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.
The term ‘hangover’ covers a range of symptoms including headache, nausea and dizziness caused by the consumption of alcoholic beverages. Some people are affected much more severely than others. The process is not fully understood.
The effect of alcohol (ethanol):-
Ethanol is a diuretic – it makes you excrete more than you normally would. The body becomes dehydrated, which can lead to many problems.
Ethanol is toxic, and is one of the few chemicals which can cross cell membranes. It can even cross the blood-brain barrier into brain cells.
It causes the blood glucose level to decrease, which can lead to weakness.
How alcohol is metabolised
Alcohol is normally metabolised in a 2 stage process. Accumulation of acetaldehyde is a real problem, as it is much more toxic than ethanol.
How alcohol is metabolised
Why some types of drink affect some people more than others?
All alcoholic beverages are a mixture of chemicals. Some such as wine are made up of hundreds, often present in very small quantities. These provide the drink’s character.
The particular chemicals depend on the raw materials, processing such as fermentation and distillation, and subsequent ageing.
Some people are adversely affected by particular chemicals. The reason may be that they are allergic, or cannot metabolise them.
I have known people have a problem with wines made from a particular grape variety, or a type of spirit. If you have very adverse reactions, it is worth investigating this possibility.
How to prevent a hangover
It shouldn’t need saying, but I will say it anyway:-
Eat food when you drink – the alcohol is absorbed more slowly.
Drink plenty of water – this limits dehydration.
Avoid drinks which have a particularly bad affect – why be a masochist?
Know your limits.
How to get rid of that hangover
Drink water to rehydrate. You may also want to use sachets of electrolyte to replace those you have lost.
Your blood glucose level is usually low after drinking. Eat carbs such as bread or cereals, as these can be readily converted into glucose.
Potassium levels are also low. Try eating foods such as bananas and kiwi fruit to boost this mineral.
‘Hair of the dog’ is often tempting, but sadly only delays the inevitable.
The only way to be guarantee a hangover-free life is to drink no alcohol, and where’s the fun in that.
Sparkling wines are more popular than ever, as they are lively and refreshing. How are they made, and what produces the bubbles?
Champagne cork and muzzle
Where do the bubbles come from?
Sparkling wines have carbon dioxide dissolved under pressure . When the bottle is opened, the pressure is released and the gas starts to evaporate. Bubbles form on irregularities on the glass, or material suspended in the wine.
What if there are no bubbles?
The main reason for bubble-free sparkling wine is dirty glasses. There is nowhere for the bubbles to nucleate.
What is the gas pressure within a bottle?
Champagne usually has a pressure of around 6 bar – 6 x atmospheric pressure – at room temperature. Which is why you get a mess if you open a warm bottle. The pressure decreases rapidly as the wine is chilled, which is one very good reason for serving cold Champagne. Other sparkling wines have a similar, or lower pressure.
Where does the carbon dioxide come from?
When sugar ferments in the presence of yeast, it produces alcohol and carbon dioxide. The more sugar you have, the more alcohol and carbon dioxide is produced.
In most sparkling wine production, grapes are fermented to a still wine. Sugar and yeast are added, and the second fermentation produces carbon dioxide for the sparkle.
In some rare cases there is just one fermentation, and the carbon dioxide retained, rather than allowed to evaporate.
The cheapest way of introducing the gas is to inject it into still wine, but this produces a coarse result.
Stopper to keep the fizz in a bottle
Producing bubbles using a second fermentation
Starting with a still wine, there are three main methods for producing the bubbles:-
The method used in Champagne, now generally known as the ‘traditional method’. Wine is put into a bottle, along with sugar, yeast and nutrients. This second fermentation produces carbon dioxide. The debris is removed, and the wine sold in the same bottle.
The transfer method, in which secondary fermentation is in a bottle, but the wine is then transferred to a vat, where the debris is filtered out. The wine is sold in a different bottle.
The Charmat or Tank Method, where the second fermentation is carried out in tanks. The wine is then filtered and bottled under pressure.
The quality factor
Quality sparkling wines undergo a number of processes and maturation to give the same depth and complexity as a fine still wine, but they also have the prickle of bursting bubbles on the tongue.
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.