Why is sugar used to preserve fruit?

Question

It has to relate with hypertonic solutions.

Answer 1

Fruits can be preserved with sugar, salt or vinegar. Mold can grow in 1 M sucrose solution. The amount of sugar used is much higher than a hypertonic solution. Solid sugar is added to the fruit. The reason sugar can be used to preserve fruits is that water is not available for the growth of microorganisms. Fruits can also be preserved by dehydration: raisin.

Answer 2

If fruit is placed in plain water (hypotonic solution), it will get soggy (because of osmosis).

If it is placed in water with more sugar than the fruit has (an isotonic solution) , the water will only go from the fruit to the water (instead of from the surrounding solution into the fruit) and therefore it will be preserved.