More than 70 countries around the world produce wine. In order to produce quality fruit, suitable for making wine, the temperature of a country should be hot enough for the sugar in the grapes to accumulate sufficiently, but long enough that the phenolic components of the grape also have time to ripen. In general, countries that lie between 30 and 50 degrees north or south of the equator are though to be suitable for grape growing, but altitude and proximity to water can also influence the climate, so countries that lie closer to the equator can grow quality grapes if they have some sort of moderating climatic influence, and countries that sit further from the equator can also be suitable. This is because distance from the equator has an effect on sunlight. The further one is from the equator, the longer the days in summer. And long summer days allow sufficient sunlight for photosynthesis. Sufficient, though not abundant, water supplies are also crucial since vines need a certain amount of water to survive. Finally, cool winters, which allow for dormancy, help to maintain healthy vines. That being said, many wine-producing countries around the world do not conform to these general guidelines, proving that grape growing is a constantly evolving experiment.
Almost any grape can be used to make fortified wine, which merely requires the addition of spirits to fortify the alcohol. However, some grapes are used almost exclusively for fortified wines.
Red, or more properly black, grapes, are so named because of the pigment in their skin. The flesh of the grapes produces white juice, and the juice only becomes red when left to macerate on the skins, allowing the pigmentation to leach out. A very few red grapes, known as teinturiers, have red-coloured flesh. And these can yield dark red-coloured juice, but these are rare and usually not vitis vinifera. In addition to colour, the skins of red grapes are generally high in tannins, a compound that helps to preserve wine.
Depending on what type of sparkling wine is being produced, the key feature for the grapes is to be either neutral (for Champagne, for example) or flavourful (for Lambrusco o, for example), but they are usually high in acid to ensure that the sparkling wine is refreshing. Sparkling wine grapes can be either white or red. Red grapes are often pressed for sparkling wine without contact with their skins, which yields a wine juice.
White grapes are actually green in colour, and are mutations of red grapes in which anthocyanins are no longer produced. They are usually crushed and pressed right away, without contact with the skins in order to maintain freshness. However, there has been a resurgence in the ancient technique of macerating white juice on the skins of white grapes, a process that extracts some tannins and usually leads to a darker yellow, even orange, hue.