You could make a Blueberry Koji syrup that will ferment slowly a couple weeks in your fridge. It would be less a jelly and more like a honey alternative if that's ok. Put it on pancakes, in drinks, cereal, ect. (until it's time to cook it again to stop fermentation.) Ratio: 10 blueberries : 5 Brown Sugar : 2 Koji Heat your pot to medium then add your blueberries, let them soften in the heat and you can crush them (don't burn) after a few minutes, when the blueberries are hot add your sugar. Let that cook down until it's a syrup then wait, and let cool to 135 degrees F before adding your koji. Blend. Then add to the jar of your choice but it needs an airlock and a Good amount of headroom, that's important so you don't have syrup coming out the top. I'm talking at least an extra 1/4 of the jar in headroom. An now you you can safely let that ferment in your fridge a few weeks. Strain and use. It will slowly gain more sour candy notes the longer you leave it in which is delicious but eventually will become too sour so what I recommend is. Stopping the fermentation at the right time Which is when You, decide it's done fermenting. Let's say after a week you don't want it any more sour. Now just reheat your mixture and pasteurize it at 165-170 for a few minutes. Then strain and store it back in the fridge for a few weeks. (Months if properly pasteurized)