Wine is produced by the fermentation of grapes by yeast. The yeast turn sugars in the grapes into alcohol. This is done without the need for additional sugars or enzymes as the grapes contain all that is necessary to transform into wine.
The different wines arise from the type of grape used, the parts of the grape that are removed from the fermenting mixture, the climate and soil characteristics where the vines grew, and the strain of yeast used.
Types of wine
There are at least 6 different types of wine. They are red, white, rose, sparkling, dessert and fortified wines. The colour of a wine is determined mostly by the skin, but the inside of any grape is generally colourless and so a few white wines are made from a black grapes.
The skin of a grape adds pigmentation and tannins to a wine. Tannins are polyphenols that add a bitter and dry quality to red wines. The seeds and stems also add tannins and are often left in the fermenting mixture that produces red wine(1).
Well known grape varieties that are used to produce white wine include: Chardonnay, Riesling, Sauvignon Blanc and Pinot Grigio. White wines are most commonly made from the inside of white grapes without all the skins, seeds and stems.
Rosé wines are sweet and pink in colour. They are made from the same black grape varieties that are used in red wine (see below). Their skins are removed from the fermenting mixture after a few hours, to prevent them turning into red wines. They may also be produced by blending white and red wines.
Grape types used to make red wine include: Pinot Noir, Cabernet Sauvignon, Merlot, Chianti, Zinfandel, Beaujolais and Grenache. The tannins that are left in the fermenting mix by the skins, seeds and stems of the grapes are responsible for the dry taste in the throuat and mouth. The tannins also preserve the wine, meaning that red wines can be aged for far longer than white wines.
Any type of grape can be used to make sparkling wine. Carbon dioxide bubbles are trapped during the fermentation process to add the fizz. Champagne is a special type of sparkling wine. Others include Cava and Prosecco.
Very sweet and often used with a dessert course!
The best known examples are probably Madeira, Port and Sherry. They are normally produced by adding brandy to a fermenting wine mixture. this stops the fermentation and adds a lot of sugar.
Wine and health
There are frequent reports in the press regarding the health benefits of wine, especially red wine. Compounds found in wine and especially in red wine are touted as improving both cardiovascular health and cancer risk. The best known of these is resveratrol. Resveratrol is found in greatest amounts in red wine (1.98-7.13mg/L), then rosé (0.43-3.52mg/L) and then white (0.05-1.80mg/L). However, alcohol has a more profound effect.
Resveratrol is associated with cardiovascular benefit. It has proved effective at preventing chemical changes associated with heart attack risk in test tube experiments. However, the amounts of resveratrol required to have these effects seems far greater than could be achieved in human blood after a few glasses of wine.
Moderate amounts of alcohol increase HDL levels(2), reduce blood clots(2) and can improve insulin sensitivity and blood sugar levels(3).
Resveratrol has been found to block cancer progresson through a number of mechanisms. These changes have been observed in test tube experiments with relatively high doses. Again it seems that the amount of red wine that would need to be drunk, to reduce cancer risk via resveratrol, would be damaging to health.
Another instance where resveratrol has been effective is with the control of blood pressure, blood sugar and triglyceride levels. Once again the amounts required are beyond that available from a few glasses of wine. For instance one study used 150mg resveratrol pills daily on 11 obese men(4). To obtain a similar amount through red wine you would need to drink 40 bottles every day. Fortunately the alcohol in red wine will provide many of these benefits at much lower doses.
A significant 2-5% of people are intolerent to some of the substances in wine. These substances include alcohol, amines, proteins peculiar to grapes as well as other chemicals including sulphites. Red wines invoke intolerance more often that white wines. Symptoms include itchiness, flushed skin, sneezing, diarrhoea, tachycardia and intestinal cramps(5).
Wine will normally have sulphur dioxide - SO2 added to it to stop it degrading. In wine sulphur dioxide becomes the anti-oxidant and taste enhancer, sulphite SO3. Without the addition of sulphur dioxide most wine would have a shelf life of less than 6 months.
In the wine industry levels of sulphites are strictly controlled. While it is possible that some people with asthma may suffer reactions to these sulphites, there is not a great deal of evidence implicating sulphites as asthma triggers(6). Sulphites levels are higher in white wines than in red wine as red wine naturally lasts for longer.
There is a common understanding that wine contains powerful anti-oxidants and other substances that can benefit the heart. However, when you look for direct evidence for this, it is not very strong(7). It appears that the benefits come mostly from the alcohol rather than any other special substances in wine.
My advice is that you are best off with 1-2 small glasses of wine daily, which may improve health if you are not underage, pregnant, lactating or prone to mental illness. Despite preferring wine myself, it may well be that a modest amount of some other alcoholic drinks on a daily basis could be equally beneficial.