Here is the email that I received from KJ Wines :
"Response from our winemaker re: gluten -
All wine barrels use a very small amount of flour and water paste to seal the joint between the barrel heads and the staves. This is the traditional method of making barrels and has been used by all coopers for many years.
This paste is a sealing material placed between two pieces of wood, not an additive to the wine. Almost none of the paste ever touches the wine, so there is essentially zero gluten in wine.
Because of this paste, we cannot say that our wine is technically gluten-free, but I would challenge any laboratory to be able to detect any gluten in our wine.
World Cooperage, our barrel partner, has tested a gluten-free paste to seal the barrel head joints. The gluten-free paste would dry and crack, resulting in leaky barrels, which is why they continue to use the traditional product."