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Here's the latest---and I think my final summary on this subject....
1. I made some calls myself. Some cooperages and wineries, including Kentucky Whisky...barrel maker, say they swab the top, outside heads with wheatpaste. Guy said that not all cooperages use wheatpaste. Some use beeswax.  Some wineries use metal barrels for some wines.
The guy from Kentucky Whisky barrels said that whiskey does seep into the wood of the barrel and back through about 3/4 of the way. He does not know if wine does, so he cannot say if the wine ever touches the wheat, but he seemed to doubt it. However, he said that they must use a food-grade sealer and not a synthetic.

I'm still waiting for responses from other cooperages, but I'm not expecting any surprising answers at this point. Short of knowing which wine is kept in which barrels and/or testing the wine, we've gone as far as we can go in our own research.  L'Chaim. Lin

Here's another response, this one from Alan Lewis: 
I spoke with a cooper at Demptos Barrel Makers here in Napa to learn more about this.... the wheat paste is only used to seal the staves & the barrel heads. It does not even come into contact with the wine. That said, there are some white wines which are completely unoaked. Many sauvignon blancs never spend any time in oak, as well as a few chardonnays. 
Champagne (or sparkling wine) is another option because no oak is ever used to make it. It is aged entirely in the bottle - oak free. If you are still concerned about any possible effects, I recommend you enjoy these wines. I hope this helps, and would be glad to speak with you if you want to ask anything else. 

Alan Lewis, Wine Scout, 800 943 9463, [log in to unmask]

3. I'm not sure if I sent you this one from Beth Hillson already:

I've called a couple of wineries in Sonoma Valley and they have never heard
of this either.  They said they do clean the barrels with sulfites, but no
flour.  

* Please remember some posters may be WHEAT-FREE, but not GLUTEN-FREE *
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