Question

what is the use of keeping food in air tight containers

Answer 1

It is because the food would not dry up when it is in a air tight container and keeps its moisture.it would also not absorb certain smells when it is kept in such a container.
Hope it helps and pls mark it as the best answer. :-)

Answer 2

when food are kept in air tight container, they remain as they are as moisture present in air don't reach there and helps in keeping it away from other fungus and from foul smell.