Thursday, August 8, 2013
Biodynamisists worship crystals: Organics are godless atheists: Conventional wine is Capitalist: Natural wine is made by stinky hippies
Tuesday, November 8, 2011
Sulfur dioxide is an important compound in winemaking, and is designated as parts per million in wine, E number: E220. It is present even in so-called unsulfurated wine at concentrations of up to 10 milligrams per litre. It serves as an antibiotic andantioxidant, protecting wine from spoilage by bacteria and oxidation. Its antimicrobial action also helps to minimize volatile acidity. Sulfur dioxide is responsible for the words "contains sulfites" found on wine labels.
Sulfur dioxide exists in wine in free and bound forms, and the combination are referred to as total SO2. Binding, for instance to the carbonyl group of acetaldehyde, varies with the wine in question. The free form exists in equilibrium between molecular SO2(as a dissolved gas) and bisulfite ion, which is in turn in equilibrium with sulfite ion. These equilibria depend on the pH of the wine. Lower pH shifts the equilibrium towards molecular (gaseous) SO2, which is the active form, while at higher pH more SO2 is found in the inactive sulfite and bisulfite forms. It is the molecular SO2 which is active as an antimicrobial and antioxidant, and this is also the form which may be perceived as a pungent odour at high levels. Wines with total SO2 concentrations below 10 ppm do not require "contains sulfites" on the label by US and EU laws. The upper limit of total SO2 allowed in wine in the US is 350 ppm; in the EU it is 160 ppm for red wines and 210 ppm for white and rosé wines. In low concentrations SO2 is mostly undetectable in wine, but at free SO2 concentrations over 50ppm, SO2 becomes evident in the nose and taste of wine.
SO2 is also a very important compound in winery sanitation. Wineries and equipment must be kept clean, and because bleach cannot be used in a winery, a mixture of SO2, water, and citric acid is commonly used to clean and sanitize equipment. Compounds of ozone (O3) are now used extensively as cleaning products in wineries due to their efficiency, and because these compounds do not affect the wine or equipment.
Monday, October 24, 2011
Monday, July 25, 2011
Monday, March 28, 2011
For those of you who will be in London between the 15th-17th of May there is a Natural wine fair being held at Borough Market. www.thenaturalwinefair.com Isabelle Legeron MW is organising this event which should be great craic. To be 'Natural' the wine must fulfill the following requirements;
* ALL grapes are, at a minimum, organic
* ALL grapes are hand-harvested
* NO added yeasts
* NO added sugar
* NO rectified acidity
* Little or no sulphites are added during fermentation or at bottling*
*For us, low sulphite levels means that the grower is ultimately aiming to add as little SO2 as possible but whether or not (s)he does so, or indeed how much they add, is dependent on the year.
These are pretty broad parameters and quite frankly they are what most quality wine producers do anyway. As someone said to me recently, "If these wines are 'Natural' does that mean that quality producers World wide are making unnatural wines!" Therefore there is a more radical element to this movement which goes one step further and shuns the use of sulphites, filtration and fining.
Sulphites in winemakiing
The use of sulphites has been common practice in winemaking since Pasteur clarified there use at the end of the 19th century. They are used for a variety of reasons. In White/Rose winemaking they are commonly added when the grapes are crushed/pressed to act as an anti-oxidant to preserve fruit characters. They also can stop any wild yeasts from kicking off while the wines are settling. Of course only a small amount is added at this stage as alcoholic fermentation can be retarded by sulphites. After fermentation sulphites are generally added when the wine is racked off yeast lees. This is to stop Malolactic fermentation occurring. Of course if it is desirable for the wines to go through MLF then sulphites will be added after it is finished. In red wines it is common to add a small amount at the crushing of the grapes to avoid oxidation and again at the completion of MLF.
The dangers of making white wines without sulphites are complex. Firstly the fresh fruit caharcters that we are used to in white wine will not be generally present in 'Natural' wines. Oxidation will effect these fruit aromas and the wines will generally smell like apples. Spoilage yeasts could detrimentally effect the fermention also. Besides throwing out funky unusual aromas the spoilage yeasts could also create toxins as a by-product which could stop fermentation. The unfermented sugar could then be consumed by numerous bacteria causing volatility (vinegar aromas) and dirty MLF which will also effect the aromas. These are worse case senarios as if the grapes are clean and have no disease then the wines will generally be better but they must have a lot of natural acidity which will be the only line of defence against bacteria and spoilage yeasts.
