay in great condition, close to harvest date, The first requirement if one is to make wine free of added chemical preservatives is sound fruit reaching the winery in original condition.
The How and Why of Preservative Free
Prior to the discovery by the Dutch that burning sulphur in wine casks enabled wooden containers to stay ‘sweet’ and the wine to remain palatable for much longer, wine was made without the addition of sulphite. Burning sulphur rings in barrels was still common practice in the 1980’s when I started making wine.
Preservative in wine is a big topic. Happs has led the way in developing techniques that enable wine to be made in the absence of sulphur dioxide. There is an interesting difference between the European definition of ‘Organic’ and the U.S. version. The Europeans allow the use of sulphur dioxide whereas the Americans insist on very low levels if a wine is to be described as ‘organic’. This illustrates the fact that we are not at all clear about what ‘organic’ actually means. Does it refer to what we do in the vineyard, how we manage the soil, whether we use certain pesticides or fungicides? Does the notion of ‘organic’ extend into the winery to govern the use of wine making additives? Does it extend to the choices between packaging materials, the use of so called ‘renewables’ to generate energy and mans influence on the environment? Is it linked to ‘sustainability’? The same sort of interpretative difficulties relate to the use of the word ‘biodynamic’ and the descriptor ‘natural wine’. This is a fertile field for vagueness, mysticism and ‘market speak’. It’s a means by which people try to differentiate themselves from their competitors. What follows will interest all who like to avoid the consumption of substances that might harm the human body. The aim is to clarify the situation.
The material is organised under the following headings:
- Sulphur Dioxide: Frequently Asked Questions
- Overview of ‘wine preservatives’.
- The place of Preservatives in our wines that do have sulphite added
- Wine Preservatives (not sulphur Dioxide) may have killed Beethoven
- Natural wine preservatives and good wine making practice
- Can we make white wine that tastes good without using sulphur dioxide?
- More information on the net
1. Sulphur Dioxide: Frequently Asked Questions
What is Sulphur dioxide? Sulphur Dioxide (SO2) is an antibacterial and antioxidant added to many foods including wine, sausages, preserved meats and dried fruit and usually represented on the label as ‘preservative 220′. It’s a colourless, non-flammable gas. In water it will dissolve to reach a concentration of 12%.
Why is sulphur dioxide used in wine making? Grapes can be damaged by birds, rodents, foxes, weather and fungi. Harvested indiscriminately they can carry a heavy load of micro-organisms. Harvested grapes are usually warmer than 20°C and at this temperature these organisms multiply rapidly. In such circumstances unfavourable outcomes are likely.
How does it affect humans? At high concentrations SO2 is highly corrosive to mucous membranes, upper respiratory tract, eyes and skin. In dry wine the maximum permissible level is 0.025% measured as free sulphite. It can be detected as a burnt match odour. This can produce air passage restriction in susceptible individuals. Some are intolerant of sulphites. Those susceptible, report headache and bodily discomfort including face flushing, feeling poorly overnight and on the following day although amounts ingested may have been small.
How does Happs manage to make preservative free wine when the prevailing wisdom is that the task is fraught with hazard and unlikely to meet with success? Firstly, due to the use of nets we begin with undamaged raw materials. Harvest by hand keeps the fruit intact. Thirdly, our grapes have naturally high phenolic content, a natural antioxidant. This is due to the fruit having a greater exposure to sunlight in turn due to our dual row trellising system that disperses the foliage to a much greater extent than other systems of viticulture, especially the more restrictive systems designed for mechanical harvesting. Fourthly we chill fruit prior to crushing. Fifthly we have developed techniques to keep wine cold for long periods of time without breaking the bank and to keep it away from the air. Alcohol levels are generous. None of this is rocket science!
Is ‘Organic’ the same as ‘Preservative Free’? Can we have both together? The short answer to this question is that the term ‘organic’ properly relates to practices in the vineyard. Most organic protocols allow the use of sulphur dioxide in the winery. It is possible to use organic methods without seeking certification. It is also possible to produce wines from grapes grown using organic methods without using sulphur dioxide or other known allergens. That is our approach with our Preservative Free wines. You then have the best of both worlds.
