Sugar plays a vital role in the wine in your glass, even if you can’t taste it directly.
What is sugar?
Sugar is the name given to a wide range of carbohydrates, but only the simpler ones are sweet.
Glucose – one of the main products of photosynthesis in a plant, making up about 50% of sugars in ripe grapes. It is one of the three simplest types of sugar, known as monosaccharides. This is absorbed straight into the bloodstream during digestion.
Fructose – another monosaccharide, making up the other 50% of sugars in ripe grapes. It too is absorbed straight into the bloodstream during digestion.
Sucrose – the type of sugar you put in your tea, is typically produced from sugar cane or sugar beet, and very little is found in ripe wine grapes. Sucrose is in fact a combination of glucose and fructose.
Production of sugar in wine grapes
There is very little sugar in a grape until véraison, when the grape starts to change colour and ripen. Acidity decreases, and sugar contents rise, see the graph in a previous post. The trick is to get the correct balance between the two. Sugar concentrations in ripe grapes can easily achieve 20%.
Adding sugar manually
Before fermentation – sugar in grapes is converted to alcohol during fermentation, but if the grapes aren’t ripe enough, sugar may be added to artificially increase the alcohol content. A process known as chaptalisation. If this is done carelessly, there isn’t enough fruit in the wine to balance the relatively high alcohol. This practice is banned in many wine regions.
Adding two lots of sugar – Champagne manufacture involves adding sugar and yeast to produce bubbles in the bottle, and then sugar at the end to take the edge off the acidity.
Fermentation Yeasts turn the simpler sugars into alcohol plus carbon dioxide, but many other reactions also happen, and some of the complex sugars remain.
Effect of residual sugar in wine
Tasting threshold – for most people this is around 1% sugar content, but those who are particularly sensitive can detect 0.2%. A dry wine which is fully fermented out will have a sugar content of < 1.5 gm/litre, which is not detectable.
Balancing other tastes – sweetness balances acid and bitter tastes, making them less harsh.
Provides food for microbes – residual sugar in wine encourages bacterial growth unless it is properly protected. Sulphur dioxide is important here, see previous post.
In most wines, sugar just has a fleeting presence for a short while before the grapes are picked. It is created by photosynthesis, and consumed by fermentation.
Yeasts are fungi, which play a vital role in wine production. The number of different species runs into tens or even hundreds of thousands, no one is quite sure. More than one may be used in fermenting the grapes, and this has a big influence on the wine produced. Yeasts produce aromatic compounds as well as alcohol and carbon dioxide.
What yeasts need to make them work
Yeasts need the right conditions to work their magic during wine fermentation:-
Temperature. They operate in a temperature range. Too low, and yeasts don’t function, too high and they are killed off. The grape juice may be actively heated or cooled to achieve this.
Nutrients.Sugar is the main one, but you need a source of nitrogen, which is provided by amino acids. Winemakers may add selected nutrients.
Alcohol level. Different yeasts work in different ranges of alcohol content.
Winemakers split yeasts into two main categories
‘Natural’ or ‘wild’ yeasts. These are the yeasts which are present in the vineyard, and stick to the grape skins. They are also on the wine equipment. These indigenous yeasts give the wine a local character, a sense of place. The term ‘terroir’ is often used to express this.
Cultured yeasts. These are developed to introduce particular characteristics to the wine, or to make fermentation more reliable. Usually, the indigenous bugs will be killed off with sulphur dioxide, and then the grape must/juice will be inoculated with the cultured yeast.
What can go wrong with a ‘wild yeast fermentation’
Problems with starting the fermentation. The grape must/juice will contain a range of bacteria as well as yeasts, and these compete for the nutrients. You may end up with acetic acid (vinegar) rather than alcohol.
Inconsistency. A number of different yeasts may be involved during a fermentation, with some dying off at quite low alcohol levels, and others taking over. If a different yeast takes over, you can end up with a different wine than you anticipated.
There is no right or wrong answer about the use of wild yeasts, it rather depends on the market you are aiming at. Cultured yeasts will help to produce a consistent product, which is going to appeal to the big brands. Small producers may well enjoy the variability.
Matching wine and food is not an exact science, and everyone’s taste is different. It is a value judgement. But there are some basic guidelines which help to avoid unpleasant clashes.
artichokes – a challenge to match with wine
The more acidic a wine, the easier it is to match with foods. Think of how a dash of lemon juice enhances some dishes.
Acidic wines deal very well with salty foods such as oysters, or oily fish like mackerel.
The wine should be more acidic than the food. In fact food can temper a wine which would otherwise be too acidic for most.
Alcohol Alcohol in wine affects the texture in the mouth, and if it is too high causes a bitterness and burning at the back of the throat.
Match the weight of the wine with that of the dish. Most foods are fairly light-weight, so it is easier to match lower alcohol, more elegant wines.
Avoid drinking high alcohol wines with chilli or very salty dishes – it just reinforces the burning.
Tannins come mainly from the skin and pips in grapes, so are most often found in red wines. They react with the saliva in your mouth to cause a puckering sensation. Tannin levels decrease as a wine ages, so young wines are more tannic than older ones.
Tannic wines clash badly with many fish dishes, leaving a metallic taste in the mouth.
Tannic wines go very well with fat and protein – grilled steak for example.
