Today I added 5 grams of Efferbaktol granules (2 grams SO2, giving about 50 ppm) to the Napa River Ranch Cabernet in the Pod, and turned off the temperature control.
I changed the water in the new barrel I'm soaking up for this wine for the last time. I was a bit disappointed when a relatively large amount of wheat paste came out of the barrel in small chunks when I emptied the third fill. Wheat paste is used in the cooperage to seal the barrel heads into croze, and sometimes its use is a bit sloppy.
I don't have strong evidence that excess wheat paste in new barrels is problematic, but it is no secret that new barrels are more likely to grow Brettanomyces than old ones.
Another issue for some might be sensitivity to wheat gluten. Online literature citations suggest that wheat gluten can be used as a fining agent for wine (indicating that it precipitates well) and the FDA has recognized its use as GRAS, but gluten protein is soluble at pH 2.0 and may be at least slightly soluble at wine pH and alcohol content. TTB has proposed rulemaking for allergen labeling in concordance with the Food Allergen Labeling and Consumer Protection Act of 2004 that would mandate listing on the packaging any wheat products used in wine processing.
For all these reasons, for the last five years I have been asking my barrel suppliers to use the minimum necessary paste to assemble my commercial cooperage.