Is elemental sulphur used in the vineyard a source of sulphur dioxide? The elemental sulphur used to protect vines from powdery mildew is not a source of sulphur dioxide in wine. Sulphur is a naturally occurring element and was used as a medicine prior to the discovery of antibiotics (Sulphur drugs). Sulphur dioxide is an oxide of Sulphur with entirely different properties.
At what point in the wine making process is sulphur dioxide added?
- In the fruit bins if harvesting by machine
- At the crusher
- At pressing of white grapes
- After fermentation
- During aging
- In conserving barrels when empty.
- Prior to bottling
Given the potential for premature spoilage in mechanically harvested vineyards, the most critical use of sulphur dioxide is undoubtedly as a bactericidal addition to the picking bin. It is useful in inhibiting oxidative enzymes. It is a low level scavenger for oxygen picked up whenever wine is exposed to air or kept in poorly sealed or air permeable containers. A supply of oxygen is all that is necessary to degrade flavour and support the growth of acetic acid bacteria. The addition of add SO2 just prior to bottling is primarily intended to neutralise some of the oxygen that can be absorbed during the bottling process.
How effective is sulphur dioxide against the growth of unwanted organisms in bottled wine? In fermentation, yeast converts sugar to alcohol. The next ferment possible is the bacterial conversion of malic acid to lactic that is sought to make an acid wine softer. From this point further fermentation is undesirable. Given sufficient air, acetic bacteria will multiply to produce vinegar. Of course if a wine goes to bottle with either sugar or malic acid, fermentation is possible. Because red colour binds sulphites, sugar or malic ferment is likely in red wines where these substrates are present after bottling. The usefulness of the ‘preservative’ therefore depends upon the wine type, the presence of fermentable substances, the presence of air and the type of organism in the bottle. Low pH helps to keep more sulphur dioxide in the active form. High alcohol and very high sugar contents are independently antagonistic to further ferment. In practice the only sure method of preventing further ferment is to exhaust that possibility beforehand or filter the wine so that the organisms are not present after bottling. The ‘antimicrobial’ or ‘preservative’ role that sulphur dioxide might perform after bottling is something that cannot be relied upon.
How important is sulphur dioxide in bottled wine as a defence against oxidation? The requirement for an antioxidant depends upon the porosity of the container and closure to air. Plastic materials admit air whereas glass and screw caps are relatively impervious. Corks admit variable quantities of air giving rise to the old adage that there are no great old wines, just great bottles. However, depending upon its constitution, a wine needs some air to facilitate the aging process. Without this air some wines become reductive and smelly. The greater the natural tannin in the wine the more protection it has against oxidation. This is why reds age longer than whites. When white grapes are exposed to more sunlight more phenolics are generated and that helps a wine resist oxidation. This is the rationale that we follow. The phenolic (tannin) content of a wine is linked with its ability to protect against heart damage because phenolics are great antioxidants. The long lived wines have their own natural protection against oxidation and they are also the wines that will guard against heart disease.
What enables some wine to evolve to a more interesting product after bottling? The natural preservative in wine is alcohol, tannin (phenolics) and natural acidity. A good natural acidity is the product of cool ripening conditions and is usually accompanied by a good depth of flavour. The presence of sulphur dioxide after bottling is largely irrelevant to a wine of healthy constitution except that it will assist in taking up oxygen that can be picked up during bottling or via a container or a stopper that is permeable to air. To suggest that sulphur dioxide is ‘the preservative’ in wine overstates the case. The aging capacity of the wine after bottling is conditional on its depth of flavour, freshness at bottling, the bottling technique, container type, closure type, the presence of fermentable substances and the presence of organisms capable of degrading the wine. Unless these latter conditions are met no amount of added ‘preservative’ will assist. A great wine lives on its natural constituents that came from the grape. A wine under cork needs freshening up to the extent that the cork seals poorly. In this case some sulphur dioxide will assist.
