Copper Sulfate Additions

Legal limit in the USA of copper sulfate ADDITIONS to wine has been raised recently from 0.5 ppm to 6.0 ppm, but the residual limit is still 0.5 ppm.

Materials Authorized for Treatment of Wine or Juice

This ruling is a key clue in what happens with copper in wines with H2S or mercaptans: if the proper amount of copper is added (that amount that will bind all the reduced compound) AND it’s allowed to precipitate or is filtered out, then NO copper is left in the wine. This is why bench trials are needed as it is impossible for most winery labs to determine quantitatively how much reduced compound is in a wine. In my opinion, there should be NO limit to the addition rate in wine, but retain the residual limit to 0.5 as the copper will precipitate out with the compound that’s being removed.

Anyway, here is how I calculate the addition rates, after they have been determined via lab trials:

0.15 mls of 1% copper sulfate per gallon of wine equates to 0.1 ppm

Interesting quote from epa site:

Copper is typically present in
mineral rich foods like vegetables (potato, legumes (beans and peas),
nuts (peanuts and pecans), grains (wheat and rye), fruits (peach and
raisins), and chocolate in levels ranging from 0.3 to 3.9 ppm. A single
day’s diet may contain 10 mg or more of copper.

and:

The Agency
has set a maximum contaminant level for copper at 1.3 ppm because the
Agency believes that this level of protection would not cause any
potential health problems, i.e. stomach and intestinal distress, liver
and kidney damage, and anemia.