Question

Before refrigeration became common, many foods were preserved by salting them heavily. Fruits were preserved by mixing them with a large amount of sugar (fruit preserves). How do salt and sugar act as preservatives?

Short answer

Sugar and salt act as preservatives by reducing the moisture content of fruits and which inhibits any microbial activities like the growth of bacteria which spoils foods.

Step-by-step solution

Step 1:

There are several ways in which salt and sugar inhibit bacterial growth. The a most simple way is by reducing the moisture content of the food, which helps in bacterial growth.

Step 2:

Every food has some quantity of water inside it called the water activity. Sugarand the salt draws the water from the food towards itself by the process of osmosisthus, the moisture content of food is reduced and the food is preserved fromany microbial damage.