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Suspicious Syrah & Fermentation Aids
The first step I would take is to look at the package and/or the packing slip that came with the grapes . . . I hope they say Syrah. If you still doubt the paperwork, certainly get in touch with your juice supplier and ask to see the paper trail from the lot of juice you received.
It seems to me like your Carmenère is a candidate for one of the “Wine Wizard’s” cheapest, easiest and most favorite ways to improve a tannic wine; egg white fining!