Question

What happens when curd or sour substances are kept in metal containers?

Answer 1

Curd and sour substances contain acids. Acids react with metals to produce salt and hydrogen gas. So, if such substances are kept in a copper container, the acid will react and the container will be corroded. Metals are the chemical substances that can easily undergo oxidation by loss of electrons. Acidic compounds when treated with metals leads to the liberation of toxic salts by undergoing a chemical change, the produced toxic salts were unfit for human leads to food poisoning.

Complete Step By Step Answer:
Curd contains lactic acid. Generally, acids react with metals to form a different compound. Thus, the curd is not stored in metal containers of brass, copper, and bronze as curd can react with them and produce compounds which are toxic to human beings and unfit for human consumption.
Pickles and curd are not stored in metal containers like brass and copper utensils because when they are kept in copper or brass utensils, curd or pickle reacts with copper and brass. This reaction will initiate formation of toxic compounds (Toxic Salts) which may be unfit for human consumption, and may cause food poisoning.
We know the taste of curd and pickle. At some point in life we all had tasted curd and pickles. So, the taste of curd and pickles is sour. We should know that sour taste is one of the five basic tastes and is evoked by acids. We should know that the sour taste of foods and beverages is due to organic acids, including acetic, citric, malic, and acids in fruits and vegetables. So, from this we came to know that curd and pickle also contain some acid.
sour substances are acidic in nature,i.e,they have acids in them. So, when they are kept in brass or copper vessels,they react with them and form poisonous or better to say toxic elements which may prove harmful for the human body. So they are not kept in metal containers.

Note:
Curd is nothing but a lactic acid bacterium, which is one of the components of an acid. Sour foods or items consist of oxalic acid, maleic acid, citric acid, and tartaric acids which are also acids. These acids react with metals and lead to chemical change.