Why should curd and sour substances not be kept in Brass or Copper vessels?

Answer

Curd and acidic substances contain acids. If we put them into metals, the acids will react with metal, so we can’t put them into metals. Steel and plastic don’t react with acids.

Metal + Acid → Salt + Hydrogen

Lactic acid is an organic acid that contains the -COOH group. Hence, it is a weak acid due to the presence of this group.

Lactic acid develops in cow milk because of the breaking down of bacteria. Fresh milk does not contain lactic acid. Dairy products such as yogurt, cheese and condensed milk contain lactic acid.

The sour taste of substances is because they contain, such as vinegar contains acetic acid, tamarind and grapes contain tartaric acid and lemons and oranges contain citric acid.