I had purchased a jar of %70 fruit blueberry jam. After consuming about %25 percent of it, I added into the jar some blueberries (10-15) that I purchased recently and I mixed it. A day after, the jam has become very very runny.
What shall I do to fix its consistency?
Jam is fruit, sugar, and pectin. You added more fruit but all that liquid in the fruit wasn't gelled with the pectin and sugar.
You could try adding sugar and heating the jam to get the pectin to gel with the new juice. This could work but is likely to be error prone. Pectin gelling is tricky and it might not re-gel.
I would recommend adding some sugar, boil it for a bit, and use it as delicious syrup.
In the future, if you have fruit and want jam, just buy some pectin and make your jam from scratch. It's easy to do.
Throw it out and replace it with a fresh jar - and don't adulterate the new one.
What was your goal in adding the blueberries? You could make a thicker jam yourself, or a sauce (without the same keeping properties as a preserved jam).
