Per FDA regs copper may not be used for storage of cooking of foods with pH < 6.00. There is one exception. Brewing!
4-101.14 Copper, Use Limitation.*
(A) Except as specified in Â¶ (B) of this section, copper and copper alloys such as brass may not be used in contact with a FOOD that has a pH below 6 such as vinegar, fruit JUICE, or wine or for a fitting or tubing installed between a backflow prevention device and a carbonator.
(B) Copper and copper alloys may be used in contact with beer brewing ingredients that have a pH below 6 in the prefermentation and fermentation steps of a beer brewing operation such as a brewpub or microbrewery
See http://www.foodservice.com/food_safety/ ... 4&type=FCT