By Louisa Hargrave

Winemaking has come a long way since the days of the ancient Roman Empire, when a recipe for wine included the addition of Alpine pitch, turpentine resin, spikenard, myrrh and iris. An 1830s American recipe for improving wine suggests that adding ground oyster shells and burnt crab claws will give a wine an "agreeable and lively taste." In fact, the greatest changes in winemaking have occurred in the past 30 years. While the fundamentals have stayed the same, scientific advances have permitted a fine-tuning of the wine that wasn't possible 40 years ago.

The basics of winemaking couldn't be simpler. In fact, it takes some intervention to keep grape juice from fermenting in the first place. Live yeasts are trapped on the waxy surface of each grape berry. Once the berries are crushed, in a frenzied attempt to reproduce itself the yeast gobbles up the sugar in the juice. Eventually, it gets suffocated by the carbon dioxide it produces. At this point, the yeasty beasties begin to sustain themselves via fermentation, producing alcohol, another byproduct that eventually kills them.

If the wine created by this process of fermentation is then exposed to oxygen, it may turn to sour vinegar. Thus, the first job of the winemaker after fermentation ends is to protect the wine from exposure to air.

There are thousands of other metabolic mechanisms at work as grapes become wine. Few of them were understood at all until the process began to be picked apart with new scientific tools.

Winemaking research in the post-Prohibition era focused first on wine stability. Poor sanitation was endemic and, as few wineries were air-conditioned, the over-heated wines had chronic spoilage problems. The biggest advance of the 1960s and '70s came with the introduction of stainless steel for all winery equipment, but especially for fermentation tanks. Unlike wooden or concrete tanks, stainless steel tanks can be fully sanitized. Their smooth surfaces allow no nasty microscopic bugs to hide and breed. Better still, because metal conducts temperature well, these tanks can be fitted with double jackets that carry coolant. This can also be used to cold-stabilize the wine, bringing those sparkly "wine diamonds" (a salt of tartaric acid) out of suspension so that the wine remains perfectly clear in the bottle.

The irony of this switch to stainless steel fermenters is that within the last few years it has become fashionable to ferment red wines in open wooden tanks again. Whether this is an homage to peasant winemaking, a marketing gimmick, or a better way to let red wine vent itself as it ferments, it's not the only way trendy winemakers have gone back to basics.

"Boutique" yeast strains, bred to bring out various desired aspects in wine, are now available. For example, a company called Vinquiry offers 15 custom yeast strains. One promises to enhance "varietal fruity/floral aromas in addition to strawberry jam, caramel and spice" while another, geared specifically for aromatic white wines, "awards greater organoleptic complexity along with mouthfeel volume and richness."

There's no guarantee that these custom yeasts will produce the desired characteristics, which depend as much on fruit quality as on yeast strain. Many winemakers, in fact, are returning to the old practice of allowing fermentation to start itself with indigenous yeast. In a place like the North Fork, where for the last century most farmers have fermented sauerkraut and made pickles, this may seem like Russian (or Polish) roulette, but winemakers may get away with it if they have ever used cultured yeast strains in their wineries. These cultured strains can overrun the native yeasts once the fruit enters the winery. While the extra complexity achieved by a variety of yeasts may be desirable, no one likes the aromas of paint thinner, hay and banana that may come from a cocktail of indigenous yeasts!

One of the biggest advances in winemaking has come with the availability of nutrient additives for the yeast. Nutrient-deficient yeast can produce stinky sulfide aromas. In dry regions (like California), where there's no rain to wash spray residue off the fruit, the wines must also be treated after they're made to get rid of the burnt-rubber smell of sulfides.

"Fining" of wine has been practiced for centuries, both to clarify and to soften the wine. That's what the crushed oyster shells and burnt crab legs were meant to do in the 19th-century American wine recipe mentioned previously. Tannins, which give wine color and structure, can be bitter and astringent. Proteins will precipitate out tannins, so winemakers may use various purified protein products, including gelatin, egg white, casein (from milk) or isinglass (from fish bladders). Clays such as bentonite and diatomaceous earth will also remove protein.

These days, the source and quality of these fining agents can vary greatly, and a winemaker has many choices. Some manmade agents, such as PVPP, may also improve wine quality. But fining agents can also enhance or strip flavors and aromas from wine, for better or worse, so they must be thoroughly tested in the lab before use.

Micro-oxidation is a new advance in winemaking. It involves the use of tiny amounts of metered oxygen to enhance both fermentation and aging. On the West Coast, where growers can't control the high sugar content of the ripening fruit, wineries now use "spinning cone" technology to reduce the alcohol, bringing it back under 14%, the legal cutoff for "table wines." Any wine with more alcohol than that is subject to "sin" taxes, so the process may pay for itself.

Oak barrels have been used for centuries to age wine, but today there are cheaper oak substitutes that will flavor the wine, even though they can't offer the subtlety barrel aging gives. Oak chips treated in various ways can be suspended in the wine, or the fermenters can be lined with wooden staves.

Other new adjuncts to winemaking include the use of ozone instead of chlorine for sanitation, enzymes to break down pectin to enhance juice yield or color, and freeze-dried innoculants. While sorbates can keep a sweet wine from refermenting, and filtration products have improved, no one has invented a substitute for sulfur dioxide, which protects wine from both oxidation and microbial spoilage. Although sulfur dioxide has been used for four centuries, now that it appears in wine label warnings some people think it's new and dangerous. In fact, Fig Newtons have more sulfur dioxide than wine, and no one worries about eating them.

Do all of these advancements and tools really make for better wine? Overall, they contribute to wine quality that's far more consistent than it used to be. It's rare to encounter wines with microbial spoilage, though cork taint is a problem that will only be solved when screw caps are universally adopted.

Still, the bottom line is that the best wine comes from the best grapes. The greatest wines are created not by design, but by a synergy of climate, soil, and the vintner's attention to detail. It's a process that's much too complex to be fully controlled, and it's exactly those nuances in wine that make it exciting. If some winemakers are returning to ancient techniques, it's with the realization that sanitized wines are not great wines. For greatness, the winemakers have to work with the forces of nature, not against them. And that's nothing new.