Why does fresh jam not spoil when berries do like if you boil and crush for 15m put it in the fridge how much longer last than why?

There are several reasons why fresh jam doesn't spoil as quickly as berries.

Sugar concentration: Jam is made by boiling berries with sugar until the mixture reaches a high sugar concentration, typically around 60-65%. This high sugar content inhibits the growth of bacteria and other microorganisms that cause spoilage. Sugar acts as a preservative by drawing water out of the berries and creating an environment that is too hostile for most microbes to survive.

Acidity: Berries are naturally acidic, and adding more acid, such as lemon juice, during the jam-making process further lowers the pH of the jam. This acidic environment can inhibit the growth of bacteria and molds.

Boiling: Boiling the jam mixture for 15 minutes or more helps to kill any remaining bacteria or molds that may be present. This sterilization process ensures that the jam is shelf-stable and can be stored for a longer period.

Refrigeration: Once the jam is made, storing it in the refrigerator further slows down the growth of any microorganisms that may have survived the boiling process. The cold temperature inhibits the activity of enzymes and slows down chemical reactions that can lead to spoilage.

As a result of these factors, fresh jam can typically last for several weeks or even months when stored in the refrigerator, while fresh berries may only last for a few days.