Here's why:

* Curd's Composition: Curd is primarily composed of milk proteins (casein), lactic acid, and some fats. These components are not strong enough to react with copper.

* Copper's Reactivity: Copper is a relatively unreactive metal. It does react with strong acids like nitric acid, but not with the weak acid present in curd (lactic acid).

What might happen if copper is in contact with curd?

* Corrosion: While copper doesn't react chemically with curd, it can still corrode if exposed to acidic conditions. The lactic acid in curd might contribute slightly to this corrosion over a long period.

* Contamination: Copper can leach into food if it's in contact for extended periods, especially if the food is acidic. This is a potential health concern, as copper can be toxic in high doses.

Bottom Line: It's best to avoid using copper utensils or containers to store or prepare curd to minimize the risk of contamination or corrosion.