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Brown Colored White Wine

TroubleShooting

Leonard Zacher — Kelseyville, California asks,
Q

I picked up Sauvignon Blanc grapes late in the day that they were harvested. I let them sit overnight and began crushing/destemming early the next morning. The free run juice was brown in color, not the pale green color of the commercial SB’s I buy. This wine is nearly completed fermentation now and although it tastes fine it has retained the brown color. Will sterile filtering give me the nice clear pale green color I am seeking?

A
Sorry to say, but it sounds like you’ve got a no-bueno situation. White grapes should always be pressed as soon as possible after picking in order to reduce juice (and subsequent wine) browning. By letting your white grapes sit overnight (and they’re juicy after being picked, especially at the lower levels of your buckets or bins) you started what effectively was a whole-cluster maceration and the juice began extracting compounds from the skins that can become brown. Grapes naturally contain an enzyme called polyphenol oxidase, which can start an oxidative chain reaction in grape juice that turns normally colorless compounds in the grapes into brown pigments. By macerating your grapes overnight you increased the concentration of the available substrate so it isn’t surprising that when you did get around to pressing the juice, it was brown, and that the subsequent wine is brown as well. It is completely normal to experience some browning when pressing white grapes, even those pressed immediately after being picked. At normal, low levels these brown pigments fall out of solution during primary fermentation and the
Response by Alison Crowe.