Copper Cookware Performance

• Cooks treasure copper pots for their quick responsiveness to heat, reserving them for delicate sauces where temperature-control is critical to success. Copper's relationship with heat is, however, only one of its interactive qualities. Copper tarnishes through interaction with the air, or oxidation, forming first a thin dull brown layer, then a greenish patina. Most cooks take action when surfaces brown, but exposure to polluted air or natural gas cooking can make cleaning copper pots a frequent chore. Fortunately, the problem is primarily aesthetic. There is general agreement that tarnish on the outside of a copper pan does not affect its heat conductivity. Tarnish does not, therefore, affect cooking, but other questions remain about its effects on cooking food.

Copper and the Human Body

• Copper is an essential trace element, linked to iron metabolism, bone development and nerve maturation, but in excess, it can be toxic, causing symptoms ranging from severe digestive upset to fatal liver damage. Consumed in the form of copper salts, formed during the second stage of copper oxidation, green deposits of copper carbonate, also called verdigris, are classified by the National Institute of Health as toxic to humans. The Federal Food and Drug Administration sets the required daily allowance of copper in adults at 890 micrograms, an amount usually absorbed in a balanced diet containing whole grains, nuts and seeds, as well as particularly copper-rich foods like beef liver and shellfish. Copper deficiency is regarded as rare.

Copper and Food Acids

• The majority of copper cooking vessels are lined with tin or, increasingly, stainless steel because of copper's interactivity with food acids. Both experienced cooks and cookware specialists recommend lined copper for the home kitchen for this reason. Food acids like fruit juice, wine or vinegar can cause discoloration on copper surfaces. More concerning, these interactions reflect the leaching of small amounts of copper into food. The question of whether leaching poses a danger to those consuming food cooked in copper pots is not easily answered. Whether and how exposure is affected by storage of food in copper, whether tarnish speeds the leaching effect and how much copper is leached in cooking all require further study.

Deciding on Copper Cookware

• Choosing cookware with a tin or stainless-steel lining can prevent acid foods from reacting with copper surfaces. Avoid very lightweight copper-cookware bargains. Both copper and the protective lining will be thin and perform poorly. Reserve copper pans for non-acid foods. Although tarnish may not affect heat conductivity, keeping copper clean can dispel any tarnish-related worries. A traditional cook's trick is to sprinkle a lemon wedge with salt and rub it over the pan before rinsing, drying and putting the pan away.