What are the allowable limits for sulphur dioxide in finished wines? The limit is defined in terms of the amount that is present by analysis and depends upon the type of wine made. In practice these legal limits are not approached in modern winemaking except when accidents or miscalculations occur. Dry wines are allowed 250 parts per million but rarely exceed 150 parts per million. Happs whites rarely exceed 100 p.p.m. at bottling and reds 50 p.p.m. At release, levels are less than that. Of course our PF Wines have none.
What is the extent of use of sulphur dioxide in modern winemaking? With the widespread use of refrigeration and inert gas to prevent exposure to air, and the availability of effective filtration, the amount of sulphur dioxide encountered in wine is much less today than it was 50 years ago. SO2 binds substances that evolve during ferment and the more that is used in the beginning, the more that is required in the end. The advantage for wine makers lies in reducing its use because a more palatable wine will result. I believe that, as we discover that we can make good wine using other tools we will rely less and less on this antiseptic. The sounder the grapes and the more considered the winemaking strategy, the less is needed. In recent years the effort to control Brettanomyces yeast has promoted the more rational use of sulphur dioxide in winemaking with less frequent but heavier additions and a higher ratio of ‘free’ to ‘total’ present in the wine. It’s worth noting that we have never seen an instance of Brett in a PF wine yet.
Is sulphur dioxide produced by yeast during ferment and therefore an inescapable constituent of wine? Under difficult fermentation conditions that apply when grapes have a low amino acid status sulphite is excreted by yeast. These fermentations commonly produce rotten egg gas. In fact, the production of sulphite by yeast is anathema in modern wine making and is a recognised difficult situation that will be avoided wherever possible. Red fermentations never produce sulphite. I do not regard the observation that yeast can produce sulphite as a defence of the practice of adding sulphur dioxide. The sulphite that can be produced by yeast is in any case fully bound and inactive in the human body.
What are the active forms of the chemical in wine? When added to wine the result is SO2, HSO3 (bisulphite) and H2SO3 (sulphurous acid). These are collectively called ‘sulphites’. The active bactericide (SO2 and HSO3) is readily absorbed into some organisms. However the bactericide is present in fractional amounts depending upon pH and the constitution of the wine. The presence of compounds that bind strongly to sulphite including acetaldehyde, pyruvic acid and anthocyanin (red wine colour) leaves only a tiny portion that is active against micro-organisms or oxygen. When added in amounts that will secure microbiological stability and freedom from the effects of oxidation at a pH which is palatable, the sulphite is all too obvious on the nose and the palate.
What organisms are controlled, not controlled, and how to control? Sulphite inhibits the action of bacteria that metabolise malic acid. However it has little activity, when present at permissible levels, against sugar fermenting yeasts, brettanomyces yeast or acetic acid bacteria. It should be noted that these are the major spoilage organisms of wine. The best safeguard against these organisms is to make sure that there is nothing further to ferment, and if there is, to filter the wine clear of the organism or to keep it cold so as to inhibit activity. Yeast, including brettanomyces species will not grow appreciably if the wine is free of fermentable sugars. Acetic acid bacteria will not grow in the absence of air. Malic bacteria will not grow unless malic acid is present.
In what form is sulphur dioxide purchased? Sulphur dioxide is usually purchased by wine makers in a gaseous or powder form and is readily soluble in water. The powder used is potassium metabisulphite.
What is a safe level for ingestion of Sulphites? The joint FAO/WHO Expert Committee on Food Additives in 1974 established an acceptable daily limit of 0.7mg per kg of body weight. This translates to 56mg for an 80kg individual (0.056grams). A 750ml bottle of wine containing 150 parts per million sulphites contains 0.225grams. On that basis the daily allowance for such an individual is met by consumption of 187 mls of such a wine. After three years in bottle the sulphite level in a white wine may drop by half. Then, twice as much wine may be consumed without exceeding the daily allowance. Red wines start their bottle life with perhaps half the level of sulphite as white wine and may also be consumed in twice the quantity. However, it should be noted that wine is not the only food containing sulphites.
