It is generally not recommended to store milk in copper containers for extended periods due to potential copper contamination, which can lead to health issues and affect the milk's taste.
Copper is a reactive metal, and acidic foods or liquids, including milk (which has a slightly acidic pH), can cause copper to leach into the food. This leaching process is accelerated over time. While trace amounts of copper are essential for human health, excessive intake can lead to copper toxicity, causing symptoms like nausea, vomiting, diarrhea, and abdominal pain. Furthermore, the copper ions can react with components in the milk, altering its flavor and potentially degrading its nutritional value. While short-term contact might not pose a significant risk, prolonged storage is best avoided. It's always safer to use food-grade containers made of materials like glass, stainless steel, or certain plastics that are specifically designed to be non-reactive with food.
If you must use a copper container temporarily, ensure it's lined with a food-grade, non-reactive material like tin or enamel to prevent direct contact between the milk and the copper. However, regularly inspect the lining for any damage, as exposed copper can still leach into the milk.