To make what is thought to be a better looking product, it is the
practice in some households to "green" pickles by heating them with
vinegar in a copper vessel. Experiments have shown that in this treatment
copper acetate is formed, and that the pickles take up very appreciable
quantities of it. _Copper acetate is poisonous._
By a ruling of the Secretary of Agriculture, made July 12, 1912, foods
greened with copper salts, all of which are poisonous, will be regarded
as adulterated.
Alum is often used for the purpose presumably of making pickles firm. The
use of alum in connection with food products is of doubtful expediency,
to say the least. If the right methods are followed in pickling, the salt
and acids in the brine will give the desired firmness. The use of alum,
or any other hardening agent, is unnecessary.