2. Overview of ‘wine preservatives’
Sulphur Dioxide (SO2) is the principle sanitation aid used in the winery. It kills bacteria. Bacteria can inhibit yeast fermentation by competing for nutrient. So it is very useful at the crushing/pressing stage and essential in the fruit bins when grapes are mechanically harvested and subject to transport delay before reaching the winery. The word ‘Preservative’ as it is used in connection to wine, is inaccurate. Used at the crush and during storage it’s more a ‘winemaking aid’ to secure a clean ferment. Used in the later stage when the wine is maturing or being prepared for bottling sulphur dioxide acts as a rather inefficient antioxidant and as an efficient way of neutralising stale smelling aldehydes that are a product of oxidation making the wine appear fresher for longer. Once in the bottle, the quantity of sulphur dioxide required rendering a wine safe against microbial action or the oxidation consequent upon the usage of cork as a closure would make a wine undrinkable. People’s tolerance to SO2 varies widely. Like bee venom and other irritants, your susceptibility increases with continued exposure. As you get older you may notice its effects. You might start waking up in the middle of the night with an itchy nose, or have asthmatic tightness, a cough or a headache.
The bottom line is that while most people are blissfully unaware of any impact, it’s a substance that should be ingested sparingly. The legal maximum level of sulphur dioxide in wine is 350 parts per million, a level that may be approached in some bulk product in non glass containers (cask wine). Containers that are permeable to oxygen have a short shelf life unless there is sulphur dioxide present. Many other foods less inherently stable than wine depend upon sulphur dioxide as a preservative of colour and condition. Dried fruits and some cold stored fresh salads and meats are examples. In winemaking hand picking and careful fruit management together with care to avoid oxidation and storage under cool conditions allows a more conservative approach. Happs Preservative Free range uses no sulphur dioxide at all. There are strong natural preservatives present in the wine including tannin, low pH and alcohol. Many consumers are under the mistaken impression that if a wine does not contain ‘sulphur dioxide’ it has a very short shelf life. My experience is that the aging of wines can be related directly to the quality of the fruit, the care with which these wines are made, the degree of oxidation allowed in processing, in bottling, and the wines content of alcohol, acid and tannin. Our experience over twenty years making two wines, a red and a white, without recourse to sulphur dioxide, suggests that wine with abundant natural preservative will last as long as any wine containing added sulphur dioxide. This is especially so if the metal cap closure is used. An ineffective closure like cork or the plastic imitations of cork yields a short shelf life with or without sulphur dioxide. How long will our PF wines live? Five years minimum. After five years there should be little difference in ‘chemically active ‘free sulphite’ between wines that initially had, and those which never had, sulphites added. This is particularly the case with reds because the colour binds up the sulphite anyway. It’s a level playing field from that time on. How long does a wine keep after you pour the first glass? It depends primarily upon temperature that governs the rate of chemical reactions and biological activity. Keep the wine in the fridge and it will be go three times the distance. Would you leave your butter, meat and vegetables out on the sink? There is an added bonus. The reds taste better at a lower temperature and its interesting to see them evolve as they warm up. There is nothing that has taught me more about winemaking than the effort to make wines free of sulphur dioxide. I reckon that the production of one preservative-free wine should be mandatory for all student winemakers. If the wine doesn’t look good at the end of the process I would fail them. The capacity to produce a high quality PF wine tells a story about ones understanding of the tools available and the intending winemakers ability to employ techniques to manage fermentation , conserve the wine and in particular to avoid oxidation. The wine would be judged after a year in the bottle and again at two years.
They say that fools with tools are still fools. You can come to that conclusion by observing behaviour but the real confirmation lies in the character of the wine produced. Will the wine age? Many a Gold Medal wine has fallen away quickly after the judging. Our first PF Red was made in 1994. The grape mix changes a little each year. It’s part of the learning process. This is frontier stuff. There are very few producers making preservative free wines. There are many more trying to be organic in the vineyard than there are trying to be natural in the winery. It’s all part of the rich texture. For my money, the sulphite free approach is the most direct approach to reducing the impact of what might be described as ‘doubtful chemical inputs’.
