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T i m P a tt e r s o n Inquiring Winemaker The Skinny on Skin Contact for Whites S ome aspects of commercial winemaking, as Donald Rumsfeld might observe, are knownunknowns. We know, for example, that a lot of wineries use Velcorin to sterilize their wines, but we have no idea how many or how often, since neither winemakers nor the supplier will talk about it in public. Then there are the unknown-unknowns, including practices that are out of official favor but still in some use anyway. It can be easy to assume that these practices fall into the "nobody does that anymore" category, yet they persist and even grow. There are, for example, far more "wild" fermentations conducted every harvest than you might imagine, and even though such uncontrolled microbial orgies are considered dangerous to your wine, most of them succeed anyway. However many that may be. In that same Rumsfeldian space is the officially unfashionable technique of intentional skin contact for white grapes and juice. It's high on the "not the best practices" list, but a lot of people do it anyway. It doesn't show up on the label, it shows up in the wine instead; when it works, it means intensified aromatics and fuller body, and possibly more aging potential. Now you might ask, if this is an unknownunknown, how do I know about it? Not from talking to winemakers, though I did some of that, but from talking to enzyme suppliers and looking through their catalogs. Turns out they do a brisk business in products explicitly packaged for use with white wine skin contact, which suggests somebody out there must be soaking their exocarps. Fear of phenolics Modern white winemaking protocols just say no to skin contact. Skin shunning is a 82 W in es & V i ne s OC TOB E R 20 13 Abe Schoener ferments white wine varieties with the skins for the Scholium Project. core element of the reigning textbook approach, along with commercial yeast inoculation, cool fermentation temperatures, reductive strategies, squeaky-clean sanitation, heat and cold stabilization and sterile filtration. While that package may sound somewhere between conservative and paranoid, it has, to be fair, resulted in a massive upgrade in the quality of the world's white wines. As recently as a couple decades ago, plenty of white wines were flat, oxidized, murky, funky or some combination of the above. Today even low-end box wines are fresh, fruity, sparkling clear and fault-free. Clearly, the modern approach works. Inevitably, successful innovations in winemaking go from experimental to trendy to dominant to something more like dogmatic. Somewhere along this continuum is the advice offered in this excerpt from the lecture notes to Enology 124, Introduction to Wine Production, at the University of California, Davis: "The goals for white wines differ from red wine production in several respects. Generally little to no skin contact is desired. This is because the principal flavor and aroma compounds are located in the pulp of the grape with the skin providing little other than bitterness and astringency. Many white wine styles are designed to be consumed relatively young (less than five years of age), which is insufficient time to allow polymerization and softening of the phenolic content. In addition to bitterness, phenolic compounds lead to off-color production under oxidizing conditions. This color change is generally undesirable in white wines… "Skin contact refers to the length of time the juice is left in contact with the skins and seeds. The longer the time of contact, the greater the extraction of the components of the skins into the juice. In contrast to red wine production, the majority of the important sensory components of white grapes are in the pulp, not in the skins. Since the microbial flora of the grapes is located on the skins, skin contact also increases the contact of these organisms with the juice. If the skins are separated from the juice quickly, the microbes also are separated, minimizing their numbers in the primary fermentation."1 (See related article on page 65.) I don't mean to pick on Davis here; I'm sure the lecture notes at Montpelier or the guidelines at the AWRI say pretty much the same thing. But this advice, however well Highlights • re-fermentation skin contact for P white grapes runs contrary to current winemaking doctrine, but many winemakers use the technique anyway. • hite grape skins yield both aromatic W and phenolic compounds, a mix that can make wines more intense or simply coarse. • kin contact holds promise particularS ly for aromatic whites and is relatively common in Alsace and Bordeaux.