I recently made custard with a huge amount of milk, custard powder and sugar. After boiling it for few minutes I added vanilla essence to it. After it was settled I added apple and pineapple. Then I placed the whole mixture in the fridge and the custard was tasting fine at that time. But after a half hour of cooling, when I tasted the mixture it was bitter. I googled about the issue and found out that milk and pineapple are not good friends, but I don't want to waste the whole thing now. Is there any way to reduce the bitterness?
You can't. This is caused by an irreversible chemical reaction. The bitterness is there to stay.
If it is just a tad too much for you, you can try diluting: make more pudding and mix it into the bitter pudding. But if it is the strong bitterness I know from mixing milk and fruit enzymes, that won't help either.