How does sugar help to preserve jam and jely?

Sugar helps to preserve jam and jelly by acting as a natural preservative through its ability to inhibit the growth of microorganisms. When sugar is added, it creates a high osmotic environment that draws water out of the fruit and any potential bacteria, preventing spoilage. Additionally, during the cooking process, sugar interacts with pectin to form a gel-like structure, which not only thickens the mixture but also helps to seal it from air, further extending its shelf life.