When we pressed the Grenache a few days ago, all seemed well. It tasted fantastic, and had surprisingly excellent structure. This will be a mighty fine wine, even cry beaujolais-like as James said: wonderful, joyful fruit but with just the rright amount of tannic backbone.
We had more whole berries at crush than usual, though. And that was okay: a whole berry ferment would only accentuate the lovely fresh fruitiness that’s the hallmark of this with for us. When we went to press, that meant that, paradoxically, the wine got sweeter them more we pressed as those whole berries now surrendered their hidden treasure – treasure a few days behind the rest of the must because the berry walls insulated the internal juice from everything outside it.
But then two days later, by the time we racked it off its gross less, the Grenache was stinking up the joint: hydrogen disulfide, and its delightfully nauseating rotten egg fragrance. Which was totally odd: there wasn’t even a hint of H2S when we pressed. What the hectare?
Here’s my theory:
Almost all of our wines from eastern Washington come in nutrient-deficient – its the heat mostly, but undoubtedly the soil profile. Since yeast react to nutrient deficient food sources by producing H2S (in addition to CO2 and alcohol), I always add nutrient for those microscope critters at set periods through the ferment, and this almost always takes care of it. Now and again, the grapes are especially nutrient deficient (like our Mourvedre this year), so you need to add more nutrient across a broader spectrum of the ferment. But even there, nutrient always takes care of it.
Except here. Why nutrient didn’t do the trick on the Grenache is, I think, the same reason our wine got sweeter when we pressed: we had a bunch of whole berries which were relatively sealed off from the outside world. And because they were sealed (more or less), the nutrient I added during the course of fermentation didn’t penetrate, leaving the yeast inside the berries to make do with still-nutrient-deficient juice. That therefore meant H2S production inside the berries, but probably also a slower, weaker fermentation inside them. So when we pressed those whole berries, we got little of bombs unfinished ferment, and soon enough, H2S.
Luckily, because you need stressed yeast at least in the beginning stages of H2S, once we racked the wine off the gross lees (which are largely spent yeast), the problem went away. But we’ll definitely want to keep an eye (and nose) on it…