3. The place of Preservatives in our wines that do have sulphite added
The commonly used form of sulphite used in wine is potassium metabisulphite. Our dry reds in both the Happs and the Three Hills range, all of which are given wood maturation for a year and then bottle maturation for a further year, have very low levels of sulphite at release. They easily meet the requirement set for European Organic wines (i.e. below 20 parts per million measured as ‘free sulphite’). Our pink and the white wines are released with total preservative levels between fifty and one hundred parts per million and free sulphite at between ten and thirty parts per million. These levels decline with time. Whites and pinks do not have the full complement of tannins that protect dry red wines. More sulphite is seen to be necessary as a defence against oxidation. Pale Gold commonly requires about one hundred parts per million sulphite added to bind up some compounds which come in fortifying spirit. Again, free sulphite levels drop with bottle aging.
4. Wine Preservatives (not sulphur Dioxide) may have killed Beethoven
Samples of Beethoven’s hair has been analysed for its lead content. The analysis reveals that he ingested toxic levels of lead. Being a sickly fellow, and having to endure much pain, it was Beethoven’s custom to drink a couple of bottles of wine every day. In those days the wine had lead in it, the water pipes and the roof had lead and so did the drinking vessels of lead glazed pottery and lead fluxed glass. The use of lead in wine predates the use of sulphur dioxide. The practice was common in pre Christian Roman times. We are told that lead much improved the taste of wine giving it a softer fuller flavour. I don’t know whether lead has antibacterial properties but would not be at all surprised if it did. Many compounds that might induce nothing worse in humans than bronchial discomfort, a nasal snort or a slight headache can be fatal to bacteria and insect life. In Beethoven’s time, (1770-1827) fermentation was a complete mystery. Modern winemaking owes much to Louis Pasteur who drew aside the veil on yeast and bacteria in 1866.
5. Natural wine preservatives and good wine making practice
The chief preservatives in wine are alcohol and tannin. There are very few organisms that will survive immersion in alcohol. It has therefore long been used to sterilize medical instruments. Alcohol is much more stable in wine than sulphur dioxide. Other factors will assist to render the use of chemical preservatives unnecessary include:
- Picking grapes by hand.
- Speed of movement between vineyard and winery.
- Clean conditions in the winery.
- Chilling grapes before they reach the crusher.
- Regularly topping barrels to reduce oxidation.
- Replacing air with carbon dioxide or nitrogen above the wine in tanks.
- Keeping stored wine cool, preferably less than 14°C.
- The use of filtration to screen out organisms that could harm the wine, especially prior to bottling.
- The presence of tannin, as in red wine, and to a much lesser extent in white.
Clever winemakers use as little SO2 as possible because they also know that sulphur dioxide produces sulphuric acid that makes a wine taste ‘hard’. Most tasters can pick it at quite low concentrations if dissolved in water. In the malolactic fermentation bacteria convert malic to lactic acid and eliminate sulphur dioxide binding compounds like acetaldehyde and pyruvic acid. Malolactic ferment renders the use of SO2 to bind these compounds unnecessary. A good clean ferment of clean grapes in clean containers, and its removal from the influence of oxygen at the end of fermentation, produces a very stable product. The problems begin with poor containers and oxidation after ferment. Wooden barrels in warm conditions are the chief risk but there is many a winery that has ill fitting lids on their tanks. The preservatives that are natural to wine are potent, and more persistent than the added chemical and it is unfortunate that we refer to sulphur dioxide as ‘the preservative’ as if it were the only active ingredient. One notes that acetobacter, the principal bacteria that takes wine to its next breakdown stage, is not inhibited by SO2. Nor is the brettanomyces yeast inhibited by SO2. Studies at the Australian Wine Research Institute confirm that acetobacter develops prolifically in bottles stoppered with cork and stored in an upright position for any length of time – even though there may be significant SO2 present. This so called ‘Preservative’ fails miserably when air is present.
6. Can we make white wine that tastes good without using sulphur dioxide?
Many tasters love the fruitiness of PF Red but they find that PF White is different to any Australian white wine they have tasted before. What’s going on? The short answer: With this wine we have to approach fermentation from a different angle. Without the activity of sulphur dioxide both yeast and bacteria multiply in the ferment. The bacteria can use up nutrient required by the yeast that can give up leaving the wine sweet. We need it to be dry because if there is fermentable substrate left in the wine a rogue yeast with tolerance to the medium can start up at any time, even after bottling. We have to select a bacteria yeast combination that is compatible. The outcome is a white wine with a unique flavour. It is softer in the acid dimension. There is a lactic character that is produced by the bacteria. The original grape character is less pronounced. However, the stronger the flavours in the original grape, the more they will appear as a part of the finished wine.
