How are jams jellies and squashes preserved from spoilage?

Jams, jellies, and squashes are preserved from spoilage primarily through the process of sterilization and high sugar content. The high sugar concentration creates an environment that inhibits the growth of spoilage microorganisms by drawing moisture out of the fruit and bacteria. Additionally, these products are often sealed in airtight containers, preventing exposure to air and further microbial growth. Canning methods, such as boiling water bath or pressure canning, also help ensure that any bacteria or spores are killed during the preservation process.