WINE-MAKING IS ONE of the simplest, oldest, worthiest enterprises of man. Most wine drinkers have a general knowledge of how the stuff is made: grapes are picked and crushed; the juice is fermented, sometimes aged in wooden barrels and bottled. Deeper knowledge of wine-making will enable the consumer to understand better what he is drinking, to differentiate between styles of wine made with the same grape and to appreciate the great vintages.

Great wine can come only from great grapes. But the process is still important; with mediocre fruit the process can make the difference between an acceptable and an unpalatable product. All fruit shold be handled carefully during picking and transportation. If the containers for the grapes are too large, the weight of the load bursts much of the fruit before it arrives at the winery. The presence of broken or rotten

fruit, and dirt and other foreign

matter on the grapes, will also

affect the taste of the wine.

The grapes are crushed at the

winery. The juice, or must, is

treated with a small amount of

sulphur dioxide, which prevents

wild fermentation before the winemaker's selected culture can be introduced and also prevents oxidation -- the mixture of air with wine that can quickly and forever taint it. Lighter-style white wines receive little or no skin contact, which impacts "extract" (soluble solids) that adds to a wine's complexity but can overpower fragile or inferior fruit. The residue left after crushing, known as "pomace," is also pressed.

In the old days fermentation took place in vats without temperature controls, when too much heat spoiled the freshness and good acidity of the resulting wine. Richer, more complex and more expensive wines, such as white burgundies and big California chardonnays and some sauvignon blancs, are fermented at higher temperatures, often in oak. Thanks to California invention, cold fermentation in refrigerated steel tanks is almost universal today for lesser white wines.

After fermentation, the wine is held in a settling tank to allow the solids to fall out of solution. It can also be fined and run through a vacuum filter or a centrifuge to clean it up, although these processes should be done sparingly, if at all.

Red wine is given skin contact to pick up color, extract and tannin, a preservative. It can be fermented in steel or in oak vats that add to the wine's character. A "cap" forms on top of the fermenting must, and has to be either pushed down into it or the liquid pumped over the cap to prevent overheating and the growth of bacteria. Pressed and fermented red wine is "racked" -- moved from one barrel to another after the wine has settled -- to leave the residue behind.

Reds and whites can be aged in oak, an ancient device for storing and transporting wine that proved also to be a powerful influence on its taste. "New" oak imparts both a strong vanilla taste and more tannin; the choice of French, Yugoslav or American oak can profoundly alter the style of a good cabernet, for instance. The barrels have been heated in the making, which adds the toasty quality one expects in fine white wines. The vast majority of wines made in the world are not aged in oak, and should not be kept for many months beyond purchase because they will not improve. Better wines that have been given the care and the potential for age are well worth the investment.