Sunday, December 23, 2007

Hole-y fermentation! Raising suger in botrytised grapes...

The 2005 Botrytised - Yakima Valley WA - Chardonnay/Chenin Blanc frozen grapes from Brehm Vineyards made a delicious sauternes-style dessert wine (indeed, a Gold-medal winning wine for me in this fall's local AWS competition). The only challenge was that the brix (sugar level) came in somewhat low, in the low/mid-20's. For dessert wine, that required sugar addition before fermentation, up to about the 32 brix level for that batch.

This year, I'm trying an experiment with a couple of pails. My plan was to pour juice as it thawed, and leave some of the remaining ice behind. That would allow for a more highly extracted, higher-sugar-level juice (though lower quantity) to start fermentation.

Thanks to Bob Thomas (who together with Lee Baldieri, operate as Winemaker Products LLC) for this tip below about how to accomplish the extraction:

First, I drilled a few holes in the center top of the frozen pails:

Then, inverting the frozen pail on top of an empty pail, I let the juice drip through as it melted:

I removed the top pail after some time, leaving a slightly sweet ice behind, but with a thicker juice in the collection bucket. I ended up with final juice in the high 20's brix - still not high enough without added sugar, but closer than if I had thawed the entire buckets.

By the way, to increase the starting brix level in a must, the formula is: add .125 pound of sugar for each 1 degree brix increase in each 1 gallon of must (or .625 pounds per brix for a five-gallon pail). I'm targeting 36 degrees starting brix for these dessert wines.

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