More about Malolactic bacteria Malolactic fermentation is conducted by some of the same bacteria involved in the making of cheese and yogurt. The bacteria produce potent flavours. Neither the wine industry nor the dairy industry is fully aware of all the habits and proclivities of these bacteria. We are aware that their numbers keep growing even after all the malic acid is gone. We guess that they are working away at some other substrate but don’t know what. These bacteria come in many varieties that give cheese the signature flavours that we see according to origin, and most particularly when it is not pasteurised prior to the cheese making process. It is very unusual in Australia to allow complete malolactic fermentation in white wine making. But it’s not unusual with the great White Burgundy of France. In Australia the current fashion is to allow a proportion of wood matured Chardonnays to go through malolactic ferment. The greater proportion of the wine will not experience the fermentation and will retain its fresh grapey character. In addition, yeast lees and oak flavours make strong contributions to the flavour of Chardonnay. Consequently, the malolactic flavours are relatively hidden, overlaid and truncated. Not so with our PF White that has been produced in stainless steel. It’s thoroughly infected, wholly fermented and exhibits the malolactic character in abundance. With a full malolactic the wine tastes softer. The palate impression will be longer and smoother. That is because the rather hard tasting malic acid has been converted to the softer tasting lactic acid. You cannot make a red wine without malolactic ferment and those who produce the great Chardonnays of Burgundy deliberately allow it to take place. Normally, if it doesn’t follow on immediately from the yeast ferment it happens in spring when the cellar warms up. The upshot is that in PF White is presenting flavours that may be new to you. Flavours are more aligned with what you might experience in red wines, dairy products like cheese and yoghurt and less like the white wines that you are used to. This is frontier stuff. There are very few producers making preservative free wines. There are many more trying to be organic in the vineyard than there are trying to be careful in the winery. Many wineries are not as well equipped to control oxidation as we are. Any wine tank equipped with a ‘breather valve’ to allow the pressure that builds up during the day to escape from the tank, is oxidising its wine overnight because that same breather valve allows the air to enter as the headspace gas cools and shrinks. Sulphur dioxide is quite insidious. The more one uses prior to fermentation, the more one needs following it, because, as sulphur dioxide binding compounds are formed during fermentation they are grabbed by the chemical and persist in greater amounts in the finished wine. It’s a chemical that once used becomes a habit and a need.
Do our white wines produce sulphite during ferment? No, because our full grass cover and dry-land regime in the vineyard is great for the growth of micro-organism and worms in the soil. Consequently our grapes are particularly high in amino acids required by yeast. The sulphite that is generated (in the white wine only) is in tiny amount that is fully bound to other wine constituents and cannot be liberated in the human body.
7. More information on the net
There is a lot of unreliable information about sulphites on the net. A recent search on ‘sulphite in wine’ brought up this article that has some statements that could be challenged but is more authoritative than most. http://www.morethanorganic.com/sulphur-in-the-bottle
This article includes the statement: The World Health Organisation recommends a maximum daily intake of 0.7mg of sulphur dioxide per kilogram of bodyweight. For a man of average weight this is less than a third of a bottle of a white wine with a concentration of 200 mg/l (the EU limit for dry white wine is 210mg/l). Looking at this figure I would double the allowed consumption for a well made white wine with 100ppm or less and allow more for red wine. However, the important factor is not the total sulphite but the free and active sulphite. The older the wine the less free and active sulphite there is. The warning simply says that sulphite was used. It doesn’t tell you anything about whether the wine is likely to harm you and it’s not possible to do that without ongoing tests after the wine has left the winery.
Consumers experience with sulphite: http://gregpye.wordpress.com/2007/11/25/sulphite-intolerance-and-wine/
Erland Happ August 3rd 2014