Red wines are a bit more robust as the grape tannins will provide some defence against spoilage. Again it is very important to have clean grapes and a strong acidity. Oxidation is a major problem as appely aromas in red wines are disgusting. The other major problem is Brettanomyces which is a common yet highly undesirable spoilage yeast. Often described as a barnyard smell and quite well liked in small quantities in red wines. However with no sulphites these yeasts can continue to chew very small amounts of sugar in bottled wines leaving the palate dry and astringent.
An interesting aside as well is that a study in Canada http://bit.ly/hgYdyY has shown that headaches caused by wine are thought to be mainly from amines from rogue MLF bacteria. Proff that sulphites are not solely responsible for headaches, hypertension and migraines in many people.
I very much wish that I could attend the 'Natural' wine fair in London. I believe that there will be some very interesting wines and great personalities involved. It would also be fascinating to talk to the producers to see how they overcome the problems that I have stated above.
Friday, January 7, 2011
What is Malolactic fermentation (MLF)?
MLF is the conversion of Malic acid to Lactic acid by Lactic bacteria. This conversion will occur in all wines but is stopped in most white wines as it adds undesirable flavours and alters the acid balance of wines.In red wines it is essential that all malic acid is converted to lactic acid. Otherwise this conversion could continue in bottle and spoil the wine. The only truely effective way to stop MLF is with Sulphur dioxide SO².
How is MLF initiated?
MLF will occur spontaneously as there is always a population of Lactic bacteria in wine. However the process can be helped by the addition of a bacterial culture. This can be added at the same time as an yeast culture is added. However this can cause an increase in acetic acid, which can impede primary fermentation, as the Lactic bacteria chews up the sugar in the must. The most common timing for this addition is at the copmpletion of primary fermentation. At this stage the inhibiting effects of any SO² adds have been reduced and there is only a tiny amount of sugar left that will not cause any acetic acid problems. Critically the temperature of the wine is generally quite warm at this stage which is necessary for the bacteria to work. The third method is allow the bacteria to occur naturally. This is the method that we employ at Domaine la Sarabande but it is crucial that the conditions are correct for a clean MLF to occur.
The optimum conditions for MLF?
There are three types of bacteria that are most common in MLF. Leuconostoc is the most favourable and is the main bacteria in any freeze dried cultures. Pediococcus and Lactobacillus are considered spoilage bacteria but are unfortunately quite common in winemaking. At the completion of primary ferment there is a tiny amount of unfermentable sugars (pentoses, arabinose and xylose) plus residual fermentable sugars ( glucose and fructose). Lactic bacteria can live on these tiny amounts of fermentable sugars. It is also important that the pH of the medium is suitable low (3.30-3.40) so that Leuconostoc can dominate the MLF. The other important factors that enable a clean MLF include temperature (+18°C), keeping SO² additions low at crush and by not overly clarifying or racking the medium.
What can go wrong?
Leuconostoc dominates at lower pH but is slower working than the other spoilage Lactic bacterias. This means nthat MLF can take several months. Therefore it is important to have vessels full so that Oxygen cannot oxidise or feed other spoilage bacterias. However if the wine has a high ph (3.50+) then you are in a world of spoilage bacteria pain! At best Pediococcus and Lactobacillus will form high levels of diacetyl. This is perceived as buttery but can also be like sour milk and is very unpleasant. Spoilage bacteria will also cause a condition which the French call Graisse or Ropiness in English. The wine will appear gassy and thick in the glass with ropy thick legs in the glass. Tourne is the French expression that is the fermentation of Tartaric acid by Lactic bacteria. This is serious spoilage as the acid is what keeps wine stable. Loss of tartaric acid can turn wines brown and open to numerous other spoilage. Wines can go cloudy and develop a mousy aroma. Again this happens in high pH wines especially if no SO² is added in the wines life. This can be quite a common fault in 'natural wines'.
It is the winemakers role to ensure that wines get to bottle unspoilt. Malolactic fermentation is a time when numerous things can go wrong. It is importatnt to have the correct conditions so that a clean MLF can occur. This is mostly down to having a stable pH at the end of primary fermentation. Easier said than done and dependent on to many factors to get into here! It can be a long winter until the wines are through MLF and SO² additions can be made. Patience is the key!!