Question

Milk can be preserved by adding a few drops of:
A. formic acid solution
B. formaldehyde solution
C. acetic acid solution
D. acetaldehyde solution

Answer 1

Hint: The function of preservatives is to increase the shelf life. So, we need to add such a kind of preservative that not only reacts with milk but also preserves it for an estimated amount of time without any harmful effects on humans.

Complete step by step solution:
- As stated above the use of preservatives is to increase the shell life. When preservatives are added in food, it prevents the process of fermentation, acidification or other decomposition of food, means they stop the growth of microorganisms in it.
- Acidic solutions are not added in the milk as acid damages the milk.
- Acetic acid and formic acid are organic carboxylic acids and so if we use them as preservatives of milk, it will damage the milk.
- Therefore, option (A) and (C) get eliminated as they both are acid.
- Now we have to check option B and D to get the correct result.
- Formaldehyde solution is an emulsifier which is added in the milk as it acts as a preserving agent for the milk.
- It kills most of the bacteria and fungi present in the solution. As it kills the microbes present in the solution, we can use it as preservative so that it will not allow the microorganisms to grow in the milk and as a result we can preserve for longer times.
- Preservatives such as BHA, propyl gallate, sodium nitrite, sodium benzoate and sulfites are listed as harmful preservatives which may cause cancer, heart diseases, allergies etc.
Therefore, from the above we conclude that option (B) formaldehyde solution is correct.

Note: Remember that acetaldehyde can also kill the bacteria and other microorganisms but it is not used as a preservative because it is not only toxic to us but it is characterized as a carcinogen as well. It is also responsible for certain types of allergies if consumed.