Question

Milk can be preserved by adding a few drops of
A) Formic acid
B) Formaldehyde solution
C) Acetic acid solution
D) Acetaldehyde solution

Answer 1

Hint: Preservatives are those substances which prevent the decomposition process of food and improves the shell-life of the substance. An ideal preservative is that chemical compound, which reacts and preserves the food and as well as it does not cause any harm for the human body.

Complete answer:
 So, here the question is, from the given options, which is the ideal preservative that can be used for increasing the shelf-life of the milk.
-Preservative is that chemical or substance which in addition improves the shelf-life of the substance.
We know that, when preservatives are added to the food items, beverages etc. it reacts with it and prevents the processes like acidification, fermentation and any other process that may damage the quality and texture of the substances.
It prevents the growth of bacteria and other microorganisms.
From daily life experience, we know that if acidic substances are added to the milk, it damages the milk.
When we add vinegar or lemon juice, the milk is completely damaged.
As formic acid and acetic acid are organic acids, so they will not preserve the milk, instead they would damage the milk.
So the option (A) and (C) can be ruled out and can’t be used as a preservative for milk.
Next we can check for other options.
The option (B), formaldehyde is used as an emulsifier and it prevents the growth of microorganisms. Hence addition of a few drops of formaldehyde in the milk will increase its shelf-life and formaldehyde is an ideal preservative among the given options.

So the correct answer is option (B)

Note: If we see the last option acetaldehyde, it also kills most of the bacteria, fungi and other microorganisms, but it can’t be used as a preservative, since it is very harmful for the human body. It is not only harmful but is also a carcinogenic substance and is known to cause certain allergies.