Both red and white wines can be oaked, but it is much more common in reds. Oak treatment is expensive, so it is done with better wines. The resulting wine has more body and tannin than lighter-styled wines.
Avoid delicate dishes, as the wine will overwhelm it.
Pick dishes with rich sauces, or where the food has been grilled rather than poached.
Are those with residual sugar. Note that they should also have a balancing acidity, or else they are just cloying and will hardly match any food at all.
The sweet wine should be sweeter than the pudding you are eating.
Semi-sweet wines go well with spicy hot food.
There is no point drinking a wine which you don’t like, just because someone on TV has declared it a perfect match with the food you are eating. In the end, you should drink what you enjoy, but perhaps use the above guidelines to avoid the worst clashes. If a wine really does clash, you can always finish it off after you’ve finished the food.
There are plenty of climate change sceptics, but it is a fact that alcohol levels in wine are increasing, and some grape varieties ripen, where they wouldn’t have 20 years ago.
Why is alcohol level an indication of higher temperatures? Higher temperatures produce riper grapes, which have more sugar. During fermentation, the sugar turns to alcohol, so more sugar leads to more alcohol. There is an associated decrease in acidity.
Some grapes need more heat to ripen
Different grape varieties prefer different temperatures
The diagram shows that some grape varieties need longer heat exposure to ripen than others.
If the temperature is higher than ideal, the grapes will ripen, but the wine will lack freshness and acidity.
If the temperature is lower than ideal, then the grapes won’t ripen properly, and the wine will be tart and acidic.
If the temperature is much higher than ideal, then the vine simply shuts down, and nothing happens.
Which countries are most affected?
Those at the current extremes of temperature for growing vines:-
Much of Australia and Spain, for example, have vineyards in regions with high temperatures. They will have to adapt to survive.
Countries further from the Equator with more marginal climates, such as England, will now be able to grow a much wider range of grape varieties.
What can the adversely affected regions do about it?
Plant different grape varieties, which are more tolerant of the hot weather.
Train the vine branches so that leaves physically shade the grapes.
Allow plants to grow between the vines, as this lowers the soil temperature, and there is less reflected heat from any stones.
Alcohol levels in wine have increased significantly over the past 20 years. That is not to everyone’s taste, but are low and zero alcohol wines worth considering?
Why have alcohol levels increased?
There are several proposed reasons, including:-
Climate change – more heat and sunshine produces riper grapes with more sugar, and hence more alcohol.
Better practice in the vineyard, producing better quality grapes, with higher sugar levels.
The influence of certain wine critics, which encourages big wines with high alcohol levels.
What influence does alcohol have on your palate?
Alcohol stimulates nerve endings in the mouth, to provide a sensation of body and texture. It spreads flavours around the mouth, which persist even after the wine has been swallowed – known as the ‘aftertaste’. If the alcohol is too high, and is not balanced by the fruit, then the aftertaste may be bitter. If the alcohol is too low, then the wine is thin and unappealing.
A quality wine with 9% alcohol
Lower alcohol wines
The most successful lower alcohol wines (less than 10%) are those made in Germany. The fermentation is stopped short, and the wine may be sweetened by adding unfermented grape juice. This combination of lower alcohol, sugar and good acidity works very well indeed.
How low and zero alcohol wines are made
A wine has to be made by fermentation of grapes; this produces mainly alcohol, but also a host of other chemicals which contribute to a wine’s taste and smell. So the alcohol needs to be stripped out, but this is likely to remove other compounds as well.
Why drink very low or zero alcohol ‘wine’?
For the reasons stated, these ‘wines’ are a mere shadow of their former selves. So why not drink unfermented fruit juice instead?
Suggestions if you are worried about alcohol consumption:-
Look for wines from cooler regions of the world, which will have lower alcohol levels.
Add water to high alcohol wines. I know this may be sacrilege, but it is better than commercially stripping out the alcohol. Please don’t add fizzy drinks unless you hate the wine, as this completely disguises what you are drinking.
Everything in wine, apart from the water, has calories. Wine is made up of many different chemicals, but the main ones are alcohol, sugar, and acid.
Alcohol has far more calories than sugar – 7 kcal/gram vs 4 kcal/gram.
Ripe grapes have acids and sugar, but no alcohol. In the simplest case, fermentation converts all the sugar to alcohol (ethanol). So, a light and fully dry Sauvignon Blanc will have around 500 calories in a 750ml bottle. A moderate-sized glass holds 150ml (5 US fl.oz.), so would provide you with 100 calories – an essential part of a balanced diet.
Riper grapes will have more sugar, which will be converted to more alcohol. So, a Cabernet Sauvignon with 15% alcohol from a hot part of the world, may well have 800 calories in a 750ml bottle.
Champagne has a moderate alcohol level of about 12%. However, almost all Champagne has an added ‘dosage’ of sugar before the cork is inserted. This means that it typically has 600 calories per bottle.
Sweet wines are a little more complicated – it depends on how they are made. These are usually served in small glasses, which lowers your alcohol and calorie consumption:-
A German Riesling Spätlese, with a low alcohol of 9% and some sugar, may be 500 calories per bottle.
A top Sauternes from a great year can achieve 1200 calories per bottle.
Port, which is made by adding alcohol to stop the fermentation, is 1200 calories or more per bottle.
This isn’t stated on most labels, but perhaps it should be.